Pro-apoptotic function of checkpoint kinase-2 in syncytia elicited by the HIV-1 envelope.
Fusogenic HIV-1 isolates induce the fusion of infected and bystander cells. Such syncytia can be found as "multinucleated giant cells" in the brain from HIV-1-infected individuals, as well as in lymphoid tissues. Syncytia elicited by the HIV-1 envelope glycoprotein (Env) manifest the aggregation of PML in discrete nuclear bodies and the recruitment of TopBP1, NBS1 and ATM to DNA damage foci containing phosphorylated ATM and histone H2AX ("-H2AX). This DNA damage response then culminates in p53-dependent activation of the mitochondrial pathway of apoptosis. Here, we show that Env-elicited syncytia also manifest activating phosphorylations of the checkpoint kinases 1 and 2 (Chk1 and Chk2), and both Chk1 and Chk2 colocalize with "-H2AX foci. However, only the siRNA-mediated knockdown of Chk2, not the depletion of Chk1, inhibits mitochondrial outer membrane permeabilization and subsequent syncytial apoptosis. Depletion of PML, TopBP1, NBS1 or ATM inhibit the activating phosphorylation of Chk2. Altogether, these results indicate that Chk2 (but not Chk1) participates in the DNA damage-elicited pro-apoptotic cascade that leads to the demise of Env-elicited syncytia.
Séror
Claire
C
INSERM, U848, Villejuif, France.
Raza
Syed Qasim
SQ
Brottes
Fanélie
F
Subra
Frédéric
F
Piacentini
Mauro
M
Perfettini
Jean-Luc
JL
Kroemer
Guido
G
D017209:Apoptosis / Q000502:physiology*; D064007:Ataxia Telangiectasia Mutated Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D015686:Gene Products, env / Q000235:genetics / Q000378:metabolism*; D015726:Giant Cells / Q000166:cytology / Q000502:physiology*; D015497:HIV-1 / Q000378:metabolism / Q000648:ultrastructure*; D006367:HeLa Cells; D006801:Humans; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D000071156:Promyelocytic Leukemia Protein; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D015686:Gene Products, env; C112156:NBN protein, human; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D034741:RNA, Small Interfering; C110513:TOPBP1 protein, human; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C070576:PML protein, human; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; C578634:CHEK2 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases