title: Signal transduction of constitutively active protein kinase C epsilon.
abstract: The protein kinase C (PKC) family is the most prominent target of tumor-promoting phorbol esters. For the PKCepsilon isozyme, different intracellular localizations and oncogenic potential in several but not all experimental systems have been reported. To obtain information about PKCepsilon-signaling, we investigated the effects of constitutively active rat PKCepsilon (PKCepsilonA/E, alanine 159 is replaced by glutamic acid) in HeLa cells in a doxycycline-inducible vector. Upon induction of PKCepsilonA/E expression by doxycycline, the major part of PKCepsilonA/E was localized to the Golgi. This led (i) to phosphorylations of PKCepsilon(S729), Elk-1(S383), PDK1(S241) and Rb(S807/S811), (ii) to elevated expression of receptor of activated C kinase 2 (RACK2) after 12 h, and (iii) increased colony formation in soft agar, increased cell migration and invasion, but not to decreased doubling time. Following induction of PKCepsilonA/E-expression by doxycycline for 24 h and additional short-term treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA), PKCepsilonA/E translocated to the plasma membrane and increased phosphorylation of MARCKS(S152/156). Treatment with doxycycline/TPA or TPA alone increased phosphorylations of Elk-1(S383), PDK1(S241), Rb(S807/S811), PKCdelta(T505), p38MAPK(T180/Y182), MEK1/2(S217/S221) and ERK2(T185/T187). MARCKS was not phosphorylated after treatment with TPA alone, demonstrating that in this system it is phosphorylated only by PKCepsilon localized to the plasma membrane but not by PKCalpha or delta, the other TPA-responsive PKC isozymes in HeLa cells. These results demonstrate that PKCepsilon can induce distinctly different signaling from the Golgi and from the plasma membrane.
authors.affiliation: Division of Medical Biochemistry, Biocenter, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Dorota
authors.initials: D
authors.lastname: Garczarczyk
authors.forename: Ewa
authors.initials: E
authors.lastname: Toton
authors.forename: Verena
authors.initials: V
authors.lastname: Biedermann
authors.forename: Erika
authors.initials: E
authors.lastname: Rosivatz
authors.forename: Florian
authors.initials: F
authors.lastname: Rechfeld
authors.forename: Maria
authors.initials: M
authors.lastname: Rybczynska
authors.forename: Johann
authors.initials: J
authors.lastname: Hofmann
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D004318:Doxycycline / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D010766:Phosphorylation; D051744:Protein Kinase C-epsilon / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D051744:Protein Kinase C-epsilon; D004318:Doxycycline; D013755:Tetradecanoylphorbol Acetate