Hsp70 and DNAJA2 limit CFTR levels through degradation

Chiaw, Patrick Kim; Hantouche, Christine; Wong, Michael; Matthes, Elizabeth; Robert, Renaud; Hanrahan, John W.; Shrier, Alvin; Young, Jason C.

doi:10.1371/journal.pone.0220984

Cited by 21 publications

(32 citation statements)

References 74 publications

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“…These misfolded ER clients, which are not suitable for ERAD must be cleared from the ER through the lysosome alternative by autophagic or non-autophagic pathways. It has been shown that Hsp70 chaperones have a dual function in protein degradation, as they can select misfolded proteins for either the general protein degradation pathways, the proteasome system, or the lysosome degradation machinery [ 33 , 34 , 45 , 46 , 47 , 48 , 57 , 58 ]. Our present data demonstrate that immature NKCC2 is recognized by STCH, a component of the Hsp70 system, and degraded by two different pathways that function in a complementary way to regulate NKCC2 turnover.…”

Section: Discussionmentioning

confidence: 99%

“…Among the members of 70 kDa heat shock proteins, Hsc70 (heat shock cognate protein, Hsp73/HSPA8) and Hsp70 (Hsp72/HSPA1A) have been extensively studied and have distinct biological functions despite their high sequence homology [ 33 , 34 , 53 ]. Consequently, the roles of Hsp70 and Hsc70 in the ERAD of several transmembrane proteins such CFTR, NCC, ENaC, and HERG have been thoroughly investigated [ 24 , 45 , 46 , 47 , 48 , 57 ]. Under cellular stress conditions, it is assumed in general that Hsc70 associates with newly synthesized misfolded proteins to induce their ER associated degradation by the proteasome.…”

Section: Discussionmentioning

confidence: 99%

“…Appropriately, one may reasonably postulate that Hsp70 works in concert, sequentially or simultaneously, with other NKCC2-binding proteins and ERAD components such as MAGE-D2 and Hsp40 to regulate the ER quality control and its associated protein degradation of the co-transporter. Indeed, it is well known that the function of Hsp70 in the ERAD pathway involves Hsp40 [ 33 , 57 , 58 ]. Most importantly, we previously provided evidence that MAGE-D2 protects the co-transporter against ER associated degradation and promotes its maturation and cell surface expression, an effect that is very likely to be mediated by Hsp40 [ 27 ].…”

Section: Discussionmentioning

confidence: 99%

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Differential Effects of STCH and Stress-Inducible Hsp70 on the Stability and Maturation of NKCC2

Bakhos-Douaihy

Seaayfan

Demaretz

et al. 2021

IJMS

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Mutations in the Na-K-2Cl co-transporter NKCC2 lead to type I Bartter syndrome, a life-threatening kidney disease. We previously showed that export from the ER constitutes the limiting step in NKCC2 maturation and cell surface expression. Yet, the molecular mechanisms involved in this process remain obscure. Here, we report the identification of chaperone stress 70 protein (STCH) and the stress-inducible heat shock protein 70 (Hsp70), as two novel binding partners of the ER-resident form of NKCC2. STCH knock-down increased total NKCC2 expression whereas Hsp70 knock-down or its inhibition by YM-01 had the opposite effect. Accordingly, overexpressing of STCH and Hsp70 exerted opposite actions on total protein abundance of NKCC2 and its folding mutants. Cycloheximide chase assay showed that in cells over-expressing STCH, NKCC2 stability and maturation are heavily impaired. In contrast to STCH, Hsp70 co-expression increased NKCC2 maturation. Interestingly, treatment by protein degradation inhibitors revealed that in addition to the proteasome, the ER associated degradation (ERAD) of NKCC2 mediated by STCH, involves also the ER-to-lysosome-associated degradation pathway. In summary, our data are consistent with STCH and Hsp70 having differential and antagonistic effects with regard to NKCC2 biogenesis. These findings may have an impact on our understanding and potential treatment of diseases related to aberrant NKCC2 trafficking and expression.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Differential Effects of STCH and Stress-Inducible Hsp70 on the Stability and Maturation of NKCC2

Bakhos-Douaihy

Seaayfan

Demaretz

et al. 2021

IJMS

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“…For example, DNAJB6 and DNAJA1 were recently shown to have opposing effects on the levels of cellular polyglutamine aggregates, meaning their cellular abundances alone modulate aggregate formation [162]. Moreover, the levels of co-chaperones DNAJA1 and DNAJA2 regulate CHIP/HSP70-mediated degradation of mutant CFTR: while both co-chaperones are needed for CFTR folding, increased levels of DNAJA2 promote degradation of CFTR [163]. Other studies show how inhibition of JDPs can regulate chaperone activities directly-a mechanism that can be used to treat chaperone-related diseases.…”

