研究者業績
基本情報
研究キーワード
1研究分野
1経歴
2-
2019年4月 - 現在
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2009年4月 - 2019年3月
論文
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The Journal of pathology 2023年10月5日Pancreatic stellate cells (PSCs) are stromal cells in the pancreas that play an important role in pancreatic pathology. In chronic pancreatitis (CP) and pancreatic ductal adenocarcinoma (PDAC), PSCs are known to get activated to form myofibroblasts or cancer-associated fibroblasts (CAFs) that promote stromal fibroinflammatory reactions. However, previous studies on PSCs were mainly based on the findings obtained using ex vivo expanded PSCs, with few studies that addressed the significance of in situ tissue-resident PSCs using animal models. Their contributions to fibrotic reactions in CP and PDAC are also lesser-known. These limitations in our understanding of PSC biology have been attributed to the lack of specific molecular markers of PSCs. Herein, we established Meflin (Islr), a glycosylphosphatidylinositol-anchored membrane protein, as a PSC-specific marker in both mouse and human by using human pancreatic tissue samples and Meflin reporter mice. Meflin-positive (Meflin+ ) cells contain lipid droplets and express the conventional PSC marker Desmin in normal mouse pancreas, with some cells also positive for Gli1, the marker of pancreatic tissue-resident fibroblasts. Three-dimensional analysis of the cleared pancreas of Meflin reporter mice showed that Meflin+ PSCs have long and thin cytoplasmic protrusions, and are localised on the abluminal side of vessels in the normal pancreas. Lineage tracing experiments revealed that Meflin+ PSCs constitute one of the origins of fibroblasts and CAFs in CP and PDAC, respectively. In these diseases, Meflin+ PSC-derived fibroblasts showed a distinctive morphology and distribution from Meflin+ PSCs in the normal pancreas. Furthermore, we showed that the genetic depletion of Meflin+ PSCs accelerated fibrosis and attenuated epithelial regeneration and stromal R-spondin 3 expression, thereby implying that Meflin+ PSCs and their lineage cells may support tissue recovery and Wnt/R-spondin signalling after pancreatic injury and PDAC development. Together, these data indicate that Meflin may be a marker specific to tissue-resident PSCs and useful for studying their biology in both health and disease. © 2023 The Pathological Society of Great Britain and Ireland.
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日本癌学会総会記事 82回 978-978 2023年9月
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Genes to cells : devoted to molecular & cellular mechanisms 2023年2月27日 査読有りEpithelial-mesenchymal transition (EMT) plays a pivotal role in cancer metastasis and treatment resistance, which worsens prognosis. In phase III trials, eribulin improved overall survival in metastatic breast cancer (MBC) patients. In preclinical studies, eribulin suppressed EMT. However, clinical data on the use of eribulin for MBC patients are limited. In this exploratory, prospective study, we examined the effect of eribulin on EMT in MBC patients. Twenty-two patients aged 44-82 years with recurrent breast cancer or MBC were treated with eribulin. Breast cancer tissue samples were obtained before treatment and on day 15 ± 5 of the first cycle of eribulin treatment. EMT markers (E-cadherin, claudin-3, vimentin, N-cadherin) were analysed using western blotting. EMT changes were evaluated based on the ratio of epithelial to mesenchymal markers before and after treatment in individual tumours. E-cadherin/vimentin, claudin-3/vimentin, E-cadherin/N-cadherin, and claudin-3/N-cadherin ratios were significantly higher after treatment (P = 0.007, P = 0.005, P = 0.006, and P = 0.011, respectively). Based on E-cadherin/vimentin, 65.0% of tumours shifted to an epithelial phenotype, as compared to 66.7% based on claudin-3/vimentin, 84.6% based on E-cadherin/N-cadherin, and 71.4% based on claudin-3/N-cadherin ratios. Thus, our results showed that eribulin suppressed EMT in breast cancer tissues.
