Papers
What controls travel lengths in vivo?
S.P. Gross, M.A. Welte, S.M. Block, E.F. Wieschaus (2000). "Dynein-mediated
cargo transport in vivo. A switch controls travel distance" J. Cell Biol.
148:945-956.
Abstract Full Text
In this paper, we investigate the regulation of cytoplasmic dynein, a
microtubule-based motor with diverse cellular roles. We 
combine mutational
analysis and bi ophysical measurements to demonstrate that this motor is responsible
for the minus-end motion of bidirectionally moving lipid droplets in early
Drosophila embryos: dynein localizes to lipid droplets, and mutations in the
heavy chain of cytoplasmic dynein alter the transport of individual lipid droplets
as well as their global distribution (top half of figure). This analysis provides
an estimate of the force that a single cytoplasmic dynein exerts in vivo (1.1
pN).
To investigate how the cell controls travel distances of dynein-driven
cargoes, we quantitate how far droplets travel in single runs (i.e. segments
of uninterrupted motion). Travel distances are much shorter than expected
based on in vitro estimates of cytoplasmic dynein processivity. We therefore
propose
the existence of a process that terminates runs before motor processivity
becomes limiting. We call this process a "switch" (see cartoon). A process
with similar properties governs plus-end motion. These switches are apparently
subject to developmental control, resulting in regulation of net transport
direction. Given dynein's diverse roles in many cellular processes, similar
switches will likely be crucial for determining net transport of other organelles
wherever bidirectional transport is observed.