Susan Ferro-Novick studies how the directionality and specificity of vesicle traffic between the endoplasmic reticulum and Golgi are achieved and the role that the GTPase Rab1 plays in these events and in autophagy. Her laboratory also studies the structure and inheritance of the endoplasmic reticulum.
Role of Trs85 in Autophagy
Role of a Ras-Like GTPase in Autophagy
Rabs are molecular switches that are active in their GTP-bound form and inactive when bound to GDP. The TRAPP complexes are multimeric guanine nucleotide exchange factors (GEFs) that activate the GTPase Rab1. A focus of our studies is to understand the role of Rab1, which has been implicated in neurodegenerative diseases such as Parkinson’s. TRAPP requires four subunits (Bet3, Bet5, Trs23, and Trs31) for its GEF activity. How each of these subunits contributes to this activity has been defined. Recently, the TRAPPIII complex was implicated in autophagy, a catabolic process that targets proteins and organelles for degradation.
Autophagy, a cellular self-digestion event conserved from yeast to humans, leads to the degradation of organelles and long-lived proteins. More than 20 genes (called ATG) required for this catabolic process have been identified. During autophagy, cytoplasm and organelles are sequestered within a compartment that is referred to as the autophagosome. Fusion of the autophagosome with lysosomes, a compartment that contains hydrolases, leads to the degradation of its contents. Autophagic dysfunction has been associated with cancer and neurodegenerative diseases. Thus, cellular self-digestion is important for fighting disease.
One possible project is to analyze TRAPPIII, a novel complex that is required for autophagy in mammalian cells. We are currently localizing this complex by fluorescence microscopy and characterizing its subunits in 3T3 cells. Another project is to identify the residues in the TRAPPIII complex that are important for targeting it to the autophagy pathway. This project will be done in yeast. The gene encoding the Trs85p subunit, which targets TRAPPIII to the autophagy pathway, will be mutagenized, and residues that are important for localization will be identified. The mutations will be made on a plasmid harboring the TRS85 gene fused to GFP, and the resulting mutants will be screened for the mislocalization of Trs85p-GFP.