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Biology subjects

Sumara, G.

Publications and source records attributed to Sumara, G..

3 recordsLinked to original sources

Resolution of collided ribosomes by ZNF598 is required for adipocyte energy dissipation

Cellular adaptation to stress evoked by high energy demand requires tight coordination between transcriptional programs, protein synthesis, and organelle function. In many physiological contexts, metabolic remodeling depends on increased mitochondrial capacity and activity, placing high demands on the translational machinery. Beige and brown adipocytes, which undergo rapid mitochondrial expansion and activation in response to physiological cues, provide a powerful model to study how cells adapt their translational output to meet increased metabolic demand. How translational fidelity is maintained, and stress-associated conflicts in protein synthesis are resolved during such adaptive processes, remains incompletely understood. Here, we identify ZNF598 as a key factor that resolves translation stress caused by ribosome collisions during metabolic adaptation of adipocytes. We show that diverse physiological stimuli, including hormonal signaling, environmental challenges, and dietary changes, induce ZNF598 and associated enzymes in metabolically active cells. ZNF598 is required for efficient mitochondrial biogenesis and function, supporting adaptive increases in respiration and energy expenditure. Loss of ZNF598 compromises these adaptive responses and leads to metabolic dysfunction, whereas enhancement of ZNF598 activity improves cellular and organismal metabolic flexibility. Together, these findings indicate that distal steps of the translational machinery are a rate-limiting factor for adaptation to increased energy demand.

cell biology↗

Dense but not alpha granules of platelets are required for insulin secretion from pancreatic beta cells

ObjectivesPlatelets, originally described for their role in blood coagulation, are now also recognized as key players in modulating inflammation, tissue regeneration, angiogenesis, and carcinogenesis. Recent evidence suggests that platelets also influence insulin secretion from pancreatic {beta} cells. The multifaceted functions of platelets are mediated by the factors stored in their alpha granules (AGs) and dense granules (DGs). AGs primarily contain proteins, while DGs are rich in small molecules, and both types of granules are released during blood coagulation. Specific components stored in AGs and DGs are implicated in various inflammatory, regenerative, and tumorigenic processes. However, the relative contributions of AGs and DGs to the regulation of pancreatic {beta} cell function have not been previously explored. MethodsIn this study, we utilized mouse models deficient in AG content (neurobeachin-like 2 (Nbeal2) -deficient mice) and models with defective DG release (Unc13d-deficiency in bone marrow-derived cells) to investigate the impact of platelet granules on insulin secretion from pancreatic {beta} cells. ResultsOur findings indicate that AG deficiency has little to no effect on pancreatic {beta} cell function and glucose homeostasis. Conversely, mice with defective DG release exhibited glucose intolerance and reduced insulin secretion. Furthermore, Unc13d-deficiency in hematopoietic stem cells led to a reduction in adipose tissue gain in obese mice. ConclusionsObtained data suggest that DGs, but not AGs, mediate the influence of platelets on pancreatic {beta} cells, thereby modulating glucose metabolism.

physiology↗

A phosphoproteomic approach reveals that PKD3 controls phenylalanine and tyrosine metabolism

Members of the Protein Kinase D (PKD) family (PKD1, 2, and 3) integrate hormonal and nutritional inputs to regulate complex cellular metabolism. Despite the fact that a number of functions have been annotated to particular PKDs, their molecular targets are relatively poorly explored. PKD3 promotes insulin sensitivity and suppresses lipogenesis in the liver. However, its substrates are largely unknown. Here we applied proteomic approaches to determine PKD3 targets. We identified over three-hundred putative targets of PKD3. Among them phenylalanine hydroxylase (PAH). PAH catalyses the conversion of phenylalanine to tyrosine and its activity is regulated by, phenylalanine concentration and glucagon-induced signaling. Consistently, we showed that PKD3 is activated by glucagon and promotes tyrosine levels in primary hepatocytes and liver of mice. Taken together, our comprehensive proteomic approach established that PKD3 determine the rate of phenylalanine to tyrosine conversion in the liver. Therefore, our data indicate that PKD3 might play a role in development of diseases related to the defective tyrosine and phenylalanine metabolism.

biochemistry↗