Enhanced proliferation and altered calcium handling in RGS2-deficient vascular smooth muscle cells

• Published in: Journal of receptors and signal transduction 2014-12, Vol.34 (6), p.476-483
• Main Authors: Momen, Abdul, Afroze, Talat, Sadi, Al-Muktafi, Khoshbin, Amir, Zhang, Hangjun, Choi, Jaehyun, Gu, Steven, Zaidi, Syed H., Heximer, Scott P., Husain, Mansoor
• Format: Article
• Language: English
• Subjects: Animals; Calcium - metabolism; Calcium Signaling - drug effects; Calcium Signaling - physiology; Cell Proliferation - drug effects; Cell Proliferation - physiology; Cells, Cultured; Mice; Mice, Knockout; Muscle, Smooth, Vascular - cytology; Muscle, Smooth, Vascular - drug effects; Muscle, Smooth, Vascular - physiology; Myocytes, Smooth Muscle - cytology; Myocytes, Smooth Muscle - drug effects; Myocytes, Smooth Muscle - physiology; Platelet-Derived Growth Factor - pharmacology; PMCA4; proliferation; RGS Proteins - genetics; RGS Proteins - metabolism; RGS2; vascular smooth muscle cell
• ISSN: 1079-9893; 1532-4281
• DOI: 10.3109/10799893.2014.920393

Abstract Context: Regulator of G-protein signaling-2 (RGS2) inhibits Gq-mediated regulation of Ca2+ signalling in vascular smooth muscle cells (VSMC). Objective: RGS2 knockout (RGS2KO) mice are hypertensive and show arteriolar remodeling. VSMC proliferation modulates intracellular Ca2+ concentration [Ca2+]i. RGS2 involvement in VSMC proliferation had not been examined. Methods: Thymidine incorporation and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) conversion assays measured cell proliferation. Fura-2 ratiometric imaging quantified [Ca2+]i before and after UTP and thapsigargin. [3H]-labeled inositol was used for phosphoinositide hydrolysis. Quantitative RT-PCR and confocal immunofluorescence of select Ca2+ transporters was performed in primary aortic VSMC. Results and discussion: Platelet-derived growth factor (PDGF) increased S-phase entry and proliferation in VSMC from RGS2KO mice to a greater extent than in VSMC from wild-type (WT) controls. Consistent with differential PDGF-induced changes in Ca2+ homeostasis, RGS2KO VSMC showed lower resting [Ca2+]i but higher thapsigargin-induced [Ca2+]i as compared with WT. RGS2KO VSMC expressed lower mRNA levels of plasma membrane Ca2+ ATPase-4 (PMCA4) and Na+ Ca2+ Exchanger (NCX), but higher levels of sarco-endoplasmic reticulum Ca2+ ATPase-2 (SERCA2). Western blot and immunofluorescence revealed similar differences in PMCA4 and SERCA2 protein, while levels of NCX protein were not reduced in RGS2KO VSMC. Consistent with decreased Ca2+ efflux activity, 45Ca-extrusion rates were lower in RGS2KO VSMC. These differences were reversed by the PMCA inhibitor La3+, but not by replacing extracellular Na+ with choline, implicating differences in the activity of PMCA and not NCX. Conclusion: RGS2-deficient VSMC exhibit higher rates of proliferation and coordinate plasticity of Ca2+-handling mechanisms in response to PDGF stimulation.