Open AccessAdapter Protein RapGEF1 Is Required for ERK1/2 Signaling in Response to Elevated Phosphate in Vascular Smooth Muscle Cells
Author(s) -
Nicholas W. Chavkin,
Elizabeth M. Leaf,
Kadin E Brooks,
Mary C. Wallingford,
Susan M Lund,
Cecilia M. Giachelli
Publication year - 2021
Publication title -
journal of vascular research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.58
H-Index - 74
eISSN - 1423-0135
pISSN - 1018-1172
DOI - 10.1159/000516044
Subject(s) - phosphorylation , vascular smooth muscle , gene knockdown , guanine nucleotide exchange factor , signal transduction , microbiology and biotechnology , rap1 , cell signaling , biology , chemistry , biochemistry , endocrinology , apoptosis , smooth muscle
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. In this study, we tested the hypothesis that RapGEF1 is a critical component of the SLC20A1-mediated Pi-induced ERK1/2 phosphorylation pathway. Co-localization of SLC20A1 and RapGEF1, knockdown of RapGEF1 with siRNA, and small molecule inhibitors of Rap1, B-Raf, and Mek1/2 were investigated. SLC20A1 and RapGEF1 were co-localized in peri-membranous structures in VSMCs. Knockdown of RapGEF1 and small molecule inhibitors against Rap1, B-Raf, and Mek1/2 eliminated elevated Pi-induced ERK1/2 phosphorylation. Knockdown of RapGEF1 inhibited SM22α mRNA expression and blocked elevated Pi-induced downregulation of SM22α mRNA. Together, these data suggest that RapGEF1 is required for SLC20A1-mediated elevated Pi signaling through a Rap1/B-Raf/Mek1/2 cell signaling pathway, thereby promoting ERK1/2 phosphorylation and inhibiting SM22α gene expression in VSMCs.