1
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Lee CT, Tsai WH, Chang CC, Chen PC, Fann CSJ, Chang HK, Liu SY, Wu MZ, Chiu PC, Hsu WM, Yang WS, Lai LP, Tsai WY, Yang SB, Chen PL. Genotype-phenotype correlation in Taiwanese children with diazoxide-unresponsive congenital hyperinsulinism. Front Endocrinol (Lausanne) 2023; 14:1283907. [PMID: 38033998 PMCID: PMC10687152 DOI: 10.3389/fendo.2023.1283907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Accepted: 10/23/2023] [Indexed: 12/02/2023] Open
Abstract
Objective Congenital hyperinsulinism (CHI) is a group of clinically and genetically heterogeneous disorders characterized by dysregulated insulin secretion. The aim of the study was to elucidate genetic etiologies of Taiwanese children with the most severe diazoxide-unresponsive CHI and analyze their genotype-phenotype correlations. Methods We combined Sanger with whole exome sequencing (WES) to analyze CHI-related genes. The allele frequency of the most common variant was estimated by single-nucleotide polymorphism haplotype analysis. The functional effects of the ATP-sensitive potassium (KATP) channel variants were assessed using patch clamp recording and Western blot. Results Nine of 13 (69%) patients with ten different pathogenic variants (7 in ABCC8, 2 in KCNJ11 and 1 in GCK) were identified by the combined sequencing. The variant ABCC8 p.T1042QfsX75 identified in three probands was located in a specific haplotype. Functional study revealed the human SUR1 (hSUR1)-L366F KATP channels failed to respond to intracellular MgADP and diazoxide while hSUR1-R797Q and hSUR1-R1393C KATP channels were defective in trafficking. One patient had a de novo dominant mutation in the GCK gene (p.I211F), and WES revealed mosaicism of this variant from another patient. Conclusion Pathogenic variants in KATP channels are the most common underlying cause of diazoxide-unresponsive CHI in the Taiwanese cohort. The p.T1042QfsX75 variant in the ABCC8 gene is highly suggestive of a founder effect. The I211F mutation in the GCK gene and three rare SUR1 variants associated with defective gating (p.L366F) or traffic (p.R797Q and p.R1393C) KATP channels are also associated with the diazoxide-unresponsive phenotype.
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Affiliation(s)
- Cheng-Ting Lee
- Department of Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
- Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Wen-Hao Tsai
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | | | - Pei-Chun Chen
- Department of Physiology, National Cheng-Kung University, Tainan, Taiwan
| | | | - Hsueh-Kai Chang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Shih-Yao Liu
- Department of Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Mu-Zon Wu
- Department of Pathology, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Pao-Chin Chiu
- Department of Pediatrics, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
| | - Wen-Ming Hsu
- Department of Surgery, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Wei-Shiung Yang
- Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
- Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Ling-Ping Lai
- Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Wen-Yu Tsai
- Department of Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Shi-Bing Yang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Pei-Lung Chen
- Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
- Department of Medical Genetics, National Taiwan University Hospital, Taipei, Taiwan
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2
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Nguyen NH, Brodsky JL. The cellular pathways that maintain the quality control and transport of diverse potassium channels. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2023; 1866:194908. [PMID: 36638864 PMCID: PMC9908860 DOI: 10.1016/j.bbagrm.2023.194908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 12/20/2022] [Accepted: 01/03/2023] [Indexed: 01/12/2023]
Abstract
Potassium channels are multi-subunit transmembrane proteins that permit the selective passage of potassium and play fundamental roles in physiological processes, such as action potentials in the nervous system and organismal salt and water homeostasis, which is mediated by the kidney. Like all ion channels, newly translated potassium channels enter the endoplasmic reticulum (ER) and undergo the error-prone process of acquiring post-translational modifications, folding into their native conformations, assembling with other subunits, and trafficking through the secretory pathway to reach their final destinations, most commonly the plasma membrane. Disruptions in these processes can result in detrimental consequences, including various human diseases. Thus, multiple quality control checkpoints evolved to guide potassium channels through the secretory pathway and clear potentially toxic, aggregation-prone misfolded species. We will summarize current knowledge on the mechanisms underlying potassium channel quality control in the secretory pathway, highlight diseases associated with channel misfolding, and suggest potential therapeutic routes.
