title: EC3, a novel heterodimeric disintegrin from Echis carinatus venom, inhibits alpha4 and alpha5 integrins in an RGD-independent manner.
abstract: EC3, a heterodimeric disintegrin (Mr = 14,762) isolated from Echis carinatus venom is a potent antagonist of alpha4 integrins. Two subunits called EC3A and EC3B were isolated from reduced and alkylated EC3 by reverse-phase high performance liquid chromatography. Each subunit contained 67 residues, including 10 cysteines, and displayed a high degree of homology to each other and to other disintegrins. EC3 inhibited adhesion of cells expressing alpha4beta1 and alpha4beta7 integrins to natural ligands vascular cell adhesion molecule 1 (VCAM-1) and mucosal addressin cell adhesion molecule 1 (MadCAM-1) with IC50 = 6-30 nM, adhesion of K562 cells (alpha5beta1) to fibronectin with IC50 = 150 nM, and adhesion of alphaIIbbeta3 Chinese hamster ovary cells to fibrinogen with IC50 = 500 nM; it did not inhibit adhesion of alphavbeta3 Chinese hamster ovary cells to vitronectin. Ethylpyridylethylated EC3B inhibited adhesion of Jurkat cells to immobilized VCAM-1 (IC50 = 6 microM), whereas EC3A was inactive in this system. The MLDG motif appeared to be essential for activity of EC3B. Linear MLDG peptide inhibited the adhesion of Jurkat to VCAM-1 in a dose-dependent manner (IC50 = 4 mM), whereas RGDS peptide was not active at the same concentration. MLDG partially inhibited adhesion of K562 cells to fibronectin (5-10 mM) in contrast to RGDS peptide (IC50 = 3 mM), inhibiting completely at 10 mM.
authors.affiliation: Department of Physiology, Sol Sherry Thrombosis Research Center, Fels Cancer Research Institute, Temple University, School of Medicine, Philadelphia, Pennsylvania 19140, USA.
authors.forename: C
authors.initials: C
authors.lastname: Marcinkiewicz
authors.forename: J J
authors.initials: JJ
authors.lastname: Calvete
authors.forename: M M
authors.initials: MM
authors.lastname: Marcinkiewicz
authors.forename: M
authors.initials: M
authors.lastname: Raida
authors.forename: S
authors.initials: S
authors.lastname: Vijay-Kumar
authors.forename: Z
authors.initials: Z
authors.lastname: Huang
authors.forename: R R
authors.initials: RR
authors.lastname: Lobb
authors.forename: S
authors.initials: S
authors.lastname: Niewiarowski
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000187:drug effects*; D016466:CHO Cells; D006224:Cricetinae; D019281:Dimerization; D019483:Disintegrins / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D039441:Integrin alpha4; D039482:Integrin alpha5; D020014:K562 Cells; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000494:pharmacology*; D017386:Sequence Homology, Amino Acid; D014757:Viper Venoms / Q000737:chemistry*
chemical_list: D015703:Antigens, CD; D019483:Disintegrins; C119089:EC3 protein, Echis carinatus; D039482:Integrin alpha5; D009842:Oligopeptides; D014757:Viper Venoms; D039441:Integrin alpha4; C047981:arginyl-glycyl-aspartic acid