Signal transduction and ligand specificity of the human monocyte chemoattractant protein-1 receptor in transfected embryonic kidney cells

Abstract

We have examined the ligand specificity and signal transduction pathways of a recently cloned receptor for monocyte chemoattractant protein-1 (MCP- 1). In human 293 cells stably transfected with the MCP-1 receptor, MCP-1 bound specifically with high affinity (K(d) = 260 pM) and induced a rapid mobilization of calcium from intracellular stores. The closely related chemokines MIP-1α, MIP-1β, RANTES, interleukin 8 (IL-8), and Gro-α were inactive at concentrations as high as 300 nM. Activation of the MCP-1 receptor potently inhibited adenylyl cyclase with an IC50 = 90 pM. Activation of the MIP-1α/RANTES receptor also mediated inhibition of adenylyl cyclase activity but with a different pharmacological profile: MIP- 1α (110 pM, IC50), RANTES (140 pM), MIP-1β (10 nM), and MCP-1 (820 nM). Mobilization of intracellular calcium and inhibition of adenylyl cyclase were blocked by pertussis toxin, suggesting that the MCP-1 receptor coupled to Gαi. These results demonstrate that the MCP-1 receptor binds and signals in response to picomolar concentrations of MCP-1 in a highly specific manner. Signaling was manifested as mobilization of intracellular calcium and inhibition of adenylyl cyclase and was mediated by a pertussis toxin- sensitive G-protein(s).