Integrinα3β1 Is an Alternative Cellular Receptor for AdenovirusSerotype5

Abstract

Many adenovirus serotypes enter cells by high-affinity binding to the coxsackievirus-adenovirus receptor (CAR) and integrin-mediated internalization. In the present study, we analyzed the possible receptor function of ␣3␤1 for adenovirus serotype 5 (Ad5). We found that penton base and integrin ␣3␤1 could interact in vitro. In vivo, both Ad5-cell binding and virus-mediated transduction were inhibited in the presence of anti-␣3 and anti-␤1 function-blocking antibodies, and this occurred in both CAR-positive and CAR-negative cell lines. Peptide library screenings and data from binding experiments with wild-type and mutant penton base proteins suggest that the Arg-Gly-Asp (RGD) in the penton base protein, the best known integrin binding motif, is only part of the binding interface with ␣3␤1, which involved multiple additional contact sites.Adenovirus (Ad) host cell entry requires an initial attachment to cells which is mediated by the fiber interaction with the coxsackievirus-Ad receptor (CAR) (2). The subsequent association of the capsid protein penton base with integrin molecules promotes Ad entry (31). Integrins are a family of structurally and functionally related cell surface heterodimeric receptors that mediate cell migration and adhesion. The major extracellular ligands for integrins are collagens, laminins, fibronectin, tenascin, vitronectin, von Willebrand factor, and fibrinogen, reflecting the primary function of integrins in cell adhesion to the extracellular matrix. The ␣v␤1, -3, -5, -6, and -8 integrins, the ␣5␤1 and ␣8␤1 integrins, and the ␣IIb␤3 integrins form a subgroup that primarily recognizes ligands containing Arg-Gly-Asp (RGD) motifs (see reference 13 and references therein). Many microorganisms utilize integrins to gain entry into cells: the SA11 rotavirus binds to ␣2␤1 and ␣4␤1 (9), ␣v␤3 and ␣v␤1 integrins are receptors of the human parechovirus 1 (30), and ␣v␤5 has been proposed, although not conclusively, as a coreceptor in adeno-associated virus type 2 infection (27, 29). The foot-and-mouth disease virus uses different integrins for cell infection (14,15,16). Integrin ␣3␤1 is a cellular receptor for Kaposi's sarcoma-associated herpesvirus (1). Yersinia pseudotuberculosis binds to members of the ␤1 integrin family in order to enter eukaryotic cells (22).Several Ad serotypes contain an RGD motif in the penton base protein. This feature, and the Ad cell-detaching property, suggested an interaction of the virus with the integrin receptors. Indeed, ␣v␤3 and ␣v␤5 are receptors for human Ad2 and Ad5, and direct binding to isolated ␣v␤5 was shown for human Ad2, Ad3, Ad4, Ad5, and Ad37 (24, 31). In hematopoietic and melanoma cells, respectively, the ␣M␤2 and b1 integrins were found to be implicated in human Ad5 infection (3, 12). More recent evidence indicates ␣v␤1 as an Ad2 and Ad5 coreceptor in the human embryonic kidney (HEK293) cell line (23). Ad interaction with the ␣v␤1, -3, and -5 integrin subtypes is efficiently competed by RGD-containing peptides (23, 31). A second integrin binding motif is...

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