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Infect. Immun. doi:10.1128/IAI.00572-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Moraxella catarrhalis binding to host cellular receptors is mediated by sequence-specific determinants not conserved among all UspA1 protein variants

Department of Molecular Genetics, University of Toronto, Toronto, Ontario, M5S1A8, Canada; Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, 75390, USA; and Department of Microbiology and Immunology, Faculty of Pharmacy, Cairo University, Cairo, Egypt 11562

^* To whom correspondence should be addressed. Email: scott.gray.owen{at}utoronto.ca.

	Abstract

The Moraxella catarrhalis ubiquitous surface proteins (UspAs) are autotransporter molecules reported to interact with a variety of different host proteins and to affect processes ranging from serum resistance to cellular adhesion. The role of UspA1 as an adhesin has been confirmed with a number of different human cell types, and is mediated by binding to eukaryotic proteins including Carcinoembryonic Antigen-related Cellular Adhesion Molecules (CEACAMs), fibronectin, and laminin. A distinct difference in the ability of prototypical M. catarrhalis strains to adhere to CEACAM-expressing cell lines prompted us to perform strain-specific, structure-function analysis of UspA1 proteins. In this study, we characterized CEACAM binding by a diverse set of UspA1 proteins and showed that 3 out of 10 UspA1 proteins were incapable of binding CEACAM. This difference resulted from the absence of a distinct CEACAM binding motif in the non-adhering strains. Our sequence analysis also revealed a single M. catarrhalis isolate that lacked the fibronectin-binding motif and was defective in adherence to Chang conjunctival epithelial cells. These results clearly demonstrate that UspA1-associated adhesive functions are not universally conserved. Instead, UspA1 proteins must be considered as variants with the potential to confer both different cell tropism and host cell responses.

This article has been cited by other articles:

• Brooks, M. J., Sedillo, J. L., Wagner, N., Laurence, C. A., Wang, W., Attia, A. S., Hansen, E. J., Gray-Owen, S. D. (2008). Modular Arrangement of Allelic Variants Explains the Divergence in Moraxella catarrhalis UspA Protein Function. Infect. Immun. 76: 5330-5340 [Abstract] [Full Text]