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determine the direction of cell polarization. This idea is further supported by a recent
study in Ptk2 cells, in which laser ablation of the centrosome caused a block in cell
migration and cell polarization (Wakida et al.
2010
). However, a leading role of the
centrosome does not appear to be universal. In a study comparing centrosome
position in migrating CHO and Ptk cells, the centrosome was localized toward the
front of the nucleus in CHO, but not in Ptk cells (Yvon et al.
2002
). In addition, there
are conflicting results on the role of the centrosome in migrating neurons. Several
studies have attributed a leading role to the centrosome in directing migration (Hi-
gginbotham and Gleeson
2007
; Tsai and Gleeson
2005
), but recent results from
Zebrafish neurons showed that there was no correlation between centrosome posi-
tioning and cell migration (Distel et al.
2010
). Indeed, it was found that the centro-
some of migrating THN neurons often trailed the nucleus. Thus, additional
experiments are needed to determine the exact role of the centrosome itself in cell
polarization.
Interestingly, several studies support an additional role for the Golgi-centrosome
relationship in the establishment of cell polarity. First, Bisel and colleagues reported
that the Golgi and the centrosome move together toward the leading edge of
migrating cells (Bisel et al.
2008
). This coordinated movement of both organelles
required the reorganization of Golgi membranes, which was mediated by ERK1-
dependent phosphorylation of the peripheral Golgi protein GRASP65. In a second
study, a role for the pericentrosomal Golgi ribbon in cell polarization and migration
was identified (Yadav et al.
2009
). By depleting the structural Golgi proteins Golgin-
160 or GMAP210, Yadav and colleagues found that the Golgi ribbon was converted
into dispersed mini-stacks. In these cells, normal protein transport to the cell surface
occurred, but there was a specific block in directional transport toward the leading
edge. As a consequence, cells did not polarize and migrate, indicating that a peri-
centrosomal Golgi ribbon is important for cell polarization. A third study asked
directly whether it is Golgi organization or Golgi position that is important for cell
polarization (Hurtado et al.
2011
). Hurtado and colleagues expressed a specific
domain of the Golgi scaffolding protein AKAP450, which resulted in the separation
of a functional, interconnected Golgi ribbon from the centrosome. Intriguingly, these
cells were unable to migrate in a wound-healing assay, indicating that the Golgi-
centrosome proximity is necessary for directional protein transport and cell polari-
zation. This study demonstrates for the first time that the physical proximity between
the Golgi and the centrosome in interphase mammalian cells is important for cell
polarization and is therefore of great functional significance.
7.4 Other Functional Interactions Between the Golgi
and the Centrosome in Interphase
In addition to this emerging role for the Golgi-centrosome interaction in cell
polarization, there are at least two other molecular associations between these two
organelles during interphase. First, there are cellular functions that are performed
