Golgi lands new role
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Microtules (green) sprout from Golgi (red) as well as
centrosomes.
KAVERINA/ELSEVIER
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When
it comes to microtubule organization, centrosomes have the lead
role. But, as Andrey Efimov, Irina Kaverina (Vanderbilt University
Medical Center, Nashville, TN), Alexey Kharitonov (Austrian
Academy of Sciences, Vienna, Austria), and colleagues now report,
the
Golgi shares some of the limelight. Unlike centrosomes,
this
new-found organizer doesn't symmetrically radiate microtubules
from
center stage, but instead directs its performance to one
cell edge.
Microtubules do not start growing spontaneously in cells; they
rely on supporting protein machinery to nucleate tubulin building
blocks and kick off polymerization. To find their origins, Efimov et
al. tracked the growth of new microtubules in living cells. They
found that the majority of new microtubules radiated out from a
central position in the cell that is consistent with centrosomes.
A significant proportion of nucleation events, however, appeared
to occur at the Golgi. When the team obliterated centrosomes using
laser beams, they found that new microtubules indeed continued to
sprout from the Golgi. Golgi, but not centrosomal, nucleation
required a microtubule-binding protein called CLASP.
Microtubules grew out from Golgi in one direction—away from the
nucleus and toward the cell's periphery. In migrating cells, this
directionality corresponded with the direction of migration, as
microtubules from the Golgi grew toward the cell's leading edge.
Golgi-mediated nucleation might therefore support the asymmetric
architecture and secretory vesicle trafficking of polarized motile
cells.
Reference:
Efimov, A., et al. 2007. Dev. Cell.
12:917–930.[CrossRef][Medline]
