Clustering of very late antigen-4 integrins modulates K⁺ currents to alter Ca²⁺-mediated monocyte function

Abstract

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 Ca2+ 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 Ca2+-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 Ca2+-mediated macrophage function, and possibly atherosclerotic plaque formation.

Quantum Proteolytic Activation of Chemokine CCL15 by Neutrophil Granulocytes Modulates Mononuclear Cell Adhesiveness

“…Chemokines, present on the endothelial surface under physiologic or pathologic conditions (19 -22), trigger rolling and firm adhesion by activation of Gi protein-coupled receptors (23)(24)(25)(26). Tethering and rolling of leukocytes at adhesive contact zones is increased by integrin clustering raising the avidity of integrin-ligand interactions (25,(27)(28)(29). Integrin-mediated arrest of leukocytes on vascular endothelium is suggested to be induced by further interaction partners.…”

ICln, a Novel Integrin αIIbβ3-Associated Protein, Functionally Regulates Platelet Activation

“…Vitronectin, but not fibrinonectin or laminin, selectively affects potassium currents in an Arg-Gly-Asp sequence-dependent manner in developing mouse hippocampal neurons (29). Similarly, ligand binding to integrins or integrin clustering modulates potassium currents, leading to hyperpolarization of monocytes and enhanced Ca 2ϩ influx (30). Integrin co-localization with ion channels has been observed in LOX tumor cells where ␤ 1 -integrins associate laterally with potassium channels during adhesion contributing to the regulation of integrin function in these cells (31).…”

Multinucleate host cells induced by Vittaforma corneae (Microsporidia)

“…To measure cell capacitance, as a reflection of cell size, in uninfected or infected E6 epithelial cells, we used the patch-clamp technique (Hamill et al 1981) with an Axopatch 200A amplifier (Axon Instruments) and 4 M borosilicate patch pipettes to gain access to the intracellular milieu using the whole-cell configuration. Under our experimental conditions we used a pipette solution containing (in mM): 150 KCl, 0.1 EGTA, 1 CaCl 2 (free [Ca 2+ ] = 26.5 nM) and 10 HEPES, pH to 7.2 with KOH and a standard bath solution containing (in mM): 137 NaCl, 5 KCl, 2 CaCl 2 , 1 MgCl 2 , 5.5 glucose, and 10 HEPES, pH to 7.3 with NaOH (Colden-Stanfield 2002). All experiments were performed at 22-24°C after correction of junction potentials.…”