title: Proteasomal degradation of TRIM5alpha during retrovirus restriction.
abstract: The host protein TRIM5alpha inhibits retroviral infection at an early post-penetration stage by targeting the incoming viral capsid. While the detailed mechanism of restriction remains unclear, recent studies have implicated the activity of cellular proteasomes in the restriction of retroviral reverse transcription imposed by TRIM5alpha. Here, we show that TRIM5alpha is rapidly degraded upon encounter of a restriction-susceptible retroviral core. Inoculation of TRIM5alpha-expressing human 293T cells with a saturating level of HIV-1 particles resulted in accelerated degradation of the HIV-1-restrictive rhesus macaque TRIM5alpha protein but not the nonrestrictive human TRIM5alpha protein. Exposure of cells to HIV-1 also destabilized the owl monkey restriction factor TRIMCyp; this was prevented by addition of the inhibitor cyclosporin A and was not observed with an HIV-1 virus containing a mutation in the capsid protein that relieves restriction by TRIMCyp IVHIV. Likewise, human TRIM5alpha was rapidly degraded upon encounter of the restriction-sensitive N-tropic murine leukemia virus (N-MLV) but not the unrestricted B-MLV. Pretreatment of cells with proteasome inhibitors prevented the HIV-1-induced loss of both rhesus macaque TRIM5alpha and TRIMCyp proteins. We also detected degradation of endogenous TRIM5alpha in rhesus macaque cells following HIV-1 infection. We conclude that engagement of a restriction-sensitive retrovirus core results in TRIM5alpha degradation by a proteasome-dependent mechanism.
authors.affiliation: Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America.
authors.forename: Christopher James
authors.initials: CJ
authors.lastname: Rold
authors.forename: Christopher
authors.initials: C
authors.lastname: Aiken
mesh_terms: D000818:Animals; D000090103:Antiviral Restriction Factors; D016645:Aotidae; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D016572:Cyclosporine / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020868:Gene Silencing; D015497:HIV-1 / Q000502:physiology; D054884:Host-Pathogen Interactions; D006801:Humans; D008253:Macaca mulatta; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D012190:Retroviridae / Q000502:physiology*; D048348:Reverse Transcription; D014162:Transfection; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases; D014758:Viral Core Proteins / Q000378:metabolism
chemical_list: D000090103:Antiviral Restriction Factors; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D011506:Proteins; D034741:RNA, Small Interfering; D000070584:Tripartite Motif Proteins; D014758:Viral Core Proteins; D016572:Cyclosporine; C477346:TRIM5 protein, human; C482587:TRIM5(alpha) protein, rhesus monkey; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex