title: Activation of the inositol (1,4,5)-triphosphate calcium gate receptor is required for HIV-1 Gag release.
abstract: The structural precursor polyprotein, Gag, encoded by all retroviruses, including the human immunodeficiency virus type 1 (HIV-1), is necessary and sufficient for the assembly and release of particles that morphologically resemble immature virus particles. Previous studies have shown that the addition of Ca(2+) to cells expressing Gag enhances virus particle production. However, no specific cellular factor has been implicated as mediator of Ca(2+) provision. The inositol (1,4,5)-triphosphate receptor (IP3R) gates intracellular Ca(2+) stores. Following activation by binding of its ligand, IP3, it releases Ca(2+) from the stores. We demonstrate here that IP3R function is required for efficient release of HIV-1 virus particles. Depletion of IP3R by small interfering RNA, sequestration of its activating ligand by expression of a mutated fragment of IP3R that binds IP3 with very high affinity, or blocking formation of the ligand by inhibiting phospholipase C-mediated hydrolysis of the precursor, phosphatidylinositol-4,5-biphosphate, inhibited Gag particle release. These disruptions, as well as interference with ligand-receptor interaction using antibody targeted to the ligand-binding site on IP3R, blocked plasma membrane accumulation of Gag. These findings identify IP3R as a new determinant in HIV-1 trafficking during Gag assembly and introduce IP3R-regulated Ca(2+) signaling as a potential novel cofactor in viral particle release.
authors.affiliation: Department of Molecular Genetics and Microbiology, Life Sciences Bldg., Stony Brook University, Stony Brook, NY 11794-5222, USA.
authors.forename: Lorna S
authors.initials: LS
authors.lastname: Ehrlich
authors.forename: Gisselle N
authors.initials: GN
authors.lastname: Medina
authors.forename: Mahfuz B
authors.initials: MB
authors.lastname: Khan
authors.forename: Michael D
authors.initials: MD
authors.lastname: Powell
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Mikoshiba
authors.forename: Carol A
authors.initials: CA
authors.lastname: Carter
mesh_terms: D002118:Calcium / Q000378:metabolism*; D020868:Gene Silencing; D015497:HIV-1 / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D057074:Virus Release; D054301:gag Gene Products, Human Immunodeficiency Virus / Q000378:metabolism*
chemical_list: D053496:Inositol 1,4,5-Trisphosphate Receptors; D034741:RNA, Small Interfering; D054301:gag Gene Products, Human Immunodeficiency Virus; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium