Direct interaction of microtubule- and actin-based transport motors

Abstract

The microtubule network is thought to be used for long-range transport of cellular components in animal cells whereas the actin network is proposed to be used for short-range transport, although the mechanism(s) by which this transport is coordinated is poorly understood. For example, in sea urchins long-range Ca2+-regulated transport of exocytotic vesicles requires a microtubule-based motor, whereas an actin-based motor is used for short-range transport. In neurons, microtubule-based kinesin motor proteins are used for long-range vesicular transport but microtubules do not extend into the neuronal termini, where actin filaments form the cytoskeletal framework, and kinesins are rapidly degraded upon their arrival in neuronal termini, indicating that vesicles may have to be transferred from microtubules to actin tracks to reach their final destination. Here we show that an actin-based vesicle-transport motor, MyoVA, can interact directly with a microtubule-based transport motor, KhcU. As would be expected if these complexes were functional, they also contain kinesin light chains and the localization of MyoVA and KhcU overlaps in the cell. These results indicate that cellular transport is, in part, coordinated through the direct interaction of different motor molecules.

Short-term regulation of bile acid uptake by microfilament-dependent translocation of rat ntcp to the plasma membrane

“…28 Very recent studies further demonstrate that transport mechanisms for microtubules and microfilaments interact with each other, allowing vesicles to move from microtubules to microfilaments. 31 We hypothesize that this also occurs for ntcp-containing vesicles in hepatocytes. Movement along microtubules allows delivery of nascent ntcp to the region of the plasma membrane; whereas, movement along microfilaments provides a mechanism for rapid regulated insertion of ntcp into the plasma membrane.…”

The HPV16 E5 oncogene inhibits endocytic trafficking

“…This demonstrates that endocytic tra cking is perturbed between early and late endocytic structures. Perturbed formation and organization, and nondirectional movements of late endocytic structures are responses to disruption of the actin cytoskeleton (Barois et al, 1998;DePina and Langford, 1999;Evans et al, 1998;Huang et al, 1999;Raposo et al, 1999;van Deurs et al, 1995) which plays an important role in endosome and lysosome propulsion (Taunton et al, 2000). Accordingly, the organization of the late endocytic structures was more dispersed in E5 transfected cells.…”

Powering membrane traffic in endocytosis and recycling

“…A curious phenomenon that is frequently observed in various cell systems is a block of movement in both directions when one of the motors (for example, cytoplasmic dynein) is downregulated 81,82 . This could be explained by the close association of both classes of motor on their cargoes, which conceivably can occur either by direct interaction 83 or coordination on the membrane 76,84 (see below and BOX 3). A potentially new twist to the story of bidirectional transport is the recent finding that purified dynein-dynactin complexes can move bidirectionally on microtubules in vitro 85 .…”