Overview

Simons begins by explaining that cholesterol and sphingolipids are made in the ER and the Golgi complex, respectively and then transported to various membranes in the cell. This sorting leads to an increased concentration of cholesterol and sphingolipids in the plasma membrane relative to other membranes. In the Golgi cholesterol and sphingolipids tend to cluster together to form lipid rafts for transport to the plasma membrane. Since certain proteins associate with cholesterol and sphingolipids, this lipid sorting directs the movement of proteins within the cell. In the second part of his talk, Simons describes mechanisms by which small nanoscale rafts can coalesce to form larger stabilized rafts that function in different cellular processes e.g. signal transduction, membrane trafficking and cell polarization. He also describes how processes such as palmitoylation and GPI-anchoring regulate the association of proteins with rafts. In Part 3, Simons demonstrates how proteins and glycolipids segregate to the apical domain in epithelial cells to support cell polarization.

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