Abstract
Diabetic nephropathy (DN) is characterized by glomerular basement membrane (GBM) thickening, primarily due to the abnormal accumulation of collagen type IV (COL4) in the extracellular matrix (ECM) of podocytes. Podocytes endocytosis is crucial for maintaining COL4 balance and GBM integrity. Previous studies have shown that G protein-coupled receptor 107 (GPR107) facilitates clathrin-dependent transferrin internalization and recycling in murine embryonic fibroblast cells. Therefore, the aim of the study is to investigate the role of GPR107 in regulating COL4 balance within the podocytes ECM and its potential as a therapeutic target for DN. Here, we found a significant decrease in GPR107 expression in renal tissues from DN patients and streptozocin (STZ)-induced DN mice. Furthermore, GPR107-deficient mice with STZ-induced DN exhibited more severe kidney damage, marked by increased GBM thickening and COL4 accumulation. In vitro, GPR107 deficiency under high-glucose conditions promoted COL4 accumulation in the ECM of podocytes due to increased COL4 production and decreased COL4 degradation. Mechanistically, we demonstrated that GPR107 contributes to angiotensin II receptor type 1 (AT1R) internalization through clathrin-mediated endocytosis (CME) in podocytes. Therefore, GPR107 deficiency impairs AT1R internalization, leading to increased membrane-bound AT1R. This, in turn, activates the AT1R/Ca(2+) signaling pathway to promote phosphorylation of cAMP-response element-binding protein (CREB), ultimately enhancing COL4 synthesis and inhibiting the expression of matrix metalloproteinase 2 (MMP-2). These findings shed light on new functions of GPR107 in DN and offer new insights into a therapeutic target for DN.