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Scientific Reports 12(1) 2022年12月Abstract Perivascular mesenchymal cells (PMCs), which include pericytes, give rise to myofibroblasts that contribute to chronic kidney disease progression. Several PMC markers have been identified; however, PMC heterogeneity and functions are not fully understood. Here, we describe a novel subset of renal PMCs that express Meflin, a glycosylphosphatidylinositol-anchored protein that was recently identified as a marker of fibroblasts essential for cardiac tissue repair. Tracing the lineage of Meflin+ PMCs, which are found in perivascular and periglomerular areas and exhibit renin-producing potential, showed that they detach from the vasculature and proliferate under disease conditions. Although the contribution of Meflin+ PMCs to conventional α-SMA+ myofibroblasts is low, they give rise to fibroblasts with heterogeneous α-SMA expression patterns. Genetic ablation of Meflin+ PMCs in a renal fibrosis mouse model revealed their essential role in collagen production. Consistent with this, human biopsy samples showed that progressive renal diseases exhibit high Meflin expression. Furthermore, Meflin overexpression in kidney fibroblasts promoted bone morphogenetic protein 7 signals and suppressed myofibroblastic differentiation, implicating the roles of Meflin in suppressing tissue fibrosis. These findings demonstrate that Meflin marks a PMC subset that is functionally distinct from classic pericytes and myofibroblasts, highlighting the importance of elucidating PMC heterogeneity.
MISC
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PLoS biology 6(12) e310-2816 2008年12月16日 査読有りSUMO-specific protease 2 (SENP2) modifies proteins by removing SUMO from its substrates. Although SUMO-specific proteases are known to reverse sumoylation in many defined systems, their importance in mammalian development and pathogenesis remains largely elusive. Here we report that SENP2 is highly expressed in trophoblast cells that are required for placentation. Targeted disruption of SENP2 in mice reveals its essential role in development of all three trophoblast layers. The mutation causes a deficiency in cell cycle progression. SENP2 has a specific role in the G-S transition, which is required for mitotic and endoreduplication cell cycles in trophoblast proliferation and differentiation, respectively. SENP2 ablation disturbs the p53-Mdm2 pathway, affecting the expansion of trophoblast progenitors and their maturation. Reintroducing SENP2 into the mutants can reduce the sumoylation of Mdm2, diminish the p53 level and promote trophoblast development. Furthermore, downregulation of p53 alleviates the SENP2-null phenotypes and stimulation of p53 causes abnormalities in trophoblast proliferation and differentiation, resembling those of the SENP2 mutants. Our data reveal a key genetic pathway, SENP2-Mdm2-p53, underlying trophoblast lineage development, suggesting its pivotal role in cell cycle progression of mitosis and endoreduplication.
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JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY 45 S26-S27 2008年10月
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Pathology international 58(5) 288-94 2008年5月 査読有りBreast cancer can be classified into several subtypes based on gene expression profiling. Basal-like breast carcinoma (BLC) has a triple negative phenotype, that is, the subtype lacks the estrogen receptor (ER), progesterone receptor (PgR) and human epidermal growth factor receptor 2 (HER2). It has been recently reported that CD109, a glycosylphosphatidylinositol (GPI)-anchored cell surface protein, is a new breast myoepithelial marker. In the present study CD109 expression was investigated in invasive ductal carcinomas (IDC) of the breast on immunohistochemistry. Eighty-eight formalin-fixed, paraffin-embedded breast carcinoma sections were immunostained with anti-CD109, anti-cytokeratin 5/6 (CK5/6), anti-calponin, anti-vimentin and anti-p63 antibodies. CD109 expression was detected in 18 of 30 basal-like breast carcinomas (BLC) but not in other types of 53 IDC (non-BLC) that were positive for ER, PgR and/or HER2. The percentage of CD109-positive tissues (60%) in BLC was similar to that of CK5/6 (63%) and higher than that of other myoepithelial markers including p63 (23%), calponin (33%) and vimentin (33%). Statistical analysis indicated that the CD109-positive group in BLC, but not the CK5/6-positive group in BLC, was associated with reduced fat invasion (P < 0.05). These findings indicate that CD109 is a useful diagnostic marker for BLC and that CD109 expression may affect biological properties of cancer cells.
