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Wang YJ, Di XJ, Zhang PP, Chen X, Williams MP, Han DY, Nashmi R, Henderson BJ, Moss FJ, Mu TW. Hsp47 promotes biogenesis of multi-subunit neuroreceptors in the endoplasmic reticulum. eLife 2024; 13:e84798. [PMID: 38963323 PMCID: PMC11257679 DOI: 10.7554/elife.84798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 05/21/2024] [Indexed: 07/05/2024] Open
Abstract
Protein homeostasis (proteostasis) deficiency is an important contributing factor to neurological and metabolic diseases. However, how the proteostasis network orchestrates the folding and assembly of multi-subunit membrane proteins is poorly understood. Previous proteomics studies identified Hsp47 (Gene: SERPINH1), a heat shock protein in the endoplasmic reticulum lumen, as the most enriched interacting chaperone for gamma-aminobutyric acid type A (GABAA) receptors. Here, we show that Hsp47 enhances the functional surface expression of GABAA receptors in rat neurons and human HEK293T cells. Furthermore, molecular mechanism study demonstrates that Hsp47 acts after BiP (Gene: HSPA5) and preferentially binds the folded conformation of GABAA receptors without inducing the unfolded protein response in HEK293T cells. Therefore, Hsp47 promotes the subunit-subunit interaction, the receptor assembly process, and the anterograde trafficking of GABAA receptors. Overexpressing Hsp47 is sufficient to correct the surface expression and function of epilepsy-associated GABAA receptor variants in HEK293T cells. Hsp47 also promotes the surface trafficking of other Cys-loop receptors, including nicotinic acetylcholine receptors and serotonin type 3 receptors in HEK293T cells. Therefore, in addition to its known function as a collagen chaperone, this work establishes that Hsp47 plays a critical and general role in the maturation of multi-subunit Cys-loop neuroreceptors.
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Affiliation(s)
- Ya-Juan Wang
- Department of Physiology and Biophysics, Case Western Reserve UniversityClevelandUnited States
| | - Xiao-Jing Di
- Department of Physiology and Biophysics, Case Western Reserve UniversityClevelandUnited States
| | - Pei-Pei Zhang
- Department of Physiology and Biophysics, Case Western Reserve UniversityClevelandUnited States
| | - Xi Chen
- Department of Physiology and Biophysics, Case Western Reserve UniversityClevelandUnited States
| | - Marnie P Williams
- Department of Physiology and Biophysics, Case Western Reserve UniversityClevelandUnited States
| | - Dong-Yun Han
- Department of Physiology and Biophysics, Case Western Reserve UniversityClevelandUnited States
| | - Raad Nashmi
- Department of Biology, University of VictoriaVictoriaCanada
| | - Brandon J Henderson
- Department of Biomedical Sciences, Marshall UniversityHuntingtonUnited States
| | - Fraser J Moss
- Department of Physiology and Biophysics, Case Western Reserve UniversityClevelandUnited States
| | - Ting-Wei Mu
- Department of Physiology and Biophysics, Case Western Reserve UniversityClevelandUnited States
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2
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Mann MJ, Melendez-Suchi C, Vorndran HE, Sukhoplyasova M, Flory AR, Irvine MC, Iyer AR, Guerriero CJ, Brodsky JL, Hendershot LM, Buck TM. Loss of Grp170 results in catastrophic disruption of endoplasmic reticulum function. Mol Biol Cell 2024; 35:ar59. [PMID: 38446639 PMCID: PMC11064666 DOI: 10.1091/mbc.e24-01-0012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 02/20/2024] [Accepted: 02/29/2024] [Indexed: 03/08/2024] Open
Abstract
GRP170 (Hyou1) is required for mouse embryonic development, and its ablation in kidney nephrons leads to renal failure. Unlike most chaperones, GRP170 is the lone member of its chaperone family in the ER lumen. However, the cellular requirement for GRP170, which both binds nonnative proteins and acts as nucleotide exchange factor for BiP, is poorly understood. Here, we report on the isolation of mouse embryonic fibroblasts obtained from mice in which LoxP sites were engineered in the Hyou1 loci (Hyou1LoxP/LoxP). A doxycycline-regulated Cre recombinase was stably introduced into these cells. Induction of Cre resulted in depletion of Grp170 protein which culminated in cell death. As Grp170 levels fell we observed a portion of BiP fractionating with insoluble material, increased binding of BiP to a client with a concomitant reduction in its turnover, and reduced solubility of an aggregation-prone BiP substrate. Consistent with disrupted BiP functions, we observed reactivation of BiP and induction of the unfolded protein response (UPR) in futile attempts to provide compensatory increases in ER chaperones and folding enzymes. Together, these results provide insights into the cellular consequences of controlled Grp170 loss and provide hypotheses as to why mutations in the Hyou1 locus are linked to human disease.
