title: Protein kinase Czeta regulates Cdk5/p25 signaling during myogenesis.
abstract: Atypical protein kinase Czeta (PKCzeta) is emerging as a mediator of differentiation. Here, we describe a novel role for PKCzeta in myogenic differentiation, demonstrating that PKCzeta activity is indispensable for differentiation of both C2C12 and mouse primary myoblasts. PKCzeta was found to be associated with and to regulate the Cdk5/p35 signaling complex, an essential factor for both neuronal and myogenic differentiation. Inhibition of PKCzeta activity prevented both myotube formation and simultaneous reorganization of the nestin intermediate filament cytoskeleton, which is known to be regulated by Cdk5 during myogenesis. p35, the Cdk5 activator, was shown to be a specific phosphorylation target of PKCzeta. PKCzeta-mediated phosphorylation of Ser-33 on p35 promoted calpain-mediated cleavage of p35 to its more active and stable fragment, p25. Strikingly, both calpain activation and the calpain-mediated cleavage of p35 were shown to be PKCzeta-dependent in differentiating myoblasts. Overall, our results identify PKCzeta as a controller of myogenic differentiation by its regulation of the phosphorylation-dependent and calpain-mediated p35 cleavage, which is crucial for the amplification of the Cdk5 activity that is required during differentiation.
authors.affiliation: Turku Centre for Biotechnology, University of Turku and Abo Akademi University, 20521 Turku, Finland.
authors.forename: Aurélie
authors.initials: A
authors.lastname: de Thonel
authors.forename: Saima E
authors.initials: SE
authors.lastname: Ferraris
authors.forename: Hanna-Mari
authors.initials: HM
authors.lastname: Pallari
authors.forename: Susumu Y
authors.initials: SY
authors.lastname: Imanishi
authors.forename: Vitaly
authors.initials: V
authors.lastname: Kochin
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Hosokawa
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Hisanaga
authors.forename: Cecilia
authors.initials: C
authors.lastname: Sahlgren
authors.forename: John E
authors.initials: JE
authors.lastname: Eriksson
mesh_terms: D000818:Animals; D019556:COS Cells; D002154:Calpain / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002522:Chlorocebus aethiops; D051360:Cyclin-Dependent Kinase 5 / Q000378:metabolism*; D007381:Intermediate Filament Proteins / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D024510:Muscle Development / Q000187:drug effects; D032446:Myoblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D009419:Nerve Tissue Proteins / Q000378:metabolism; D064231:Nestin; D010766:Phosphorylation / Q000187:drug effects; D010770:Phosphotransferases / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects; D000099221:Protein Kinase C zeta
chemical_list: D002154:Calpain; D051360:Cyclin-Dependent Kinase 5; D007381:Intermediate Filament Proteins; D009419:Nerve Tissue Proteins; D064231:Nestin; D010770:Phosphotransferases; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D000099221:Protein Kinase C zeta; C492236:Cdk5r1 protein, mouse; C577485:Nes protein, mouse; C495906:Cdk5 protein, mouse