Requirement of calmodulin binding by HIV-1 gp160 for enhanced FAS-mediated apoptosis.
Accelerated apoptosis is one mechanism proposed for the loss of CD4+ T-lymphocytes in human immunodeficiency virus type 1 (HIV-1) infection. The HIV-1 envelope glycoprotein, gp160, contains two C-terminal calmodulin-binding domains. Expression of gp160 in Jurkat T-cells results in increased sensitivity to FAS- and ceramide-mediated apoptosis. The pro-apoptotic effect of gp160 expression is blocked by two calmodulin antagonists, tamoxifen and trifluoperazine. This enhanced apoptosis in response to FAS antibody or C(2)-ceramide is associated with activation of caspase 3, a critical mediator of apoptosis. A point mutation in the C-terminal calmodulin-binding domain of gp160 (alanine 835 to tryptophan, A835W) eliminates gp160-dependent enhanced FAS-mediated apoptosis in transiently transfected cells, as well as in vitro calmodulin binding to a peptide corresponding to the C-terminal calmodulin-binding domain of gp160. Stable Tet-off Jurkat cell lines were developed that inducibly express wild type gp160 or gp160A835W. Increasing expression of wild type gp160, but not gp160A835W, correlates with increased calmodulin levels, increased apoptosis, and caspase 3 activation in response to anti-FAS treatment. The data indicate that gp160-enhanced apoptosis is dependent upon calmodulin up-regulation, involves the activation of caspase 3, and requires calmodulin binding to the C-terminal binding domain of gp160.
Micoli
K J
KJ
Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
Pan
G
G
Wu
Y
Y
Williams
J P
JP
Cook
W J
WJ
McDonald
J M
JM
D000409:Alanine; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001665:Binding Sites; D002147:Calmodulin / Q000378:metabolism*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D004789:Enzyme Activation; D019302:HIV Envelope Protein gp160 / Q000737:chemistry* / Q000378:metabolism*; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D019169:Jurkat Cells; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009219:Myosin-Light-Chain Kinase / Q000737:chemistry; D010446:Peptide Fragments / Q000737:chemistry; D017354:Point Mutation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology; D014162:Transfection; D014364:Tryptophan; D019014:fas Receptor / Q000502:physiology*
D002147:Calmodulin; D019302:HIV Envelope Protein gp160; C064769:N-acetylsphingosine; D010446:Peptide Fragments; D011994:Recombinant Proteins; D019014:fas Receptor; D014364:Tryptophan; D009219:Myosin-Light-Chain Kinase; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D013110:Sphingosine; D000409:Alanine