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Affiliation(s)
- Nga H Nguyen
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA.
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3
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Barrabi C, Zhang K, Liu M, Chen X. Pancreatic beta cell ER export in health and diabetes. Front Endocrinol (Lausanne) 2023; 14:1155779. [PMID: 37152949 PMCID: PMC10160654 DOI: 10.3389/fendo.2023.1155779] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 04/10/2023] [Indexed: 05/09/2023] Open
Abstract
In the secretory pathway of the pancreatic beta cell, proinsulin and other secretory granule proteins are first produced in the endoplasmic reticulum (ER). Beta cell ER homeostasis is vital for normal beta cell functions and is maintained by the delicate balance between protein synthesis, folding, export and degradation. Disruption of ER homeostasis leads to beta cell death and diabetes. Among the four components to maintain ER homeostasis, the role of ER export in insulin biogenesis or beta cell survival was not well-understood. COPII (coat protein complex II) dependent transport is a conserved mechanism for most cargo proteins to exit ER and transport to Golgi apparatus. Emerging evidence began to reveal a critical role of COPII-dependent ER export in beta cells. In this review, we will first discuss the basic components of the COPII transport machinery, the regulation of cargo entry and COPII coat assembly in mammalian cells, and the general concept of receptor-mediated cargo sorting in COPII vesicles. On the basis of these general discussions, the current knowledge and recent developments specific to the beta cell COPII dependent ER export are summarized under normal and diabetic conditions.
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Affiliation(s)
- Cesar Barrabi
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI, United States
| | - Kezhong Zhang
- Center for Molecular Medicine and Genetics, School of Medicine, Wayne State University, Detroit, MI, United States
| | - Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Xuequn Chen
- Department of Physiology, School of Medicine, Wayne State University, Detroit, MI, United States
- *Correspondence: Xuequn Chen,
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4
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Bakhos-Douaihy D, Seaayfan E, Frachon N, Demaretz S, Kömhoff M, Laghmani K. Diacidic Motifs in the Carboxyl Terminus Are Required for ER Exit and Translocation to the Plasma Membrane of NKCC2. Int J Mol Sci 2022; 23:ijms232112761. [PMID: 36361553 PMCID: PMC9656672 DOI: 10.3390/ijms232112761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 10/18/2022] [Accepted: 10/21/2022] [Indexed: 11/25/2022] Open
Abstract
Mutations in the apical Na-K-2Cl co-transporter, NKCC2, cause type I Bartter syndrome (BS1), a life-threatening kidney disease. We have previously demonstrated that the BS1 variant Y998X, which deprives NKCC2 from its highly conserved dileucine-like motifs, compromises co-transporter surface delivery through ER retention mechanisms. However, whether these hydrophobic motifs are sufficient for anterograde trafficking of NKCC2 remains to be determined. Interestingly, sequence analysis of NKCC2 C-terminus revealed the presence of consensus di-acidic (D/E-X-D/E) motifs, 949EEE951 and 1019DAELE1023, located upstream and downstream of BS1 mutation Y998X, respectively. Di-acidic codes are involved in ER export of proteins through interaction with COPII budding machinery. Importantly, whereas mutating 949EEE951 motif to 949AEA951 had no effect on NKCC2 processing, mutating 1019DAE1021 to 1019AAA1021 heavily impaired complex-glycosylation and cell surface expression of the cotransporter in HEK293 and OKP cells. Most importantly, triple mutation of D, E and E residues of 1019DAELE1023 to 1019AAALA1023 almost completely abolished NKCC2 complex-glycosylation, suggesting that this mutant failed to exit the ER. Cycloheximide chase analysis demonstrated that the absence of the terminally glycosylated form of 1019AAALA1023 was caused by defects in NKCC2 maturation. Accordingly, co-immunolocalization experiments revealed that 1019AAALA1023 was trapped in the ER. Finally, overexpression of a dominant negative mutant of Sar1-GTPase abolished NKCC2 maturation and cell surface expression, clearly indicating that NKCC2 export from the ER is COPII-dependent. Hence, our data indicate that in addition to the di-leucine like motifs, NKCC2 uses di-acidic exit codes for export from the ER through the COPII-dependent pathway. We propose that any naturally occurring mutation of NKCC2 interfering with this pathway could form the molecular basis of BS1.
