Eukaryotic cells utilize small membrane-bound vesicles to transport cargo between subcellular organelles, and to the plasma membrane for secretion. The proper function and specificity of the vesicular transport and membrane fusion processes are crucial for maintenance of cellular integrity, growth, cellular movement and secretory events such as hormone release and neurotransmission. Vesicle transport and fusion at the plasma membrane require many essential proteins, including the SNARE proteins and Sec1p that are involved in the membrane fusion process, the Rab and Rho GTPases, and a large complex called the exocyst. The exocyst complex has been implicated in a number of different functions: selection of the site of exocytosis;physical tethering of secretory vesicles to these sites;communicating with cytoskeletal and cell cycle proteins;and regulating the specificity and assembly of the SNARE proteins. None of these are well understood at the molecular level.
Our aim i s to combine biochemical and biophysical techniques with genetics and cell biological methods in order to understand the molecular functions of the exocyst complex. We have chosen to study the exocyst proteins from the model organism Saccharomyces cerevisiae so as to take advantage of the wealth of genetic and cell biological techniques available. To accomplish this goal, we are i) investigating the protein- protein interactions within the exocyst complex through biochemical and biophysical studies in vitro and analyzing the function of the exocyst in vivo through characterization of specific mutants;(ii) characterizing the role of the exocyst in SNARE complex assembly;and (iii) identifying and characterizing several novel regulators of the exocyst and SNARE complex assembly. Because these proteins are conserved from yeast to human neurons, this research will advance our knowledge of how secretion and growth are regulated in all eukaryotic cells.

Public Health Relevance

Life depends upon proper cellular growth and development, from simple processes such as cell growth and division of unicellular eukaryotes, to very complicated interactions between the neurons in the brain. Cellular growth, development, movement and communication absolutely require proper vesicle targeting and membrane fusion. An essential component of these fundamental cell biological processes is the exocyst complex, which is conserved from yeast to man. Our studies of the exocyst and its regulation of the membrane fusion proteins will lead to a molecular understanding of the function of the yeast exocyst complex. In addition, our research will also lead to the development of many constructs, reagents and ideas that will be valuable tools for studying how the exocyst complex regulates secretion in all eukaryotic cells.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM068803-08
Application #
8286228
Study Section
Membrane Biology and Protein Processing (MBPP)
Program Officer
Ainsztein, Alexandra M
Project Start
2005-07-01
Project End
2014-06-30
Budget Start
2012-07-01
Budget End
2013-06-30
Support Year
8
Fiscal Year
2012
Total Cost
$341,163
Indirect Cost
$133,769
Name
University of Massachusetts Medical School Worcester
Department
Biochemistry
Type
Schools of Medicine
DUNS #
603847393
City
Worcester
State
MA
Country
United States
Zip Code
01655
Heider, Margaret R; Munson, Mary (2012) Exorcising the exocyst complex. Traffic 13:898-907
Morgera, Francesca; Sallah, Margaret R; Dubuke, Michelle L et al. (2012) Regulation of exocytosis by the exocyst subunit Sec6 and the SM protein Sec1. Mol Biol Cell 23:337-46
Jin, Yui; Sultana, Azmiri; Gandhi, Pallavi et al. (2011) Myosin V transports secretory vesicles via a Rab GTPase cascade and interaction with the exocyst complex. Dev Cell 21:1156-70
Redfern, Roberta E; Daou, Marie-Claire; Li, Li et al. (2010) A mutant form of PTEN linked to autism. Protein Sci 19:1948-56
MacDonald, Chris; Munson, Mary; Bryant, Nia J (2010) Autoinhibition of SNARE complex assembly by a conformational switch represents a conserved feature of syntaxins. Biochem Soc Trans 38:209-12
Furgason, Melonnie L M; MacDonald, Chris; Shanks, Scott G et al. (2009) The N-terminal peptide of the syntaxin Tlg2p modulates binding of its closed conformation to Vps45p. Proc Natl Acad Sci U S A 106:14303-8
Struthers, Marion S; Shanks, Scott G; MacDonald, Chris et al. (2009) Functional homology of mammalian syntaxin 16 and yeast Tlg2p reveals a conserved regulatory mechanism. J Cell Sci 122:2292-9
Croteau, Nicole J; Furgason, Melonnie L M; Devos, Damien et al. (2009) Conservation of helical bundle structure between the exocyst subunits. PLoS One 4:e4443
Songer, Jennifer A; Munson, Mary (2009) Sec6p anchors the assembled exocyst complex at sites of secretion. Mol Biol Cell 20:973-82
Munson, Mary (2009) Tip20p reaches out to Dsl1p to tether membranes. Nat Struct Mol Biol 16:100-2

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