title: Protein kinase C-beta II Is an apoptotic lamin kinase in polyomavirus-transformed, etoposide-treated pyF111 rat fibroblasts.
abstract: The role of protein kinase C-beta(II) (PKC-beta(II)) in etoposide (VP-16)-induced apoptosis was studied using polyomavirus-transformed pyF111 rat fibroblasts in which PKC-beta(II) specific activity in the nuclear membrane (NM) doubled and the enzyme was cleaved into catalytic fragments. No PKC-beta(II) complexes with lamin B1 and/or active caspases were immunoprecipitable from the NM of proliferating untreated cells, but large complexes of PKC-beta(II) holoprotein and its catalytic fragments with lamin B1, active caspase-3 and -6, and inactive phospho-CDK-1, but not PKC-beta(I) or PKC-delta, could be immunoprecipitated from the NM of VP-16-treated cells, suggesting that PKC-beta(II) is an apoptotic lamin kinase. By 30 min after normal nuclei were mixed with cytoplasms from VP-16-treated, but not untreated, cells, PKC-beta(II) holoprotein had moved from the apoptotic cytoplasm to the normal NM, and lamin B1 was phosphorylated before cleavage by caspase-6. Lamin B1 phosphorylation was partly reduced, but its cleavage was completely prevented, despite the presence of active caspase-6, by adding a selective PKC-betas inhibitor, hispidin, to the apoptotic cytoplasms. Thus, a PKC-beta(II) response to VP-16 seems necessary for lamin B1 cleavage by caspase-6 and nuclear lamina dissolution in apoptosing pyF111 fibroblasts. The possibility of PKC-beta(II) being an apoptotic lamin kinase in these cells was further suggested by lamin B1-bound PKC-delta being inactive or only slightly active and by PKC-alpha not combining with the lamin.
authors.affiliation: Histology and Embryology Unit, Department of Biomedical and Surgical Sciences, Medical School, University of Verona, Verona I-37134, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Chiarini
authors.forename: James F
authors.initials: JF
authors.lastname: Whitfield
authors.forename: Ubaldo
authors.initials: U
authors.lastname: Armato
authors.forename: Ilaria
authors.initials: I
authors.lastname: Dal Pra
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D053178:Caspase 6; D020169:Caspases / Q000378:metabolism; D002472:Cell Transformation, Viral; D005047:Etoposide / Q000494:pharmacology*; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology; D016195:G2 Phase / Q000187:drug effects; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008969:Molecular Sequence Data; D011120:Polyomavirus / Q000502:physiology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D064546:Protein Kinase C beta; D021381:Protein Transport; D051381:Rats; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D007527:Isoenzymes; D005047:Etoposide; D011493:Protein Kinase C; D064546:Protein Kinase C beta; C505410:Casp3 protein, rat; C505518:Casp6 protein, rat; D053148:Caspase 3; D053178:Caspase 6; D020169:Caspases