GRP78, a Coreceptor for Coxsackievirus A9, Interacts with Major Histocompatibility Complex Class I Molecules Which Mediate Virus Internalization

Abstract

It is becoming apparent that over the years cell infection by virus seems to have evolved into a multistep process in which many viruses employ distinct cell surface molecules for their attachment and cell entry. In this study the attachment and entry pathway of coxsackievirus A9 (CAV-9), a member of the Picornaviridae family, was investigated. It has been known that, although integrin ␣ v ␤3 is utilized as a receptor, its presence alone is insufficient for CAV-9 infection and that CAV-9 also requires a 70-kDa major histocompatibility complex class I (MHC-I)-associated protein (MAP-70) as a coreceptor molecule. We document by protein isolation and peptide sequencing that the 70-kDa protein is GRP78, a member of the heat shock protein 70 family of stress proteins. Furthermore we show by using fluorescence resonance energy transfer (FRET) that GRP78 is also expressed on the cell surface and associates with MHC-I molecules. In addition CAV-9 infection of permissive cells requires GRP78 and also MHC-I molecules, which are essential for virus internalization. The identification of GRP78 as a coreceptor for CAV-9 and the revelation of GRP78 and MHC-I associations have provided new insights into the life cycle of CAV-9, which utilizes integrin ␣ v ␤3 and GRP78 as receptor molecules whereas MHC-I molecules serve as the internalization pathway of this virus to mammalian cells.It has been clear for many years that viruses which propagate within vertebrate hosts have had to adapt to survive the hostile environment imposed by the host immunity by utilizing more than one cell surface molecule for their attachment and cell entry (24). Identification of virus receptors and characterization of their interaction with the virus are major goals in virology.In this study we focused on receptor interactions of coxsackievirus A9 (CAV-9), a nonenveloped RNA virus which causes flaccid paralysis and chronic dilated cardiomyopathy (10) and which is implicated in autoimmune episodes that lead to insulin-dependent diabetes mellitus (IDDM) (22,23). Substantial knowledge of the receptors utilized by CAV-9 will allow some mechanisms of host recognition by the virus to be understood and consequently open ways for therapeutic intervention. It has been known that integrin ␣ v ␤3 is a receptor for CAV-9 (21, 32, 33). However its presence alone is insufficient for CAV-9 infection, thus leading us to believe that other cell surface molecules may be required for efficient CAV-9 infection (33).Our previous studies have identified a 70-kDa major histocompatibility complex class I (MHC-I)-associated protein (MAP-70) as another receptor molecule for CAV-9 (31). Here we present evidence that this 70-kDa protein is GRP78. This glucose-regulated 78-kDa protein is a member of the heat shock protein 70 (HSP70) family. GRP78 acts as a molecular chaperon and is involved in the folding and translocation of nascent peptide chains including the folding and assembly of MHC-I molecules (8, 9). Even though mostly intracellular, HSPs have been found to be expressed o...

A new tumor-specific variant of GRP78 as target for antibody-based therapy

“…3,7,32 The 78-kDa GRP (GRP78) is also known as immunoglobulin heavy-chainbinding protein. Parts of synthesized GRP78 are found translocated to the cell surface, where it is involved in MHC class I antigen presentation, 31 acts as co-receptor for ligands as viruses, 33,34 serves as receptor for the angiogenesis inhibitor kringle 5 19 or for activated forms of plasma proteinase inhibitor a2-macroglobulin (a 2 M*). Binding of a2-macroglobulin to plasma membrane associated GRP78 induces mitogenic signaling, proliferation and increases metastatic potential.…”

Evaluation of Genetically Engineered Derivatives of a Chinese Strain of Foot-and-Mouth Disease Virus Reveals a Novel Cell-Binding Site Which Functions in Cell Culture and in Animals

“…Although this hypothesis would seem to be the most reasonable, given the extensive amount of data on RGD-integrin interactions (see the introduction), our findings that the KGEexpressing viruses cause disease raise the possibility that a non-RGD-integrin interaction could be responsible for the generation of FMD in the natural host. Even so, it should be noted that work with an RGD-less coxsackievirus A9 shows that even in the absence of the RGD sequence, the virus can bind to integrin ␣V␤3 (53), and that other work suggests that although this integrin is required for binding, coreceptors are also required for internalization (52). Finally, the fact that neither RGD nor KGE peptides inhibited plaque formation by the pig-virulent KGE virus we generated suggests that multiple receptors and viral components can be utilized for mediating infection and disease by FMDV.…”

Role of Membrane Rafts in Viral Infection

“…The Raf/ mitogen-activated protein kinase (MAPK) signaling pathway is activated in lipid rafts upon CAV-A9 infection. The signaling machinery of Raf/MAPK activation after binding of CAV-A9 is unclear [37,38]. CAV B4 infection causes insulin-dependent diabetes mellitus, also known as type I diabetes, by progressive destruction of pancreatic cells.…”

“…The role of membrane rafts in entry of nonenveloped viruses has been investigated for simian virus 40 (SV40; Papovaviridae) [4][5][6][7][8][9][10][11][12], BK virus (Papovaviridae) [13][14][15], JC virus (Papovaviridae) [16], bovine papillomavirus (Papovaviridae) [17], human papillomavirus (HPV; Papovaviridae) [18][19][20][21][22][23][24][25][26], rotavirus (Reoviridae) [27][28][29], echovirus type 1 [30] and 11 (Picornaviridae) [31][32][33][34][35], enterovirus (Picornaviridae) [31], rhinovirus (Picornaviridae) [36], Coxsackievirus A9 and B4 (CAV; Picornaviridae) [37][38][39], and species C human adenovirus (HAdV; Adenoviridae) [40,41].…”