title: Csk homologous kinase (CHK), unlike Csk, enhances MAPK activation via Ras-mediated signaling in a Src-independent manner.
abstract: Substantial evidence exists supporting the notion that Csk and CHK, two negative regulatory kinases of the Src tyrosine kinase family, play distinct roles during development of the nervous system. One of the differences relies on the effects of both kinases on the MAPK transduction pathway. Specifically, CHK was shown to enhance MAPK signaling, while the role of Csk was unclear. In this work, we compared the effect of CHK versus Csk on MAPK signaling and elucidated the signaling pathway mediated by CHK leading to the activation of Erk1/2. Exogenous expression of wild-type CHK, but not Csk or a dead-kinase mutant of CHK, resulted in enhanced Erk1/2 phosphorylation in PC12 cells. CHK inhibited Src activity following stimulation of the cells with NGF. However, stimulation of Erk1/2 activation by CHK was independent of the NGF stimulation or the inhibition of Src kinase by CHK. CHK induced a complex formation between SHP-2 and Grb2, subsequently leading to the increased activity of Ras as well as Erk1/2 activation via the Raf/MEK1/2 pathway. Down-regulation of the expression of endogenous CHK by RNAi in PC12 cells led to a significant decrease in MAPK activation following NGF stimulation. Stimulation of CHK-overexpressing PC12 cells with EGF induced neurite outgrowth in the majority of cells. Taken together, this study describes for the first time the Src-independent actions of CHK and provides novel insights into CHK function in neural cells.
authors.affiliation: Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Harvard Institutes of Medicine, 4 Blackfan Circle, 3rd floor, Boston, MA 02115, USA.
authors.forename: Radoslaw
authors.initials: R
authors.lastname: Zagozdzon
authors.forename: Rafal
authors.initials: R
authors.lastname: Kaminski
authors.forename: Yigong
authors.initials: Y
authors.lastname: Fu
authors.forename: Wei
authors.initials: W
authors.lastname: Fu
authors.forename: Cecile
authors.initials: C
authors.lastname: Bougeret
authors.forename: Hava Karsenty
authors.initials: HK
authors.lastname: Avraham
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D002478:Cells, Cultured; D000071877:Checkpoint Kinase 1; D005822:Genetic Vectors; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D020932:Nerve Growth Factor / Q000494:pharmacology; D016716:PC12 Cells / Q000166:cytology / Q000187:drug effects*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D015854:Up-Regulation; D018631:ras Proteins / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D020932:Nerve Growth Factor; D011494:Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; C085377:MATK protein, human; D016392:Proto-Oncogene Proteins pp60(c-src); D019061:src-Family Kinases; D000071877:Checkpoint Kinase 1; D011493:Protein Kinase C; D048052:Mitogen-Activated Protein Kinase 3; D018631:ras Proteins