Addition of a Single Glycosylation Site to hAPN Blocks Human Coronavirus-229E Receptor Activity DAVID E. WENTWORTH AND KATHRYN V. HOLMES Department of Microbiology, University of Colorado Health Sciences Center, Denver, Colorado 1. INTRODUCTION The cellular receptor for HCoV-229E is human aminopeptidase N (hAPN). Murine fibroblasts that are nonpennissive for HCoV-229E become susceptible after transfection with an hAPN expression plasmid (Yeager et al., 1992). In addition, antibodies to hAPN block infection of human neural cells by HCoV-229E (Lachance et aI., 1998). hAPN, also called CD13, is a 150 kDa glycoprotein that is a membrane peptidase (Look et aI., 1989). APN is expressed by many cell types including epithelial cells of the kidney, intestine, respiratory tracts and at synaptic junctions in the CNS (Kenny and Maroux, 1982; Look et aI., 1989; Riemann et aI., 1999; Noren et al., 1997). Aminopeptidase N (APN) also serves as the major receptor for serogroup I coronaviruses that infect pigs, cats and dogs (Delmas et al., 1992; Delmas et al., 1993; Tresnan et aI., 1996). In general, APN is used in a species specific manner. However, feline APN (fAPN) , serves as a receptor for many serogroup I coronaviruses including feline (FECoV and FIPV), porcine (TGEV), human (HCoV-229E), and canine (CCoV) (Tresnan et al., 1996). Studies using chimeras between the human, feline, and porcine APN glycoproteins have identified two regions that are important in coronavirus receptor activity. Amino acids 717-813 of the pAPN are required for TGEV receptor activity (Delmas et al., 1994) and amino acids 670-840 offAPN are important for receptor activity of feline and porcine viruses (Hegyi and Kolb, 1998). Furthennore, substitution of amino acids 283-290 of pAPN The Nidoviruses (Coronaviruses and Arteriviruses). Edited by Ehud Lavi et al., Kluwer Academic/Plenum Publishers, 2001. 199