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

Area of Science:

• Cardiovascular Biology
• Cellular Physiology
• Molecular Medicine

Background:

• Regulator of G-protein signaling-2 (RGS2) normally inhibits Gq-mediated calcium (Ca2+) signaling in vascular smooth muscle cells (VSMC).
• RGS2 knockout (RGS2KO) mice exhibit hypertension and arteriolar remodeling, suggesting a role for RGS2 in vascular health.

Purpose of the Study:

• To investigate the role of RGS2 in VSMC proliferation, as this had not been previously examined.
• To understand how RGS2 deficiency impacts Ca2+ homeostasis and proliferation in VSMC.

Main Methods:

• Cell proliferation was assessed using thymidine incorporation and MTT assays.
• Intracellular Ca2+ concentration ([Ca2+]) was measured using Fura-2 imaging.
• Gene and protein expression of Ca2+ transporters (PMCA4, NCX, SERCA2) were analyzed via RT-PCR, Western blot, and immunofluorescence.

Main Results:

• Platelet-derived growth factor (PDGF) significantly increased proliferation in RGS2KO VSMC compared to wild-type (WT).
• RGS2KO VSMC displayed altered Ca2+ handling, with lower resting [Ca2+] but higher thapsigargin-induced [Ca2+].
• RGS2KO VSMC showed reduced mRNA and protein for PMCA4, increased SERCA2, and altered Ca2+ extrusion rates, implicating PMCA activity.

Conclusions:

• RGS2-deficient VSMC exhibit increased proliferation rates.
• RGS2 deficiency leads to coordinated plasticity in Ca2+-handling mechanisms, particularly in response to PDGF stimulation.
• These findings highlight RGS2's critical role in regulating VSMC function and vascular tone.