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Curr Biol. 2004 Mar 9;14(5):363-71.

MAP2c, but not tau, binds and bundles F-actin via its microtubule binding domain.

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  • 1Department of Cell Biology and Institute for Childhood and Neglected Diseases, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.

Abstract

BACKGROUND:

MAP2 and tau are abundant microtubule-associated proteins (MAPs) in neurons. The development of neuronal dendrites and axons requires a dynamic interaction between microtubules and actin filaments. MAPs represent good candidates to mediate such interactions. Although MAP2c and tau have similar, well-characterized microtubule binding activities, their actin interaction is poorly understood.

RESULTS:

Here, we show by using a cosedimentation assay that MAP2c binds F-actin. Upon actin binding, MAP2c organizes F-actin into closely packed actin bundles. Moreover, we show by using a deletion approach that MAP2c's microtubule binding domain (MTBD) is both necessary and sufficient for both F-actin binding and bundling activities. Surprisingly, even though the MAP2 and tau MTBDs share high sequence homology and possess similar microtubule binding activities, tau is unable to bind or bundle F-actin. Furthermore, experiments with chimeric proteins demonstrate that the actin binding activity fully correlates with the ability to promote neurite initiation in neuroblastoma cells.

CONCLUSIONS:

These results provide the first demonstration that the MAP2c and tau MTBD domains exhibit distinct properties, diverging in actin binding and neurite initiation activities. These results implicate a novel actin function for MAP2c in neuronal morphogenesis and furthermore suggest that actin interactions could contribute to functional differences between MAP2 and tau in neurons.

PMID:
15028210
[PubMed - indexed for MEDLINE]
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