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Recruitment of RGS5 Protein to Mechanically Activated AT 1 R in Arteriolar VSMC
Author(s) -
Hong Kwangseok,
Li Min,
Meininger Gerald,
Hill Michael
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.636.5
Subject(s) - chemistry , arteriole , angiotensin ii , receptor , vascular smooth muscle , g protein , diacylglycerol kinase , protein kinase c , microbiology and biotechnology , vasoconstriction , candesartan , g protein coupled receptor , medicine , signal transduction , endocrinology , biology , biochemistry , circulatory system , smooth muscle
Ligand‐independent activation of G protein‐coupled receptors (GPCR) contributes to pressure‐induced vasoconstriction. Thus, stretch/mechanical activation of angiotensin II (Ang II) type 1 receptors (AT 1 R) likely mobilizes second messengers (e.g. Ca 2+ and diacylglycerol) leading to constriction through ion channel activation and/or PKC‐dependent Ca 2+ sensitization or actin polymerization. As enhanced pressure‐induced constriction may contribute to vascular disorders, mechanoactivation of AT 1 R is likely regulated by negative feedback mechanisms. This study explored whether regulators of G‐protein signaling (RGS) proteins, key molecules for the negative regulation of GPCR signaling, are co‐localized with mechanically activated AT 1 R in vascular smooth muscle cells (VSMC). An in situ proximity ligation assay (PLA) was performed with or without candesartan, an AT 1 R blocker, in cremaster arteriolar VSMC. VSMC were treated with Ang II or hypotonic solution to determine if ligand dependent‐ or independent‐activation of AT 1 R leads to translocation of RGS proteins. qPCR data indicated that RGS5 protein was abundantly expressed in cremaster arterioles (n=6). In PLA using antibodies specific for AT 1 R and RGS5 protein there were significantly higher fluorescent labeling, indicative of co‐localization, per VSMC detected in the presence of Ang II (1 µM, 24.25 ± 2.19) or hypotonic solution (150 mOsm/L, 22.86 ± 2.83) than at baseline (7.23 ± 0.89). Labeling produced by hypotonic solution was significantly reduced by candesartan (10 µM) (24.00 ± 5.00 VS 11.46 ± 1.30). These findings indicate that mechanoactivation of AT 1 R causes recruitment of RGS5 protein, which may prevent exaggerated AT 1 R‐mediated myogenic vasoconstriction by terminating GPCR signaling.