Study of protein misfolding associated with Cystic Fibrosis, Hypogonadism, Immune Deficiency, and Neurodegenerative disease by the Cyr group is revealing mechanisms for protein triage that are essential for organismal viability. This proposal focuses on understanding quality control (QC) of membrane proteins (MP) in the endoplasmic reticulum (ER). Approximately 30% of total protein synthesis occurs in the ER with defects in MP biogenesis resulting from natural inefficiencies in folding, missense mutations, and ER-stress. ABC-Transporters, P-Type ATPases and G-protein coupled receptors contain very large cytoplasmic domains, so their folding requires coordinated action of ER-associated and cytosol molecular chaperones. We find that misfolded forms of the same MP accumulate in globally misfolded, partially misfolded and aggregated states, which necessitates employment of conformation specific triage mechanisms. The ER- transmembrane Hsp40 JB12 is identified as a triage factor recruits Hsp70 to the cytoplasmic face of the ER for it to mediate the delivery of globally misfolded MPs to ERAD machinery. Remarkably, JB12/Hsp70 senses accumulation of partially folded and ERAD-resistant MPs to initiate a site-specific induction of ERQC- autophagy for their disposal. Function of JB12/Hsp70 in ERQC is critical because the sequestration of JB12 by pools of aggregated membrane proteins leads to rapid induction of ER-stress induced apoptosis. The proposed studies will identify new mechanisms for triage of MPs and define nodes for crosstalk between the Hsp70 system, ERAD machinery, and the autophagy pathway. The study design incorporates use of model cells systems and cultures of primary lung cells from Cystic Fibrosis patients. This is approach permits the translation of basic finding to uncover mechanisms for protein homeostasis in patients with a terminal lung disease.

Public Health Relevance

Membrane Protein misfolding is causal for Cystic Fibrosis and Neurodegeneration. This study is identifying novel Hsp70 and Hsp40 proteins the meditate cross talk between ER quality control and autophagy machinery in degradation of mutant channels. Aspects of protein homeostasis in disease states are being uncovered.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Membrane Biology and Protein Processing Study Section (MBPP)
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Gindhart, Joseph G
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University of North Carolina Chapel Hill
Schools of Medicine
Chapel Hill
United States
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Sopha, Pattarawut; Ren, Hong Yu; Grove, Diane E et al. (2017) Endoplasmic reticulum stress-induced degradation of DNAJB12 stimulates BOK accumulation and primes cancer cells for apoptosis. J Biol Chem 292:11792-11803
Cheng, Zhaokang; Zhu, Qiang; Dee, Rachel et al. (2017) Focal Adhesion Kinase-mediated Phosphorylation of Beclin1 Protein Suppresses Cardiomyocyte Autophagy and Initiates Hypertrophic Growth. J Biol Chem 292:2065-2079
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Wolfe, Katie J; Ren, Hong Yu; Trepte, Philipp et al. (2014) Polyglutamine-rich suppressors of huntingtin toxicity act upstream of Hsp70 and Sti1 in spatial quality control of amyloid-like proteins. PLoS One 9:e95914
Houck, Scott A; Ren, Hong Yu; Madden, Victoria J et al. (2014) Quality control autophagy degrades soluble ERAD-resistant conformers of the misfolded membrane protein GnRHR. Mol Cell 54:166-179
Suzuki, Shingo; Shuto, Tsuyoshi; Sato, Takashi et al. (2014) Inhibition of post-translational N-glycosylation by HRD1 that controls the fate of ABCG5/8 transporter. Sci Rep 4:4258
Ren, Hong Yu; Grove, Diane E; De La Rosa, Oxana et al. (2013) VX-809 corrects folding defects in cystic fibrosis transmembrane conductance regulator protein through action on membrane-spanning domain 1. Mol Biol Cell 24:3016-24

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