title: Functional PAK-2 knockout and replacement with a caspase cleavage-deficient mutant in mice reveals differential requirements of full-length PAK-2 and caspase-activated PAK-2p34.
abstract: p21-Activated protein kinase 2 (PAK-2) has both anti- and pro-apoptotic functions depending on its mechanism of activation. Activation of full-length PAK-2 by the monomeric GTPases Cdc42 or Rac stimulates cell survival, whereas caspase activation of PAK-2 to the PAK-2p34 fragment is involved in the apoptotic response. In this study we use functional knockout of PAK-2 and gene replacement with the caspase cleavage-deficient PAK-2D212N mutant to differentiate the biological functions of full-length PAK-2 and caspase-activated PAK-2p34. Knockout of PAK-2 results in embryonic lethality at early stages before organ development, whereas replacement with the caspase cleavage-deficient PAK-2D212N results in viable and healthy mice, indicating that early embryonic lethality is caused by deficiency of full-length PAK-2 rather than lack of caspase activation to the PAK-2p34 fragment. However, deficiency of caspase activation of PAK-2 decreased spontaneous cell death of primary mouse embryonic fibroblasts and increased cell growth at high cell density. In contrast, stress-induced cell death by treatment with the anti-cancer drug cisplatin was not reduced by deficiency of caspase activation of PAK-2, but switched from an apoptotic to a nonapoptotic, caspase-independent mechanism. Homozygous PAK-2D212N primary mouse embryonic fibroblasts that lack the ability to generate the proapoptotic PAK-2p34 show less activation of the effector caspase 3, 6, and 7, indicating that caspase activation of PAK-2 amplifies the apoptotic response through a positive feedback loop resulting in more activation of effector caspases.
authors.affiliation: Department of Biochemistry, Kansas City University of Medicine and Biosciences, 1750 Independence Avenue, Kansas City, MO 64106, USA.
authors.forename: Jerry W
authors.initials: JW
authors.lastname: Marlin
authors.forename: Yu-Wen E
authors.initials: YW
authors.lastname: Chang
authors.forename: Margaret
authors.initials: M
authors.lastname: Ober
authors.forename: Amy
authors.initials: A
authors.lastname: Handy
authors.forename: Wenhao
authors.initials: W
authors.lastname: Xu
authors.forename: Rolf
authors.initials: R
authors.lastname: Jakobi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics*; D015139:Blotting, Southern; D015153:Blotting, Western; D053468:CARD Signaling Adaptor Proteins / Q000235:genetics* / Q000378:metabolism; D053470:Caspases, Effector / Q000378:metabolism; D002945:Cisplatin; D017931:DNA Primers / Q000235:genetics; D025461:Feedback, Physiological; D005347:Fibroblasts; D005822:Genetic Vectors; D051379:Mice; D018345:Mice, Knockout; D020125:Mutation, Missense / Q000235:genetics; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D054462:p21-Activated Kinases / Q000235:genetics* / Q000378:metabolism*
chemical_list: D053468:CARD Signaling Adaptor Proteins; D017931:DNA Primers; D010446:Peptide Fragments; C515909:Pak2 protein, mouse; D054462:p21-Activated Kinases; D053470:Caspases, Effector; D002945:Cisplatin