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Genes to cells : devoted to molecular & cellular mechanisms 13(4) 365-74 2008年4月 査読有りWell-organized spermatogenesis, including the maintenance of spermatogonial stem cells (SSCs), is indispensable for continuous male fertility. Signaling by glial cell line-derived neurotrophic factor (GDNF) via the RET/GDNF family receptor alpha1 (GFRalpha1) receptor complex is essential for self-renewal of murine SSCs and may also regulate their differentiation. When phosphorylated, tyrosine 1062 in RET presents a binding site for the phosphotyrosine-binding domains of several adaptor and effector proteins that are important for activation of a variety of intracellular signaling pathways. In this study, we investigated the role of signaling via RET tyrosine 1062 in spermatogenesis using RET Y1062F knockin mice (Y1062F mice), in which tyrosine 1062 was replaced with phenylalanine. Homozygous Y1062F mice showed marked atrophy of testes due to reduced production of germ cells. RET-expressing spermatogonia in seminiferous tubules of homozygous Y1062F mice decreased after postnatal day (P) 7 and germ cells were almost undetectable by P21. These phenomena appeared to be due to a lack of SSC self-renewal and inability to maintain the undifferentiated state. Our findings suggest that RET signaling via tyrosine 1062 is essential for self-renewal of SSCs and regulation of their differentiation.
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Cancer research 68(5) 1310-8 2008年3月1日 査読有りGirdin (girders of actin filaments) is a novel actin-binding Akt substrate that plays an important role in actin organization and Akt-dependent cell motility in fibroblasts. Here, we find that Girdin is expressed in a variety of cancer cell lines, including the breast cancer cell line MDA-MB-231, and is phosphorylated by the stimulation of insulin-like growth factor (IGF-I). In vitro migration and invasion assays showed that Girdin is required for the IGF-I-dependent cell movement of MDA-MB-231 cells. Short hairpin interfering RNA directed against Girdin markedly inhibited the metastasis of s.c. transplanted MDA-MB-231 cells in nude mice. In addition, Girdin is highly expressed in a variety of human malignant tissues, including breast, colon, lung, and uterine cervical carcinomas. These findings highlight the important role of Girdin in tumor progression in which the Akt signaling pathway is aberrantly activated.
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Experimental cell research 313(17) 3755-66 2007年10月15日 査読有りGZF1 is a zinc finger protein induced by glial cell-line-derived neurotrophic factor (GDNF). It is a sequence-specific transcriptional repressor with a BTB/POZ (Broad complex, Tramtrack, Bric a brac/Poxvirus and zinc finger) domain and ten zinc finger motifs. In the present study, we used immunoprecipitation and mass spectrometry to identify nucleolin as a GZF1-binding protein. Deletion analysis revealed that zinc finger motifs 1-4 of GZF1 mediate its association with nucleolin. When zinc fingers 1-4 were deleted from GZF1 or nucleolin expression was knocked down by short interference RNA (siRNA), nuclear localization of GZF1 was impaired. These results suggest that nucleolin is involved in the proper subcellular distribution of GZF1. In addition, overexpression of nucleolin moderately inhibited the transcriptional repressive activity of GZF1 whereas knockdown of nucleolin expression by siRNA enhanced its activity. Thus, the repressive activity of GZF1 is modulated by the level at which nucleolin is expressed. Finally, we found that knockdown of GZF1 and nucleolin expression markedly impaired cell proliferation. These findings suggest that the physiological functions of GZF1 may be regulated by the protein's association with nucleolin.
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Cancer science 98(6) 815-21 2007年6月 査読有りThe Sprouty (SPRY) family of proteins includes important regulators of downstream signaling initiated by receptor tyrosine kinases. In the present study, we investigated the role of SPRY proteins in intracellular signaling via the RET receptor tyrosine kinase activated by glial cell line-derived neurotrophic factor (GDNF). Expression of SPRY1, SPRY2, SPRY3 and SPRY4 in HEK293T cells transfected with RET and GDNF receptor family alpha1 (GFRalpha1) genes significantly reduced sustained ERK activation as well as ELK-1 activation. Because expression of SPRY2 was efficiently induced by GDNF in TGW human neuroblastoma cells expressing RET and GFRalpha1, we further investigated the role of SPRY2 in the growth and differentiation of TGW cells. Expression of wild-type SPRY2 (WT-SPRY2) decreased the growth of TGW cells. In contrast, expression of a dominant negative form of SPRY2 (MT-SPRY2, with a mutated tyrosine residue) enhanced cell proliferation. In addition, expression of WT-SPRY2 reduced GDNF-dependent neurite outgrowth of TGW cells, whereas expression of MT-SPRY2 enhanced it. Taken together, our results suggest that SPRY2 regulates GDNF-dependent proliferation and differentiation of TGW neuroblastoma cells mediated by RET tyrosine kinase.
