title: Clathrin- and caveolin-1-independent endocytosis: entry of simian virus 40 into cells devoid of caveolae.
abstract: Simian Virus 40 (SV40) has been shown to enter host cells by caveolar endocytosis followed by transport via caveosomes to the endoplasmic reticulum (ER). Using a caveolin-1 (cav-1)-deficient cell line (human hepatoma 7) and embryonic fibroblasts from a cav-1 knockout mouse, we found that in the absence of caveolae, but also in wild-type embryonic fibroblasts, the virus exploits an alternative, cav-1-independent pathway. Internalization was rapid (t1/2 = 20 min) and cholesterol and tyrosine kinase dependent but independent of clathrin, dynamin II, and ARF6. The viruses were internalized in small, tight-fitting vesicles and transported to membrane-bounded, pH-neutral organelles similar to caveosomes but devoid of cav-1 and -2. The viruses were next transferred by microtubule-dependent vesicular transport to the ER, a step that was required for infectivity. Our results revealed the existence of a virus-activated endocytic pathway from the plasma membrane to the ER that involves neither clathrin nor caveolae and that can be activated also in the presence of cav-1.
authors.affiliation: Institute of Biochemistry, Swiss Federal Institute of Technology Zürich (ETHZ), CH-8093 Zürich, Switzerland.
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Damm
authors.forename: Lucas
authors.initials: L
authors.lastname: Pelkmans
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kartenbeck
authors.forename: Anna
authors.initials: A
authors.lastname: Mezzacasa
authors.forename: Teymuras
authors.initials: T
authors.lastname: Kurzchalia
authors.forename: Ari
authors.initials: A
authors.lastname: Helenius
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000502:physiology; D008841:Actin Cytoskeleton / Q000187:drug effects / Q000502:physiology; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000957:Antigens, Viral, Tumor / Q000378:metabolism; D020126:Brefeldin A / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000235:genetics; D021941:Caveolae / Q000502:physiology*; D051242:Caveolin 1; D051243:Caveolin 2; D022461:Caveolins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000172:deficiency / Q000502:physiology; D002966:Clathrin / Q000502:physiology*; D003902:Detergents / Q000737:chemistry; D034285:Dynamin II / Q000235:genetics / Q000502:physiology; D004622:Embryo, Mammalian / Q000166:cytology; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D018871:Endoplasmic Reticulum, Smooth / Q000737:chemistry / Q000502:physiology; D005347:Fibroblasts / Q000187:drug effects / Q000648:ultrastructure / Q000821:virology; D015870:Gene Expression; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D021962:Membrane Microdomains / Q000737:chemistry / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000187:drug effects / Q000502:physiology; D015739:Nocodazole / Q000494:pharmacology; D010750:Phosphoproteins / Q000235:genetics; D012672:Semliki forest virus / Q000502:physiology; D013539:Simian virus 40 / Q000378:metabolism*; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D014168:Transferrin / Q000378:metabolism; D022161:Transport Vesicles / Q000502:physiology / Q000648:ultrastructure; D014404:Tubulin / Q000235:genetics; D033921:Vesicular Transport Proteins
chemical_list: D000089982:ADP-Ribosylation Factor 6; D048868:Adaptor Proteins, Signal Transducing; D000957:Antigens, Viral, Tumor; D019086:Bridged Bicyclo Compounds, Heterocyclic; C495540:CAV1 protein, human; D002135:Calcium-Binding Proteins; C495541:Cav1 protein, mouse; D051242:Caveolin 1; D051243:Caveolin 2; D022461:Caveolins; D002966:Clathrin; D003902:Detergents; C082729:Eps15 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010750:Phosphoproteins; D013844:Thiazoles; D053778:Thiazolidines; D014168:Transferrin; D014404:Tubulin; D033921:Vesicular Transport Proteins; C093846:early endosome antigen 1; D020126:Brefeldin A; D002784:Cholesterol; D019833:Genistein; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; C000715727:Arf6 protein, mouse; D034285:Dynamin II; D015739:Nocodazole; C037067:latrunculin A