Special Colloquium - The 2007 Sackler Biophysics Prize, 2-5 pm

Date: May 13, 2007

Prof. Clare Waterman-Storer, Scripps Inst., La Jolla & NIH

Title: Microscopes and Motility: Integrating Cytoskeletal Systems in
Cell Migration

Abstract: 
The ability of individual cells to resist stress, change shape, and
move is critical to functions of the nervous system, immune response,
and cardiovascular system.  These functions are accomplished by a
remarkable system of protein polymers called the cytoskeleton.  The
cytoskeletal polymers self-assemble into networks and bundles that
mediate the establishment of cell shape.  Cell movement is
accomplished by spatially and temporally coordination of cytoskeletal
assembly, disassembly and interaction with motor proteins and
extracellular adhesion receptors.  We have developed light microscopic
methods to quantitatively analyze these dynamics of cytoskeletal
polymers and their interactions with other proteins to gain basic
insight into the mechanism of cell movement.

Prof. Frank Juelicher, MPI - Physics of Complex Systems, Dresden

Title: Theoretical Approaches to Cellular Force Generation and
Dynamics

Abstract: 
A fascinating feature of living cells is their inherently dynamic
nature, which is exemplified by their ability to generate spontaneous
movements.  A prototype system to study active processes in cells is
the cytoskeleton, a complex gel-like filament network which governs
the material properties of cells.  Cellular forces and dynamics are
driven by active processes on the molecular scale, for example the
action of motor molecules.  Such active molecular processes can result
in complex behaviors on the cellular scale which emerge from the
collective interplay of many molecules.  An important example is
spontaneous oscillations which can result from the concerted action of
a large number of motors that act against an elastic element.  This
mechanism can account for the oscillations of the mitotic spindle
which is observed during asymmetric cell divisions.  The analysis of
the underlying physical mechanisms provides insights in the force
balances that occur during cell division.  Similar physical mechanisms
are also at work in eukaryotic flagella.  The periodic and regular
beat of many flagella, such as those which propel sperm, is a
collective mode which results from the interplay of a large number of
motor proteins with elastic filaments.  Finally, spontaneous
oscillations play a key role in the amplification of mechanical
vibrations by sensory cells of our ear.  The nonlinear and active
properties of this cellular amplifier are essential to endow the ear
with its exquisite abilities to detect sound.