Regulation of Neogenin in Glomerular Mesangial Cells

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Background Diabetic Nephropathy (DN) is the leading cause of chronic kidney disease. Renal inflammation is known to contribute to the onset and progression of DN. Glomerular mesangial cells (MCs) are the major cell type involved in the pathogenesis of DN. Store operated calcium entry (SOCE) regulates many MC functions. Neogenin is the multifunctional transmembrane receptor that plays an important role in some organ development and homeostasis. Studies also demonstrated that neogenin was associated with inflammatory responses. However, whether neogenin is involved in DN and how it is regulated in MCs is currently not known. The aim of the present study was to determine if and how neogenin protein abundance in MCs was altered by diabetes/high glucose. Methods Human MCs were cultured in normal glucose (NG, 5mM) with/without an activator (thapsigargin-1 μM) or inhibitor (BTP2-5 µM) of SOCE for different time periods. Tunicamycin (10 ug/ml) was used to induce ER stress. High glucose (HG, 25 mM) treatment was used to mimic diabetic environment in vitro. The protein abundance of neogenin was assessed by western blot of the whole cell lysates. Glomerular neogenin expression in the control and eNOS-/- db/db mice at 20 weeks of age was evaluated using immunofluorescence staining in the paraffin embedded kidney sections. Results Thapsigargin significantly reduced the protein abundance of neogenin beginning at 4 h of treatment, which was partially reversed by BTP2. Tunicamycin for 4 h decreased the protein content of neogenin as well. HG treatment for one and two days increased neogenin level. Furthermore, the glomerular neogenin expression in eNOS-/- db/db mice was decreased at 20 weeks of age, possibly indicating the effect of late stage of the disease. Conclusion Neogenin protein content in MCs was reduced by SOCE and ER stress, and neogenin might play a role in the pathogenesis of DN.