Abstract: The surface of a eukaryotic cell interfaces with the external milieu constantly decoding signals in the form of chemical and physical cues, interpreted primarily by membrane receptors. These receptors are embedded in a plasma membrane that is templated by an active cortical actin meshwork. Active mechanics of actin filaments at the inner leaflet of the membrane orchestrate nanoclusters of membrane proteins and lipids. Nanoclusters of GPI-anchored proteins and glycolipids at the outer leaflet require long acyl chain containing moieties in each leaflet as well as cholesterol to link to the active cortical actin at the inner leaflet. A combination of active contractile stresses and transbilayer coupling drive the creation of active emulsions, mesoscale liquid ordered (lo) domains of GPI-anchored proteins and lipids. Force transducing signalling receptors such as extra-cellular matrix ligand-activated integrin receptors orchestrates the creation of these membrane domains by triggering the acto-myosin machinery and activating the mechano-transducer, Vinculin. This translates into a substrate encoded mechano-chemical signal in the form of a localised lo-domain. These domains serve to crucial aspects of integrin receptor function, including cell spreading, migration, and sensing mechanical stiffness of the matrix. The active actin-membrane composite membrane therefore behaves as a mechano-responsive medium, serving to integrate chemical and physical cues presented at the cell surface.

Biography: Professor Satyajit Mayor is a distinguished cell biologist. He has worked on various aspects of trafficking of molecules into and out of cells. Particularly noteworthy is his study of GPI-linked proteins, and the elucidation of nano-scale ‘rafts’ in cell membranes. His work has been recognised by several national and international awards, such as the Shanti Swarup Bhatnagar Award and the Infosys Prize. He has also been elected Foreign Associate of the US National Academy of Sciences.