Relaxin Activates Multiple cAMP Signaling Pathway Profiles in Different Target Cells

Although RXFP1-cAMP signaling in HEK293T cell systems is now relatively well-defined, the signaling pathways activated by relaxin in its target cells and tissues are still unclear. This study aimed to examine the cAMP signaling of RXFP1 in cells that endogenously express the receptor. Seven cell types derived from various backgrounds were screened for receptor expression. Only in THP-1 cells and rat cardiac fibroblasts was there activation of the G alpha(i3)-G beta gamma-phosphatidylinositol 3-kinase-protein kinase C zeta pathway, leading to cAMP accumulation. In all other cells there was activation of a combination of the initial pathways to affect cAMP. T-47D cells could activate only G alpha(s), whereas Colo 16 and rat renal fibroblasts from obstructed kidney could activate both G alpha(s) and G alpha(oB) pathways. Thus, the signaling pathways activated by relaxin are highly dependent upon the cell type under investigation, and this may help to explain the varied physiological responses exerted by relaxin in its different target tissues.