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Nucleic acids research 35(18) e123 2007年 査読有りWe developed a simple algorithm, i-Score (inhibitory-Score), to predict active siRNAs by applying a linear regression model to 2431 siRNAs. Our algorithm is exclusively comprised of nucleotide (nt) preferences at each position, and no other parameters are taken into account. Using a validation dataset comprised of 419 siRNAs, we found that the prediction accuracy of i-Score is as good as those of s-Biopredsi, ThermoComposition21 and DSIR, which employ a neural network model or more parameters in a linear regression model. Reynolds and Katoh also predict active siRNAs efficiently, but the numbers of siRNAs predicted to be active are less than one-eighth of that of i-Score. We additionally found that exclusion of thermostable siRNAs, whose whole stacking energy (DeltaG) is less than -34.6 kcal/mol, improves the prediction accuracy in i-Score, s-Biopredsi, ThermoComposition21 and DSIR. We also developed a universal target vector, pSELL, with which we can assay an siRNA activity of any sequence in either the sense or antisense direction. We assayed 86 siRNAs in HEK293 cells using pSELL, and validated applicability of i-Score and the whole DeltaG value in designing siRNAs.
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Development (Cambridge, England) 133(22) 4507-16 2006年11月 査読有りThe RET receptor tyrosine kinase plays a critical role in the development of the enteric nervous system (ENS) and the kidney. Upon glial-cell-line-derived neurotrophic factor (GDNF) stimulation, RET can activate a variety of intracellular signals, including the Ras/mitogen-activated protein kinase, phosphatidylinositol 3-kinase (PI3K)/AKT, and RAC1/JUN NH(2)-terminal kinase (JNK) pathways. We recently demonstrated that the RAC1/JNK pathway is regulated by serine phosphorylation at the juxtamembrane region of RET in a cAMP-dependent manner. To determine the importance of cAMP-dependent modification of the RET signal in vivo, we generated mutant mice in which serine residue 697, a putative protein kinase A (PKA) phosphorylation site, was replaced with alanine (designated S697A mice). Homozygous S697A mutant mice lacked the ENS in the distal colon, resulting from a migration defect of enteric neural crest cells (ENCCs). In vitro organ culture showed an impaired chemoattractant response of the mutant ENCCs to GDNF. JNK activation by GDNF but not ERK, AKT and SRC activation was markedly reduced in neurons derived from the mutant mice. The JNK inhibitor SP600125 and the PKA inhibitor KT5720 suppressed migration of the ENCCs in cultured guts from wild-type mice to comparable degrees. Thus, these findings indicated that cAMP-dependent modification of RET function regulates the JNK signaling responsible for proper migration of the ENCCs in the developing gut.
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Journal of cell science 119(Pt 15) 3067-77 2006年8月1日 査読有りDuring development of the central and peripheral nervous systems, neurite extension mediated via glial-cell-line-derived neurotrophic factor (GDNF) and its receptor RET is critical for neuronal differentiation. In the present study, we investigated the role of the RET substrate Dok-4 in neurite outgrowth induced by the GDNF/RET signaling pathway. In TGW neuroblastoma cells, which endogenously express both RET and Dok-4, depletion of Dok-4 through treatment with small interfering RNA resulted in a marked decrease in GDNF-stimulated neurite outgrowth. By contrast, exogenous expression of wild-type Dok-4 induced sustained p44/42 mitogen-activated protein kinase (ERK1/2) activation and enhanced neurite outgrowth. Expression of Dok-4 mutants in which the tyrosine residues at codons 187, 220 and 270, conserved between Dok-4, -5, and -6, were each replaced with a phenylalanine inhibited sustained ERK1/2 activation and neurite outgrowth. We also found that Dok-4 induced a significant activation of the small G protein Rap1 and that expression of a dominant active Rap1 mutant restored neurite outgrowth in Dok-4-depleted cells. By contrast, expression of a dominant negative Rap1 mutant impaired GDNF-stimulated neurite outgrowth from TGW cells. Finally, we found that neurite formation in cultured rat hippocampal neurons was enhanced by the expression of Dok-4. Together, our results suggest that Dok-4, through activation of the Rap1-ERK1/2 pathway, regulates GDNF-mediated neurite outgrowth during neuronal development.
