Regulation of conventional kinesin by Enabled, an Abelson tyrosine kinase substrate involved in actin cytoskeleton dynamics. M.A. Martin 1, S.M. Ahern-Djamali 2, F.M. Hoffmann 2, W.M. Saxton 1. 1) Department of Biology, Indiana University, Bloomington, IN; 2) McArdle Lab, University of Wisconsin, Madison, WI.
Investigations into the mechanisms by which the microtubule motor kinesin is regulated in its transport of organelles and by which the VASP-relative Enabled (Ena) modulates the actin cytoskeleton have converged. This convergence reveals a link between the functions of the two major filament systems and implicates a mechanism for regulation of motor proteins in response to signal transduction cascades, in this case mediated by the Ableson tyrosine kinase (Abl). The Abl substrate Ena is proposed to be involved in regulating actin cytoskeleton dynamics and is essential for axon pathfinding during development. Conventional kinesin is an important motor for fast anterograde axonal transport and mutations cause large accumulations of fast transport organelles and posterior paralysis in larvae. Abl was identified as a dominant enhancer of Kinesin heavy chain (Khc) mutations via a screen of the Deficiency kits (Bloomington Stock Center). Khcnull/+; Abl-/+ animals have organelle-filled axonal swellings and posterior paralysis, conditions that are reduced or absent from either heterozygote alone. Moreover, ena mutations dominantly suppress the Abl-Khc interaction. The genetic interaction of ena and Khc is likely to represent a direct Ena-KHC protein interaction in vivo. We isolated KHC with Ena bait in a yeast two hybrid screen. Ena and KHC co-immunoprecipitate from fly head cytosol with Ena or KHC antibodies. This interaction is independent of Ena phosphorylation by Abl. These biochemical and genetic interactions taken together suggest that Ena, when not fully phosphorylated by Abl, is a negative regulator of kinesin function. It may act to promote kinesin-cargo detachment at actin-rich cortical sites. MAM and SAD are equal contributors.