Molecular mechanism of α2β1 integrin interaction with human echovirus 1

Abstract

Conformational activation increases the affinity of integrins to their ligands. On ligand binding, further changes in integrin conformation elicit cellular signalling. Unlike any of the natural ligands of a2b1 integrin, human echovirus 1 (EV1) seemed to bind more avidly a 'closed' than an activated 'open' form of the a2I domain. Furthermore, a mutation E336A in the a2 subunit, which inactivated a2b1 as a collagen receptor, enhanced a2b1 binding to EV1. Thus, EV1 seems to recognize an inactive integrin, and not even the virus binding could trigger the conformational activation of a2b1. This was supported by the fact that the integrin clustering by EV1 did not activate the p38 MAP kinase pathway, a signalling pathway that was shown to be dependent on E336-related conformational changes in a2b1. Furthermore, the mutation E336A did neither prevent EV1 induced and a2b1 mediated protein kinase C activation nor EV1 internalization. Thus, in its entry strategy EV1 seems to rely on the activation of signalling pathways that are dependent on a2b1 clustering, but do not require the conformational regulation of the receptor.

Structural and Functional Analysis of Coxsackievirus A9 Integrin α v β 6 Binding and Uncoating

“…If only one integrin conformation can be bound, then there are fewer potential binding partners per cell, but if virus binding then immediately triggered a conformational change (two-state model) leading to integrin signaling and uptake, the probability of entry at this second step would be improved. Echovirus 1, for instance, which binds to the bent ␣ 2 ␤ 1 integrin conformation, causes integrin clustering, probably mediating signaling for endocytosis, and at later time points colocalizes with internalized integrin (15,25,58). It is likely that avidity plays a role in the in vivo situation, resulting in an even higher overall affinity of the virus for the cell surface.…”

Integrin β1 Mediates Vaccinia Virus Entry through Activation of PI3K/Akt Signaling

“…Integrins are involved in the entry of many viruses (2,5,19,21,26,34,36,44,59,64) and bacteria (16,27,40). The pathogen-host interaction may promote the clustering of integrins and focal adhesion formation but subvert the downstream signaling network to modify membrane traffic and cytoskeletal dynamics to meet their own needs (1,17).…”

Novel α2β1 Integrin Inhibitors Reveal That Integrin Binding to Collagen under Shear Stress Conditions Does Not Require Receptor Preactivation

“…CHO cells were stably transfected with expression constructs of wild-type human ␣2 integrin (CHO-␣2wt), ␣2 integrin variants (CHO-␣2Y285F, CHO-␣2E336A, CHO-␣2E318W), or ␣1 integrin expression constructs (17,24,25). In adhesion assays, cells (1.5 ϫ 10 5 cells/well) were allowed to attach to plates coated with rat tail collagen I, collagen IV (BD Biosciences), laminin-332, vitronectin, or ␣-chymotryptic fragments (120 or 40 kDa) of fibronectin (10 g/ml; Chemicon) for 2 h at 37°C.…”

“…We have previously shown that the Glu-336 residue may act as a link between ␣2I and ␤1I domains (16) in a manner similar to that of Glu-320 in ␣M (12,13) and Glu-310 in ␣L (14) and regulate the activity of the receptor. However, the function of ␣2␤1 does not seem to be entirely dependent on conformational activation because ␣2␤1 can bind even a large ligand (human echovirus-1) in a non-activated conformation (17).…”