title: cAMP-dependent protein kinase and c-Jun N-terminal kinase mediate stathmin phosphorylation for the maintenance of interphase microtubules during osmotic stress.
abstract: Dynamic microtubule changes after a cell stress challenge are required for cell survival and adaptation. Stathmin (STMN), a cytoplasmic microtubule-destabilizing phosphoprotein, regulates interphase microtubules during cell stress, but the signaling mechanisms involved are poorly defined. In this study ectopic expression of single alanine-substituted phospho-resistant mutants demonstrated that STMN Ser-38 and Ser-63 phosphorylation were specifically required to maintain interphase microtubules during hyperosmotic stress. STMN was phosphorylated on Ser-38 and Ser-63 in response to hyperosmolarity, heat shock, and arsenite treatment but rapidly dephosphorylated after oxidative stress treatment. Two-dimensional PAGE and Phos-tag gel analysis of stress-stimulated STMN phospho-isoforms revealed rapid STMN Ser-38 phosphorylation followed by subsequent Ser-25 and Ser-63 phosphorylation. Previously, we delineated stress-stimulated JNK targeting of STMN. Here, we identified cAMP-dependent protein kinase (PKA) signaling as responsible for stress-induced STMN Ser-63 phosphorylation. Increased cAMP levels induced by cholera toxin triggered potent STMN Ser-63 phosphorylation. Osmotic stress stimulated an increase in PKA activity and elevated STMN Ser-63 and CREB (cAMP-response element-binding protein) Ser-133 phosphorylation that was substantially attenuated by pretreatment with H-89, a PKA inhibitor. Interestingly, PKA activity and subsequent phosphorylation of STMN were augmented in the absence of JNK activation, indicating JNK and PKA pathway cross-talk during stress regulation of STMN. Taken together our study indicates that JNK- and PKA-mediated STMN Ser-38 and Ser-63 phosphorylation are required to preserve interphase microtubules in response to hyperosmotic stress.
authors.affiliation: From the Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Victoria 3010, Australia.
authors.forename: Yan Y
authors.initials: YY
authors.lastname: Yip
authors.forename: Yvonne Y C
authors.initials: YY
authors.lastname: Yeap
authors.forename: Marie A
authors.initials: MA
authors.lastname: Bogoyevitch
authors.forename: Dominic C H
authors.initials: DC
authors.lastname: Ng
mesh_terms: D000818:Animals; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases; D007399:Interphase / Q000502:physiology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000235:genetics / Q000378:metabolism*; D009997:Osmotic Pressure / Q000502:physiology*; D016716:PC12 Cells; D010766:Phosphorylation / Q000502:physiology; D051381:Rats; D015398:Signal Transduction / Q000502:physiology*; D050777:Stathmin / Q000235:genetics / Q000378:metabolism*
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D050777:Stathmin; C061082:Stmn1 protein, rat; D017868:Cyclic AMP-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases
keywords: Cytoskeleton; Jun N-terminal Kinase (JNK); Osmotic Stress; Protein Kinase A (PKA); Protein Phosphorylation; Signal Transduction; Stathmin