Consequences of motor copy number on the intacellular transport of Kinesin-1-driven lipid droplets

Author :G.T. Shubeita, S.L. Tran, J. Xu, M. Vershinin, S. Cermelli, S.L. Cotton, M.A. Welte, and S.P. Gross.
Publication :Cell
Volume :135
Number :6
Year :2008

The microtubule motor kinesin-1 plays central roles in
intracellular transport. It has been widely assumed
that many cellular cargos are moved by multiple kinesins
and that cargos with more motors move faster
andfor longer distances;concrete evidence, however,
is sparse. Here we rigorously test these notions using
lipid droplets in Drosophila embryos. We first employ
antibody inhibition, genetics, biochemistry, and particle
tracking to demonstrate that kinesin-1 mediates
plus-end droplet motion.Wethen measure howvariation
in kinesin-1 expression affects the forces driving
individual droplets and estimate the number of kinesins
actively engaged per droplet. Unlike in vitro, increased
motor number results in neither longer travel
distances nor higher velocities. Our data suggest that
cargos in vivo can simultaneously engage multiple
kinesins and that transport properties are largely unaffected
by variation in motor number. Apparently,
higher-order regulatory mechanisms rather than motor
number per se dominate cargo transport in vivo.