SUNDAY, DECEMBER 4- Late Abstracts 1 - Molecular Biology of the ...

SUNDAY
2058
The F-BAR domain protein PACSIN2 associates to Rac1 and regulates cell spreading and
migration.
B-J. de Kreuk 1 , M. Nethe 1,2 , M. Fernandez-Borja 1 , E. Anthony 1 , P. Hensbergen 3 , A. Deelder 3 , M.
Plomann 4 , P. Hordijk 1 ; 1 Molecular Cell Biology, Sanquin Research, University of Amsterdam,
Amsterdam, Netherlands, 2 University of Virginia, Charlottesville, VA, 3 Leiden University Medical
Center, Leiden, Netherlands,, 4 Institute for Biochemistry 2, University of Cologne, Germany
The Rac1 GTPase controls cytoskeletal dynamics and is a key regulator of cell spreading and
migration via signaling through effector proteins such as the PAK kinases and the Scar/WAVE
proteins. We previously identified a series of regulatory proteins that associate with Rac1
through its hypervariable C-terminal domain. These include the Rac1 activator β-Pix, which
recruits Rac1 to focal adhesions, and the membrane adapter Caveolin1, which regulates the
poly-ubiquitylation and degradation of activated Rac1. Here, we show that Rac1 associates with
the F-BAR domain protein PACSIN2, an inducer of membrane tubulation and a regulator of
endocytosis. We show that loss of PACSIN2 increases Rac1-GTP loading and promotes cell
spreading and –migration. Conversely, expression of PACSIN2 reduces Rac1-GTP levels in a
fashion which is dependent on the PACSIN2-Rac1 interaction, on the membrane-tubulating
capacity of PACSIN2, and on Dynamin. In addition, we show that GEF-mediated Rac1-GTP
loading is unaffected when PACSIN2 is expressed. These results demonstrate that PACSIN2 is
an important regulator of the small GTPase Rac1 and that PACSIN2 limits Rac1-GTP signaling
by promoting Rac1 inactivation.
2059
Control over acquisition of cell motility and cell migration by the RNA binding protein
Dead end.
M. Goudarzi 1 , T. U. Banisch 1 , E. Raz 1 ; 1 Cell Biology, ZMBE, Muenster, Germany
Specification of zebrafish primordial germ cells (PGCs) depends on maternally inherited
determinants. These factors, collectively termed the germ-plasm direct cells to enter the
germline fate and to acquire proper cell behavior. An important such maternally-provided germplasm
component in zebrafish is encoded by the dead end (dnd) gene. The Dnd protein
contains an RNA recognition motif and is specifically expressed in PGCs, where it is localized to
the perinuclear granules. Knockdown of dead end results in severe defects in cell behavior (e.g.
the acquisition of motility), cell fate maintenance and survival.
We could previously show that Dnd functions by protecting specific mRNAs (e.g. tdrd7, nanos1
and hub) from micro RNA–mediated translational inhibition and degradation in the germ cells, a
process by which the same RNAs are repressed and degraded in somatic cells. To determine
the molecular basis of the dramatic changes in PGC properties upon loss of Dnd, we identified
RNAs regulated by miRNAs and the Dnd protein. The functional role the proteins encoded by
these mRNAs play in controlling cell shape and behavior will be discussed.
2060
Nonmuscle Myosin II Isoforms regulate microtubule dynamics in three-dimensional cell
migration through the distinct MLC phosphorylations.
S. Komatsu 1 , M. Ikebe 2 ; 1 Microbiology and Physiological Systems, UMass Medical School,
Worcester, MA, 2 UMass Medical School, Worcester, MA
Cell migration is an extremely complex process which is controlled by the rearrangement of
cytoskeletal systems. Most studies of cell migration have been focused on controlling the
actomyosin and microtubule networks, and studied a migrating cell on two-dimensional (2D)