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Affiliation(s)
- Melissa J. Mann
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Chris Melendez-Suchi
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Hannah E. Vorndran
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Maria Sukhoplyasova
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Ashley R. Flory
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Mary Carson Irvine
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Anuradha R. Iyer
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | | | - Jeffrey L. Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Linda M. Hendershot
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Teresa M. Buck
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
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3
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Porter A, Vorndran HE, Marciszyn A, Mutchler SM, Subramanya AR, Kleyman TR, Hendershot LM, Brodsky JL, Buck TM. Excess dietary sodium partially restores salt and water homeostasis caused by loss of the endoplasmic reticulum molecular chaperone, GRP170, in the mouse nephron. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.13.575426. [PMID: 38260467 PMCID: PMC10802592 DOI: 10.1101/2024.01.13.575426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
The maintenance of fluid and electrolyte homeostasis by the kidney requires proper folding and trafficking of ion channels and transporters in kidney epithelia. Each of these processes requires a specific subset of a diverse class of proteins termed molecular chaperones. One such chaperone is GRP170, which is an Hsp70-like, endoplasmic reticulum (ER)-localized chaperone that plays roles in protein quality control and protein folding in the ER. We previously determined that loss of GRP170 in the mouse nephron leads to hypovolemia, electrolyte imbalance, and rapid weight loss. In addition, GRP170-deficient mice develop an AKI-like phenotype, typified by tubular injury, elevation of clinical kidney injury markers, and induction of the unfolded protein response (UPR). By using an inducible GRP170 knockout cellular model, we confirmed that GRP170 depletion induces the UPR, triggers an apoptotic response, and disrupts protein homeostasis. Based on these data, we hypothesized that UPR induction underlies hyponatremia and volume depletion in rodents, but that these and other phenotypes might be rectified by supplementation with high salt. To test this hypothesis, control and GRP170 tubule-specific knockout mice were provided with a diet containing 8% sodium chloride. We discovered that sodium supplementation improved electrolyte imbalance and reduced clinical kidney injury markers, but was unable to restore weight or tubule integrity. These results are consistent with UPR induction contributing to the kidney injury phenotype in the nephron-specific GR170 knockout model, and that the role of GRP170 in kidney epithelia is essential to both maintain electrolyte balance and cellular protein homeostasis.
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Affiliation(s)
- Aidan Porter
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
- Division of Pediatric Nephrology, University of Pittsburgh, Pittsburgh, PA
| | - Hannah E. Vorndran
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
| | - Allison Marciszyn
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA
| | - Stephanie M. Mutchler
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA
| | - Arohan R. Subramanya
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA
| | - Thomas R. Kleyman
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA
| | - Linda M. Hendershot
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Jeffrey L. Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
| | - Teresa M. Buck
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
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4
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Sukhoplyasova M, Keith AM, Perrault EM, Vorndran HE, Jordahl AS, Yates ME, Pastor A, Li Z, Freaney ML, Deshpande RA, Adams DB, Guerriero CJ, Shi S, Kleyman TR, Kashlan OB, Brodsky JL, Buck TM. Lhs1 dependent ERAD is determined by transmembrane domain context. Biochem J 2023; 480:1459-1473. [PMID: 37702403 PMCID: PMC11040695 DOI: 10.1042/bcj20230075] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 09/12/2023] [Accepted: 09/13/2023] [Indexed: 09/14/2023]
Abstract
Transmembrane proteins have unique requirements to fold and integrate into the endoplasmic reticulum (ER) membrane. Most notably, transmembrane proteins must fold in three separate environments: extracellular domains fold in the oxidizing environment of the ER lumen, transmembrane domains (TMDs) fold within the lipid bilayer, and cytosolic domains fold in the reducing environment of the cytosol. Moreover, each region is acted upon by a unique set of chaperones and monitored by components of the ER associated quality control machinery that identify misfolded domains in each compartment. One factor is the ER lumenal Hsp70-like chaperone, Lhs1. Our previous work established that Lhs1 is required for the degradation of the unassembled α-subunit of the epithelial sodium channel (αENaC), but not the homologous β- and γENaC subunits. However, assembly of the ENaC heterotrimer blocked the Lhs1-dependent ER associated degradation (ERAD) of the α-subunit, yet the characteristics that dictate the specificity of Lhs1-dependent ERAD substrates remained unclear. We now report that Lhs1-dependent substrates share a unique set of features. First, all Lhs1 substrates appear to be unglycosylated, and second they contain two TMDs. Each substrate also contains orphaned or unassembled TMDs. Additionally, interfering with inter-subunit assembly of the ENaC trimer results in Lhs1-dependent degradation of the entire complex. Finally, our work suggests that Lhs1 is required for a subset of ERAD substrates that also require the Hrd1 ubiquitin ligase. Together, these data provide hints as to the identities of as-yet unconfirmed substrates of Lhs1 and potentially of the Lhs1 homolog in mammals, GRP170.
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Affiliation(s)
- Maria Sukhoplyasova
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Abigail M. Keith
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Emma M. Perrault
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Hannah E. Vorndran
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Alexa S. Jordahl
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Megan E. Yates
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Ashutosh Pastor
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Zachary Li
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Michael L. Freaney
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Riddhi A. Deshpande
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - David B. Adams
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | | | - Shujie Shi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Thomas R. Kleyman
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA, U.S.A
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, U.S.A
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Ossama B. Kashlan
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Jeffrey L. Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Teresa M. Buck
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
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5
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Sun S, Li X, Mariappan M. Signal sequences encode information for protein folding in the endoplasmic reticulum. J Cell Biol 2023; 222:213733. [PMID: 36459117 PMCID: PMC9723807 DOI: 10.1083/jcb.202203070] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 09/22/2022] [Accepted: 10/26/2022] [Indexed: 12/05/2022] Open
Abstract
One-third of newly synthesized proteins in mammals are translocated into the endoplasmic reticulum (ER) through the Sec61 translocon. How protein translocation coordinates with chaperone availability in the ER to promote protein folding remains unclear. We find that marginally hydrophobic signal sequences and transmembrane domains cause transient retention at the Sec61 translocon and require the luminal BiP chaperone for efficient protein translocation. Using a substrate-trapping proteomic approach, we identify that nascent proteins bearing marginally hydrophobic signal sequences accumulate on the cytosolic side of the Sec61 translocon. Sec63 is co-translationally recruited to the translocation site and mediates BiP binding to incoming polypeptides. BiP binding not only releases translocationally paused nascent chains but also ensures protein folding in the ER. Increasing hydrophobicity of signal sequences bypasses Sec63/BiP-dependent translocation, but translocated proteins are prone to misfold and aggregate in the ER under limited BiP availability. Thus, the signal sequence-guided protein folding may explain why signal sequences are diverse and use multiple protein translocation pathways.
