Pericyte-specific expression of RGs5: implications for PDGF and EDG receptor signaling during vascular maturation

Cho H, Kozasa T, Bondjers C, Betsholtz C and Kehrl JH
FASEB J (2003) 17(3): 440-442
Research Area:
Immunotherapy / Hematology
Nucleofector™ I/II/2b
The authors studied signaling during fetal vascular maturation and the role of RGS5 (regulator G-protein signaling) in PDGF (platelet-derived growth factor) and EDG (endothelial differentiation gene) signaling processes. Experiment 1: CHO cells were nucleofected with RGS5, ERK-2 or EDG-1 expression plasmids. Cells were then treated with PMA (protein kinase C activator) or S-1-P. RGS5 inhibited S-1-P induced ERK-2 phosphorylation via the EDG-1 receptor. Experiment 2: Human aortic smooth muscle cells were transfected with RGS5 and treated with 3 different ERK agonists. RGS5 attenuated all 3 agonists and induced ERK phosphorylation. Experiment 3: To reveal the intracellular localization of RGS5 following exposure to S-1-P or PDGF human aortic smooth muscle cells were nucleofected with a RGS5-GFP fusion protein. Time lapse recordings revealed a decreased mobility of RGS5 expressing cells compared to non-transfected cells.
RGS proteins finely tune heterotrimeric G-protein signaling. Implying the need for such fine-tuning in the developing vascular system, in situ hybridization revealed a striking and extensive expression pattern of Rgs5 in the arterial walls of E12.5-E17.5 mouse embryos. The distribution and location of the Rgs5-positive cells typified that of pericytes and strikingly overlapped the known expression pattern of platelet-derived growth factor receptor (PDGFR)-beta. Both E14.5 PDGFR-beta- and platelet-derived growth factor (PDGF)-B-deficient mice exhibited markedly reduced levels of Rgs5 in their vascular plexa and small arteries. This likely reflects the loss of pericytes in the mutant mice. RGS5 acts as a potent GTPase activating protein for Gi(alpha) and Gq(alpha) and it attenuated angiotensin II-, endothelin-1-, sphingosine-1-phosphate-, and PDGF-induced ERK-2 phosphorylation. Together these results indicate that RGS5 exerts control over PDGFR-beta and GPCR-mediated signaling pathways active during fetal vascular maturation.