The fidelity of the protein maturation steps in the endoplasmic reticulum (ER) is monitored by a quality control process that interrogates the structural integrity of the protein byproducts, and allows properly folded proteins to pass further through the secretory pathway. In contrast, non-native proteins are targeted for ER retention so that the aberration can be repaired, or if irreparable, selected for degradation and the recycling of components. A well-organized network of macromolecular complexes controls the processes of the ER. The carbohydrate binding (or lectin) chaperones, calnexin and calreticulin, direct the folding and trafficking of secretory pathway cargo by selectively binding to monoglucosylated side chains on maturing proteins in a region-specific manner. These chaperones can control the trajectory of the folding reaction and the flow of proteins through the secretory pathway. Therefore, the proper maturation and flux of the enormously diverse range of proteins that passage through the ER is in large part controlled by their glucosylation state. How these critical tags are added in the natural setting of the ER is an outstanding question that is currently poorly understood. The glucosylation status of ER-trafficked proteins is controlled by uridine diphosphate-glucose (UDP-Glc): glycoprotein glucosyltransferase 1 (UGGT1), which selectively modifies unglucosylated immature and non-native clients to support persistent chaperone binding and ER retention. Our main hypothesis is that UGGT1 serves as the central quality control gatekeeper that controls folding and the passage of thousands of substrates in the mammalian secretory pathway. Although UGGT1 has been studied extensively in isolation using purified and engineered components, little is known about it, and its homologue (UGGT2), activity in live cells. The focus of this proposal is to understand the mechanism of action and the roles of the UGGT proteins in their natural environment, the ER lumen. The long-term goal of this project is to understand the mechanism by which the quality control system aids the folding of complex proteins and evaluates the fidelity of the maturation process to regulate trafficking through the secretory pathway. The studies proposed in three aims will provide a deeper understanding of how the UGGTs select cargo for modification and how they control their flux through the secretory pathway (aim 1). These studies will include how clients are extracted from the lectin chaperone binding cycle and selected for destruction (aim 2), and how the quality control machinery is organized within the ER to maintain cellular homeostasis (aim 3).

Public Health Relevance

Successful completion of this project will lead to a better understanding of the fundamental mechanism of protein quality control, and have a potential impact on the development of therapeutic strategies directed towards the growing number of conformational diseases.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Cubano, Luis Angel
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Massachusetts Amherst
Schools of Arts and Sciences
United States
Zip Code
Lamriben, Lydia; Oster, Michela E; Tamura, Taku et al. (2018) EDEM1's mannosidase-like domain binds ERAD client proteins in a redox-sensitive manner and possesses catalytic activity. J Biol Chem 293:13932-13945
Krishnan, Beena; Hedstrom, Lizbeth; Hebert, Daniel N et al. (2017) Expression and Purification of Active Recombinant Human Alpha-1 Antitrypsin (AAT) from Escherichia coli. Methods Mol Biol 1639:195-209
Braakman, Ineke; Lamriben, Lydia; van Zadelhoff, Guus et al. (2017) Analysis of Disulfide Bond Formation. Curr Protoc Protein Sci 90:14.1.1-14.1.21
Lamriben, Lydia; Graham, Jill B; Adams, Benjamin M et al. (2016) N-Glycan-based ER Molecular Chaperone and Protein Quality Control System: The Calnexin Binding Cycle. Traffic 17:308-26
Hebert, Daniel N; Clerico, Eugenia M; Gierasch, Lila M (2016) Division of Labor: ER-Resident BiP Co-Chaperones Match Substrates to Fates Based on Specific Binding Sequences. Mol Cell 63:721-3
Chandrasekhar, Kshama; Ke, Haiping; Wang, Ning et al. (2016) Cellular folding pathway of a metastable serpin. Proc Natl Acad Sci U S A 113:6484-9
Tannous, Abla; Pisoni, Giorgia Brambilla; Hebert, Daniel N et al. (2015) N-linked sugar-regulated protein folding and quality control in the ER. Semin Cell Dev Biol 41:79-89
Tannous, Abla; Patel, Nishant; Tamura, Taku et al. (2015) Reglucosylation by UDP-glucose:glycoprotein glucosyltransferase 1 delays glycoprotein secretion but not degradation. Mol Biol Cell 26:390-405
Sunryd, Johan C; Cheon, Banyoon; Graham, Jill B et al. (2014) TMTC1 and TMTC2 are novel endoplasmic reticulum tetratricopeptide repeat-containing adapter proteins involved in calcium homeostasis. J Biol Chem 289:16085-99
Guiliano, David B; Fussell, Helen; Lenart, Izabela et al. (2014) Endoplasmic reticulum degradation-enhancing ?-mannosidase-like protein 1 targets misfolded HLA-B27 dimers for endoplasmic reticulum-associated degradation. Arthritis Rheumatol 66:2976-88

Showing the most recent 10 out of 20 publications