Monocyte chemoattractant protein-1: receptor interactions and calcium signaling mechanisms.
Monocyte chemoattractant protein-1 (MCP-1) is a member of the Cys-Cys chemokine family. Two related MCP-1 receptors have been identified (CC-CKR2A and CC-CKR2B), although the precise kinetics of ligand binding and calcium signaling of these receptors has yet to be investigated. To examine this more closely, the human MCP-1 receptors were cloned and expressed in Chinese hamster ovary (CHO) cells. Membranes prepared from cells expressing CC-CKR2B bind MCP-1 selectively and with high affinity (Kd = 120 pM). MCP-1 stimulation of recombinant CHO cells expressing CC-CKR2B induces a rapid increase in intracellular Ca2+ through both receptor-operated Ca2+ channels and mobilization of Ca2+ from intracellular stores, and leads to a rapid temperature-dependent internalization of the ligand/receptor complexes. In contrast, recombinant CHO cells expressing CC-CKR2A, and membranes prepared from these cells, fail to bind detectable levels of MCP-1. However, MCP-1 stimulation of cells expressing CC-CKR2A induces a small but significant increase in intracellular Ca2+. Repeated stimulation of these cells with MCP-1 leads to a potentiation of the response to a level comparable to that seen in cells expressing CC-CKR2B. These observations suggest that the levels of cell surface CC-CKR2A are controlled by novel mechanisms.
Needham
M
M
Cardiovascular & Musculoskeletal Research Department, ZENECA Pharmaceuticals, Mereside, Cheshire, United Kingdom.
Sturgess
N
N
Cerillo
G
G
Green
I
I
Warburton
H
H
Wilson
R
R
Martin
L
L
Barratt
D
D
Anderson
M
M
Reilly
C
C
Hollis
M
M
D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D018932:Chemokine CCL2 / Q000502:physiology*; D003001:Cloning, Molecular; D006224:Cricetinae; D004705:Endocytosis; D006801:Humans; D054390:Receptors, CCR2; D019707:Receptors, Chemokine; D018121:Receptors, Cytokine / Q000737:chemistry / Q000502:physiology*; D011994:Recombinant Proteins; D015398:Signal Transduction; D013997:Time Factors
C515334:CCR2 protein, human; D018932:Chemokine CCL2; D054390:Receptors, CCR2; D019707:Receptors, Chemokine; D018121:Receptors, Cytokine; D011994:Recombinant Proteins; D002118:Calcium