Isoform-specific Regulation of the Coxsackie and Adenovirus Receptor in Polarized Epithelia

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 DESCRIPTION (provided by applicant): Adenovirus is a common human pathogen that was first identified from tonsils in 1953. Over the past 6 decades, adenovirus research has yielded impressive knowledge about the pathogenesis of viral pneumonias, vaccination, and basic aspects of molecular virology and cellular biology. However, adenovirus remains a significant civilian and military threat since no specific therapeutic treatment for adenoviral infection exist. Adenovirus is also clinically significant because it is the most common viral vector used in human gene therapy clinical trials. New techniques that enhance adenovirus infection would, thus, improve the therapeutic index of these innovative therapies. Most adenoviruses and group B coxsackieviruses share a common receptor: coxsackievirus and adenovirus receptor (CAR). A major unanswered question has been how these pathogenic viruses initiate infection from the air-exposed lung epithelial surface. Our group has recently discovered that one of the two transmembrane isoforms of CAR (CAREx8) can localize at the air-exposed apical epithelial surface. Moreover, we have found that a cellular scaffolding protein, membrane-associated guanylate kinase with inverted domain structure 1 (MAGI-1), serves as a master negative regulator for cellular CAREx8 protein expression levels and apical adenovirus entry. Understanding the mechanism by which MAGI-1 regulates CAREx8 may lead to novel and specific therapeutics able to alter the susceptibility of an epithelium to adenovirus infection. We hypothesize that MAGI-1 downregulates CAREx8 protein expression by marking CAREx8 as a substrate for the protein-surveillance endoplasmic reticulum associated-degradation (ERAD) pathway. We further hypothesize that molecules that block the MAGI-1-CAREx8 interaction will directly affect the susceptibility of an epithelium to adenovirus infection. We aim to understand the molecular basis of MAGI- 1-mediated CAREx8 down regulation and whether specific cell-permeable peptides can interrupt this interaction to either decrease or increase apical adenovirus infection in polarized epithelia. Understanding these molecular mechanisms is clinically significant for several reasons. Currently there is no specific treatment for coxsackievirus or adenovirus infection; thus, the ability to block virus binding in the face of virl outbreaks would be a significant therapeutic advance. On the other hand, the ability to augment apical expression of the receptor would have high relevance for efficient adenoviral-mediated gene therapy for lung diseases, such as cancer. Finally, this work will expose a team of graduate and undergraduate students to vital research at the interface of virology and medicine.