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Affiliation(s)
- Sha Sun
- Department of Cell Biology, Nanobiology Institute, Yale School of Medicine, Yale West Campus, West Haven, CT
| | - Xia Li
- Department of Cell Biology, Nanobiology Institute, Yale School of Medicine, Yale West Campus, West Haven, CT
| | - Malaiyalam Mariappan
- Department of Cell Biology, Nanobiology Institute, Yale School of Medicine, Yale West Campus, West Haven, CT
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6
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Wang YJ, Di XJ, Mu TW. Quantitative interactome proteomics identifies a proteostasis network for GABA A receptors. J Biol Chem 2022; 298:102423. [PMID: 36030824 PMCID: PMC9493394 DOI: 10.1016/j.jbc.2022.102423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 08/17/2022] [Accepted: 08/19/2022] [Indexed: 11/29/2022] Open
Abstract
Gamma-aminobutyric acid type A (GABAA) receptors are the primary inhibitory neurotransmitter-gated ion channels in the mammalian central nervous system. Maintenance of GABAA receptor protein homeostasis (proteostasis) in cells utilizing its interacting proteins is essential for the function of GABAA receptors. However, how the proteostasis network orchestrates GABAA receptor biogenesis in the endoplasmic reticulum is not well understood. Here, we employed a proteomics-based approach to systematically identify the interactomes of GABAA receptors. We carried out a quantitative immunoprecipitation-tandem mass spectrometry analysis utilizing stable isotope labeling by amino acids in cell culture. Furthermore, we performed comparative proteomics by using both WT α1 subunit and a misfolding-prone α1 subunit carrying the A322D variant as the bait proteins. We identified 125 interactors for WT α1-containing receptors, 105 proteins for α1(A322D)-containing receptors, and 54 overlapping proteins within these two interactomes. Our bioinformatics analysis identified potential GABAA receptor proteostasis network components, including chaperones, folding enzymes, trafficking factors, and degradation factors, and we assembled a model of their potential involvement in the cellular folding, degradation, and trafficking pathways for GABAA receptors. In addition, we verified endogenous interactions between α1 subunits and selected interactors by using coimmunoprecipitation in mouse brain homogenates. Moreover, we showed that TRIM21 (tripartite motif containing-21), an E3 ubiquitin ligase, positively regulated the degradation of misfolding-prone α1(A322D) subunits selectively. This study paves the way for understanding the molecular mechanisms as well as fine-tuning of GABAA receptor proteostasis to ameliorate related neurological diseases such as epilepsy.
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Affiliation(s)
- Ya-Juan Wang
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA; Center for Proteomics and Bioinformatics, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
| | - Xiao-Jing Di
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Ting-Wei Mu
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
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7
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Porter AW, Nguyen DN, Clayton DR, Ruiz WG, Mutchler SM, Ray EC, Marciszyn AL, Nkashama LJ, Subramanya AR, Gingras S, Kleyman TR, Apodaca G, Hendershot LM, Brodsky JL, Buck TM. The molecular chaperone GRP170 protects against ER stress and acute kidney injury in mice. JCI Insight 2022; 7:e151869. [PMID: 35104250 PMCID: PMC8983141 DOI: 10.1172/jci.insight.151869] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 01/28/2022] [Indexed: 01/26/2023] Open
Abstract
Molecular chaperones are responsible for maintaining cellular homeostasis, and one such chaperone, GRP170, is an endoplasmic reticulum (ER) resident that oversees both protein biogenesis and quality control. We previously discovered that GRP170 regulates the degradation and assembly of the epithelial sodium channel (ENaC), which reabsorbs sodium in the distal nephron and thereby regulates salt-water homeostasis and blood pressure. To define the role of GRP170 - and, more generally, molecular chaperones in kidney physiology - we developed an inducible, nephron-specific GRP170-KO mouse. Here, we show that GRP170 deficiency causes a dramatic phenotype: profound hypovolemia, hyperaldosteronemia, and dysregulation of ion homeostasis, all of which are associated with the loss of ENaC. Additionally, the GRP170-KO mouse exhibits hallmarks of acute kidney injury (AKI). We further demonstrate that the unfolded protein response (UPR) is activated in the GRP170-deficient mouse. Notably, the UPR is also activated in AKI when originating from various other etiologies, including ischemia, sepsis, glomerulonephritis, nephrotic syndrome, and transplant rejection. Our work establishes the central role of GRP170 in kidney homeostasis and directly links molecular chaperone function to kidney injury.