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Affiliation(s)
- Dalal Bakhos-Douaihy
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, F-75006 Paris, France
- CNRS-ERL8228, F-75006 Paris, France
| | - Elie Seaayfan
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, F-75006 Paris, France
- CNRS-ERL8228, F-75006 Paris, France
| | - Nadia Frachon
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, F-75006 Paris, France
- CNRS-ERL8228, F-75006 Paris, France
| | - Sylvie Demaretz
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, F-75006 Paris, France
- CNRS-ERL8228, F-75006 Paris, France
| | - Martin Kömhoff
- Division of Pediatric Nephrology and Transplantation, University Children’s Hospital, Philipps-University, 35043 Marburg, Germany
| | - Kamel Laghmani
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, F-75006 Paris, France
- CNRS-ERL8228, F-75006 Paris, France
- Correspondence:
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5
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Yang HQ, Echeverry FA, ElSheikh A, Gando I, Anez Arredondo S, Samper N, Cardozo T, Delmar M, Shyng SL, Coetzee WA. Subcellular trafficking and endocytic recycling of K ATP channels. Am J Physiol Cell Physiol 2022; 322:C1230-C1247. [PMID: 35508187 PMCID: PMC9169827 DOI: 10.1152/ajpcell.00099.2022] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 04/27/2022] [Accepted: 04/30/2022] [Indexed: 11/22/2022]
Abstract
Sarcolemmal/plasmalemmal ATP-sensitive K+ (KATP) channels have key roles in many cell types and tissues. Hundreds of studies have described how the KATP channel activity and ATP sensitivity can be regulated by changes in the cellular metabolic state, by receptor signaling pathways and by pharmacological interventions. These alterations in channel activity directly translate to alterations in cell or tissue function, that can range from modulating secretory responses, such as insulin release from pancreatic β-cells or neurotransmitters from neurons, to modulating contractile behavior of smooth muscle or cardiac cells to elicit alterations in blood flow or cardiac contractility. It is increasingly becoming apparent, however, that KATP channels are regulated beyond changes in their activity. Recent studies have highlighted that KATP channel surface expression is a tightly regulated process with similar implications in health and disease. The surface expression of KATP channels is finely balanced by several trafficking steps including synthesis, assembly, anterograde trafficking, membrane anchoring, endocytosis, endocytic recycling, and degradation. This review aims to summarize the physiological and pathophysiological implications of KATP channel trafficking and mechanisms that regulate KATP channel trafficking. A better understanding of this topic has potential to identify new approaches to develop therapeutically useful drugs to treat KATP channel-related diseases.
