cAMP-dependent protein kinase and c-Jun N-terminal kinase mediate stathmin phosphorylation for the maintenance of interphase microtubules during osmotic stress [Cell Biology]

December 3rd, 2013 by Yip, Y. Y., Yeap, Y. Y., Bogoyevitch, M. A., Ng, D. C. H.

Dynamic microtubule changes following 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 signalling mechanisms involved are poorly defined. In this study, through the ectopic expression of single alanine-substituted phospho-resistant mutants demonstrated that STMN S38 and S63 phosphorylation were specifically required to maintain interphase microtubules during hyperosmotic stress (OS). STMN was phosphorylated on S38 and S63 in response to hyperosmolarity, heat shock and arsenite treatment but rapidly dephosphorylated following oxidative stress treatment. 2D-PAGE and Phos-tag gel analysis of stress-stimulated STMN phospho-isoforms revealed rapid STMN S38 phosphorylation followed by subsequent S25 and S63 phosphorylation. Previously, we delineated stress-stimulated JNK targeting of STMN. Here, we identified cAMP-dependent protein kinase (PKA) signalling as responsible for stress-induced STMN S63 phosphorylation. Increased cAMP levels induced by cholera toxin triggered potent STMN S63 phosphorylation. OS stimulated an increase in PKA activity and elevated STMN S63 and CREB S133 phosphorylation that was substantially attenuated by pretreatment with H-89, a PKA inhibitor. Interestingly, PKA activity and subsequent phosphorylation of STMN were augmented in 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 S38 and S63 phosphorylation are required to preserve interphase microtubules in response to hyperosmotic stress.
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