title: PTEN-mediated ERK1/2 inhibition and paradoxical cellular proliferation following Pnck overexpression.
abstract: Pregnancy upregulated non-ubiquitous calmodulin kinase (Pnck), a novel calmodulin kinase, is significantly overexpressed in breast and renal cancers. We present evidence that at high cell density, overexpression of Pnck in HEK 293 cells inhibits serum-induced extracellular signal-regulated kinase (ERK1/ERK2) activation. ERK1/2 inhibition is calcium-dependent and Pnck kinase activity is required for ERK1/2 inhibition, since expression of a kinase-dead (K44A) and a catalytic loop phosphorylation mutant (T171A) Pnck protein is unable to inhibit ERK1/2 activity. Ras is constitutively active at high cell density, and Pnck does not alter Ras activation, suggesting that Pnck inhibition of ERK1/2 activity is independent of Ras activity. Pnck inhibition of serum-induced ERK1/2 activity is lost in cells in which phosphatase and tensin homolog (PTEN) is suppressed, suggesting that Pnck inhibition of ERK1/2 activity is mediated by PTEN. Overexpression of protein phosphatase-active but lipid phosphatase-dead PTEN protein inhibits ERK1/2 activity in control cells and enhances Pnck-mediated ERK1/2 inhibition, suggesting that Pnck increases availability of protein phosphatase active PTEN for ERK1/2 inhibition. Pnck is a stress-responsive kinase; however, serum-induced p38 MAP kinase activity is also downregulated by Pnck in a Pnck kinase- and PTEN-dependent manner, similar to ERK1/2 inhibition. Pnck overexpression increases proliferation, which is inhibited by PTEN knockdown, implying that PTEN acts as a paradoxical promoter of proliferation in ERK1/2 and p38 MAP kinase phosphorylation-inhibited, Pnck-overexpressing cells. Overall, these data reveal a novel function of Pnck in the regulation of ERK1/2 and p38 MAP kinase activity and cell proliferation, which is mediated by paradoxical PTEN functions. The possible biological implications of these data are discussed.
authors.affiliation: Lombardi Comprehensive Cancer Center and Department of Oncology; Georgetown University Medical Center; Georgetown University; Washington, DC USA.
authors.forename: Tushar B
authors.initials: TB
authors.lastname: Deb
authors.affiliation: Lombardi Comprehensive Cancer Center and Department of Oncology; Georgetown University Medical Center; Georgetown University; Washington, DC USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Barndt
authors.affiliation: Lombardi Comprehensive Cancer Center and Department of Oncology; Georgetown University Medical Center; Georgetown University; Washington, DC USA.
authors.forename: Annie H
authors.initials: AH
authors.lastname: Zuo
authors.affiliation: Lombardi Comprehensive Cancer Center and Department of Oncology; Georgetown University Medical Center; Georgetown University; Washington, DC USA.
authors.forename: Surojeet
authors.initials: S
authors.lastname: Sengupta
authors.affiliation: Lombardi Comprehensive Cancer Center and Department of Oncology; Georgetown University Medical Center; Georgetown University; Washington, DC USA.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Coticchia
authors.affiliation: Lombardi Comprehensive Cancer Center and Department of Oncology; Georgetown University Medical Center; Georgetown University; Washington, DC USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Johnson
mesh_terms: D000841:Anisomycin / Q000494:pharmacology; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1 / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation; D004789:Enzyme Activation; D020536:Enzyme Activators / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000378:metabolism*; D010766:Phosphorylation; D011725:Pyridines / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism
chemical_list: D020536:Enzyme Activators; D007093:Imidazoles; D011725:Pyridines; D004815:Epidermal Growth Factor; D000841:Anisomycin; D066246:ErbB Receptors; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1; C517606:PNCK protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D018631:ras Proteins; C093642:SB 203580
keywords: ERK1/2; PTEN; Pnck; breast cancer; cell signaling; p38 MAPK; phosphorylation; phosphotyrosine; proliferation; protein phosphatase