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Affiliation(s)
- Hua-Qian Yang
- Cyrus Tang Hematology Center, Soochow University, Suzhou, People's Republic of China
| | | | - Assmaa ElSheikh
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, Oregon
- Department of Medical Biochemistry, Tanta University, Tanta, Egypt
| | - Ivan Gando
- Department of Pathology, NYU School of Medicine, New York, New York
| | | | - Natalie Samper
- Department of Pathology, NYU School of Medicine, New York, New York
| | - Timothy Cardozo
- Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
| | - Mario Delmar
- Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
- Department of Medicine, NYU School of Medicine, New York, New York
| | - Show-Ling Shyng
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, Oregon
| | - William A Coetzee
- Department of Pathology, NYU School of Medicine, New York, New York
- Department of Neuroscience & Physiology, NYU School of Medicine, New York, New York
- Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
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6
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Tang D, Xu J, Li Y, Zhao P, Kong X, Hu H, Liang S, Tang C, Liu Z. Molecular mechanisms of centipede toxin SsTx-4 inhibition of inwardly rectifying potassium channels. J Biol Chem 2021; 297:101076. [PMID: 34391777 PMCID: PMC8413892 DOI: 10.1016/j.jbc.2021.101076] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 08/05/2021] [Accepted: 08/11/2021] [Indexed: 11/29/2022] Open
Abstract
Inwardly rectifying potassium channels (Kirs) are important drug targets, with antagonists for the Kir1.1, Kir4.1, and pancreatic Kir6.2/SUR1 channels being potential drug candidates for treating hypertension, depression, and diabetes, respectively. However, few peptide toxins acting on Kirs are identified and their interacting mechanisms remain largely elusive yet. Herein, we showed that the centipede toxin SsTx-4 potently inhibited the Kir1.1, Kir4.1, and Kir6.2/SUR1 channels with nanomolar to submicromolar affinities and intensively studied the molecular bases for toxin–channel interactions using patch-clamp analysis and site-directed mutations. Other Kirs including Kir2.1 to 2.4, Kir4.2, and Kir7.1 were resistant to SsTx-4 treatment. Moreover, SsTx-4 inhibited the inward and outward currents of Kirs with different potencies, possibly caused by a K+ “knock-off” effect, suggesting the toxin functions as an out pore blocker physically occluding the K+-conducting pathway. This conclusion was further supported by a mutation analysis showing that M137 located in the outer vestibule of the Kir6.2/ΔC26 channel was the key residue mediating interaction with SsTx-4. On the other hand, the molecular determinants within SsTx-4 for binding these Kir channels only partially overlapped, with K13 and F44 being the common key residues. Most importantly, K11A, P15A, and Y16A mutant toxins showed improved affinity and/or selectivity toward Kir6.2, while R12A mutant toxin had increased affinity for Kir4.1. To our knowledge, SsTx-4 is the first characterized peptide toxin with Kir4.1 inhibitory activity. This study provides useful insights for engineering a Kir6.2/SUR1 channel–specific antagonist based on the SsTx-4 template molecule and may be useful in developing new antidiabetic drugs.
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Affiliation(s)
- Dongfang Tang
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China; College of Chemistry and Bioengineering, Hunan University of Science and Engineering, Yongzhou, Hunan, China
| | - Jiahui Xu
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Yinping Li
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Piao Zhao
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Xiangjin Kong
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Haoliang Hu
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Songping Liang
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Cheng Tang
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China.
| | - Zhonghua Liu
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China.
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7
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Production and purification of ATP-sensitive potassium channel particles for cryo-electron microscopy. Methods Enzymol 2021; 653:121-150. [PMID: 34099169 DOI: 10.1016/bs.mie.2021.02.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
ATP-sensitive potassium (KATP) channels are multimeric protein complexes made of four inward rectifying potassium channel (Kir6.x) subunits and four ABC protein sulfonylurea receptor (SURx) subunits. Kir6.x subunits form the potassium ion conducting pore of the channel, and SURx functions to regulate Kir6.x. Kir6.x and SURx are uniquely dependent on each other for expression and function. In pancreatic β-cells, channels comprising SUR1 and Kir6.2 mediate glucose-stimulated insulin secretion and are the targets of antidiabetic sulfonylureas. Mutations in genes encoding SUR1 or Kir6.2 are linked to insulin secretion disorders, with loss- or gain-of-function mutations causing congenital hyperinsulinism or neonatal diabetes mellitus, respectively. Defects in the KATP channel in other tissues underlie human diseases of the cardiovascular and nervous systems. Key to understanding how channels are regulated by physiological and pharmacological ligands and how mutations disrupt channel assembly or gating to cause disease is the ability to observe structural changes associated with subunit interactions and ligand binding. While recent advances in the structural method of single-particle cryo-electron microscopy (cryoEM) offers direct visualization of channel structures, success of obtaining high-resolution structures is dependent on highly concentrated, homogeneous KATP channel particles. In this chapter, we describe a method for expressing KATP channels in mammalian cell culture, solubilizing the channel in detergent micelles and purifying KATP channels using an affinity tag to the SURx subunit for cryoEM structural studies.
