HIV type 1 Gag and nucleocapsid proteins: cytoskeletal localization and effects on cell motility.
Cell motility is likely to play a pivotal role in HIV infection by promoting the dissemination of infected cells. On the basis of observations indicating an interaction between HIV-1 Gag and target cell filamentous actin, we hypothesized that these interactions would promote cell motility of HIV-infected cells. Indeed, we have found that HIV-1 infection enhances the chemotactic response of macrophages. To specifically investigate the significance of the interactions between Gag and cellular actin, we transfected NIH 3T3 fibroblasts and HeLa cells with a construct that permits the expression of HIV-1 Gag in the absence of any other viral protein. Fractionation experiments showed that Gag was present in cytoskeletal fraction containing long actin filaments and in a high-speed postcytoskeletal fraction with short actin filaments. We have also localized HIV-1 Gag to the lamellipodia of chemoattractant-stimulated cells. Significantly, the motility of Gag-expressing cells was enhanced in chemotaxis assays. In vitro mutagenesis experiments showed that HIV-1 Gag binds filamentous actin through the nucleocapsid domain (NC). An NC-green fluorescent protein fusion had the same cellular distribution as the complete protein, and its expression increased cell motility. These data suggest that interactions between HIV-1 Gag and actin in infected cells enhance cell motility. Ultimately this enhanced motility of infected cells could promote the dissemination of virus into the brain and other tissues.
Ibarrondo
F J
FJ
Department of Pediatrics, UCLA School of Medicine, Los Angeles, California 90095, USA.
Choi
R
R
Geng
Y Z
YZ
Canon
J
J
Rey
O
O
Baldwin
G C
GC
Krogstad
P
P
D016475:3T3 Cells / Q000502:physiology / Q000821:virology; D000199:Actins / Q000378:metabolism; D000818:Animals; D002633:Chemotaxis / Q000502:physiology*; D003599:Cytoskeleton / Q000378:metabolism*; D015683:Gene Products, gag / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000472:pathogenicity* / Q000502:physiology; D006367:HeLa Cells / Q000502:physiology / Q000821:virology; D006801:Humans; D008264:Macrophages / Q000502:physiology* / Q000821:virology; D051379:Mice; D009000:Monocytes / Q000502:physiology / Q000821:virology; D019251:Nucleocapsid / Q000378:metabolism*; D014162:Transfection
D000199:Actins; D015683:Gene Products, gag