Project description:The highly conserved chaperonin GroESL performs a crucial role in protein folding, however the essential cellular pathways that rely on this chaperone are underexplored. Loss of GroESL leads to severe septation defects in diverse bacteria, suggesting the folding function of GroESL may be integrated with the bacterial cell cycle at the point of cell division. Here, we describe new connections between GroESL and the bacterial cell cycle using the model organism Caulobacter crescentus. Using a proteomics approach, we identify candidate GroESL client proteins that become insoluble or are degraded specifically when GroESL folding is insufficient, revealing several essential proteins that participate in cell division and peptidoglycan biosynthesis. We demonstrate that other cell cycle events such as DNA replication and chromosome segregation are able to continue when GroESL folding is insufficient. We further find that deficiency of two FtsZ-interacting proteins, the bacterial actin homologue FtsA and the constriction regulator FzlA, mediate the GroESL-dependent block in cell division. Our data show that sufficient GroESL is required to maintain normal dynamics of the FtsZ scaffold and divisome functionality in C. crescentus. In addition to supporting divisome function, we show that GroESL is required to maintain the flow of peptidoglycan precursors into the growing cell wall. Linking a chaperone to cell division may be a conserved way to coordinate environmental and internal cues that signal when it is safe to divide.
Project description:In Drosophila melanogaster larvae the ring gland is a control center that orchestrates major developmental transitions. It is a composite organ, consisting of the prothoracic gland, the corpus allatum and the corpora cardiaca, each of which synthesizes and secretes a different hormone. Until now, the ring gland’s broader developmental roles beyond endocrine secretion have not been explored. RNA sequencing and analysis of a new transcriptome resource from D. melanogaster wandering third instar larval ring glands has provided a fascinating insight into the diversity of developmental signalling in this organ. We have found strong enrichment of expression of two gene pathways not previously associated with the ring gland: immune response and fatty acid metabolism. We have also uncovered strong expression for many uncharacterized genes. Additionally, RNA interference against ring gland-enriched cytochrome p450s Cyp6u1 and Cyp6g2 produced a lethal ecdysone deficiency and a juvenile hormone deficiency respectively, flagging a critical role for these genes in hormone synthesis. This transcriptome provides a valuable new resource for investigation of roles played by the ring gland in governing insect development.
Project description:Clear cell renal cell carcinoma (ccRCC) is the most common variant of kidney cancer in the adult population. Late diagnosis, resistance to therapeutics and recurrence of metastatic lesions account for the highest mortality rate among kidney cancer patients. Identifying novel biomarkers for early cancer detection and the mechanisms underlying ccRCC growth and progression will provide clues to treat this aggressive malignant tumor. Here, we report that the RING ligase praja2 is a novel component of the endocytic system that supports clathrin-mediated receptor endocytosis. At molecular level, we identify the adaptor protein AP2 as a binding partner and substrate of praja2. Functionally, we demonstrate that praja2 is required for AP2-mediated receptor endocytosis and clearance. Downregulation of praja2 in RCC cells and tissues is associated with a marked upregulation of membrane receptors, as EGFR, VEGFR and TfR. A negative feedback loop links EGF signaling to proteolysis of praja2 and sustains downstream mitogenic and proliferative pathways. Restoring praja2 expression in RCC cells remarkably decreases EGFR levels, rewires cancer cell metabolism and inhibits RCC growth and metastatic diffusion. In praja2 knockout mice, upregulation of RTKs levels associates with profound histopathological renal alterations. Our findings identify praja2 as a component of the endocytic pathway that supports receptor endocytosis and clearance. Downregulation of praja2 in RCC cells, thus, sustains RTK signaling and promotes kidney cancer growth and diffusion.