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First published online 23 June 2009
doi: 10.1242/jcs.040162

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Nonprimed and DYRK1A-primed GSK3β-phosphorylation sites on MAP1B regulate microtubule dynamics in growing axons

Timothy M. E. Scales, Shen Lin, Michaela Kraus, Robert G. Goold^* and Phillip R. Gordon-Weeks

The MRC Centre for Developmental Neurobiology, New Hunt's House, Guy's Campus, King's College London, London SE1 1UL, UK

Author for correspondence (e-mail: phillip.gordon-weeks{at}kcl.ac.uk)

Accepted 21 April 2009

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 GSK3β site and compared it with two nonprimed GSK3β 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. This showed that the nonprimed sites are restricted to growing axons, whereas the primed sites are also expressed in the neuronal cell body. To identify kinases phosphorylating MAP1B, we added kinase inhibitors to cultured embryonic cortical neurons and monitored MAP1B phosphorylation with our panel of phosphospecific antibodies. These experiments identified dual-specificity tyrosine-phosphorylation-regulated kinase (DYRK1A) as the kinase that primes sites of GSK3β 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 GSK3β sites that are involved in the regulation of microtubule stability in growing axons.

Key words: Neuritogenesis, MAP1B, GSK3β, DYRK1A, Microtubule dynamics, Mass spectrometry

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