Monkey Rotavirus Binding to α2β1 Integrin Requires the α2 I Domain and Is Facilitated by the Homologous β1 Subunit

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Abstract
Rotaviruses utilize integrins during virus-cell interactions that lead to infection. Cell binding and infection by simian rotavirus SA11 were inhibited by antibodies (Abs) to the inserted (I) domain of the α2 integrin subunit. To determine directly which integrins or other proteins bind rotaviruses, cell surface proteins precipitated by rotaviruses were compared with those precipitated by anti-α2β1 Abs. Two proteins precipitated by SA11 and rhesus rotavirus RRV from MA104 and Caco-2 cells migrated indistinguishably from α2β1 integrin, and SA11 precipitated β1 from α2β1-transfected CHO cells. These viruses specifically precipitated two MA104 cell proteins only, but an additional 160- to 165-kDa protein was precipitated by SA11 from Caco-2 cells. The role of the α2 I domain in rotavirus binding, infection, and growth was examined using CHO cell lines expressing wild-type or mutated human α2 or α2β1. Infectious SA11 and RRV, but not human rotavirus Wa, specifically bound CHO cell-expressed human α2β1 and, to a lesser extent, human α2 combined with hamster β1. Binding was inhibited by anti-α2 I domain monoclonal Abs (MAbs), but not by non-I domain MAbs to α2, and required the presence of the α2 I domain. Amino acid residues 151, 221, and 254 in the metal ion-dependent adhesion site of the α2 I domain that are necessary for type I collagen binding to α2β1 were not essential for rotavirus binding. Rotavirus-α2β1 binding led to increased virus infection and RRV growth. SA11 and RRV require the α2 I domain for binding to α2β1, and their binding to this integrin is distinguishable from that of collagen.

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