Neuronal growth regulator 1 modulates actin dynamics to control intracellular GLUT4 trafficking.

NEGR1 (neuronal growth regulator 1) has been genetically linked to metabolic and neuropsychiatric disorders; however, its cellular function in insulin-responsive tissues remains poorly understood. Here, we investigated the role of NEGR1 in regulating actin cytoskeletal dynamics and insulin-stimulated GLUT4 trafficking in skeletal muscle. We found that loss of Negr1 reduced GLUT4 abundance selectively in predominantly glycolytic skeletal muscles in vivo. Despite preserved insulin-induced Akt phosphorylation, insulin-stimulated GLUT4 translocation was markedly impaired in both Negr1-deficient and NEGR1-overexpressing muscle cells. Mechanistically, Negr1 deficiency was associated with enhanced PAK-cofilin signaling and excessive intracellular F-actin accumulation that likely impedes GLUT4 vesicle trafficking. In contrast, NEGR1 overexpression did not increase total F-actin content but induced abnormal peripheral actin organization, resulting in constitutive GLUT4 surface localization and elevated basal glucose uptake. Consistent with these findings, both loss and overexpression of NEGR1 disrupted insulin-induced Rac1-dependent actin remodeling without affecting Akt signaling. Collectively, these results identify NEGR1 as a critical modulator of actin homeostasis required for proper insulin-stimulated GLUT4 trafficking and glucose uptake in skeletal muscle, providing mechanistic insight into the metabolic abnormalities associated with NEGR1 dysregulation.NEW & NOTEWORTHY Neuronal growth regulator 1 (NEGR1) regulates actin cytoskeletal homeostasis required for insulin-stimulated GLUT4 trafficking in skeletal muscle. NEGR1 dysregulation alters PAK-cofilin signaling, induces aberrant F-actin organization, and impairs GLUT4 vesicle movement independent of Akt signaling. Because NEGR1 is a major genetic risk factor for major depressive disorder, these findings reveal a shared actin-based mechanism linking metabolic dysfunction and neuropsychiatric disease.