6th Annual Symposium
Physics of Cancer
Leipzig, Germany
September 7-9, 2015
Invited Talk
Actin and Myosin Drive Membrane Protein Dynamics in an Cell Inspired in vitro Active Composite
Darius Köster
National Centre for Biological Sciences, Bangalore, India
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The surface of a living cell provides a platform for processes such as receptor signaling, protein
sorting, transport and endocytosis. The regulation of these processes requires the controllable
organisation of membrane components. A recent framework for the organisation of a certain class
of plasma membrane components is based on the active mechanics of acto-myosin juxtaposed to the
membrane (Gowrishankar et al., 2012; Rao & Mayor, 2014). A systematic study of the dynamics and consequences of this active composite in living cells is challenging. Here we reconstitute an active composite in vitro, by a stepwise addition
of the minimal ingredients: a supported lipid bilayer with an actin-binding component, short actin
filaments and myosin motors. By systematically varying the concentrations of actin and myosin
as well as the level of ATP we find a rich phase diagram of membrane-confined actin and myosin
configurations. By increasing the level of available ATP we induce a constitutively remodeling state,
in which asters composed of short actin filaments form and dissolve. In this state, the coupling of
actin to the bilayer drives the membrane components out of equilibrium, imparting distinct signatures
of activity in a manner entirely consistent with measurements in the living cell. These results highlight
the fundamental basis of the active composite framework and indicate its relevance in the study of
membrane organisation.
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