Gliding movement of and bidirectional transport along single native microtubules from squid axoplasm: evidence for an active role of microtubules in cytoplasmic transport.

Abstract

Native microtubules prepared from extruded and dissociated axoplasm have been observed to transport organelles and vesicles unidirectionally in fresh preparations and more slowly and bidirectionally in older preparations. Both endogenous and exogenous (fluorescent polystyrene) particles in rapid Brownian motion alight on and adhere to microtubules and are transported along them. Particles can switch from one intersecting microtubule to another and move in either direction. Microtubular segments 1 to 30/~m long, produced by gentle homogenization, glide over glass surfaces for hundreds of micrometers in straight lines unless acted upon by obstacles. While gliding they transport particles either in the same (forward) direction and]or in the backward direction. Particle movement and gliding of microtubule segments require ATe and are insensitive to taxol (30/~M). It appears, therefore, that the mechanisms producing the motive force are very closely associated with the native microtubule itself or with its associated proteins.Although these movements appear irreconcilable with several current theories of fast axoplasmic transport, in this article we propose two models that might explain the observed phenomena and, by extension, the process of fast axoplasmic transport itself. The findings presented and the possible mechanisms proposed for fast axoplasmic transport have potential applications across the spectrum of microtubule-based motility processes.

Further Characterization of Dopamine Release by Permeabilized PC 12 Cells

“…This clearly indicates that intracellular vesicle transport may not be necessary in cells that do not depend on ATP during stimulation for exocytosis. The ATP requirement for intracellular vesicle transport is well established (Adams, 1982;Allen et al, 1985;Vale et al, 1985). The absence ofa requirement for exocytotic membrane fusion agrees with the finding that isolated secretory vesicles undergo Cazf-induced fusion without added ATP (Gratzl et al, 1980;Ekerdt et al, 1981).…”

Identification of a novel force-generating protein, kinesin, involved in microtubule-based motility

“…The squid giant axon, because of its large size, has been particularly useful for studying organelle movement Brady et al, 1982). Axoplasm from the giant axon also can be dissociated, allowing bidirectional organelle movements to be visualized along individual cytoplasmic filaments with video-enhanced differential interference contrast microscopy (Vale et al, 1985a;Allen et al, 1985). These cytoplasmic filaments were identified as single microtubules by electron microscopy and immunofluorescence using antitubulin antibodies (Schnapp et al, 1985).…”

“…Native microtubules in extruded squid axoplasm also move along a glass coverslip (Allen et al, 1985). The soluble translocator from axoplasm that induces bead movement might also be responsible for moving inert beads after they are microinjected into axons or cultured cells (Adams and Bray, 1983;Beckerle, 1984).…”

Kinesin motors as molecular machines

“…(3)(4)(5) Kinesin was shown to be capable of binding to microtubules and, in the presence of ATP, of moving towards the fast polymerizing/depolymerizing plus ends of microtubules, (6) representing the first cytoplasmic microtubule motor protein to be discovered. Conventional kinesin is a tetramer of two heavy chains, each consisting of a motor domain, coiled-coil dimerization domain and tail, (7) and two light chains, which are thought to bind to membranes associated with cellular vesicles or organelles (Fig.…”