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8
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Bisnett BJ, Condon BM, Lamb CH, Georgiou GR, Boyce M. Export Control: Post-transcriptional Regulation of the COPII Trafficking Pathway. Front Cell Dev Biol 2021; 8:618652. [PMID: 33511128 PMCID: PMC7835409 DOI: 10.3389/fcell.2020.618652] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Accepted: 12/14/2020] [Indexed: 11/13/2022] Open
Abstract
The coat protein complex II (COPII) mediates forward trafficking of protein and lipid cargoes from the endoplasmic reticulum. COPII is an ancient and essential pathway in all eukaryotes and COPII dysfunction underlies a range of human diseases. Despite this broad significance, major aspects of COPII trafficking remain incompletely understood. For example, while the biochemical features of COPII vesicle formation are relatively well characterized, much less is known about how the COPII system dynamically adjusts its activity to changing physiologic cues or stresses. Recently, post-transcriptional mechanisms have emerged as a major mode of COPII regulation. Here, we review the current literature on how post-transcriptional events, and especially post-translational modifications, govern the COPII pathway.
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Affiliation(s)
- Brittany J Bisnett
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, United States
| | - Brett M Condon
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, United States
| | - Caitlin H Lamb
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, United States
| | - George R Georgiou
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, United States
| | - Michael Boyce
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, United States
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9
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Zangerl-Plessl EM, Qile M, Bloothooft M, Stary-Weinzinger A, van der Heyden MAG. Disease Associated Mutations in K IR Proteins Linked to Aberrant Inward Rectifier Channel Trafficking. Biomolecules 2019; 9:biom9110650. [PMID: 31731488 PMCID: PMC6920955 DOI: 10.3390/biom9110650] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 10/22/2019] [Accepted: 10/23/2019] [Indexed: 12/28/2022] Open
Abstract
The ubiquitously expressed family of inward rectifier potassium (KIR) channels, encoded by KCNJ genes, is primarily involved in cell excitability and potassium homeostasis. Channel mutations associate with a variety of severe human diseases and syndromes, affecting many organ systems including the central and peripheral neural system, heart, kidney, pancreas, and skeletal muscle. A number of mutations associate with altered ion channel expression at the plasma membrane, which might result from defective channel trafficking. Trafficking involves cellular processes that transport ion channels to and from their place of function. By alignment of all KIR channels, and depicting the trafficking associated mutations, three mutational hotspots were identified. One localized in the transmembrane-domain 1 and immediately adjacent sequences, one was found in the G-loop and Golgi-export domain, and the third one was detected at the immunoglobulin-like domain. Surprisingly, only few mutations were observed in experimentally determined Endoplasmic Reticulum (ER)exit-, export-, or ER-retention motifs. Structural mapping of the trafficking defect causing mutations provided a 3D framework, which indicates that trafficking deficient mutations form clusters. These “mutation clusters” affect trafficking by different mechanisms, including protein stability.
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Affiliation(s)
- Eva-Maria Zangerl-Plessl
- Department of Pharmacology and Toxicology, University of Vienna, 1090 Vienna, Austria; (E.-M.Z.-P.); (A.S.-W.)
| | - Muge Qile
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, 3584 CM Utrecht, The Netherlands; (M.Q.); (M.B.)
| | - Meye Bloothooft
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, 3584 CM Utrecht, The Netherlands; (M.Q.); (M.B.)
| | - Anna Stary-Weinzinger
- Department of Pharmacology and Toxicology, University of Vienna, 1090 Vienna, Austria; (E.-M.Z.-P.); (A.S.-W.)
| | - Marcel A. G. van der Heyden
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, 3584 CM Utrecht, The Netherlands; (M.Q.); (M.B.)
