Adapter Protein RapGEF1 Is Required for ERK1/2 Signaling in Response to Elevated Phosphate in Vascular Smooth Muscle Cells.

The sodium-dependent phosphate transporter, SLC20A1, is required for elevated inorganic phosphate (Pi) induced vascular smooth muscle cell (VSMC) matrix mineralization and phenotype transdifferentiation. Recently, elevated Pi was shown to induce ERK1/2 phosphorylation through SLC20A1 by Pi uptake-independent functions in VSMCs, suggesting a cell signaling response to elevated Pi. Previous studies identified Rap1 guanine nucleotide exchange factor (RapGEF1) as an SLC20A1-interacting protein and RapGEF1 promotes ERK1/2 phosphorylation through Rap1 activation.