Binding of Par-4 to the actin cytoskeleton is essential for Par-4/Dlk-mediated apoptosis.
Prostate apoptosis response-4 (Par-4) is a 38-kDa protein originally identified as a gene product upregulated in prostate cancer cells undergoing apoptosis. Cell death mediated by Par-4 and its interaction partner DAP like kinase (Dlk) is characterized by dramatic changes of the cytoskeleton. To uncover the role of the cytoskeleton in Par-4/Dlk-mediated apoptosis, we analyzed Par-4 for a direct association with cytoskeletal structures. Confocal fluorescence microscopy revealed that endogenous Par-4 is specifically associated with stress fibers in rat fibroblasts. In vitro cosedimentation analyses and in vivo FRET analyses showed that Par-4 directly binds to F-actin. Actin binding is mediated by the N-terminal 266 amino acids, but does not require the C-terminal region of Par-4 containing the leucine zipper and the death domain. Furthermore, the interaction of Par-4 with actin filaments leads to the formation of actin bundles in vitro and in vivo. In rat fibroblasts, this microfilament association is essential for the pro-apoptotic function of Par-4, since both disruption of the actin cytoskeleton by cytochalasin D treatment and overexpression of Par-4 constructs impaired in actin binding result in a significant decrease of apoptosis induction by Par-4 and Dlk. We propose a model, in which Par-4 recruits Dlk to stress fibers, leading to enhanced phosphorylation of the regulatory light chain of myosin II (MLC) and to the induction of apoptosis.
Vetterkind
Susanne
S
Institute of Genetics, University of Bonn, Römerstr. 164, D-53117 Bonn, Germany.
Illenberger
Susanne
S
Kubicek
Jan
J
Boosen
Meike
M
Appel
Sarah
S
Naim
Hassan Y
HY
Scheidtmann
Karl-Heinz
KH
Preuss
Ute
U
D008841:Actin Cytoskeleton / Q000737:chemistry / Q000378:metabolism*; D000199:Actins / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D024722:Cardiac Myosins / Q000378:metabolism; D045744:Cell Line, Tumor; D064550:Death-Associated Protein Kinases; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D020930:MAP Kinase Kinase Kinases; D008297:Male; D051379:Mice; D009154:Mutation / Q000235:genetics; D018994:Myosin Light Chains / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D015854:Up-Regulation
D000199:Actins; D051017:Apoptosis Regulatory Proteins; D047908:Intracellular Signaling Peptides and Proteins; D018994:Myosin Light Chains; C107184:myosin light chain 2; C101296:prostate apoptosis response-4 protein; D064550:Death-Associated Protein Kinases; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020930:MAP Kinase Kinase Kinases; C090757:mitogen-activated protein kinase kinase kinase 12; D024722:Cardiac Myosins