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Nair, V. M.

Publications and source records attributed to Nair, V. M..

2 recordsLinked to original sources

PTPRF is a stress responsive cytoskeletal checkpoint that coordinates metabolic adaptation in hepatocytes and β cells

Cytoskeletal remodeling is essential for adaptation to nutrient availability, yet how cells coordinate actin dynamics with glucose homeostasis in metabolic organs remains unclear. Here, we identify a pathway linking metabolic stress to actin reorganization in hepatocytes and pancreatic {beta} cells. This mechanism involves transcriptional repression of the receptor protein tyrosine phosphatase PTPRF by spliced XBP1, a key unfolded protein response factor. In hepatocytes, PTPRF loss under dietary stress enhances insulin signaling, increases mitochondrial respiration and reduces steatosis. Proteomic analyses show that PTPRF interacts with regulators of actin polymerization and cell junctions, and its deletion promotes actin filament organization, shifting metabolism toward oxidative pathways. In {beta} cells, PTPRF deficiency similarly enhances actin polymerization and augments glucose-stimulated insulin secretion in obesity. Collectively, these findings place PTPRF as a nutrient-responsive regulator of cytoskeletal remodeling that coordinates hepatic metabolism and {beta}-cell function, highlighting its potential as a therapeutic target for improving systemic glucose control.

physiology↗

Fluorescence recovery in the Super-Resolution regime reveals subcompartments of 53BP1 foci

We combine Lattice Structured Illumination Microscopy (diSIM with [~]60 nm resolution), Lattice Light-sheet microscopy and Fluorescence Recovery After Photobleaching (FRAP) to explore 53BP1 dynamics in Retinal Pigment Epithelial cells. 53BP1 forms liquid condensates during double-strand DNA repair, long-range DNA end-joining and heterochromatin maintenance. Our super-resolution movies reveal differences in 53BP1 foci contour: some foci are compact and stationary while others appear amorphous, dynamically changing shapes. To explore them, we developed FRAP in the Super-Resolution regime (FRAP-SR). 53BP1 foci with an amorphous loose contour display subcompartments that recover 53BP1-eGFP signals rapidly, indicating differential protein mobilities and 53BP1 functions within a single foci. In contrast, 53BP1-eGFP foci with a compact contour recover uniformly as single foci but show higher heterogeneity in 53BP1-eGFP recovery rates compared to foci that recover as multiple subcompartments. In cells released from aphidicolin, amorphous foci show faster 53BP1 recovery compared to compact foci. We discuss the conceptual implications of different 53BP1 mobilities, and how the FRAP-SR method transforms studies of dynamic 60-100 nm structures.

cell biology↗