Keisuke Hitachi

Mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) is an intractable form of epilepsy involving the hippocampus, and temporal lobectomy remains an effective treatment. Human herpesvirus 6B (HHV-6B) establishes latency in the hippocampus and may contribute to MTLE-HS pathogenesis by altering host gene expression; however, transcriptomic data from healthy controls remain limited. This study investigated the role of HHV-6B to MTLE-HS pathogenesis by analyzing gene expression in resected hippocampal tissues. Samples were collected from 12 to 43 HHV-6 DNA-positive and -negative patients, respectively, and three controls. RNA sequencing was performed on eight representative samples, followed by RT-qPCR validation of nine selected genes in 58 samples. RNA sequencing identified 600 differentially expressed genes (210 upregulated, 390 downregulated) between HHV-6B-positive MTLE-HS and controls. Pathway enrichment analysis revealed involvement of synaptic signaling and inflammatory responses, with prostaglandin biosynthesis specifically upregulated in HHV-6B-positive tissues. Two genes were significantly upregulated in HHV-6B-positive compared with HHV-6B-negative samples. RT-qPCR confirmed elevated cholesterol 25-hydroxylase and interleukin 1 beta expression in HHV-6 DNA-positive samples (both p = 0.031). These findings suggest that HHV-6B may contribute to MTLE-HS pathogenesis by modulating the expression of host inflammatory genes, supporting a role for neuroinflammation and the potential benefits of anti-inflammatory therapies.

Transforming growth factorβ (TGFβ) signaling regulates diverse aspects of vertebrate skeletal muscle tissue including differentiation, homeostasis, regeneration and pathogenic degeneration. Ubiquitination of SMAD2, an intracellular transducer of TGFβ signaling, is a well-studied negative feedback regulation of the signaling pathway in the field of cell biology, but it's relevance in skeletal muscle tissue has been elusive. In this study, to elucidate the in vivo role of SMAD2 ubiquitination, we generated Smad2dPY mutant mice in which a 15 bp sequence encoding the PY motif of SMAD2 protein is deleted from Smad2 gene. By removing this motif, the SMAD2 protein escapes from protein-protein interaction with NEDD4 family E3 ligases and thus is devoid of ubiquitination-dependent negative regulation. Smad2dPY mice showed no obvious abnormality in development, growth or fertility, indicating that SMAD2 ubiquitination through PY motif is dispensable for these processes. The skeletal muscle of Smad2dPY mice demonstrated reduced weight and myofiber size reduction at 12 months old. SMAD2 protein level was increased in the skeletal muscle of Smad2dPY mice while SMAD2 ubiquitination was reduced. Primary myoblasts of Smad2dPY mice displayed higher TGFβ responsiveness and suppressed terminal differentiation, which may explain the reduced muscle mass. The TGFβ responsiveness of the interstitial fibroblast population was also increased. Fibrotic tissue remodeling triggered by cardiotoxin injection was exacerbated in Smad2dPY mice. Altogether, our study identified SMAD2 ubiquitination through PY motif as an important regulatory mechanism operating in skeletal muscle tissue to maintain the TGFβ signaling pathway at the desired level in homeostasis and tissue remodeling.

Skeletal muscle regeneration depends on muscle stem cells (MuSCs), in which cadherin-mediated adhesion and planar cell polarity (PCP) signaling play critical roles. M-Cadherin is the major cadherin expressed in MuSCs; however, its functional link to PCP proteins remains unclear. In this study, we demonstrate that the PCP core component Vangl2 co-localizes with M-cadherin at the MuSC-myofiber boundary and directly interacts with it in C2C12 cells. Mutagenesis analyses revealed that the catenin-binding domain of M-cadherin and the C-terminal domain of Vangl2 are required for this interaction, which uniquely enables M-cadherin to form a ternary complex with Vangl2 and β-catenin. Knockdown of Vangl2 impaired myoblast fusion, reduced the expression of MyoD and Myomixer, and decreased the cell surface stability of M- and N-cadherins, while canonical Wnt/β-catenin and Akt signaling were unaffected. These findings demonstrate that Vangl2 stabilizes cadherins at the plasma membrane and promotes myogenic differentiation, suggesting a previously unrecognized role of PCP signaling in skeletal muscle maintenance and regeneration.

Small extracellular vesicles (sEVs) mediate cell-to-cell communication by carrying RNAs and proteins. Ubiquitin-like 3 (UBL3) functions as a posttranslational modification factor, regulating protein sorting to sEVs. Programmed cell death ligand 1 (PD-L1) binds to programmed cell death 1 (PD-1) on immune cells, suppressing their function. Although immune checkpoint inhibitors, anti-PD-L1 and anti-PD-1 antibodies, have improved cancer treatment, efficacy remains limited (~ 25%). Per recent studies, PD-L1-containing sEVs are elevated in cancer patients, contributing to impaired immunotherapy responses. Herein, we discovered that PD-L1 is modified by UBL3 and that its sorting to sEVs is regulated by UBL3. Furthermore, we found that statins, commonly prescribed for hypercholesterolemia, inhibit UBL3 modification, thereby reducing PD-L1 sorting to sEVs. Among patients with a high tumor proportion score, serum levels of PD-L1-containing sEVs were significantly lower in those using statins. Consistently, bioinformatic analysis revealed that UBL3 and PD-L1 expression levels affect lung cancer survival. Integrating statins into existing combination therapies may therefore offer a promising strategy to enhance immunotherapy efficacy.

Lower grade gliomas frequently harbor mutations in isocitrate dehydrogenase (IDH), which define biologically distinct tumor subtypes. Although IDH-mutant and IDH-wildtype gliomas share similar histological morphology, they display markedly different metabolic profiles that may be exploited for targeted therapy. In this study, we investigated therapeutic approaches tailored to these metabolic differences. Using capillary electrophoresis-mass spectrometry, we compared the metabolomes of engineered IDH-wildtype and IDH-mutant glioma cell models. IDH-mutant cells exhibited elevated asparagine levels and reduced glutamine and glutamate levels compared with IDH-wildtype cells. These differences were corroborated in vivo by proton magnetic resonance spectroscopy of 130 patients with diffuse gliomas, showing lower glutamine and glutamate in IDH-mutant tumors. Pharmacological depletion of asparagine with L-asparaginase, which converts asparagine to aspartate, preferentially inhibited the growth of IDH-wildtype glioma cells, and this effect was potentiated by inhibition of asparagine synthetase. In contrast, inhibition of glutamate dehydrogenase 1 (GLUD1), the enzyme catalyzing the conversion of glutamate to α-ketoglutarate, selectively suppressed proliferation of IDH-mutant glioma cells by inducing reactive oxygen species accumulation and apoptosis. In vivo, L-asparaginase suppressed tumor growth in xenografted IDH-wildtype gliomas, whereas GLUD1 inhibition significantly reduced tumor growth in IDH-mutant glioma xenografts. These findings reveal distinct amino acid metabolic vulnerabilities defined by IDH mutation status and identify L-asparaginase and GLUD1 inhibition (via R162) as promising, mutation-specific therapeutic strategies. L-asparaginase demonstrated potent antitumor activity against IDH-wildtype gliomas, while GLUD1 inhibition selectively suppressed IDH-mutant gliomas both in vitro and in vivo. These results highlight the clinical potential of targeting amino acid metabolism in gliomas and provide a strong rationale for translating these mutation-specific approaches into future clinical trials.