Our goal is to elucidate the physical and molecular basis of homeostasis and misfolded protein stress in the endoplasmic reticulum (ER). Correct folding and quality control of secretory proteins by ER chaperones is essential for the viability of cells and organisms. Failure to correctly fold proteins results in loss of protein function, can activate the Unfolded Protein Response (UPR), and stimulate apoptotic death. Whether chaperones are sufficiently available for nascent or misfolded proteins under different environmental conditions is critical to understanding chaperone function. The ER chaperone network at steady state could be buffered with redundancy and an excess of chaperones or the network could be operating at the edge of protein folding capacity. The nature of the ER chaperone network has deep implications for how the ER senses and copes with misfolded protein stress. A system operating at capacity leaves little room for error, will have an explicit threshold for stress, and is likely to exhibit biphasic extremes. In contrast, stress and homeostasis could exist as a gradient of states in a buffered and redundant system. Small perturbations in folding requirements could be sensed and responded to, without upsetting the global folding environment. We hypothesize that the complexity and buffering capacity of the ER chaperone network regulates activation of ER stress pathways and maintenance of ER homeostasis. Chaperone network complexity will depend on the distribution, dynamics, organization, and occupancy of lumenal ER chaperones. While genetics and test-tube biochemistry have helped define the folding activities of chaperones, it remains poorly understood how ER chaperones encounter and interact with their substrates in cells in real time. We will employ biochemical, pharmacologic, and quantitative single cell fluorescence microscopy methods to establish a model of the ER chaperone network with exquisite spatio-temporal resolution. Our biophysical systems approach will define the hierarchy of the ER chaperone network during homeostasis and misfolded protein stress.

Public Health Relevance

The processes of correct secretory protein folding and quality control are vital for cell viability and human health. We are studying, at the cellular level, the mechanisms that maintain and regulate the secretory protein folding environment.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM086530-01
Application #
7566786
Study Section
Membrane Biology and Protein Processing (MBPP)
Program Officer
Shapiro, Bert I
Project Start
2009-09-14
Project End
2011-08-31
Budget Start
2009-09-14
Budget End
2010-08-31
Support Year
1
Fiscal Year
2009
Total Cost
$315,400
Indirect Cost
Name
Albert Einstein College of Medicine
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
110521739
City
Bronx
State
NY
Country
United States
Zip Code
10461
Ordóñez, Adriana; Snapp, Erik L; Tan, Lu et al. (2013) Endoplasmic reticulum polymers impair luminal protein mobility and sensitize to cellular stress in alpha1-antitrypsin deficiency. Hepatology 57:2049-60
Lajoie, Patrick; Snapp, Erik Lee (2013) Detecting soluble polyQ oligomers and investigating their impact on living cells using split-GFP. Methods Mol Biol 1017:229-39
Costantini, Lindsey M; Subach, Oksana M; Jaureguiberry-bravo, Matias et al. (2013) Cysteineless non-glycosylated monomeric blue fluorescent protein, secBFP2, for studies in the eukaryotic secretory pathway. Biochem Biophys Res Commun 430:1114-9
Costantini, Lindsey M; Snapp, Erik Lee (2013) Fluorescent proteins in cellular organelles: serious pitfalls and some solutions. DNA Cell Biol 32:622-7
Guo, Feng; Snapp, Erik L (2013) ERdj3 regulates BiP occupancy in living cells. J Cell Sci 126:1429-39
Haataja, Leena; Snapp, Erik; Wright, Jordan et al. (2013) Proinsulin intermolecular interactions during secretory trafficking in pancreatic ? cells. J Biol Chem 288:1896-906
Windsor, Miriam; Hawes, Philippa; Monaghan, Paul et al. (2012) Mechanism of collapse of endoplasmic reticulum cisternae during African swine fever virus infection. Traffic 13:30-42
Costantini, Lindsey M; Fossati, Matteo; Francolini, Maura et al. (2012) Assessing the tendency of fluorescent proteins to oligomerize under physiologic conditions. Traffic 13:643-9
Kung, Leslie F; Pagant, Silvere; Futai, Eugene et al. (2012) Sec24p and Sec16p cooperate to regulate the GTP cycle of the COPII coat. EMBO J 31:1014-27
Lajoie, Patrick; Moir, Robyn D; Willis, Ian M et al. (2012) Kar2p availability defines distinct forms of endoplasmic reticulum stress in living cells. Mol Biol Cell 23:955-64

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