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Affiliation(s)
- Aidan W. Porter
- Department of Biological Sciences
- Department of Pediatrics, Nephrology Division
| | | | | | - Wily G. Ruiz
- Department of Medicine, Renal-Electrolyte Division
| | | | - Evan C. Ray
- Department of Medicine, Renal-Electrolyte Division
| | | | | | | | | | - Thomas R. Kleyman
- Department of Medicine, Renal-Electrolyte Division
- Department of Cell Biology, and
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | | | - Linda M. Hendershot
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, Tennessee, USA
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8
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Shi S, Buck TM, Nickerson AJ, Brodsky JL, Kleyman TR. Paraoxonase 2 is an ER chaperone that regulates the epithelial Na + channel. Am J Physiol Cell Physiol 2022; 322:C111-C121. [PMID: 34852210 PMCID: PMC8759969 DOI: 10.1152/ajpcell.00335.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The mammalian paraoxonases (PONs) have been linked to protection against oxidative stress. However, the physiological roles of members in this family (PON1, PON2, and PON3) are still being characterized. PON2 and PON3 are expressed in the aldosterone-sensitive distal nephron of the kidney and have been shown to negatively regulate expression of the epithelial sodium channel (ENaC), a trimeric ion channel that orchestrates salt and water homeostasis. To date, the nature of this phenomenon has not been explored. Therefore, to investigate the mechanism by which PON2 regulates ENaC, we expressed PON2 along with the ENaC subunits in fisher rat thyroid (FRT) cells, a system that is amenable to biochemical analyses of ENaC assembly and trafficking. We found that PON2 primarily resides in the endoplasmic reticulum (ER) in FRT cells, and its expression reduces the abundance of each ENaC subunit, reflecting enhanced subunit turnover. In contrast, no effect on the levels of mRNAs encoding the ENaC subunits was evident. Inhibition of lysosome function with chloroquine or NH4Cl did not alter the inhibitory effect of PON2 on ENaC expression. In contrast, PON2 accelerates ENaC degradation in a proteasome-dependent manner and acts before ENaC subunit ubiquitination. As a result of enhanced ENaC subunit ubiquitination and degradation, both channel surface expression and ENaC-mediated Na+ transport in FRT cells were reduced by PON2. Together, our data suggest that PON2 functions as an ER chaperone to monitor ENaC biogenesis and redirects the channel for ER-associated degradation.
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Affiliation(s)
- Shujie Shi
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Teresa M. Buck
- 2Deparment of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Andrew J. Nickerson
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Jeffrey L. Brodsky
- 2Deparment of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Thomas R. Kleyman
- 1Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania,3Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania,4Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
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9
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Kong KYE, Coelho JPL, Feige MJ, Khmelinskii A. Quality control of mislocalized and orphan proteins. Exp Cell Res 2021; 403:112617. [PMID: 33930402 DOI: 10.1016/j.yexcr.2021.112617] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 04/10/2021] [Accepted: 04/18/2021] [Indexed: 12/16/2022]
Abstract
A healthy and functional proteome is essential to cell physiology. However, this is constantly being challenged as most steps of protein metabolism are error-prone and changes in the physico-chemical environment can affect protein structure and function, thereby disrupting proteome homeostasis. Among a variety of potential mistakes, proteins can be targeted to incorrect compartments or subunits of protein complexes may fail to assemble properly with their partners, resulting in the formation of mislocalized and orphan proteins, respectively. Quality control systems are in place to handle these aberrant proteins, and to minimize their detrimental impact on cellular functions. Here, we discuss recent findings on quality control mechanisms handling mislocalized and orphan proteins. We highlight common principles involved in their recognition and summarize how accumulation of these aberrant molecules is associated with aging and disease.
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Affiliation(s)
| | - João P L Coelho
- Department of Chemistry and Institute for Advanced Study, Technical University of Munich, Garching, Germany
| | - Matthias J Feige
- Department of Chemistry and Institute for Advanced Study, Technical University of Munich, Garching, Germany
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10
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Shi S, Montalbetti N, Wang X, Rush BM, Marciszyn AL, Baty CJ, Tan RJ, Carattino MD, Kleyman TR. Paraoxonase 3 functions as a chaperone to decrease functional expression of the epithelial sodium channel. J Biol Chem 2020; 295:4950-4962. [PMID: 32079677 DOI: 10.1074/jbc.ra119.011789] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 02/17/2020] [Indexed: 01/11/2023] Open
Abstract
The paraoxonase (PON) family comprises three highly conserved members: PON1, PON2, and PON3. They are orthologs of Caenorhabditis elegans MEC-6, an endoplasmic reticulum-resident chaperone that has a critical role in proper assembly and surface expression of the touch-sensing degenerin channel in nematodes. We have shown recently that MEC-6 and PON2 negatively regulate functional expression of the epithelial Na+ channel (ENaC), suggesting that the chaperone function is conserved within this family. We hypothesized that other PON family members also modulate ion channel expression. Pon3 is specifically expressed in the aldosterone-sensitive distal tubules in the mouse kidney. We found here that knocking down endogenous Pon3 in mouse cortical collecting duct cells enhanced Na+ transport, which was associated with increased γENaC abundance. We further examined Pon3 regulation of ENaC in two heterologous expression systems, Fisher rat thyroid cells and Xenopus oocytes. Pon3 coimmunoprecipitated with each of the three ENaC subunits in Fisher rat thyroid cells. As a result of this interaction, the whole-cell and surface abundance of ENaC α and γ subunits was reduced by Pon3. When expressed in oocytes, Pon3 inhibited ENaC-mediated amiloride-sensitive Na+ currents, in part by reducing the surface expression of ENaC. In contrast, Pon3 did not alter the response of ENaC to chymotrypsin-mediated proteolytic activation or [2-(trimethylammonium)ethyl]methanethiosulfonate-induced activation of αβS518Cγ, suggesting that Pon3 does not affect channel open probability. Together, our results suggest that PON3 regulates ENaC expression by inhibiting its biogenesis and/or trafficking.
