TRANSPORT OF PROTEIN-KINASE-C-ALPHA INTO THE NUCLEUS REQUIRES INTACT CYTOSKELETON WHILE THE TRANSPORT OF A PROTEIN CONTAINING A CANONICAL NUCLEAR-LOCALIZATION SIGNAL DOES NOT
D. Schmalz et al., TRANSPORT OF PROTEIN-KINASE-C-ALPHA INTO THE NUCLEUS REQUIRES INTACT CYTOSKELETON WHILE THE TRANSPORT OF A PROTEIN CONTAINING A CANONICAL NUCLEAR-LOCALIZATION SIGNAL DOES NOT, Journal of Cell Science, 109, 1996, pp. 2401-2406
Protein kinase C undergoes a redistribution from the cytosol into the
nucleus upon various stimuli. Since protein kinase C does not contain
any known nuclear localization signal, the exact pathway and mechanism
of the translocation into the nucleus is not known. We used immunoflu
orescence microscopy to investigate the role of the cytoskeleton in th
is process, and to detect the subcellular distribution of protein kina
se C alpha in NIH 3T3 fibroblasts. In these cells protein kinase C alp
ha is translocated into the nucleus after stimulation with phorbol est
er, We observed that cells treated with the cytoskeleton disrupting ag
ents cytochalasin B or colchicine do not show the nuclear translocatio
n of protein kinase C alpha after stimulation. In contrast, the nuclea
r accumulation of a nuclear localization signal containing reporter pr
otein in an in vitro nuclear transport assay is not affected by these
drugs, This observation has been confirmed for intact cells by microin
jection experiments: cells which have been incubated with cytochalasin
B or colchicine prior to microinjection of the reporter protein show
the same accumulation in the nucleus as untreated cells. Our data show
that intact cytoskeleton plays an important role in the translocation
of protein kinase C alpha into the nucleus but not in the nuclear imp
ort of a karyophilic reporter protein.