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Pathology international 56(4) 164-72 2006年4月 査読有りGain-of-function mutations within the receptor tyrosine kinase gene RET cause inherited and non-inherited thyroid cancer. Somatic gene rearrangements of RET have been found in papillary thyroid carcinoma and germline point mutations in multiple endocrine neoplasia (MEN) types 2A and 2B and familial medullary thyroid carcinoma (FMTC). Conversely, loss-of-function mutations are responsible for the development of Hirschsprung's disease, a congenital malformation of the enteric nervous system. Comparison between normal RET signaling activated by the RET ligand glial cell line-derived neurotrophic factor (GDNF) and abnormal RET signaling caused by various mutations has led to a deeper understanding of disease mechanisms. The focus of the present review is on recent progress in the study of RET signaling dysfunction in human diseases.
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Pituitary 9(3) 179-92 2006年 査読有りThe RET proto-oncogene encodes a receptor tyrosine kinase that is a main component of the signaling pathway activated by the glial cell line-derived neurotrophic factor family ligands. Gene targeting studies revealed that signaling through RET plays a crucial role in neuronal and renal organogenesis. It is well-known that germline mutations in RET lead to the human inherited diseases, multiple endocrine neoplasia type 2 (MEN 2) and Hirschsprung's disease, and that somatic rearrangements of RET cause papillary thyroid carcinoma. Due to marked advances in understanding of the molecular mechanisms of the development of MEN 2, a consensus on MEN 2 management associated with RET status is being reached and currently put into general use as a guideline. In this review, we summarize progress in the study of RET from bench to bedside, focusing on pathophysiology of neuroendocrine tumors.
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Developmental cell 9(3) 389-402 2005年9月 査読有りThe serine/threonine kinase Akt (also called protein kinase B) is well known as an important regulator of cell survival and growth and has also been shown to be required for cell migration in different organisms. However, the mechanism by which Akt functions to promote cell migration is not understood. Here, we identify an Akt substrate, designated Girdin/APE (Akt-phosphorylation enhancer), which is an actin binding protein. Girdin expresses ubiquitously and plays a crucial role in the formation of stress fibers and lamellipodia. Akt phosphorylates serine at position 1416 in Girdin, and phosphorylated Girdin accumulates at the leading edge of migrating cells. Cells expressing mutant Girdin, in which serine 1416 was replaced with alanine, formed abnormal elongated shapes and exhibited limited migration and lamellipodia formation. These findings suggest that Girdin is essential for the integrity of the actin cytoskeleton and cell migration and provide a direct link between Akt and cell motility.
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Genes to cells : devoted to molecular & cellular mechanisms 10(7) 655-63 2005年7月 査読有りIt is well known that the cell cycle is controlled by several cyclin/cyclin-dependent kinase (Cdk) complexes whose expression and phosphorylation states vary with orderly periodicity. During the cell cycle, activity of the cyclin/Cdk complexes can be regulated directly or indirectly by a number of molecules, including protein kinases and phosphatases, p53, and Cdk inhibitors. Here, we show that the addition of glial cell line-derived neurotrophic factor (GDNF) induced G2/M cell cycle delay in human SK-N-MC neuroectodermal tumor cells that express RET tyrosine kinase, accompanying actin reorganization. Cell cycle delay at G2/M was characterized by accelerated and prolonged Cdc2 phosphorylation and stabilization of cyclin B1 and Wee1 kinase expression. Interestingly, we found that phosphorylation and/or expression of Cdc2, cyclinB1, and Wee1 was controlled by the Rac1/c-Jun NH2-terminal kinase (JNK) pathway. Immunohistochemical analysis suggested that the G2/M cell cycle delay may be necessary to prevent the mitotic progression of SK-N-MC cells with perturbed actin cytoskeletons.
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Cancer science 96(3) 143-8 2005年3月 査読有りThe RET proto-oncogene is responsible for the development of several human inherited and non-inherited diseases. Germline point mutations were identified in multiple endocrine neoplasia types 2A and 2B, and familial medullary thyroid carcinoma. More than 10 rearranged forms of RET, referred to as RET/PTC 1-9, ELKS/RET and RFP/RET, have been cloned from sporadic and radiation-associated papillary thyroid carcinomas. These mutations induced oncogenic activation of RET tyrosine kinase by different mechanisms. To date, various kinds of therapeutic approaches have been developed for the treatment of RET-associated cancers, including tyrosine kinase inhibitors, gene therapy with dominant negative RET mutants, and RNA interference to abrogate oncogenic mutant RET expression. RET and some signaling molecules that function downstream of RET could be potential targets for the development of selective cancer therapeutics.
