RACK1 Regulates Angiotensin II-Induced Contractions of SHR Preglomerular Vascular Smooth Muscle Cells.

RACK1 Regulates Angiotensin II-Induced Contractions of SHR Preglomerular Vascular Smooth Muscle Cells. Am J Physiol Renal Physiol. 2017 Jan 18;:ajprenal.00547.2016 Authors: Zhu X, Jackson EK Abstract The preglomerular microcirculation of spontaneously hypertensive rats (SHR) is hypersensitive to angiotensin II, and studies show that this is likely due to enhanced convergent signaling between G-protein subunits αq (Gαq; released by angiotensin II) and G-protein subunits βγ (Gβγ; released by Gi-coupled receptors) to active phospholipase C (PLC). Here we investigated the molecular basis for the enhanced convergent signaling between Gβγ and Gαq in SHR preglomerular vascular smooth muscle cells (PGVSMCs). Because receptor for activated C kinase 1 (RACK1; scaffolding protein) organizes interactions between Gβγ, Gαq and PLC, we included RACK1 in this investigation. Cell fractionation studies demonstrated increased levels of membrane (but not cytosolic) Gβ, Gαq, PLCβ3 and RACK1 in SHR PGVSMCs compared with Wistar-Kyoto rat PGVSMCs. In SHR PGVSMCs, co-immunoprecipitation demonstrated RACK1 binding to Gβ and PLCβ3, but only at cell membranes. Pertussis toxin (blocks Gβγ) and U73122 (blocks PLC) reduced membrane RACK1; however, RACK1 knockdown (shRNA) did not affect membrane levels of Gβ, Gαq or PLCβ3 In a novel gel contraction assay RACK1 knockdown in SHR PGVSMCs attenuated contractions to angiotensin II and abrogated the...
Source: Am J Physiol Renal P... - Category: Urology & Nephrology Authors: Tags: Am J Physiol Renal Physiol Source Type: research