Neogenin pathway positively regulates fibronectin production by glomerular mesangial cells

Neogenin, a transmembrane receptor, was recently found in kidney cells and immune cells. However, the function of neogenin signaling in kidney is not clear. Mesangial cells (MCs) are a major source of extracellular matrix (ECM) proteins in glomerulus. In many kidney diseases, MCs are impaired and manifest myofibroblast phenotype. Overproduction of ECM by the injured MCs pro-motes renal injury and accelerates the progression of kidney diseases. The present study aimed to determine if neogenin recep-tor was expressed in MCs and if the receptor signaling regulated ECM protein production by MCs. We showed that neogenin was expressed in the glomerular MCs. Deletion of neogenin using CRISPR/Cas9 lentivirus system significantly reduced the abun-dance of fibronectin, an ECM protein. Netrin-1, a ligand for neogenin, also significantly decreased fibronectin production by MCs and decreased neogenin protein expression in MCs. Furthermore, treatment of human MCs with high glucose (HG, 25 mM) sig-nificantly increased the protein abundance of neogenin as early as 8 h. Consistently, neogenin expression in glomerulus signifi- cantly increased in the eNOS(-/-) db/db diabetic mice starting as early as the age of 8 wk and this increase sustained at least to the age of 24 wk. We further found that the HG-induced increase in neogenin abundance was blunted by antioxidant PEG-cata-lase and N-acetyl cysteine. Taken together, our results suggest a new mechanism of regulation of fibronectin production by MCs. This previously unrecognized neogenin-fibronectin pathway may contribute to glomerular injury responses during the course of diabetic nephropathy.