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Nucleic acids research 33(13) 4191-201 2005年 査読有りThe RET tyrosine kinase receptor and its ligand, glial cell line-derived neurotrophic factor (GDNF) are critical regulators of renal and neural development. It has been demonstrated that RET activates a variety of downstream signaling cascades, including the RAS/mitogen-activated protein kinase and phosphatidylinositol-3-kinase(PI3-K)/AKT pathways. However, nuclear targets specific to RET-triggered signaling still remain elusive. We have previously identified a novel zinc finger protein, GZF1, whose expression is induced during GDNF/RET signaling and may play a role in renal branching morphogenesis. Here, we report the DNA binding property of GZF1 and its potential target gene. Using the cyclic amplification and selection of targets technique, the consensus DNA sequence to which GZF1 binds was determined. This sequence was found in the 5' regulatory region of the HOXA10 gene. Electrophoretic mobility shift assay revealed that GZF1 specifically binds to the determined consensus sequence and suppresses transcription of the luciferase gene from the HOXA10 gene regulatory element. These findings thus suggest that GZF1 may regulate the spatial and temporal expression of the HOXA10 gene which plays a role in morphogenesis.
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Oncogene 18 1975-1982-1982 1999年3月 査読有り
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BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 255(3) 587-590 1999年2月 査読有りMutations at aspartic acid 631 in Ret were reported in sporadic pheochromocytoma and medullary thyroid carcinoma. We replaced this aspartic acid with four other amino acids including tyrosine, glycine, asparagine, and alanine and investigated the transforming activity of these mutant cDNAs. Among them, RET cDNA with a mutation of aspartic acid to tyrosine (D631Y) that was reported in sporadic pheochromocytoma showed high transforming activity. The D631Y mutation activated Ret by inducing its disulfide-linked dimerization in the transfectant as observed for multiple endocrine neoplasia (MEN) 2A mutations at cysteine 609, 611, 618, 620, 630, or 634. Further mutation analysis suggested that cysteine 630 or 634 could be involved in the disulfide-linked Ret dimerization induced by the D631Y mutation. (C) 1999 Academic Press.
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Jpn J Cancer Res 90(1) 86-92-92 1999年1月
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ONCOGENE 16(3) 293-299 1998年1月 査読有りGlial cell line-derived neurotrophic factor (GDNF) and neurturin (NTN) define a new family of neurotrophic factors that play crucial roles in survival and differentiation of various neurons. Recent studies demonstrated that GDNF and NTN use a multicomponent receptor system in which glycosyl-phosphatidylinositol (GPI)-linked cell surface proteins and Ret receptor tyrosine kinase function as the ligand-binding and signalling components, respectively. In the present study, we investigated the role of Ca2+ ions for biochemical and biological activities of Ret because Ret has a unique structure of the extracellular domain with the cadherin-like motif. The results demonstrated that Ca2+ ions might be required for the complex formation of Ret and GDNF or NTN that induces Ret oligomerization and autophosphorylation. Full morphological differentiation of neuroblastoma cells by these neurotrophic factors was also Ca2+-dependent. These findings thus suggested that, in addition to GPI-linked cell surface proteins, Ca2+ ions are components of the signal transducing complex formed by Ret and GDNF protein family.
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NATURE 387(6634) 717-721 1997年6月 査読有りGlial-cell-line-derived neurotrophic factor (GDNF) and neurturin (NTN) are two structurally related, potent survival factors for sympathetic, sensory and central nervous system neurons(1-6). GDNF mediates its actions through a multicomponent receptor system composed of a ligand-binding glycosyl-phosphatidylinositol (GPI)-linked protein (designated GDNFR-alpha) and the trans-membrane protein tyrosine kinase Ret(7-12). In contrast, the mechanism by which the NTN signal is transmitted is not well understood. Here we describe the identification and tissue distribution of a GPI-linked protein (designated NTNR-alpha) that is structurally related to GDNFR-alpha. We further demonstrate that NTNR-alpha binds NTN (K-d-10 pM) but not GDNF with high affinity; that GDNFR-alpha binds to GDNF but not NTN with high affinity; and that cellular responses to NTN require the presence of NTNR-alpha. Finally, we show that NTN, in the presence of NTNR-alpha, induces tyrosine-phosphorylation of Ret, and that NTN, NTNR-alpha and Ret form a physical complex on the cell surface. These findings identify Ret and NTNR-alpha as signalling and ligand-binding components, respectively, of a receptor for NTN and define a novel family of receptors for neurotrophic and differentiation factors composed of a shared transmembrane protein tyrosine kinase and a ligand-specific GPI-linked protein.
