Journal of cell science
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Journal of cell science · Jul 2009
Comparative StudyNonprimed and DYRK1A-primed GSK3 beta-phosphorylation sites on MAP1B regulate microtubule dynamics in growing axons.
MAP1B is a developmentally regulated microtubule-associated phosphoprotein that regulates microtubule dynamics in growing axons and growth cones. We used mass spectrometry to map 28 phosphorylation sites on MAP1B, and selected for further study a putative primed GSK3 beta site and compared it with two nonprimed GSK3 beta sites that we had previously characterised. We raised a panel of phosphospecific antibodies to these sites on MAP1B and used it to assess the distribution of phosphorylated MAP1B in the developing nervous system. ⋯ These experiments identified dual-specificity tyrosine-phosphorylation-regulated kinase (DYRK1A) as the kinase that primes sites of GSK3 beta phosphorylation in MAP1B, and we confirmed this by knocking down DYRK1A in cultured embryonic cortical neurons by using shRNA. DYRK1A knockdown compromised neuritogenesis and was associated with alterations in microtubule stability. These experiments demonstrate that MAP1B has DYRK1A-primed and nonprimed GSK3 beta sites that are involved in the regulation of microtubule stability in growing axons.