- Correspondence: ; Tel.: +31-887558901
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10
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Galcheva S, Demirbilek H, Al-Khawaga S, Hussain K. The Genetic and Molecular Mechanisms of Congenital Hyperinsulinism. Front Endocrinol (Lausanne) 2019; 10:111. [PMID: 30873120 PMCID: PMC6401612 DOI: 10.3389/fendo.2019.00111] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 02/06/2019] [Indexed: 12/13/2022] Open
Abstract
Congenital hyperinsulinism (CHI) is a heterogenous and complex disorder in which the unregulated insulin secretion from pancreatic beta-cells leads to hyperinsulinaemic hypoglycaemia. The severity of hypoglycaemia varies depending on the underlying molecular mechanism and genetic defects. The genetic and molecular causes of CHI include defects in pivotal pathways regulating the secretion of insulin from the beta-cell. Broadly these genetic defects leading to unregulated insulin secretion can be grouped into four main categories. The first group consists of defects in the pancreatic KATP channel genes (ABCC8 and KCNJ11). The second and third categories of conditions are enzymatic defects (such as GDH, GCK, HADH) and defects in transcription factors (for example HNF1α, HNF4α) leading to changes in nutrient flux into metabolic pathways which converge on insulin secretion. Lastly, a large number of genetic syndromes are now linked to hyperinsulinaemic hypoglycaemia. As the molecular and genetic basis of CHI has expanded over the last few years, this review aims to provide an up-to-date knowledge on the genetic causes of CHI.
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Affiliation(s)
- Sonya Galcheva
- Department of Paediatrics, University Hospital St. Marina, Varna Medical University, Varna, Bulgaria
| | - Hüseyin Demirbilek
- Department of Paediatric Endocrinology, Hacettepe University Faculty of Medicine, Ankara, Turkey
| | - Sara Al-Khawaga
- Division of Endocrinology, Department of Paediatric Medicine, Sidra Medicine, Doha, Qatar
| | - Khalid Hussain
- Division of Endocrinology, Department of Paediatric Medicine, Sidra Medicine, Doha, Qatar
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11
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Tinker A, Aziz Q, Li Y, Specterman M. ATP‐Sensitive Potassium Channels and Their Physiological and Pathophysiological Roles. Compr Physiol 2018; 8:1463-1511. [DOI: 10.1002/cphy.c170048] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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12
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Yang YY, Long RK, Ferrara CT, Gitelman SE, German MS, Yang SB. A new familial form of a late-onset, persistent hyperinsulinemic hypoglycemia of infancy caused by a novel mutation in KCNJ11. Channels (Austin) 2017; 11:636-647. [PMID: 29087246 PMCID: PMC5786184 DOI: 10.1080/19336950.2017.1393131] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The ATP-sensitive potassium channel (KATP) functions as a metabo-electric transducer in regulating insulin secretion from pancreatic β-cells. The pancreatic KATP channel is composed of a pore-forming inwardly-rectifying potassium channel, Kir6.2, and a regulatory subunit, sulphonylurea receptor 1 (SUR1). Loss-of-function mutations in either subunit often lead to the development of persistent hyperinsulinemic hypoglycemia of infancy (PHHI). PHHI is a rare genetic disease and most patients present with immediate onset within the first few days after birth. In this study, we report an unusual form of PHHI, in which the index patient developed hyperinsulinemic hypoglycemia after 1 year of age. The patient failed to respond to routine medication for PHHI and underwent a complete pancreatectomy. Genotyping of the index patient and his immediate family members showed that the patient and other family members with hypoglycemic episodes carried a heterozygous novel mutation in KCNJ11 (C83T), which encodes Kir6.2 (A28V). Electrophysiological and cell biological experiments revealed that A28V hKir6.2 is a dominant-negative, loss-of-function mutation and that KATP channels carrying this mutation failed to reach the cell surface. De novo protein structure prediction indicated that this A28V mutation reoriented the ER retention motif located at the C-terminal of the hKir6.2, and this result may explain the trafficking defect caused by this point mutation. Our study is the first report of a novel form of late-onset PHHI that is caused by a dominant mutation in KCNJ11 and exhibits a defect in proper surface expression of Kir6.2.