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Biochemical and Biophysical Research Communications 237(3) 747-751 1997年
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HUMAN MOLECULAR GENETICS 5(10) 1577-1580 1996年10月 査読有りHirschsprung disease (HSCR) is a congenital disorder associated with the absence of intrinsic ganglion cells in the distal gastrointestinal tract, Recently, many missense, nonsense and frameshift mutations of the ref proto-oncogene were found in familial and sporadic cases of HSCR, Consistent with the view that the HSCR phenotype is the result of inactivation of Ret, the missense mutations detected in the tyrosine kinase domain were demonstrated to result in a marked decrease of the kinase activity of Ret, However, the effects of missense mutations found in the extracellular domain remain unknown, We now report that five mutations in the extracellular domain examined inhibit transport of the Ret protein to the plasma membrane, As a consequence, they significantly decreased the transforming activity of Ret with multiple endocrine neoplasia (MEN) 2A mutation for which cell surface expression is required, Our results also demonstrated that long segment HSCR mutations more severely impair transport of Ret to the plasma membrane than a short segment HSCR mutation, suggesting that the level of its cell surface expression may correlate to the HSCR phenotype.
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JOURNAL OF BIOLOGICAL CHEMISTRY 271(30) 17644-17649 1996年7月 査読有りGerm line mutations of the ret proto-oncogene are associated with the development of three dominantly inherited neoplastic disorders, multiple endocrine neoplasia (MEN) 2A, MEN 2B, and familial medullary thyroid carcinoma, It has been demonstrated that the mutations result in constitutive activation of the Ret protein, leading to transformation of MH 3T3 cells, In the present study we investigated the role of tyrosine residues present in the carboxyl-terminal sequence for the transforming activity of Ret with the MEN 2A or MEN 2B mutation (MENSA-Ret or MEN2B-Ret). Substitution of phenylalanine for tyrosine 1062 (designated Y1062F) markedly impaired the transforming activity of both MEN2A-Ret and MEN2B-Ret, whereas substitution or deletion for four other tyrosines (codons 981, 1015, 1090, and 1096) did not affect their activity, The She adaptor proteins bound to the MEN2A-Ret and MEN2B-Ret proteins and were phosphorylated on tyrosine in the transfectants. The binding of She to the Y1062F mutant proteins was reduced by approximately 80%, indicating that tyrosine 1062 is a major binding site for She. In addition, phosphopeptide analysis of MENSA-Ret demonstrated that tyrosine 1062 represents an autophosphorylation site of the mutant Ret proteins.
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NATURE 382(6586) 80-83 1996年7月 査読有りGLIAL-CELL-LINE-DERIVED neurotrophic factor (GDNF)(1) is a potent survival factor for central and peripheral neurons(2-6), and is essential for the development of kidneys and the enteric nervous system(7-9). Despite the potential clinical and physiological importance of GDNF, its mechanism of action is unknown. Here we show that physiological responses to GDNF require the presence of a novel glycosyl-phosphatidylinositol (GPI)-linked protein (designated GDNFR-alpha) that is expressed on GDNF-responsive cells and binds GDNF with a high affinity. We further demonstrate that GDNF promotes the formation of a physical complex between GDNFR-alpha and the orphan tyrosine kinase receptor Ret(10-12), thereby inducing its tyrosine phosphorylation. These findings support the hypothesis that GDNF uses a multi-subunit receptor system in which GDNFR-alpha and Ret function as the ligand-binding and signalling components, respectively.
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ONCOGENE 12(3) 481-487 1996年2月 査読有りThe c-ret proto-oncogene with multiple endocrine neoplasia (MEN) 2A or 2B mutation can transform NIH3T3 cells with high efficiencies as a consequence of its constitutive activation. The MEN2A mutation induces ligand-independent homodimerization of the Ret protein on the cell surface while the MEN2B mutation appears to alter the catalytic activity without dimerization. In the present study, we investigated the role of tyrosine residues present in the kinase domain for the transforming activity of the mutant Ret proteins. Substitution of phenylalanine for tyrosine 905 (Y905F) that corresponds to tyrosine 416 of the Src protein abolished the transforming activity of Ret with the MEN2A mutation (MEN2A-Ret) but not with the MEN2B mutation (MEN2B-Ret). On the other hand, the transforming activity of MEN2B-Ret but not MEN2A-Ret significantly decreased by changing tyrosine 864 or 952 to phenylalanine. In addition, double mutations of these tyrosines (Y864/952F) completely abolished the activity of MEN2B-Ret. The Y905F and Y864/952F mutations resulted in severe impairment of the kinase activity of MEN2A-Ret and MEN2B-Ret, respectively. These results thus indicated that tyrosine residues essential for the transforming activity are different between MEN2A-Ret and MEN2B-Ret.
