The HSP70 co-chaperone DNAJC14 targets misfolded pendrin for unconventional protein secretion.

Jinsei Jung,Ikhyun Jun,Robert D Sampson,Heon Yung Gee,Jiyoon Kim,Jae Young Choi,Min Goo Lee,Shin Hye Roh

doi:10.1038/ncomms11386

Jinsei Jung, Ikhyun Jun + Show 6 more

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https://doi.org/10.1038/ncomms11386

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Abstract

Mutations in SLC26A4, which encodes pendrin, are responsible for hearing loss with an enlarged vestibular aqueduct and Pendred syndrome. The most prevalent mutation in East Asia is p.H723R (His723Arg), which leads to defects in protein folding and cell-surface expression. Here we show that H723R-pendrin can be rescued to the cell surface by an HSP70 co-chaperone DNAJC14-dependent unconventional trafficking pathway. Blockade of ER-to-Golgi transport or activation of ER stress signals induced Golgi-independent cell-surface expression of H723R-pendrin and restored its cell-surface Cl−/HCO3− exchange activity. Proteomic and short interfering RNA screenings with subsequent molecular analyses showed that Hsc70 and DNAJC14 are required for the unconventional trafficking of H723R-pendrin. Moreover, DNAJC14 upregulation was able to induce the unconventional cell-surface expression of H723R-pendrin. These results indicate that Hsc70 and DNAJC14 play central roles in ER stress-associated unconventional protein secretion and are potential therapeutic targets for diseases such as Pendred syndrome, which arise from transport defects of misfolded proteins.

Highlights

Mutations in SLC26A4, which encodes pendrin, are responsible for hearing loss with an enlarged vestibular aqueduct and Pendred syndrome
In the case of CFTR, the immature endoplasmic reticulum (ER) form of core-glycosylated protein can be unconventionally expressed on the cell surface by ER-to-Golgi blockade[17]
We examined whether a similar phenomenon exists with pendrin

Summary

Introduction

Mutations in SLC26A4, which encodes pendrin, are responsible for hearing loss with an enlarged vestibular aqueduct and Pendred syndrome. DNAJC14 upregulation was able to induce the unconventional cell-surface expression of H723R-pendrin These results indicate that Hsc[70] and DNAJC14 play central roles in ER stress-associated unconventional protein secretion and are potential therapeutic targets for diseases such as Pendred syndrome, which arise from transport defects of misfolded proteins. The HSP70 proteins are involved in protein folding and degradation and function in a myriad of biological processes, including protein–protein interaction and intracellular trafficking of various proteins[15,16] This multitude of roles is not reconciled with the simple activity of HSP70s in ATP-dependent substrate protein binding and release cycles. ER-to-Golgi blockade or activation of ER stress signals induced the plasma membrane expression of DF508-CFTR via a Golgi-bypass trafficking pathway and restored CFTR Cl À channel activity at the cell surface[17]. Golgi reassembly and stacking proteins (GRASPs) were identified as a cargo-recruiting factor in this unconventional transport of DF508-CFTR, the mechanisms underlying ER-toGolgi blockade or ER stress-associated unconventional protein secretion pathway are largely unknown

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