Alpha-dystroglycan receptor signaling likely influences basement membrane laminin α2 mediated pathology in the stria vascularis of Alport mice.

We previously demonstrated that endothelin A receptor (ET(A)R) signaling plays a major role in regulating strial pathology in the COL4A3 knockout mouse model for Alport syndrome. Blocking the receptor prevented accumulation of extracellular matrix (ECM) in the strial capillary basement membranes (SCBMs) including laminin α2. Herein, we explored whether α-dystroglycan receptors for laminin α2 are present on cultured strial pericytes, marginal cells, and intermediate cells, as well as in intact stria vascularis. We performed comparative analysis of gene expression in isolated glomeruli and stria vascularis from wild type and Alport mice using RNA-seq. We examined the effects of endothelin treatment of pericytes on cytoskeletal dynamics and CDC42 activation using immunofluorescence, and on cell signaling using phosphoantibody microarrays. mRNA encoding α-dystroglycan receptors are present in strial cell lines as well as RNA from micro dissected stria vascularis. These same receptors were found adjacent to the capillary basement membranes on strial endothelial cells, marginal cells, intermediate cells, and pericytes in vivo by immunofluorescence. RNA-seq analysis of RNA from wild type and Alport glomeruli and stria vascularis revealed similar regulation of genes implicated in the pathogenesis of both organs. Treatment of pericytes with endothelin-1 (ET-1) resulted in changes in cell signaling consistent with observed reduction of filamentous to globular actin ratios and cell adhesion. Therefore, the induction of laminin α2 likely contributes to strial pathology in Alport syndrome via signaling through α-dystroglycan receptors. ET-1 activation of ET(A)Rs directly contributes to altered cell signaling in strial pericytes, resulting in changes in actin cytoskeletal dynamics.