Induction of neurites by the regulatory domains of PKCdelta and epsilon is counteracted by PKC catalytic activity and by the RhoA pathway.
We have shown that protein kinase C (PKC) epsilon, independently of its kinase activity, via its regulatory domain (RD), induces neurites in neuroblastoma cells. This study was designed to evaluate whether the same effect is obtained in nonmalignant neural cells and to dissect mechanisms mediating the effect. Overexpression of PKCepsilon resulted in neurite induction in two immortalised neural cell lines (HiB5 and RN33B). Phorbol ester potentiated neurite outgrowth from PKCepsilon-overexpressing cells and led to neurite induction in cells overexpressing PKCdelta. The effects were potentiated by blocking the PKC catalytic activity with GF109203X. Furthermore, kinase-inactive PKCdelta induced more neurites than the wild-type isoform. The isolated regulatory domains of novel PKC isoforms also induced neurites. Experiments with PKCdelta-overexpressing HiB5 cells demonstrated that phorbol ester, even in the presence of a PKC inhibitor, led to a decrease in stress fibres, indicating an inactivation of RhoA. Active RhoA blocked PKC-induced neurite outgrowth, and inhibition of the RhoA effector ROCK led to neurite outgrowth. This demonstrates that neurite induction by the regulatory domain of PKCdelta can be counteracted by PKCdelta kinase activity, that PKC-induced neurite outgrowth is accompanied by stress fibre dismantling indicating an inactivation of RhoA, and that the RhoA pathway suppresses PKC-mediated neurite outgrowth.
Ling
Mia
M
Department of Laboratory Medicine, Molecular Medicine, Lund University, Malmö University Hospital, 205 02 Malmö, Sweden.
Trollér
Ulrika
U
Zeidman
Ruth
R
Lundberg
Cecilia
C
Larsson
Christer
C
D000199:Actins / Q000378:metabolism; D000577:Amides / Q000494:pharmacology; D002384:Catalysis; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D049452:Green Fluorescent Proteins; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007527:Isoenzymes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D008301:Maleimides / Q000494:pharmacology; D008954:Models, Biological; D016501:Neurites / Q000187:drug effects / Q000502:physiology*; D009447:Neuroblastoma / Q000473:pathology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010703:Phorbol Esters / Q000494:pharmacology; D011493:Protein Kinase C / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D011725:Pyridines / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D022502:Stress Fibers / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
D000199:Actins; D000577:Amides; D004791:Enzyme Inhibitors; D007211:Indoles; D007527:Isoenzymes; D008164:Luminescent Proteins; D008301:Maleimides; D010703:Phorbol Esters; D011725:Pyridines; D011993:Recombinant Fusion Proteins; C108830:Y 27632; D049452:Green Fluorescent Proteins; D011493:Protein Kinase C; D020742:rhoA GTP-Binding Protein; C070515:bisindolylmaleimide I