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Affiliation(s)
- Shujie Shi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Xueqi Wang
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Nephrology, Second Xiangya Hospital of Central South University, Changsha 410011, Hunan, China
| | - Brittney M Rush
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Allison L Marciszyn
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Catherine J Baty
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Roderick J Tan
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Thomas R Kleyman
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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11
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Vakirlis N, Acar O, Hsu B, Castilho Coelho N, Van Oss SB, Wacholder A, Medetgul-Ernar K, Bowman RW, Hines CP, Iannotta J, Parikh SB, McLysaght A, Camacho CJ, O'Donnell AF, Ideker T, Carvunis AR. De novo emergence of adaptive membrane proteins from thymine-rich genomic sequences. Nat Commun 2020; 11:781. [PMID: 32034123 PMCID: PMC7005711 DOI: 10.1038/s41467-020-14500-z] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 12/20/2019] [Indexed: 11/14/2022] Open
Abstract
Recent evidence demonstrates that novel protein-coding genes can arise de novo from non-genic loci. This evolutionary innovation is thought to be facilitated by the pervasive translation of non-genic transcripts, which exposes a reservoir of variable polypeptides to natural selection. Here, we systematically characterize how these de novo emerging coding sequences impact fitness in budding yeast. Disruption of emerging sequences is generally inconsequential for fitness in the laboratory and in natural populations. Overexpression of emerging sequences, however, is enriched in adaptive fitness effects compared to overexpression of established genes. We find that adaptive emerging sequences tend to encode putative transmembrane domains, and that thymine-rich intergenic regions harbor a widespread potential to produce transmembrane domains. These findings, together with in-depth examination of the de novo emerging YBR196C-A locus, suggest a novel evolutionary model whereby adaptive transmembrane polypeptides emerge de novo from thymine-rich non-genic regions and subsequently accumulate changes molded by natural selection. There is increasing evidence that protein-coding genes can emerge de novo from noncoding genomic regions. Vakirlis et al. propose that sequences encoding transmembrane polypeptides can emerge de novo in thymine-rich genomic regions and provide organisms with fitness benefits.
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Affiliation(s)
- Nikolaos Vakirlis
- Smurfit Institute of Genetics, Trinity College Dublin, University of Dublin, Dublin, 2, Ireland
| | - Omer Acar
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States.,Pittsburgh Center for Evolutionary Biology and Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States
| | - Brian Hsu
- Department of Medicine, Division of Medical Genetics, University of California San Diego, La Jolla, CA, 92093, United States
| | - Nelson Castilho Coelho
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States.,Pittsburgh Center for Evolutionary Biology and Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States
| | - S Branden Van Oss
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States.,Pittsburgh Center for Evolutionary Biology and Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States
| | - Aaron Wacholder
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States.,Pittsburgh Center for Evolutionary Biology and Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States
| | - Kate Medetgul-Ernar
- Department of Medicine, Division of Medical Genetics, University of California San Diego, La Jolla, CA, 92093, United States
| | - Ray W Bowman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, 15260, United States
| | - Cameron P Hines
- Department of Medicine, Division of Medical Genetics, University of California San Diego, La Jolla, CA, 92093, United States
| | - John Iannotta
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States.,Pittsburgh Center for Evolutionary Biology and Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States
| | - Saurin Bipin Parikh
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States.,Pittsburgh Center for Evolutionary Biology and Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States
| | - Aoife McLysaght
- Smurfit Institute of Genetics, Trinity College Dublin, University of Dublin, Dublin, 2, Ireland
| | - Carlos J Camacho
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States
| | - Allyson F O'Donnell
- Pittsburgh Center for Evolutionary Biology and Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States. .,Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, 15260, United States.
| | - Trey Ideker
- Department of Medicine, Division of Medical Genetics, University of California San Diego, La Jolla, CA, 92093, United States.
| | - Anne-Ruxandra Carvunis
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States. .,Pittsburgh Center for Evolutionary Biology and Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States.
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12
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Ware AW, Rasulov SR, Cheung TT, Lott JS, McDonald FJ. Membrane trafficking pathways regulating the epithelial Na + channel. Am J Physiol Renal Physiol 2019; 318:F1-F13. [PMID: 31657249 DOI: 10.1152/ajprenal.00277.2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Renal Na+ reabsorption, facilitated by the epithelial Na+ channel (ENaC), is subject to multiple forms of control to ensure optimal body blood volume and pressure through altering both the ENaC population and activity at the cell surface. Here, the focus is on regulating the number of ENaCs present in the apical membrane domain through pathways of ENaC synthesis and targeting to the apical membrane as well as ENaC removal, recycling, and degradation. Finally, the mechanisms by which ENaC trafficking pathways are regulated are summarized.
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Affiliation(s)
- Adam W Ware
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Sahib R Rasulov
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Tanya T Cheung
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - J Shaun Lott
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Fiona J McDonald
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
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13
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Doonan LM, Guerriero CJ, Preston GM, Buck TM, Khazanov N, Fisher EA, Senderowitz H, Brodsky JL. Hsp104 facilitates the endoplasmic-reticulum-associated degradation of disease-associated and aggregation-prone substrates. Protein Sci 2019; 28:1290-1306. [PMID: 31050848 DOI: 10.1002/pro.3636] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Accepted: 04/29/2019] [Indexed: 12/20/2022]
Abstract
Misfolded proteins in the endoplasmic reticulum (ER) are selected for ER-associated degradation (ERAD). More than 60 disease-associated proteins are substrates for the ERAD pathway due to the presence of missense or nonsense mutations. In yeast, the Hsp104 molecular chaperone disaggregates detergent-insoluble ERAD substrates, but the spectrum of disease-associated ERAD substrates that may be aggregation prone is unknown. To determine if Hsp104 recognizes aggregation-prone ERAD substrates associated with human diseases, we developed yeast expression systems for a hydrophobic lipid-binding protein, apolipoprotein B (ApoB), along with a chimeric protein harboring a nucleotide-binding domain from the cystic fibrosis transmembrane conductance regulator (CFTR) into which disease-causing mutations were introduced. We discovered that Hsp104 facilitates the degradation of ER-associated ApoB as well as a truncated CFTR chimera in which a premature stop codon corresponds to a disease-causing mutation. Chimeras containing a wild-type version of the CFTR domain or a different mutation were stable and thus Hsp104 independent. We also discovered that the detergent solubility of the unstable chimera was lower than the stable chimeras, and Hsp104 helped retrotranslocate the unstable chimera from the ER, consistent with disaggregase activity. To determine why the truncated chimera was unstable, we next performed molecular dynamics simulations and noted significant unraveling of the CFTR nucleotide-binding domain. Because human cells lack Hsp104, these data indicate that an alternate disaggregase or mechanism facilitates the removal of aggregation-prone, disease-causing ERAD substrates in their native environments.
