Sequential Regulation of ct4131 and ct5131 Integrin Avidity by CC Chemokines in Monocytes: Implications for Transendothelial Chemotaxis

Leukocyte emigration possibly requires dynamic regulation of integrin adhesiveness for endothelial and extracellular matrix ligands. Adhesion assays on purified vascular cell adhesion molecule (VCAM)-I, fibronectin, and fibronectin fragments revealed distinct kinetic patterns for the regulation of very late antigen (VLA)-4 (a4131) and VLA-5 (et5131) avidity by the CC chemokines monocyte inflammatory protein (MIP)-la , RANTES (regulated on activation, normal T expressed and secreted), or monocyte chemoattractant protein (MCP)-I in monocytes. CC chemokines induced early activation and subsequent deactivation of VLA-4, whereas upregulation of VLA-5 avidity occurred later and persisted. Controlled detachment assays in shear flow suggested that adhesive strength of VLA-4 for VCAM-1 or the 40-kD fragment of fibronectin (FN40) is more rapidly increased and subsequently reduced by MCP-1 than by MIP-la , and confirmed late and sustained activation of the adhesive strength of VLA-5 for the 120-kD fragment of fibronectin (FN120). Mn 2÷ or the stimulating 131 mAb TS2/16 strongly and stably enhanced monocyte binding to VCAM-1 or fibronectin, and locked [31 integrins in a high avidity state, which was not further modulated by CC chemokines. Mn 2÷ and mAb TS2/16 inhibited CC chemokine-induced transendothelial migration, particularly chemotaxis across stimulated endothelium that involved VLA-4 and VCAM-1. VLA-4 on Jurkat cells is of constitutively high avidity and interfered with migration across barriers expressing VCAM-1. Low but not high site densities of VCAM-1 or FN40 promoted, while FN120 impaired, 131 integrin-dependent monocyte chemotaxis to MCP-1 across filters coated with these substrates. Thus, we show that CC chemokines can differentially and selectively regulate avidity of integrins sharing common 13 subunits. Transient activation and deactivation of VLA-4 may serve to facilitate transendothelial diapedesis, whereas late and prolonged activation of VLA-5 may mediate subsequent interactions with the basement membrane and extracellular matrix. T RANSENDOTHELIAL migration of leukocytes into sites of inflammation is regulated by traffic signal molecules, displayed on activated endothelium, which are considered to act sequentially (7, 59). Tethering and rolling of leukocytes on the vessel wall (39) results in exposure to chemoattractants, such as chemokines presented in the endothelial proximity. Chemokines are divided into two subfamilies according to sequence homology and the arrangement of the first cysteines. CXC chemokines preferentially stimulate neutrophils, and CC chemokines preferentially stimulate monocytes, T lymphocytes, eosinophils, and basophils (2). Chemokines can be found associated with the endothelial surface or complexed to proteoglycan-containing moieties in the subendothelial extracellular Address all correspondence to Timothy A. Springer, The Center for Blood Research and Department of Pathology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115. Tel.: (617) 278-3200. Fax: (617) 278-3232. matrix (ECM) 1 (52). Immobilized or soluble chemokines induce adhesion of leukocytes to endothelium or purified ligands, implicating their role in integrin activation (14, 29, 59, 60). Integrins bind to Ig superfamily members on endothelium. Like selectins, a4 integrins can support rolling. The integrins et4131 and et4137 mediate rolling on vascular cell adhesion molecule (VCAM)-I and mucosal addressin cell adhesion molecule (MAdCAM)-I, respectively (1, 5). After activation, 132 integrins and or4 integrins on leukocytes support firm adhesion (1, 39). Chemokine gradients can promote diapedesis of leukocytes (29), stimulating di1. Abbreviations used in this paper: BCECF/AM, 2',7'-bis-2-carboxyethyl5-(6)-carboxyfluorescein-acetoxymethylester; ECM, extracellular matrix; HSA, human serum albumin; HUVEC, human umbilical vein endothelial cell; ICAM, intercellular adhesion molecule; IL, interleukin; MCP, monocyte chemoattractant protein; MIP, monocyte inflammatory protein; RANTES, regulated on activation, normal T expressed and secreted; TNF-c~, tumor necrosis factor a; VCAM, vascular cellular adhesion molecule; VLA, very late antigen. © The Rockefeller University Press, 0021-9525/96/08/1063/11 $2.00 The Journal of Cell Biology, Volume 134, Number 4, August 1996 1063-1073 1063 on A ril 2, 2017 D ow nladed fom Published August 15, 1996