The long term goal of this research is to determine the molecular basis of membrane traffic in mammalian cells. The focus is on mannose 6-phosphate receptors (MPRs) that deliver newly synthesized lysosomal enzymes from the Golgi to pre-lysosomes, and then return to the Golgi to pick up more cargo. Several recently discovered proteins are needed for MPR transport from late endosomes to the trans Golgi network: a cargo selection protein that recognizes the MPRs in late endosomes (TIP47), a pathway- specific SNARE complex for fusion of MPR-vesicles at the TGN, and two proteins that function in vesicle tethering at the Golgi (GCC185 and RhoBTB3). The goals of this application are (1) to define precisely, the distinct routes taken by cargoes that are transported from early endosomes back to the Golgi, with focus on MPRs in comparison with cholera toxin;(2) to carry out a genome-wide, automated siRNA screen for proteins needed for MPR recycling. The screen will make use of the fact that depletion of proteins needed for MPR recycling leads to dispersal of MPRs into peripherally localized cellular compartments. Computer software can detect this dispersal, permitting automated analysis of the effects of 22,000 siRNAs transfected into cultured cells. (3) Also proposed are experiments to further characterize two novel Rab9 effectors that are important for this trafficking pathway: RhoBTB3 and RUTBC1. In summary, these experiments open up entirely new areas of investigation in the area of MPR trafficking and will provide fundamental information regarding the mechanisms of receptor trafficking in human cells. The work has broad application to our understanding of a number of disease states including diabetes, cancer, heart disease and neurological disorders.
Membrane traffic is essential for our ability to both secrete and respond to insulin, to clear cholesterol from the bloodstream, and for cells of the immune system to kill pathogens. Defects in membrane traffic underlie a number of disease states and virus infection depends upon this process. By understanding the molecular events responsible for membrane traffic, we will be better able to intervene in a variety of disease states.
|Li, Jian; Pfeffer, Suzanne R (2016) Lysosomal membrane glycoproteins bind cholesterol and contribute to lysosomal cholesterol export. Elife 5:|
|Johnson, Tory A; Pfeffer, Suzanne R (2016) Ezetimibe-sensitive cholesterol uptake by NPC1L1 protein does not require endocytosis. Mol Biol Cell 27:1845-52|
|Cheung, Pak-Yan P; Pfeffer, Suzanne R (2016) Transport Vesicle Tethering at the Trans Golgi Network: Coiled Coil Proteins in Action. Front Cell Dev Biol 4:18|
|Li, Xiaochun; Saha, Piyali; Li, Jian et al. (2016) Clues to the mechanism of cholesterol transfer from the structure of NPC1 middle lumenal domain bound to NPC2. Proc Natl Acad Sci U S A 113:10079-84|
|Pfeffer, Suzanne R (2016) Lipoprotein secretion: It takes two to TANGO. J Cell Biol 213:297-9|
|Pfeffer, Suzanne R (2016) Clues to NPC1-mediated cholesterol export from lysosomes. Proc Natl Acad Sci U S A 113:7941-3|
|Cheung, Pak-yan Patricia; Limouse, Charles; Mabuchi, Hideo et al. (2015) Protein flexibility is required for vesicle tethering at the Golgi. Elife 4:|
|Li, Jian; Deffieu, Maika S; Lee, Peter L et al. (2015) Glycosylation inhibition reduces cholesterol accumulation in NPC1 protein-deficient cells. Proc Natl Acad Sci U S A 112:14876-81|
|Lee, Peter L; Ohlson, Maikke B; Pfeffer, Suzanne R (2015) Rab6 regulation of the kinesin family KIF1C motor domain contributes to Golgi tethering. Elife 4:|
|Nottingham, Ryan M; Pfeffer, Suzanne R (2015) Measuring Rab GTPase-activating protein (GAP) activity in live cells and extracts. Methods Mol Biol 1298:61-71|
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