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Affiliation(s)
- Lynley M Doonan
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260
| | - Christopher J Guerriero
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260
| | - G Michael Preston
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260
| | - Teresa M Buck
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260
| | - Netaly Khazanov
- Department of Chemistry, Bar Ilan University, Ramat Gan, 5290002, Israel
| | - Edward A Fisher
- Division of Cardiology, Department of Medicine and Cell Biology, New York University, New York, New York, 10016
| | - Hanoch Senderowitz
- Department of Chemistry, Bar Ilan University, Ramat Gan, 5290002, Israel
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260
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14
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Marinko J, Huang H, Penn WD, Capra JA, Schlebach JP, Sanders CR. Folding and Misfolding of Human Membrane Proteins in Health and Disease: From Single Molecules to Cellular Proteostasis. Chem Rev 2019; 119:5537-5606. [PMID: 30608666 PMCID: PMC6506414 DOI: 10.1021/acs.chemrev.8b00532] [Citation(s) in RCA: 162] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Indexed: 12/13/2022]
Abstract
Advances over the past 25 years have revealed much about how the structural properties of membranes and associated proteins are linked to the thermodynamics and kinetics of membrane protein (MP) folding. At the same time biochemical progress has outlined how cellular proteostasis networks mediate MP folding and manage misfolding in the cell. When combined with results from genomic sequencing, these studies have established paradigms for how MP folding and misfolding are linked to the molecular etiologies of a variety of diseases. This emerging framework has paved the way for the development of a new class of small molecule "pharmacological chaperones" that bind to and stabilize misfolded MP variants, some of which are now in clinical use. In this review, we comprehensively outline current perspectives on the folding and misfolding of integral MPs as well as the mechanisms of cellular MP quality control. Based on these perspectives, we highlight new opportunities for innovations that bridge our molecular understanding of the energetics of MP folding with the nuanced complexity of biological systems. Given the many linkages between MP misfolding and human disease, we also examine some of the exciting opportunities to leverage these advances to address emerging challenges in the development of therapeutics and precision medicine.
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Affiliation(s)
- Justin
T. Marinko
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - Hui Huang
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - Wesley D. Penn
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - John A. Capra
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
- Department
of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37245, United States
| | - Jonathan P. Schlebach
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Charles R. Sanders
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
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15
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Fu YL, Han DY, Wang YJ, Di XJ, Yu HB, Mu TW. Remodeling the endoplasmic reticulum proteostasis network restores proteostasis of pathogenic GABAA receptors. PLoS One 2018; 13:e0207948. [PMID: 30481215 PMCID: PMC6258528 DOI: 10.1371/journal.pone.0207948] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 11/08/2018] [Indexed: 01/12/2023] Open
Abstract
Biogenesis of membrane proteins is controlled by the protein homeostasis (proteostasis) network. We have been focusing on protein quality control of γ-aminobutyric acid type A (GABAA) receptors, the major inhibitory neurotransmitter-gated ion channels in mammalian central nervous system. Proteostasis deficiency in GABAA receptors causes loss of their surface expression and thus function on the plasma membrane, leading to epilepsy and other neurological diseases. One well-characterized example is the A322D mutation in the α1 subunit that causes its extensive misfolding and expedited degradation in the endoplasmic reticulum (ER), resulting in autosomal dominant juvenile myoclonic epilepsy. We aimed to correct misfolding of the α1(A322D) subunits in the ER as an approach to restore their functional surface expression. Here, we showed that application of BIX, a specific, potent ER resident HSP70 family protein BiP activator, significantly increases the surface expression of the mutant receptors in human HEK293T cells and neuronal SH-SY5Y cells. BIX attenuates the degradation of α1(A322D) and enhances their forward trafficking and function. Furthermore, because BiP is one major target of the two unfolded protein response (UPR) pathways: ATF6 and IRE1, we continued to demonstrate that modest activations of the ATF6 pathway and IRE1 pathway genetically enhance the plasma membrane trafficking of the α1(A322D) protein in HEK293T cells. Our results underlie the potential of regulating the ER proteostasis network to correct loss-of-function protein conformational diseases.
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Affiliation(s)
- Yan-Lin Fu
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America
| | - Dong-Yun Han
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America
| | - Ya-Juan Wang
- Center for Proteomics and Bioinformatics and Department of Epidemiology and Biostatistics, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America
| | - Xiao-Jing Di
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America
| | - Hai-Bo Yu
- School of Chemistry and Molecular Bioscience & Molecular Horizons, University of Wollongong, Wollongong, Australia
| | - Ting-Wei Mu
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America
- * E-mail:
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16
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Sheng S, Chen J, Mukherjee A, Yates ME, Buck TM, Brodsky JL, Tolino MA, Hughey RP, Kleyman TR. Thumb domains of the three epithelial Na + channel subunits have distinct functions. J Biol Chem 2018; 293:17582-17592. [PMID: 30228189 PMCID: PMC6231141 DOI: 10.1074/jbc.ra118.003618] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 09/13/2018] [Indexed: 01/10/2023] Open
Abstract
The epithelial Na+ channel (ENaC) possesses a large extracellular domain formed by a β-strand core enclosed by three peripheral α-helical subdomains, which have been dubbed thumb, finger, and knuckle. Here we asked whether the ENaC thumb domains play specific roles in channel function. To this end, we examined the characteristics of channels lacking a thumb domain in an individual ENaC subunit (α, β, or γ). Removing the γ subunit thumb domain had no effect on Na+ currents when expressed in Xenopus oocytes, but moderately reduced channel surface expression. In contrast, ENaCs lacking the α or β subunit thumb domain exhibited significantly reduced Na+ currents along with a large reduction in channel surface expression. Moreover, channels lacking an α or γ thumb domain exhibited a diminished Na+ self-inhibition response, whereas this response was retained in channels lacking a β thumb domain. In turn, deletion of the α thumb domain had no effect on the degradation rate of the immature α subunit as assessed by cycloheximide chase analysis. However, accelerated degradation of the immature β subunit and mature γ subunit was observed when the β or γ thumb domain was deleted, respectively. Our results suggest that the thumb domains in each ENaC subunit are required for optimal surface expression in oocytes and that the α and γ thumb domains both have important roles in the channel's inhibitory response to external Na+ Our findings support the notion that the extracellular helical domains serve as functional modules that regulate ENaC biogenesis and activity.
