Butsch, T. | Search bioRxiv

bioRxiv2026

Phosphoglycerate mutase 5 regulates lipid metabolism and mitochondrial homeostasis in hepatocellular cancer cells

The mitochondrial membrane protein phosphoglycerate mutase 5 (PGAM5) is a protein of interest in the complex transition from hepatic steatosis to hepatocellular carcinoma. PGAM5 is a serine/threonine/histidine phosphatase that plays a role in mitochondrial biogenesis, mitophagy, and multiple cell death pathways. Increased expression of PGAM5 in hepatocellular carcinoma is correlated with reduced patient survival. In this study, we demonstrate that loss of PGAM5 alters the bioenergetic landscape of liver cancer by promoting mitochondrial oxidant injury and suppressing the glycerophospholipid and lysophospholipid pathways, leading to accumulation of the bioactive phospholipid lysophosphatidylcholine. Additionally, PGAM5 deletion downregulates fatty acid biosynthesis, resulting in reduced cellular diacylglycerol concentrations through two probable mechanisms: attenuated long chain fatty acid uptake and suppressed de novo synthesis. These findings underscore the broad impact of a single phosphatase on mitochondrial function and provide a rationale for therapeutically targeting PGAM5 to disrupt lipid metabolism in hepatocellular carcinoma.

cancer biology↗

bioRxiv2022

VCP acts downstream of tTAFs to downregulate mono-ubiquitinated H2A and promote spermatocyte differentiation in Drosophila

Valosin-containing protein (VCP) binds and extracts ubiquitinated cargo to regulate protein homeostasis. While VCP has been studied primarily in aging and disease contexts, it also affects germline development. However, the precise molecular functions of VCP in the germline, particularly in males, are poorly understood. Using the Drosophila male germline as a model system, we find that VCP translocates from the cytosol to the nucleus as germ cells transition into the meiotic spermatocyte stage. Importantly, nuclear translocation of VCP appears to be one critical event stimulated by testis-specific TBP-associated factors (tTAFs) to drive spermatocyte differentiation. Like tTAF mutants, spermatocyte gene expression fails to properly activate in VCP-RNAi testes, and germ cells arrest in early meiosis. At a molecular level, VCP activity supports spermatocyte gene expression by downregulating a repressive histone modification, mono-ubiquitinated H2A (H2Aub), at this developmental transition. Remarkably, experimentally blocking H2Aub in VCP-RNAi testes is sufficient to overcome the meiotic-arrest phenotype and to promote development through meiosis. Collectively, our data highlight VCP as a novel downstream effector of tTAFs that downregulates H2Aub to facilitate meiotic progression. SUMMARY STATEMENTVCP promotes the downregulation of mono-ubiquitinated H2A (H2Aub), potentially by driving H2A turnover. VCP-dependent downregulation of H2Aub occurs downstream of testis-specific TBP-associated factors and supports spermatocyte gene expression and differentiation.

developmental biology↗