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BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 218(2) 606-609 1996年1月 査読有りUsing transfection of NTH 3T3 cells, we have recently demonstrated that multiple endocrine neoplasia (MEN) 2A mutations activate the c-Ret protein by inducing its disulfide-linked homodimerization on the cell surface. To investigate whether the homodimers are present in original tumors, the expression of the c-Ret protein was analyzed in eight sporadic and two MEN 2A-associated pheochromocytomas, the latter two of which contained mutations in cysteine 618 or 634 of Ret. The c-Ret protein was expressed at variable levels in all pheochromocytomas examined. By labeling the c-Ret protein immunoprecipitated from tumor tissues with [gamma-P-32]ATP in vitro, its homodimers were detected in pheochromocytomas from MEN 2A patients but not in a sporadic tumor. This result represents the first demonstration of Ret homodimers in original tumors. (C) 1996 Academic Press, Inc.
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MOLECULAR AND CELLULAR BIOLOGY 15(3) 1613-1619 1995年3月 査読有りTransforming activity of the c-ret proto-oncogene,vith multiple endocrine neoplasia (MEN) 2A mutations was investigated by transfection of NIH 3T3 cells. Mutant c-ret genes driven by the simian virus 40 or cytomegalovirus promoter induced transformation with high efficiencies, The 170-kDa Ret protein present on the cell surface of transformed cells was highly phosphorylated on tyrosine and formed disulfide-linked homodimers. This result indicated that MEN 2A mutations induced ligand-independent dimerization of the c-Ret protein on the cell surface, leading to activation of its intrinsic tyrosine kinase. In addition to the MEN 2A mutations, we further introduced a mutation (lysine for asparaginic acid at codon 300 [D300K]) in a putative Ca2+-binding site of the cadherin-like domain. When c-ret cDNA with both MEN 2A and D300K mutations was transfected into NIH 3T3 cells, transforming activity drastically decreased. Western blot (immunoblot) analysis revealed that very little of the 170-kDa Ret protein with the D300K mutation was expressed in transfectants while expression of the 150-kDa Ret protein retained in the endoplasmic reticulum was not affected. This result also demonstrated that transport of the Ret protein to the plasma membrane is required for its transforming activity.
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Oncogene 10(1) 191-198-198 1995年1月 査読有り
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ONCOGENE 8(11) 2925-2929 1993年11月 査読有りThe ret proto-oncogene (proto-ret) encodes a receptor type tyrosine kinase with a cadherin-related sequence in the extracellular domain. To investigate whether the proto-Ret protein functions as a cell adhesion molecule like cadherins, we transfected the human proto-ret gene fused to the SV40 promoter or cytomegalovirus (CMV) promoter into mouse L cells in which cadherins are not expressed. Three transfectants with high levels of expression of the proto-Ret proteins were obtained. The proto-Ret proteins were expressed as 150 kDa and 170 kDa glycoproteins in transfectants as observed in human neuroblastoma cells. Cell fractionation experiments revealed that the 170 kDa protein but not the 150 kDa protein was detected predominantly in the plasma membrane fraction, indicating that the 170 kDa protein represents the mature glycosylated form of the proto-Ret protein present on the cell surface. Both 150 kDa and 170 kDa proto-Ret proteins showed tyrosine kinase activity in immunocomplex kinase assay. It is known that cadherins have Ca2+-dependent homophilic binding activity and are resistant to trypsinization in the presence of Ca2+. When L cells expressing the proto-Ret proteins were treated with trypsin in the presence of Ca2+, the 170 kDa protein was resistant to its digestion. On the other hand, it was completely digested in the presence of EGTA, suggesting the possibility that the proto-Ret protein interacts with Ca2+ like cadherins. However, the transfectants did not show clear adhesive properties in cell aggregation assays.
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