Being one of the best characterized coat complexes, Coat Protein I (COPI) has been a model to elucidate fundamental mechanisms of how coat proteins drive the initial step of intracellular transport - the formation of transport carriers. W have been at the forefront in studying COPI transport, and propose four lines of investigation in further defining its mechanisms and physiology. First, in studying how key lipids act in fission, which is the process that completes vesicle formation, we have recently uncovered a new principle for how lipid geometry promotes membrane curvature to drive the late stage of COPI vesicle fission. Thus, we will determine whether this novel mechanism also operates in early fission. We will also determine whether the key factors that we have identified thus far to act in COPI vesicle fission will allow us to reconstitute this process using purified components. Second, we have recently discovered that COPI generates not only vesicles but also tubules. Whereas COPI vesicles act in retrograde Golgi transport, COPI tubules act in anterograde Golgi transport. Mechanistically, we have further elucidated that cdc42 promotes COPI tubule formation through an intrinsic ability to generate membrane curvature. Thus, we will seek a molecular understanding of this novel role. We will also explore how other Rho family members act in bidirectional COPI transport by targeting the two major functions of COPI - carrier formation and the sorting of cargoes into transport carriers. Third, we note that the KDEL receptor has also been found to regulate bidirectional Golgi transport, which has been elucidated recently to involve signaling through G proteins. However, as the KDEL receptor does not possess structural features typical of G protein-coupled receptors, we will elucidate how it couples ligand binding with recruitment of G proteins. Fourth, we have recently found that glyceraldehyde-3- phosphate dehydrogenase (GAPDH) inhibits COPI transport. As evidence suggests that it targets COPI vesicle fission, we will determine how this is achieved. Additional evidence suggests that the inhibition of COPI transport by GAPDH acts in energy balance. Thus, we will also further elucidate how GAPDH achieves this role. We anticipate that the completion of these four aims will advance a fundamental understanding of how COPI acts to generate transport carriers, as well shed new insights into the physiology of this transport. Moreover, as intracellular transport is a basic cellular process that underlies physiology and pathologic states, our studies will contribute to a better understanding of disease mechanisms.

Public Health Relevance

We study how proteins and membranes are transported in the cell, known as intracellular transport. We have been focusing on the initial step of this process that involves the generation of transport carriers. As intracellular transport is a fundamental cellular process that underlies physiology and pathologic states, our studies will contribute to a better understanding of disease mechanisms.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Method to Extend Research in Time (MERIT) Award (R37)
Project #
3R37GM058615-14S1
Application #
9322096
Study Section
Program Officer
Ainsztein, Alexandra M
Project Start
2001-02-01
Project End
2020-11-30
Budget Start
2015-12-01
Budget End
2016-11-30
Support Year
14
Fiscal Year
2016
Total Cost
$250,000
Indirect Cost
Name
Brigham and Women's Hospital
Department
Type
DUNS #
030811269
City
Boston
State
MA
Country
United States
Zip Code
02115
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Farhan, Hesso; Hsu, Victor W (2016) Cdc42 and Cellular Polarity: Emerging Roles at the Golgi. Trends Cell Biol 26:241-248
Bai, Ming; Gad, Helge; Turacchio, Gabriele et al. (2011) ARFGAP1 promotes AP-2-dependent endocytosis. Nat Cell Biol 13:559-67
Yang, Jia-Shu; Valente, Carmen; Polishchuk, Roman S et al. (2011) COPI acts in both vesicular and tubular transport. Nat Cell Biol 13:996-1003