Vipera lebetina Venom Contains Two Disintegrins Inhibiting Laminin-binding β1 Integrins

Abstract

To explain the myotoxic effects of snake venoms, we searched for inhibitors of ␣ 7 ␤ 1 integrin, the major laminin-binding integrin in skeletal muscle. We discovered two inhibitors in the venom of Vipera lebetina. One of them, lebein-1 (known as lebein), has already been proposed to be a disintegrin because of its RGD-containing primary sequence. The other, lebein-2, is a novel protein that also interacts firmly with ␣ 3 ␤ 1 , ␣ 6 ␤ 1 , and ␣ 7 ␤ 1 integrins, but not with the collagen-binding ␣ 1 ␤ 1 and ␣ 2 ␤ 1 integrins. Ligand binding of laminin-recognizing ␤ 1 integrins was efficiently blocked by both lebein-1 and lebein-2. In cell attachment assays, lebein-1 and lebein-2 inhibited myoblast attachment not only to laminin, but also to fibronectin. However, neither lebein-1 nor lebein-2 interacted with ␣ 7 ␤ 1 integrin in an RGD-dependent manner, similar to the interaction of the laminin with ␣ 7 ␤ 1 integrin. Identical divalent cation dependence of integrin binding to laminin and to either of the two inhibitors and their mutually exclusive binding suggest that both lebein-1 and lebein-2 interact with the ligandbinding site of laminin-binding ␤ 1 integrins by mimicking the yet unknown integrin-binding structure of laminins. Like lebein-1, lebein-2 is a soluble heterodimeric disintegrin of low molecular mass. Together with membrane-bound ADAM-2 and ADAM-9, the two inhibitors seem to form a small group of disintegrins that can bind to laminin-binding ␤ 1 integrins. Because of their inhibitory capability both in vitro and in vivo, lebein-1 and lebein-2 may be valuable tools in influencing laminininduced, integrin-mediated cell functions such as cell anchorage, migration, and mechanical force transduction on laminin-rich basement membranes.

Mechanically enforced bond dissociation reports synergistic influence of Mn2+ and Mg2+ on the interaction between integrin α7β1 and invasin

“…Ligation of invasin to integrins, such as laminin-binding integrins: a 7 b 1 , a 3 b 1 , and a 6 b 1 (Hamburger et al, 1999) generates strong forces which together with integrin-triggered signaling events lead to the entrapment and uptake of the bacterium into the host cell (Isberg, 1989;Van Nhieu et al, 1996;Dersch and Isberg, 1999). The binding affinity of invasin to the respective integrins exceeds the bond affinities between integrins and their cognate extracellular matrix (ECM) ligands by two orders of magnitude (Eble et al, 1998(Eble et al, , 2003von der Mark et al, 2002). This enables invasin to compete successfully with the excess of ECM ligands for integrin binding (Van Nhieu and Isberg, 1991).…”

Impaired Axonal Regeneration by Isolectin B4-Binding Dorsal Root Ganglion NeuronsIn Vitro

“…An EcoRI fragment containing the full-length coding sequence of mouse ␣7-integrin was cut out of PUC/␣7BX2 (Eble et al, 2003) and ligated into pcDNA3.1. After checking its orientation, the insert was removed and subcloned into the green fluorescent protein (GFP) site in the latency-associated transcript (LAT) region of pR19 -GFP (Lilley et al, 2001), resulting in pR19 -␣7-integrin.…”

Non-cytotoxic Cobra Cardiotoxin A5 Binds to αvβ3 Integrin and Inhibits Bone Resorption

“…Although ␣IIb␤3 integrin in platelets is the primary target for the action of viper RGD-containing disintegrins such as trigramin, echistatin, and flavoridin (24 -26), several non-RGD disintegrins also interact with ␣4␤1 and ␣9␤1 integrins in T-cells and neutrophils (27). Two disintegrins from Vipera lebetina venom inhibit laminin-binding ␤1 integrins (28).…”