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Affiliation(s)
- Yen-Yu Yang
- a Institute of Biomedical Sciences, Academia Sinica , Taipei , Taiwan
| | - Roger K Long
- b Department of Pediatrics , University of California San Francisco , USA
| | | | - Stephen E Gitelman
- b Department of Pediatrics , University of California San Francisco , USA.,c Diabetes Center , University of California San Francisco , USA
| | - Michael S German
- c Diabetes Center , University of California San Francisco , USA.,d Department of Medicine and Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research , University of California San Francisco , USA
| | - Shi-Bing Yang
- a Institute of Biomedical Sciences, Academia Sinica , Taipei , Taiwan
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13
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Bai C, Gao Y, Zhang X, Yang W, Guan W. MicroRNA-34c acts as a bidirectional switch in the maturation of insulin-producing cells derived from mesenchymal stem cells. Oncotarget 2017; 8:106844-106857. [PMID: 29290993 PMCID: PMC5739778 DOI: 10.18632/oncotarget.21883] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 09/21/2017] [Indexed: 01/08/2023] Open
Abstract
miRNAs regulate insulin secretion, pancreatic development, and beta-cell differentiation. However, their function in the differentiation of IPCs from MSCs is poorly understood. In this study, to screen for miRNAs and their targets that function during the formation of IPCs from MSCs, we examined the miRNA expression profiles of MSCs and IPCs using RNA-seq and qPCR to confirm the above results. We found that miR-34c exhibited transient upregulation at an early stage of the formation of IPCs derived from MSCs. Next, we analyzed the biological function of miR-34c by predicting its targets using bioinformatic tools. Combining our data with those from previous reports, we found that miR-34c and its targets play an important role in the formation of IPCs. Therefore, we overexpressed miR-34c and expressed small interfering RNAs of its targets in MSCs to investigate their functions in IPC formation. We found that miR-34c acts as a bidirectional switch in the formation of IPCs derived from MSCs by regulating the expression of targets to affect insulin synthesis and secretion. miR-34c was shown to downregulate its targets, including PDE7B, PDGFRA, and MAP2K1, to increase proinsulin synthesis, but when miR-34c continually dysregulated such expression, it suppressed the expression of other targets, namely ACSL4 and SAR1A, weakening insulin secretion in IPCs. These results suggest that endogenous miRNAs involved in the formation of IPCs from stem cells should be considered in the development of effective cell transplant therapy for diabetes.
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Affiliation(s)
- Chunyu Bai
- Key Laboratory of Precision Oncology of Shandong Higher Education, Institute of Precision Medicine, Jining Medical University, Jining, 272067, PR China.,Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
| | - Yuhua Gao
- College of Basic Medicine, Jining Medical University, Jining, 272067, PR China.,Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
| | - Xiangyang Zhang
- College of Basic Medicine, Jining Medical University, Jining, 272067, PR China
| | - Wancai Yang
- Key Laboratory of Precision Oncology of Shandong Higher Education, Institute of Precision Medicine, Jining Medical University, Jining, 272067, PR China.,Department of Pathology, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Weijun Guan
- Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
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14
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Guo D, Liu H, Ruzi A, Gao G, Nasir A, Liu Y, Yang F, Wu F, Xu G, Li YX. Modeling Congenital Hyperinsulinism with ABCC8-Deficient Human Embryonic Stem Cells Generated by CRISPR/Cas9. Sci Rep 2017; 7:3156. [PMID: 28600547 PMCID: PMC5466656 DOI: 10.1038/s41598-017-03349-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 04/27/2017] [Indexed: 02/08/2023] Open
Abstract
Congenital hyperinsulinism (CHI) is a rare genetic disorder characterized by excess insulin secretion, which results in hypoglycemia. Mutation of sulfonylurea receptor 1 (SUR1), encoded by the ABCC8 gene, is the main cause of CHI. Here, we captured the phenotype of excess insulin secretion through pancreatic differentiation of ABCC8-deficient stem cells generated by the CRISPR/Cas9 system. ABCC8-deficient insulin-producing cells secreted higher insulin than their wild-type counterparts, and the excess insulin secretion was rescued by nifedipine, octreotide and nicorandil. Further, we tested the role of SUR1 in response to different potassium levels and found that dysfunction of SUR1 decreased the insulin secretion rate in low and high potassium environments. Hence, pancreatic differentiation of ABCC8-deficient cells recapitulated the CHI disease phenotype in vitro, which represents an attractive model to further elucidate the function of SUR1 and to develop and screen for novel therapeutic drugs.
