Protein kinase C‐θ is specifically activated in murine erythroleukaemia cells during mitosis

Abstract

Protein kinase C-a a is a member of the n-protein kinase C subfamily that in mitotic cells translocates to centrosomes and kinetochores. Although this kinase is expressed in comparable amounts in murine erythroleukaemia cells during the interphase or metaphase, when localized in the mitotic structures, it selectively phosphorylates a 66 kDa protein, also associated to chromosomes. Moreover, protein kinase C-a a immunoprecipitated from cells at the metaphase results four times more active in the absence of lipid cofactors as compared with the kinase obtained from cells in the interphase. This activation is accomplished by interaction of protein kinase C-a a with a protein factor which also promotes an increased autophosphorylation of the kinase. These findings indicate that in the mitotic phase of the cell cycle, protein kinase C-a a recognizes a protein factor which operates as a positive modulator of the kinase activity in the absence lipids.z 1999 Federation of European Biochemical Societies.

Human Neuroblastoma Cell Differentiation Requires Protein Kinase C-θ

“…Then, to rule out the occurrence of cytotoxic effects, cell growth, viability and apoptotic index have been measured. Cells treated with the PKC-antisense oligonucleotide display a 30% slower growth rate, in agreement with previous observations indicating a positive role for this kinase in the cell cycle progression (15). However, cell viability, evaluated by trypan blue exclusion staining, and the apoptotic index, determined with the acridine orangestaining (22), are not significantly modified.…”

“…In mitotic cells this kinase interacts with activating protein cofactors promoting the phosphorylation of chromosome protein targets (15). In different cell models, it has been demonstrated that PKC-associates to cell structures undergoing a dynamic reorganization (6,18,24).…”

“…Total RNA was obtained by using a RNeasy kit (Qiagen) and cDNA was prepared from 5 g of RNA using an oligo (dT) 15 as a primer and Moloney murine leukemia virus reverse transcriptase. The primers used for PCR were 5Ј-GAAATTGGTCTCCCATGCTC-3Ј (nucleotides 1043-1062); 5Ј-CCC-AGCCTCTTCTCAGGTTC-3Ј (complementary to nucleotides 1943-1962) (11).…”

“…It has been shown that the liberation of PKC-free catalytic domain by caspase-3 activity is directly involved in the induction of apoptosis (14). Several functional roles have been described for PKC-in the cell cycle progression (14,15) in the reorganization of actin cytoskeleton (16) and in T cell activation (17). We have observed previously that in LAN-5 cells PKC-associates to the centrosomes and kinetochores during mitosis (18).…”

Protein kinases required for segregation of vimentin filaments in mitotic process

“…Some PKC isoforms were also demonstrated to be mitotically activated (Goss et al, 1994;Thompson and Fields, 1996;Passalacqua et al, 1999), but mitotic PKC function remained largely unknown. We previously demonstrated that PKC phosphorylated vimentin by mitotic reorganization of intracellular membrane systems and the interaction of vesicles with vimentin ®laments (Takai et al, 1996).…”