9707583 Lemmon This is a Career Advancement Award for Women Scientists and Engineers. A major long-term goal of Dr. Lemmon's laboratory is to understand the function of clathrin-mediated vesicular transport and to identify and characterize the proteins involved in this pathway. Studies in her laboratory have taken advantage of the powerful molecular genetic methods available in yeast to analyze the function of clathrin. In the last several years, her studies of yeast clathrin have led to the identification of a number of additional gene products that may be involved in vesicular transport at late stages of the secretory / endocytic pathway. Two new classes of genes are being studied. The first group encodes homologues of subunits of the clathrin adaptor (AP) complexes. The adaptors are involved in the capture of specific membrane proteins into clathrin coated pits and they facilitate the assembly of clathrin onto membranes, which drives vesicle budding. There is evidence for up to four distinct AP complexes in yeast, yet the function of these adaptors is still not clear. The second group of genes was identified on the basis of their ability to rescue the inviability of lethal strains of clathrin heavy chain-deficient yeast. These genes are referred to as suppressors of clathrin deficiency (SCD genes). The five SCD genes encode two novel proteins, two that had been previously identified in yeast, and one that encodes a member of the widely distributed 14-3-3 protein family. Mutants and biochemical reagents have been developed that will enable Dr. Lemmon to further examine the function of these gene products and their role in clathrin-mediated transport pathways. However, her laboratory currently lacks the expertise to carry out an in depth investigation of the role of these proteins in endocytosis. Therefore, she has arranged to spend a sabbatical year in the laboratory of Dr. Howard Riezman at the Biozentrum of the University of Basel, Sw itzerland. Dr. Riezman's group has made many of the most significant advances in our understanding of endocytosis in yeast and has developed methods to study both the internalization and post-internalization steps of uptake from the cell surface. The goal of this sabbatical project is to combine the efforts of these two scientists and examine in detail the potential endocytic roles of the adaptor complexes and the Scd proteins. In addition, a more complete analysis of endocytosis in clathrin mutants will be performed. Studies to be carried out during this sabbatical will enable them to dissect the specific steps in the endocytic pathway requiring clathrin function. Endocytosis is a fundamental function of most eukaryotic cells. The group of proteins collectively known as clathrin is important for endocytosis of many nutrients and signal transducing receptors and for sorting or retention at the trans Golgi. This collaboration should provide new information on the machinery required for endocytosis and uncover new regulatory mechanisms in the endocytic pathway. Pursuing these studies during a sabbatical year in Dr. Riezman's laboratory will also allow the rapid development of the project and will enable Dr. Lemmon to acquire important expertise that is crucial for the continuing research in her own laboratory. ***
