Eukaryotic cells are defined by the membrane bound organelles that sub-compartmentalize specialized biochemical reactions required for life.  The membrane of these organelles has a unique composition that is required to regulate both protein recruitment and function.  For this reason, much focus has been placed on the cellular mechanisms of transporting and distributing lipids for the formation these distinct membrane compartments.   The best known mechanism is the vesicular trafficking model.  However, this mechanism is energetically taxing and relatively slow for some cellular processes such as signaling between organelles.   An alternative and more rapid means of transporting lipids and small molecules between organelles is through the formation of membrane contact sites (MCS) where two distinct organelles are closely apposed (10-30 nm).

First described some 50 years ago, only recently has significant progress been made in our understanding of MCS.  Recent studies have demonstrated that MCS are found between many organelles and form both transient and long-lived connections that play a critical role in maintaining cellular homeostasis.  MCS sites allow the movement of lipids such as ceramide, cholesterol and phosphatidylinositol against a concentration gradient to establish a polarized lipid distribution between the different sub-cellular compartments. These differential distributions of lipids are essential not only for the distinction of different organelles but for their function.

In this course, we will explore current literature on the mechanisms of MCS formation, the nature of small molecule exchange between organelles, and its contribution to cell homeostasis and viability. We will also examine how some pathogens can commandeer MCS for their own propagation.  Limitations of current approaches and novel methodologies to address MCS function will also be addressed.