Membrane proteins comprise over 30% of the proteins encoded by the genome, and their efficient and accurate localization is essential for the structure and function of all cells. Compared to the well-studied co-translational protein targeting pathway, post- translational membrane protein targeting poses additional challenges due to the presence of highly hydrophobic transmembrane domains on the substrate protein. Our general goal is to use the Guided Entry of Tail-anchored protein (GET) pathway as a paradigm to understand the molecular mechanism of post-translational membrane protein targeting. Our specific goals are to understand the physical and functional coupling of the GET machinery with the cellular chaperone network, and to establish the roles of the latter in the conformational maintenance and triage of newly synthesized membrane proteins. In addition, we aim to decipher the molecular mechanisms by which targeting complexes containing tail anchored protein substrates are captured, remodeled and inserted by the receptor complex at the ER membrane. These studies will establish a comprehensive, high-resolution molecular model for this conserved and essential cellular pathway. Moreover, the lessons from the GET pathway will establish new roles and mechanisms for the cellular chaperone network, and suggest generalizable principles for ensuring the efficiency and fidelity of membrane protein localization and minimizing protein homeostasis stress during these processes. The proposed research is of a most basic nature, and will contribute profoundly to our general understanding of physiology and pathology of living cells at the molecular level. !

Public Health Relevance

Membrane proteins impart essential functionality to the cellular membrane, and their proper localization is essential for all cells. This proposal aims to understand the molecular mechanisms by which an essential class of membrane proteins is efficiently and accurately delivered to the correct cellular membrane without perturbing protein homeostasis in the cell. Failures in this process cause impaired cellular function in fungi and embryonic lethality in mammals. The proposed studies will significantly advance our understanding of the mechanism of membrane protein biogenesis and homeostasis within the cell, and contribute to our general understanding of physiology and pathology of eukaryotic cells at a molecular level.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM107368-05
Application #
9600585
Study Section
Nuclear and Cytoplasmic Structure/Function and Dynamics Study Section (NCSD)
Program Officer
Flicker, Paula F
Project Start
2014-08-01
Project End
2022-07-31
Budget Start
2018-09-15
Budget End
2019-07-31
Support Year
5
Fiscal Year
2018
Total Cost
Indirect Cost
Name
California Institute of Technology
Department
Type
Schools of Arts and Sciences
DUNS #
009584210
City
Pasadena
State
CA
Country
United States
Zip Code
91125
Cho, Hyunju; Shan, Shu-Ou (2018) Substrate relay in an Hsp70-cochaperone cascade safeguards tail-anchored membrane protein targeting. EMBO J 37:
Cho, Hyunju; Chio, Un Seng; Shan, Shu-Ou (2018) In vitro Assays for Targeting and Insertion of Tail-Anchored Proteins Into the ER Membrane. Curr Protoc Cell Biol 81:e63
Kobayashi, Kan; Jomaa, Ahmad; Lee, Jae Ho et al. (2018) Structure of a prehandover mammalian ribosomal SRP·SRP receptor targeting complex. Science 360:323-327
Chio, Un Seng; Cho, Hyunju; Shan, Shu-Ou (2017) Mechanisms of Tail-Anchored Membrane Protein Targeting and Insertion. Annu Rev Cell Dev Biol 33:417-438
Chio, Un Seng; Chung, SangYoon; Weiss, Shimon et al. (2017) A protean clamp guides membrane targeting of tail-anchored proteins. Proc Natl Acad Sci U S A 114:E8585-E8594
Rao, Meera; Okreglak, Voytek; Chio, Un Seng et al. (2016) Multiple selection filters ensure accurate tail-anchored membrane protein targeting. Elife 5:
Shan, Shu-Ou (2016) ATPase and GTPase Tangos Drive Intracellular Protein Transport. Trends Biochem Sci 41:1050-1060
Gristick, Harry B; Rome, Michael E; Chartron, Justin W et al. (2015) Mechanism of Assembly of a Substrate Transfer Complex during Tail-anchored Protein Targeting. J Biol Chem 290:30006-17
Gristick, Harry B; Rao, Meera; Chartron, Justin W et al. (2014) Crystal structure of ATP-bound Get3-Get4-Get5 complex reveals regulation of Get3 by Get4. Nat Struct Mol Biol 21:437-42
Rome, Michael E; Chio, Un Seng; Rao, Meera et al. (2014) Differential gradients of interaction affinities drive efficient targeting and recycling in the GET pathway. Proc Natl Acad Sci U S A 111:E4929-35

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