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Affiliation(s)
- Shaohu Sheng
- From the Renal-Electrolyte Division, Department of Medicine and
| | - Jingxin Chen
- From the Renal-Electrolyte Division, Department of Medicine and
| | | | | | | | | | | | - Rebecca P Hughey
- From the Renal-Electrolyte Division, Department of Medicine and
- Cell Biology
- Microbiology and Molecular Genetics, and
| | - Thomas R Kleyman
- From the Renal-Electrolyte Division, Department of Medicine and
- Cell Biology
- Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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17
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Epithelial sodium channel biogenesis and quality control in the early secretory pathway. Curr Opin Nephrol Hypertens 2018; 27:364-372. [DOI: 10.1097/mnh.0000000000000438] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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18
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Kim CS, Ahmad S, Wu T, Walton WG, Redinbo MR, Tarran R. SPLUNC1 is an allosteric modulator of the epithelial sodium channel. FASEB J 2018; 32:2478-2491. [PMID: 29295861 PMCID: PMC5901381 DOI: 10.1096/fj.201701126r] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 12/04/2017] [Indexed: 01/20/2023]
Abstract
Cystic fibrosis (CF) is a common genetic disease with significantly increased mortality. CF airways exhibit ion transport abnormalities, including hyperactivity of the epithelial Na+ channel (ENaC). Short-palate lung and nasal epithelial clone 1 (SPLUNC1) is a multifunctional innate defense protein that is secreted into the airway lumen. We have previously demonstrated that SPLUNC1 binds to and inhibits ENaC to maintain fluid homeostasis in airway epithelia and that this process fails in CF airways. Despite this, how SPLUNC1 actually regulates ENaC is unknown. Here, we found that SPLUNC1 caused αγ-ENaC to internalize, whereas SPLUNC1 and β-ENaC remained at the plasma membrane. Additional studies revealed that SPLUNC1 increased neural precursor cell-expressed developmentally down-regulated protein 4-2-dependent ubiquitination of α- but not β- or γ-ENaC. We also labeled intracellular ENaC termini with green fluorescent protein and mCherry, and found that extracellular SPLUNC1 altered intracellular ENaC Forster resonance energy transfer. Taken together, our data indicate that SPLUNC1 is an allosteric regulator of ENaC that dissociates αβγ-ENaC to generate a new SPLUNC1-β-ENaC complex. These data indicate a novel mode for regulating ENaC at the plasma membrane.-Kim, C. S., Ahmad, S., Wu, T., Walton, W. G., Redinbo, M. R., Tarran, R. SPLUNC1 is an allosteric modulator of the epithelial sodium channel.
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Affiliation(s)
- Christine Seulki Kim
- Cystic Fibrosis Center, Marsico Lung Institute, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Saira Ahmad
- Cystic Fibrosis Center, Marsico Lung Institute, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Tongde Wu
- Cystic Fibrosis Center, Marsico Lung Institute, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - William G. Walton
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Matthew R. Redinbo
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Robert Tarran
- Cystic Fibrosis Center, Marsico Lung Institute, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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19
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Kashlan OB, Kinlough CL, Myerburg MM, Shi S, Chen J, Blobner BM, Buck TM, Brodsky JL, Hughey RP, Kleyman TR. N-linked glycans are required on epithelial Na + channel subunits for maturation and surface expression. Am J Physiol Renal Physiol 2017; 314:F483-F492. [PMID: 29187368 DOI: 10.1152/ajprenal.00195.2017] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Epithelial Na+ channel (ENaC) subunits undergo N-linked glycosylation in the endoplasmic reticulum where they assemble into an αβγ complex. Six, 13, and 5 consensus sites (Asn-X-Ser/Thr) for N-glycosylation reside in the extracellular domains of the mouse α-, β-, and γ-subunits, respectively. Because the importance of ENaC N-linked glycans has not been fully addressed, we examined the effect of preventing N-glycosylation of specific subunits on channel function, expression, maturation, and folding. Heterologous expression in Xenopus oocytes or Fischer rat thyroid cells with αβγ-ENaC lacking N-linked glycans on a single subunit reduced ENaC activity as well as the inhibitory response to extracellular Na+. The lack of N-linked glycans on the β-subunit also precluded channel activation by trypsin. However, channel activation by shear stress was N-linked glycan independent, regardless of which subunit was modified. We also discovered that the lack of N-linked glycans on any one subunit reduced the total and surface levels of cognate subunits. The lack of N-linked glycans on the β-subunit had the largest effect on total levels, with the lack of N-linked glycans on the γ- and α-subunits having intermediate and modest effects, respectively. Finally, channels with wild-type β-subunits were more sensitive to limited trypsin proteolysis than channels lacking N-linked glycans on the β-subunit. Our results indicate that N-linked glycans on each subunit are required for proper folding, maturation, surface expression, and function of the channel.
