Research Seminar by Dr ENRICH

Dr Carlos ENRICH (Department of Cell Biology, University of Barcelona, Barcelona, Spain) has given a research seminar on Tuesday , 26 April 2011 entitled:


"Physiological consequences of Annexin A6-induced alterations in cholesterol homeostasis: from membrane trafficking to signalling"


Date: Tuesday, 26 April 2011 Time: 11:00 AM Venue: Seminar Room 7, Laboratory Block, Faculty of Medicine Building, 21 Sassoon Road, Pokfulam, Hong Kong About the speaker:

Dr. Enrich finished his Bsc. in Biology at the University of Barcelona in 1977 and his Ph.D in Cell Biology at the University of Barcelona in 1983. After completion of his PhD, he worked with Prof. Dr. Carl G.Gahmberg at the department of Biochemistry, University of Helsinki in 1983. From 1986 to 1987, he worked with Dr. W. Howard Evans at the National Institute for Medical Research in London and from 1992 to 1993 he worked with Drs. Richard J. Havel and Keith E. Mostov at the Cardiovascular Research Institute of the University of California, San Francisco (UCSF). In 2005 and 2006, Dr. Enrich worked with Drs. Thomas Grewal and Katharina Gaus of the University of New South Wales in Sydney, Australia. Since October 1997, Dr. Enrich is a full Professor of Cell Biology at the University of Barcelona. From 2002 to 2005, he also served as the Director of the department of Cell Biology and Pathology at the University of Barcelona Faculty of Medicine.

Abstract:

Annexin A6 (AnxA6) belongs to a conserved family of Ca2+-dependent membrane-binding proteins. Like other annexins, the function of AnxA6 is linked to its ability to bind phospholipids in cellular membranes in a dynamic and reversible fashion, in particular during the regulation of endocytic and exocytic pathways. High amounts of AnxA6 sequester cholesterol in late endosomes, thereby lowering the levels of cholesterol in the Golgi and the plasma membrane. These AnxA6-dependent redistributions of cellular cholesterol pools give rise to reduced cytoplasmic phospholipase A2 (cPLA2) activity, retention of caveolin in the Golgi apparatus and a reduced number of caveolae at the cell surface. In addition to regulating cholesterol and caveolin distribution, AnxA6 acts as a scaffold/targeting protein for several signalling proteins, the best characterized being the Ca2+-dependent membrane targeting of p120GAP to downregulate Ras activity. AnxA6 also stimulates the Ca2+-inducible involvement of PKC in the regulation of H-Ras and possibly EGFR signal transduction pathways. The ability of AnxA6 to recruit regulators of the EGFR/Ras pathway is likely potentiated by AnxA6-induced actin remodelling. Accordingly, AnxA6 may function as an organizer of membrane domains (i) to modulate intracellular cholesterol homeostasis, (ii) to create a scaffold for the formation of multifactorial signaling complexes, and (iii) to regulate transient membrane-actin interactions during endocytic and exocytic transport.