Golgi Membrane Compartmentalization: Biophysical Aspects and Physiological Implications

Abstract

The Golgi complex is the central organelle of the secretory pathway, where proteins are sequentially glycosylated and sorted out to be transported to their final cellular destinations. Although much is known about how the Golgi complex works, there is still a large debate in the field about some of its essential features. Interestingly, it is still not clear how different secretory proteins are transported along the Golgi stack or how membrane domains regulate intra-Golgi transport by laterally segregating secretory proteins from Golgi resident glycosylating enzymes.Here I will focus on the biophysical and molecular characterization of such membrane domains as well as their role in protein glycosylation and protein transport at the Golgi membranes. More specifically, I will present experimental evidence of the role that the structural lipid sphingomyelin plays on the organization of functional enzymatic domains and also for the biogenesis of transport carriers at the Golgi membranes. I will also discuss our findings on transmembrane protein sorting at the Golgi complex mediated by the membrane biophysical properties.Finally I would like to stress out the idea that cells do not only organize biochemical reactions using three-dimensional compartmentalization in the form of membrane-bound organelles (such as the Golgi complex itself), but they also use a more subtle and dynamic two-dimensional organization mechanism, which happens to be essential for the proper functioning of cell membranes.