Posttranslational modifications affect the activity of the human monocyte chemotactic proteins MCP-1 and MCP-2: identification of MCP-2(6-76) as a natural chemokine inhibitor.
Chemokines are important mediators in infection and inflammation. The monocyte chemotactic proteins (MCPs) form a subclass of structurally related C-C chemokines. MCPs select specific target cells due to binding to a distinct set of chemokine receptors. Recombinant and synthetic MCP-1 variants have been shown to function as chemokine antagonists. In this study, posttranslationally modified immunoreactive MCP-1 and MCP-2 were isolated from mononuclear cells. Natural forms of MCP-1 and MCP-2 were biochemically identified by Edman degradation and mass spectrometry and functionally characterized in chemotaxis and Ca2+-mobilization assays. Glycosylated MCP-1 (12 and 13.5 kDa) was found to be two- to threefold less chemotactic for monocytes and THP-1 cells than nonglycosylated MCP-1 (10 kDa). Natural, NH2-terminally truncated MCP-1(5-76) and MCP-1(6-76) were practically devoid of bioactivity, whereas COOH-terminally processed MCP-1(1-69) fully retained its chemotactic and Ca2+-inducing capacity. The capability of naturally modified MCP-1 forms to desensitize the Ca2+ response induced by intact MCP-1 in THP-1 cells correlated with their agonistic potency. In contrast, naturally modified MCP-2(6-76) was devoid of activity, but could completely block the chemotactic effect of intact MCP-2 as well as that of MCP-1, MCP-3, and RANTES. Carboxyl-terminally processed MCP-2(1-74) did retain its chemotactic potency. Although comparable as a chemoattractant, natural intact MCP-2 was found to be 10-fold less potent than MCP-1 in inducing an intracellular Ca2+ increase. It can be concluded that under physiologic or pathologic conditions, posttranslational modification affects chemokine potency and that natural MCP-2(6-76) is a functional C-C chemokine inhibitor that might be useful as an inhibitor of inflammation.
Proost
P
P
Rega Institute for Medical Research, Laboratory of Molecular Immunology, University of Leuven, Belgium.
Struyf
S
S
Couvreur
M
M
Lenaerts
J P
JP
Conings
R
R
Menten
P
P
Verhaert
P
P
Wuyts
A
A
Van Damme
J
J
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D018932:Chemokine CCL2 / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D054412:Chemokine CCL8; D018925:Chemokines / Q000037:antagonists & inhibitors*; D002634:Chemotaxis, Leukocyte / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D018945:Monocyte Chemoattractant Proteins / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D009000:Monocytes / Q000187:drug effects / Q000502:physiology; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology; D011499:Protein Processing, Post-Translational; D054390:Receptors, CCR2; D019707:Receptors, Chemokine / Q000037:antagonists & inhibitors
C515453:CCL8 protein, human; C515334:CCR2 protein, human; C515454:Ccl8 protein, mouse; C515335:Ccr2 protein, mouse; D018932:Chemokine CCL2; D054412:Chemokine CCL8; D018925:Chemokines; D018945:Monocyte Chemoattractant Proteins; D010446:Peptide Fragments; D054390:Receptors, CCR2; D019707:Receptors, Chemokine; D002118:Calcium