Clustering of very late antigen-4 integrins modulates K(+) currents to alter Ca(2+)-mediated monocyte function.
Endothelial cell vascular cell adhesion molecule-1 (VCAM-1) activates adherent monocytes by clustering their very late antigen-4 (VLA-4) receptors, resulting in the modulation of the inwardly rectifying (I(ir)) and delayed rectifying (I(dr)) K(+) currents, hyperpolarization of the cells, and enhanced Ca(2+) influx (Colden-Stanfield M and Gallin EK. Am J Physiol Cell Physiol 275: C267-C277, 1998; Colden-Stanfield M and Scanlon M. Am J Physiol Cell Physiol 279: C488-C494, 2000). The present study was undertaken to test the hypothesis that monoclonal antibodies (MAbs) against VLA-4 (MAbVLA-4) mimic VCAM-1 to cluster VLA-4 integrins, which play a key role in signaling an increase in the secretion of the proinflammatory cytokine interleukin-8 (IL-8). Whole cell ionic currents and IL-8 secretion from THP-1 monocytes that were incubated on polystyrene, VCAM-1-immobilized MAbVLA-4 or an isotype-matched MAb against CD45 (MAbCD45) were measured. Clustering of VLA-4 integrins with a cross-linked MAbVLA-4, but not a monovalent MAbVLA-4, modulated the K(+) currents in an identical manner to incubation of cells on VCAM-1. Similarly, cross-linked MAbVLA-4 or VCAM-1 augmented Ca(2+)-mediated IL-8 secretion from THP-1 monocytes and was completely abolished by exposure to CsCl, an I(ir) blocker. Thus VLA-4 integrin clustering by cross-linked MAbVLA-4 mimics VCAM-1/VLA-4 interactions sufficiently to be associated with events leading to monocyte differentiation, enhanced Ca(2+)-mediated macrophage function, and possibly atherosclerotic plaque formation.
Colden-Stanfield
Margaret
M
Department of Physiology, Morehouse School of Medicine, Atlanta, Georgia 30310, USA. stanfiel@msm.edu
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D051668:Delayed Rectifier Potassium Channels; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D039041:Integrin alpha4beta1; D016023:Integrins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016209:Interleukin-8 / Q000096:biosynthesis; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated; D011940:Receptor Aggregation / Q000187:drug effects / Q000502:physiology*; D016201:Receptors, Lymphocyte Homing / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
D000911:Antibodies, Monoclonal; D051668:Delayed Rectifier Potassium Channels; D039041:Integrin alpha4beta1; D016023:Integrins; D016209:Interleukin-8; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D016201:Receptors, Lymphocyte Homing; D019010:Vascular Cell Adhesion Molecule-1; D011188:Potassium; D002118:Calcium