The skin of a living cell: an active actin-membrane composite influencing membrane receptor function.
The plasma membrane of a living animal cell is a lipid bilayer composed of a remarkably complex mixture of lipid species and proteins, draped over a dynamic cortical actin mesh. While the composition of the lipid layer of a given cell type is reproducibly maintained, the cell also regulates the local composition of its membrane at the meso scale. This is achieved by actively controlling the formation of nano-domains, templated at the cytoplasmic leaflet by juxta membrane acto-myosin machinery. A specific subset of acto-myosin templated nano-domains consist of lipid anchored proteins at the outer leaflet engaged in trans-bilayer interactions via their lipid tails with phosphatidylserine at the inner leaflet. These domains form mesoscopic domains exhibiting liquid-ordered (lo) character.
In my talk, I will describe how a specific membrane receptor, the fibronectin-binding integrin receptor activates a signaling cascade which triggers actin polymerization and myosin activation to generate these nanodomains in a mechanically gated manner. This feature regulates crucial aspects of integrin receptor function, including cell spreading, migration, sensing of the mechanical stiffness of the matrix, as well as molecular orientation of the integrin receptor. The active composite membrane therefore acts to coordinate several effector cascades that are a prerequisite for cells to integrate chemical and physical cues presented to the animal cell, fine tuning receptor output.
Hosted by Professor Zheng Shi