A Novel Regulation Of Adrenomedullin Receptor By PDGF In Mesangial Cells- Role Of Receptor Activity Modifying Protein-3

Receptor activity modifying protein-3 (RAMP-3) has been shown to complex with the calcitonin receptor-like receptor establishing a functional receptor for adrenomedullin (AM). AM exhibits potent anti-proliferative and anti-migratory effects on rat mesangial cells (RMC). In this study we investigated the effect of platelet-derived growth factor (PDGF) on RAMP-3 expression in RMC. We show here that PDGF-BB stimulates RAMP-3 mRNA expression in a concentration-dependent manner. Pre-treatment with actinomycin-D and α-amanitin demonstrates that this effect is independent of new RNA synthesis. Furthermore, PDGF increased the half-life of RAMP-3 mRNA from 66.5 to 331.6 min. Using selective inhibitors, our results also indicate that the increase in RAMP3 mRNA is MAPKK/MAPK and p38 MAPK dependent. PDGF also caused a corresponding elevation in membrane-associated RAMP-3 protein. Associated with this increase, PDGF pretreatment led to a significantly higher AM-mediated adenylate cyclase activity, suggesting a functional consequence for the PDGF-induced increase in RAMP-3 expression. Taken together, these data identify PDGF-dependent regulation of RAMP-3 expression as a possible mechanism for modulating mesangial cell’s responsiveness to AM.