Emerging Role of SH3BP2 as Regulator of Immune and Nonimmune Cells in Nephrotic Syndrome

Minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) are major forms of nephrotic syndrome that remain difficult to treat. MCD and FSGS have distinct but also overlapping clinical, histological, metabolic, and molecular features. Effective use of immunosuppressive drugs, activated immune cells, altered cytokine profiles, and upregulated signaling pathways suggest a link between immune dysfunction and nephrotic syndrome, but the exact mechanism of immunopathogenesis is unclear. Immune dysfunction is an area of ongoing research for identifying novel molecular targets for treating nephrotic syndrome. However, the available animal models do not directly address the role of immune dysfunction in nephrotic syndrome.

Genetic analysis indicates that heterogeneous genes related to the podocyte-specific proteins may indirectly cause damage to filtration barrier and influence the onset and progression of nephrotic syndrome. SH3BP2 protein regulates several pathways through its role as a scaffold for many signaling mediators and enzymes. SH3BP2 is expressed in immune as well as in nonimmune cells including podocytes. The role of SH3BP2 is discussed in the context of cells and molecules of adaptive and innate immune systems. Available information on the importance of SH3BP2 in diseases other than nephrotic syndrome and its role in the immunopathogenesis of human nephrotic syndrome are summarized. We outline the key features of a transgenic mouse strain with a gain-in-function mutation (Sh3bp2 ^KI/KI ) as a potential model to study immunopathogenesis of nephrotic syndrome.

Non-receptor, non-catalytic proteins such as SH3BP2 are a novel group of proteins that regulate the innate and adaptive immune responses in nephrotic syndrome. New evidence suggests a critical role of SH3BP2 in immunopathogenesis of nephrotic syndrome. Our recent results demonstrate that transgenic mice (Sh3bp2 ^KI/KI ) with a gain-in-function mutation will likely be a unique model to study immunopathogenesis of nephrotic syndrome.