title: Huntingtin promotes cell survival by preventing Pak2 cleavage.
abstract: Huntington's disease is caused by a polyglutamine expansion in the huntingtin protein. Wild-type huntingtin, by contrast, appears to protect cells from pro-apoptotic insults. Here we describe a novel anti-apoptotic function for huntingtin. When cells are exposed to Fas-related signals, the ubiquitously expressed p21-activated kinase 2 (Pak2) can be activated via cleavage by caspases to release a constitutively active C-terminal fragment, which mediates cell death. Our data show that huntingtin interacts with Pak2. Overexpression of huntingtin significantly inhibits caspase-3-mediated and caspase-8-mediated cleavage of Pak2 in cells. Moreover, huntingtin prevents Pak2 cleavage by caspase-3 and caspase-8 in vitro. Although huntingtin is cytoprotective in wild-type cells that are exposed to TNFalpha, it has no significant benefit in TNFalpha-treated cells with Pak2 knockdown. Thus, huntingtin exerts anti-apoptotic effects by binding to Pak2, which reduces the abilities of caspase-3 and caspase-8 to cleave Pak2 and convert it into a mediator of cell death.
authors.affiliation: Department of Medical Genetics, Cambridge Institute for Medical Research, Wellcome/MRC Building, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK.
authors.forename: Shouqing
authors.initials: S
authors.lastname: Luo
authors.forename: David C
authors.initials: DC
authors.lastname: Rubinsztein
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D051379:Mice; D050505:Mutant Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D054462:p21-Activated Kinases / Q000378:metabolism*
chemical_list: D050505:Mutant Proteins; D009419:Nerve Tissue Proteins; D014409:Tumor Necrosis Factor-alpha; C515907:PAK2 protein, human; D054462:p21-Activated Kinases; D053148:Caspase 3; D053181:Caspase 8