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Affiliation(s)
- Ossama B Kashlan
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania.,Department of Computational and Systems Biology, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Carol L Kinlough
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Michael M Myerburg
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Shujie Shi
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Jingxin Chen
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Brandon M Blobner
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Teresa M Buck
- Department of Biological Sciences, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Rebecca P Hughey
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania.,Department of Cell Biology, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Thomas R Kleyman
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania.,Department of Cell Biology, University of Pittsburgh , Pittsburgh, Pennsylvania.,Department of Pharmacology and Chemical Biology, University of Pittsburgh , Pittsburgh, Pennsylvania
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20
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Shi S, Buck TM, Kinlough CL, Marciszyn AL, Hughey RP, Chalfie M, Brodsky JL, Kleyman TR. Regulation of the epithelial Na + channel by paraoxonase-2. J Biol Chem 2017; 292:15927-15938. [PMID: 28768768 DOI: 10.1074/jbc.m117.785253] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 07/14/2017] [Indexed: 01/11/2023] Open
Abstract
Paraoxonase-2 (PON-2) is a membrane-bound lactonase with unique anti-oxidative and anti-atherosclerotic properties. PON-2 shares key structural elements with MEC-6, an endoplasmic reticulum-resident molecular chaperone in Caenorhabditis elegans MEC-6 modulates the expression of a mechanotransductive ion channel comprising MEC-4 and MEC-10 in touch-receptor neurons. Because pon-2 mRNA resides in multiple rat nephron segments, including the aldosterone-sensitive distal nephron where the epithelial Na+ channel (ENaC) is expressed, we hypothesized that PON-2 would similarly regulate ENaC expression. We observed PON-2 expression in aquaporin 2-positive principal cells of the distal nephron of adult human kidney. PON-2 also co-immunoprecipitated with ENaC when co-expressed in HEK293 cells. When PON-2 was co-expressed with ENaC in Xenopus oocytes, ENaC activity was reduced, reflecting a reduction in ENaC surface expression. MEC-6 also reduced ENaC activity when co-expressed in Xenopus oocytes. The PON-2 inhibitory effect was ENaC-specific, as PON-2 had no effect on functional expression of the renal outer medullary potassium channel. PON-2 did not alter the response of ENaC to extracellular Na+, mechanical shear stress, or α-chymotrypsin-mediated proteolysis, suggesting that PON-2 did not alter the regulation of ENaC by these factors. Together, our data suggest that PON-2 regulates ENaC activity by modulating its intracellular trafficking and surface expression.
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Affiliation(s)
- Shujie Shi
- From the Renal-Electrolyte Division, Department of Medicine
| | | | | | | | - Rebecca P Hughey
- From the Renal-Electrolyte Division, Department of Medicine.,Department of Cell Biology.,Department of Microbiology and Molecular Genetics, and
| | - Martin Chalfie
- the Department of Biological Sciences, Columbia University, New York, New York 10027
| | | | - Thomas R Kleyman
- From the Renal-Electrolyte Division, Department of Medicine, .,Department of Cell Biology.,Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261 and
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21
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Guerriero CJ, Reutter KR, Augustine AA, Preston GM, Weiberth KF, Mackie TD, Cleveland-Rubeor HC, Bethel NP, Callenberg KM, Nakatsukasa K, Grabe M, Brodsky JL. Transmembrane helix hydrophobicity is an energetic barrier during the retrotranslocation of integral membrane ERAD substrates. Mol Biol Cell 2017; 28:2076-2090. [PMID: 28539401 PMCID: PMC5509421 DOI: 10.1091/mbc.e17-03-0184] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 05/12/2017] [Accepted: 05/16/2017] [Indexed: 12/25/2022] Open
Abstract
Integral membrane proteins fold inefficiently and are susceptible to turnover via the endoplasmic reticulum-associated degradation (ERAD) pathway. During ERAD, misfolded proteins are recognized by molecular chaperones, polyubiquitinated, and retrotranslocated to the cytoplasm for proteasomal degradation. Although many aspects of this pathway are defined, how transmembrane helices (TMHs) are removed from the membrane and into the cytoplasm before degradation is poorly understood. In this study, we asked whether the hydrophobic character of a TMH acts as an energetic barrier to retrotranslocation. To this end, we designed a dual-pass model ERAD substrate, Chimera A*, which contains the cytoplasmic misfolded domain from a characterized ERAD substrate, Sterile 6* (Ste6p*). We found that the degradation requirements for Chimera A* and Ste6p* are similar, but Chimera A* was retrotranslocated more efficiently than Ste6p* in an in vitro assay in which retrotranslocation can be quantified. We then constructed a series of Chimera A* variants containing synthetic TMHs with a range of ΔG values for membrane insertion. TMH hydrophobicity correlated inversely with retrotranslocation efficiency, and in all cases, retrotranslocation remained Cdc48p dependent. These findings provide insight into the energetic restrictions on the retrotranslocation reaction, as well as a new computational approach to predict retrotranslocation efficiency.
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Affiliation(s)
| | - Karl-Richard Reutter
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Andrew A Augustine
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - G Michael Preston
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Kurt F Weiberth
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Timothy D Mackie
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | | | - Neville P Bethel
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158
| | - Keith M Callenberg
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Kunio Nakatsukasa
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260.,Division of Biological Science, Graduate School of Natural Sciences, Nagoya City University, Nagoya, Aichi 467-8501, Japan
| | - Michael Grabe
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
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