title: PDGF receptor-α does not promote HCMV entry into epithelial and endothelial cells but increased quantities stimulate entry by an abnormal pathway.
abstract: Epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor-α (PDGFRα) were reported to mediate entry of HCMV, including HCMV lab strain AD169. AD169 cannot assemble gH/gL/UL128-131, a glycoprotein complex that is essential for HCMV entry into biologically important epithelial cells, endothelial cells, and monocyte-macrophages. Given this, it appeared incongruous that EGFR and PDGFRα play widespread roles in HCMV entry. Thus, we investigated whether PDGFRα and EGFR could promote entry of wild type HCMV strain TR. EGFR did not promote HCMV entry into any cell type. PDGFRα-transduction of epithelial and endothelial cells and several non-permissive cells markedly enhanced HCMV TR entry and surprisingly, promoted entry of HCMV mutants lacking gH/gL/UL128-131 into epithelial and endothelial cells. Entry of HCMV was not blocked by a panel of PDGFRα antibodies or the PDGFR ligand in fibroblasts, epithelial, or endothelial cells or by shRNA silencing of PDGFRα in epithelial cells. Moreover, HCMV glycoprotein induced cell-cell fusion was not increased when PDGFRα was expressed in cells. Together these results suggested that HCMV does not interact directly with PDGFRα. Instead, the enhanced entry produced by PDGFRα resulted from a novel entry pathway involving clathrin-independent, dynamin-dependent endocytosis of HCMV followed by low pH-independent fusion. When PDGFRα was expressed in cells, an HCMV lab strain escaped endosomes and tegument proteins reached the nucleus, but without PDGFRα virions were degraded. By contrast, wild type HCMV uses another pathway to enter epithelial cells involving macropinocytosis and low pH-dependent fusion, a pathway that lab strains (lacking gH/gL/UL128-131) cannot follow. Thus, PDGFRα does not act as a receptor for HCMV but increased PDGFRα alters cells, facilitating virus entry by an abnormal pathway. Given that PDGFRα increased infection of some cells to 90%, PDGFRα may be very useful in overcoming inefficient HCMV entry (even of lab strains) into the many difficult-to-infect cell types.
authors.affiliation: Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, Oregon, USA.
authors.forename: Adam L
authors.initials: AL
authors.lastname: Vanarsdall
authors.forename: Todd W
authors.initials: TW
authors.lastname: Wisner
authors.forename: Hetian
authors.initials: H
authors.lastname: Lei
authors.forename: Andrius
authors.initials: A
authors.lastname: Kazlauskas
authors.forename: David C
authors.initials: DC
authors.lastname: Johnson
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D016645:Aotidae; D001549:Benzamides / Q000494:pharmacology; D002459:Cell Fusion; D002460:Cell Line; D002966:Clathrin / Q000378:metabolism; D003587:Cytomegalovirus / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D003586:Cytomegalovirus Infections / Q000378:metabolism / Q000821:virology; D034281:Dynamins / Q000378:metabolism; D004705:Endocytosis; D042783:Endothelial Cells / Q000821:virology; D004847:Epithelial Cells / Q000821:virology; D066246:ErbB Receptors / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism / Q000821:virology; D006367:HeLa Cells; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D000068877:Imatinib Mesylate; D008562:Membrane Glycoproteins / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D034622:RNA Interference; D034741:RNA, Small Interfering; D051381:Rats; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D053586:Virus Internalization / Q000187:drug effects
chemical_list: D000911:Antibodies, Monoclonal; D001549:Benzamides; D002966:Clathrin; D008562:Membrane Glycoproteins; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D034741:RNA, Small Interfering; D000068877:Imatinib Mesylate; D066246:ErbB Receptors; D020796:Receptor, Platelet-Derived Growth Factor alpha; D034281:Dynamins