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Trafficking of axonal K+ channels: Potential role of Hsc70

Authors

  • John R. Clay,

    Corresponding author
    1. Ion Channel Biophysics Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
    2. Marine Biological Laboratory, Woods Hole, Massachusetts
    • National Institutes of Health, Building 36, Room 4A21, 9000 Rockville Pike, Bethesda, MD 20892
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  • Alan Kuzirian

    1. Marine Biological Laboratory, Woods Hole, Massachusetts
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  • This article is a US Government work and, as such, is in the public domain in the United States of America.

Abstract

Voltage-gated potassium ion channels in axons underlie the repolarization phase of the membrane action potential and help to set the resting potential. In addition to being present in the axolemma, they are also found in axoplasm in small vesicles, 30–50 nm in diameter, which may serve as a reserve pool of K+ channel protein (Clay and Kuzirian [2000] J Neurobiol 45:172–184). We have developed a novel technique for extracting these vesicles from axoplasm, which relies on the ability of Texas red to bind to them, thereby reducing their buoyancy so that they are amenable to pelleting by ultracentrifugation (Clay and Kuzirian [2000] J Neurobiol 45:172–184). The mechanism underlying this process may be binding of Texas red to Hsc70, which is primarily a cytosolic protein. However, a small portion of it is located on the surface of vesicles. Kinesin is also on the vesicle surface. This protein is membrane bound in our in vitro vesicle preparation when solutions that do not contain MgATP are added to extruded axoplasm. The addition of MgATP to the solution appears to release a significant amount of kinesin from the vesicles, possibly by the Hsc70-MgATP catalysis mechanism recently proposed by Tsai et al. Published 2002 Wiley-Liss, Inc.

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