Section: Regulation Of Chaperone Activitymentioning

confidence: 99%

Co-Chaperones in Targeting and Delivery of Misfolded Proteins to the 26S Proteasome

et al. 2020

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Protein homeostasis (proteostasis) is essential for the cell and is maintained by a highly conserved protein quality control (PQC) system, which triages newly synthesized, mislocalized and misfolded proteins. The ubiquitin-proteasome system (UPS), molecular chaperones, and co-chaperones are vital PQC elements that work together to facilitate degradation of misfolded and toxic protein species through the 26S proteasome. However, the underlying mechanisms are complex and remain partly unclear. Here, we provide an overview of the current knowledge on the co-chaperones that directly take part in targeting and delivery of PQC substrates for degradation. While J-domain proteins (JDPs) target substrates for the heat shock protein 70 (HSP70) chaperones, nucleotide-exchange factors (NEFs) deliver HSP70-bound substrates to the proteasome. So far, three NEFs have been established in proteasomal delivery: HSP110 and the ubiquitin-like (UBL) domain proteins BAG-1 and BAG-6, the latter acting as a chaperone itself and carrying its substrates directly to the proteasome. A better understanding of the individual delivery pathways will improve our ability to regulate the triage, and thus regulate the fate of aberrant proteins involved in cell stress and disease, examples of which are given throughout the review.

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“…This activity of DJA2 is comparable to re-folding of the model substrate luciferase, such that DJA1 is unable to substitute 45,46 . Recent findings suggest that DJA2 also promotes CHIP-mediated ERAD of CFTR 47 . How these conflicting outcomes are determined remains largely unknown.…”

mentioning

confidence: 99%

Selective Binding of HSC70 and its Co-Chaperones to Structural Hotspots on CFTR

Baaklini

Gonçalves

Lukacs

et al. 2020

Sci Rep

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Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) channel cause cystic fibrosis. Chaperones, including HSC70, DNAJA1 and DNAJA2, play key roles in both the folding and degradation of wild-type and mutant CFTR at multiple cellular locations. DNAJA1 and HSC70 promote the folding of newly synthesized CFTR at the endoplasmic reticulum (ER), but are required for the rapid turnover of misfolded channel at the plasma membrane (PM). DNAJA2 and HSC70 are also involved in the ERassociated degradation (ERAD) of misfolded CFTR, while they assist the refolding of destabilized channel at the PM. These outcomes may depend on the binding of chaperones to specific sites within CFTR, which would be exposed in non-native states. A CFTR peptide library was used to identify binding sites for HSC70, DNAJA1 and DNAJA2, validated by competition and functional assays. Each chaperone had a distinct binding pattern, and sites were distributed between the surfaces of the CFTR cytosolic domains, and domain interfaces known to be important for channel assembly. The accessibility of sites to chaperones will depend on the degree of CFTR folding or unfolding. Different folded states may be recognized by unique combinations of HSC70, DNAJA1 and DNAJA2, leading to divergent biological effects. Autosomal recessive cystic fibrosis (CF) is one of the most common lethal genetic diseases in the North American and European populations 1. Typical outcomes include meconium ileus in newborns, pancreatic insufficiency, and recurrent lung infection due to bacterial colonization with uncontrolled inflammation, leading to the airway destruction and respiratory failure, the predominant cause of mortality in CF patients 2. CF is caused by mutations in the ABCC7 gene encoding the Cystic Fibrosis Transmembrane conductance Regulator (CFTR), a transmembrane channel that has a critical role in regulating transepithelial movement of water and electrolyte in epithelial cells. CFTR allows the flow of Cl − and HCO 3 − ions to maintain hydration, for example in lung airways. CF mutations in the channel render it dysfunctional or unstable. The most common mutation in CFTR is ΔF508, but many others are known 2,3. CFTR is a member of the ATP-binding cassette (ABC) transporter superfamily with the typical two transmembrane domains (TMD1 and TMD2), alternating with two cytosolic nucleotide-binding domains (NBD1 and NBD2) (Fig. 1a). Each TMD contains six transmembrane helices and two cytosolic loops (L1 and L2 in TMD1, L3 and L4 in TMD2). There is an additional N-terminal (NT) extension in the cytosol, and a unique regulatory (R) region lies between NBD1 and TMD2 (Fig. 1a) 3. Homology models and structural studies including recent high-resolution cryo-EM structures of the full-length channel, established the arrangement of its domains 4-7. The NT region packs onto the sides of L1 and L4, NBD1 is assembled onto the tips of L1 and L4, and NBD2 onto L2 and L3 4-7. In the unphosphorylated nucleotide-free state, the channel is closed at the extracellular si...

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Hsp70 and DNAJA2 limit CFTR levels through degradation

Cited by 21 publications

References 74 publications

Differential Effects of STCH and Stress-Inducible Hsp70 on the Stability and Maturation of NKCC2

Differential Effects of STCH and Stress-Inducible Hsp70 on the Stability and Maturation of NKCC2

Co-Chaperones in Targeting and Delivery of Misfolded Proteins to the 26S Proteasome

Selective Binding of HSC70 and its Co-Chaperones to Structural Hotspots on CFTR

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