Integrin αvβ1 Modulation Affects Subtype B Avian Metapneumovirus Fusion Protein-mediated Cell-Cell Fusion and Virus Infection

Abstract

Avian metapneumovirus (aMPV) fusion (F) protein mediates virus-cell membrane fusion to initiate viral infection, which requires F protein binding to its receptor(s) on the host cell surface. However, the receptor(s) for aMPV F protein is still not identified. All known subtype B aMPV (aMPV/B) F proteins contain a conserved Arg-Asp-Asp (RDD) motif, suggesting that the aMPV/B F protein may mediate membrane fusion via the binding of RDD to integrin. When blocked with integrin-specific peptides, aMPV/B F protein fusogenicity and viral replication were significantly reduced. Specifically we identified integrin ␣v and/or ␤1-mediated F protein fusogenicity and viral replication using antibody blocking, small interfering RNAs (siRNAs) knockdown, and overexpression. Additionally, overexpression of integrin ␣v and ␤1 in aMPV/B non-permissive cells conferred aMPV/B F protein binding and aMPV/B infection. When RDD was altered to RAE (Arg-Ala-Glu), aMPV/B F protein binding and fusogenic activity were profoundly impaired. These results suggest that integrin ␣v␤1 is a functional receptor for aMPV/B F protein-mediated membrane fusion and virus infection, which will provide new insights on the fusogenic mechanism and pathogenesis of aMPV. Avian metapneumovirus (aMPV)3 belongs to the genus Metapneumovirus in the subfamily Pneumovirinae of paramyxoviridae (1, 2). aMPV is a major cause of acute rhinotracheitis in turkeys and is associated with swollen head syndrome in chickens. Thus, aMPV is considered a major threat to the poultry industry (1, 2). Based on phylogenetic analysis, aMPV has been divided into four subtypes: aMPV/A, aMPV/B, aMPV/C, and aMPV/D (3).The entry of a paramyxovirus into the host cell initially requires fusion of the viral envelope and cellular membrane, which is mediated by the glycoproteins on the viral envelope (4 -6). For viruses of the Paramyxovirinae subfamily, such as Newcastle disease virus, fusion (F) protein-mediated membrane fusion requires the assistance of the hemagglutininneuraminidase (HN) protein (7-10). However, viruses in the Pneumovirinae subfamily including human respiratory syncytial virus (hRSV), human metapneumovirus (hMPV), and aMPV, the F protein alone in the absence of the small hydrophobic and attachment (G) proteins can mediate membrane fusion and viral infection (11-15), suggesting that the mechanism by which hRSV, hMPV, and aMPV mediate virus-cell membrane fusion might be unique among the Paramyxovirinae subfamily.The F protein of Paramyxovirinae viruses is activated by a non-F attachment glycoprotein bound to its receptor(s) on the host cell (10, 16). The F protein then undergoes a coordinated series of conformational changes to its most stable form to promote membrane fusion (17-20). Thus, binding of the attachment glycoprotein to the cellular receptor(s) is critical for triggering the fusion process (21,22). For example, Newcastle disease virus HN protein attaches to sialic acid-containing receptors on the host cell surface and then activates the F protein to induce membrane fu...

Avian Hepatitis E Virus ORF2 Protein Interacts with Rap1b to Induce Cytoskeleton Rearrangement That Facilitates Virus Internalization

“…Increasing evidence suggests that viruses may harness host integrin-induced cytoskeleton-based processes to enter host cells ( 34 , 48 ). Integrin α5/β1 has been shown to act as a potential receptor for several viruses, such as foot-and-mouth disease virus ( 37 ), adeno-associated virus type 2 ( 35 ), and subtype B avian metapneumovirus ( 36 ). Moreover, integrin α5/β1 triggers the FAK-RAC1&CDC42-PAK-LIMK-Cofilin pathway, and cytoskeletal rearrangement appears to promote porcine hemagglutinating encephalomyelitis virus infection of permissive cells ( 34 ).…”

Integrin β1 Promotes Peripheral Entry by Rabies Virus

“…ITGB1 mediates Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV) attachment and entry into target cells via the RGD motif of viral glycoprotein (34,35). Similarly, ITGB1 links with integrin ␣v-mediated avian metapneumovirus (aMPV) membrane fusion and virus infection via the similar RGD motif of viral fusion protein (19). ITGB1 functions as an entry receptor for human cytomegalovirus (HCMV) and is involved in internalization but not cellular attachment via the conserved disintegrin-like domain of HCMV glycoprotein B (12), and it also mediates internalization of mammalian reovirus via the RGD motif of viral 2 protein (15).…”

“…Integrin-specific antibodies have been proposed to decrease viral infection (18,19). We speculated that RABV infection would be decreased by ITGB1-specific antibody.…”

Proteome Analysis in a Mammalian Cell Line Reveals that PLK2 Is Involved in Avian Metapneumovirus Type C (aMPV/C)-Induced Apoptosis

“…To date, there is no report on the cellular proteome changes after aMPV/C infection. Cultured Vero cells are the best available substrate for aMPV and have been used to study fuctions of aMPV proteins, entry to cells, mediation to membrane fusion, replication, induction of autophagy and vaccine preparation in previous reports [42][43][44][45][46][47]. aMPV/C is more closely related to hMPV and may have larger cellular host ranges potentially including mammalian than other subtypes [12,48].…”