title: Entry of human papillomavirus type 16 by actin-dependent, clathrin- and lipid raft-independent endocytosis.
abstract: Infectious endocytosis of incoming human papillomavirus type 16 (HPV-16), the main etiological agent of cervical cancer, is poorly characterized in terms of cellular requirements and pathways. Conflicting reports attribute HPV-16 entry to clathrin-dependent and -independent mechanisms. To comprehensively describe the cell biological features of HPV-16 entry into human epithelial cells, we compared HPV-16 pseudovirion (PsV) infection in the context of cell perturbations (drug inhibition, siRNA silencing, overexpression of dominant mutants) to five other viruses (influenza A virus, Semliki Forest virus, simian virus 40, vesicular stomatitis virus, and vaccinia virus) with defined endocytic requirements. Our analysis included infection data, i.e. GFP expression after plasmid delivery by HPV-16 PsV, and endocytosis assays in combination with electron, immunofluorescence, and video microscopy. The results indicated that HPV-16 entry into HeLa and HaCaT cells was clathrin-, caveolin-, cholesterol- and dynamin-independent. The virus made use of a potentially novel ligand-induced endocytic pathway related to macropinocytosis. This pathway was distinct from classical macropinocytosis in regards to vesicle size, cholesterol-sensitivity, and GTPase requirements, but similar in respect to the need for tyrosine kinase signaling, actin dynamics, Na⁺/H⁺ exchangers, PAK-1 and PKC. After internalization the virus was transported to late endosomes and/or endolysosomes, and activated through exposure to low pH.
authors.affiliation: Emmy-Noether Group 'Virus Endocytosis', Institutes of Molecular Virology and Medical Biochemistry, University of Münster, Münster, Germany. schelhaas@uni-muenster.de
authors.forename: Mario
authors.initials: M
authors.lastname: Schelhaas
authors.forename: Bhavin
authors.initials: B
authors.lastname: Shah
authors.forename: Michael
authors.initials: M
authors.lastname: Holzer
authors.forename: Peter
authors.initials: P
authors.lastname: Blattmann
authors.forename: Lena
authors.initials: L
authors.lastname: Kühling
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Day
authors.forename: John T
authors.initials: JT
authors.lastname: Schiller
authors.forename: Ari
authors.initials: A
authors.lastname: Helenius
mesh_terms: D000199:Actins / Q000378:metabolism*; D022461:Caveolins / Q000378:metabolism; D002966:Clathrin / Q000378:metabolism*; D004705:Endocytosis; D006367:HeLa Cells; D052162:Human papillomavirus 16 / Q000502:physiology*; D006801:Humans; D021962:Membrane Microdomains / Q000378:metabolism*; D030361:Papillomavirus Infections / Q000235:genetics / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D015398:Signal Transduction; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D053586:Virus Internalization; D054462:p21-Activated Kinases / Q000378:metabolism
chemical_list: D000199:Actins; D022461:Caveolins; D002966:Clathrin; D017923:Sodium-Hydrogen Exchangers; C515903:PAK1 protein, human; D054462:p21-Activated Kinases; D011493:Protein Kinase C