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Four isoforms of Microtubule-associated protein 2s (MAP2a-d) are produced from a single gene in humans by alternative splicing.  These are known to bind actin in vitro (Nishida et al, 1981; Sattilaro, 1986; Selden & Pollard, 1983). The region of this family that binds microtubule also encompasses the actin-binding region.  The region is composed of three or  four repeats of about 18aminoacids in length, contained within which are cAMP dependent protein kinase phosphorylation sites that have been shown previously to regulate microtubule binding in vitro and very possibly in vivo (Ozer & Halpain, 2000).  Binding of microtubules appear to be stronger that the interactions with microfilaments and so in cells, microtubule co-localizations is seen, only when this interaction is disrupted by phosphorylation can MAP2 be observed in regions rich in actin and presumably bound by microfilaments (Ozer & Halpain, 2000).  A complication with the study of MAPs in vivo and their binding microtubules and microfilaments is  mapmodulin, a 31-kDa protein.  Mapmodulin binds MAPs via a tubulin-like domain (Ulitzur et al, 1997).


Ozer, R.S. & Halpain, S. (2000). "Phosphorylation-dependent localization of Microtubule-associate protein MAP2c to the actin cytoskeleton." Mol.Biol.Cell 11, 3573-3587.

Nishida, E., Kuwaki, T., & Sakai, H. (1981). "Phosphorylation of microtubule-associated proteins (MAPs) and pH of the medium control interactions between MAPs and actin filaments." J.Biochem. 90, 575-578.

Sattilaro, W. (1986). "Interaction of microtubule-associated protein 2 with actin filaments." Biochemistry 25, 2203-2009.

Selden, S.C. & Pollard, T.D. (1983). "Phosphorylation of microtubule-associated proteins regulates their interaction with actin filaments." J.Biol.Chem. 258, 7064-7071.

Ulitzur, N., Humbert, M., & Pfeffer, S.R. (1997). "". PNAS 94, 5084-5089.

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