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Affiliation(s)
- Dongsheng Guo
- Institute of Public Health, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,University of Chinese Academy of Sciences, Beijing, China.,Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,Guangdong Provincial Key Laboratory of Biocomputing, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Haikun Liu
- Institute of Public Health, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,Guangdong Provincial Key Laboratory of Biocomputing, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Aynisahan Ruzi
- Institute of Public Health, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,University of Chinese Academy of Sciences, Beijing, China.,Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,Guangdong Provincial Key Laboratory of Biocomputing, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Ge Gao
- Institute of Public Health, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,Guangdong Provincial Key Laboratory of Biocomputing, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Abbas Nasir
- Institute of Public Health, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,University of Chinese Academy of Sciences, Beijing, China.,Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,Guangdong Provincial Key Laboratory of Biocomputing, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Yanli Liu
- Institute of Public Health, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,University of Chinese Academy of Sciences, Beijing, China.,Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,Guangdong Provincial Key Laboratory of Biocomputing, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Fan Yang
- Institute of Public Health, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,Guangdong Provincial Key Laboratory of Biocomputing, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Feima Wu
- Institute of Public Health, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,University of Chinese Academy of Sciences, Beijing, China.,Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,Guangdong Provincial Key Laboratory of Biocomputing, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Guosheng Xu
- Institute of Public Health, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,University of Chinese Academy of Sciences, Beijing, China.,Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.,Guangdong Provincial Key Laboratory of Biocomputing, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Yin-Xiong Li
- Institute of Public Health, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China. .,University of Chinese Academy of Sciences, Beijing, China. .,Key Laboratory of Regenerative Biology, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China. .,Guangdong Provincial Key Laboratory of Biocomputing, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China.
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15
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Fang J, Liu M, Zhang X, Sakamoto T, Taatjes DJ, Jena BP, Sun F, Woods J, Bryson T, Kowluru A, Zhang K, Chen X. COPII-Dependent ER Export: A Critical Component of Insulin Biogenesis and β-Cell ER Homeostasis. Mol Endocrinol 2015; 29:1156-69. [PMID: 26083833 DOI: 10.1210/me.2015-1012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Pancreatic β-cells possess a highly active protein synthetic and export machinery in the endoplasmic reticulum (ER) to accommodate the massive production of proinsulin. ER homeostasis is vital for β-cell functions and is maintained by the delicate balance between protein synthesis, folding, export, and degradation. Disruption of ER homeostasis by diabetes-causing factors leads to β-cell death. Among the 4 components to maintain ER homeostasis in β-cells, the role of ER export in insulin biogenesis is the least understood. To address this knowledge gap, the present study investigated the molecular mechanism of proinsulin ER export in MIN6 cells and primary islets. Two inhibitory mutants of the secretion-associated RAS-related protein (Sar)1 small GTPase, known to specifically block coat protein complex II (COPII)-dependent ER export, were overexpressed in β-cells using recombinant adenoviruses. Results from this approach, as well as small interfering RNA-mediated Sar1 knockdown, demonstrated that defective Sar1 function blocked proinsulin ER export and abolished its conversion to mature insulin in MIN6 cells, isolated mouse, and human islets. It is further revealed, using an in vitro vesicle formation assay, that proinsulin was packaged into COPII vesicles in a GTP- and Sar1-dependent manner. Blockage of COPII-dependent ER exit by Sar1 mutants strongly induced ER morphology change, ER stress response, and β-cell apoptosis. These responses were mediated by the PKR (double-stranded RNA-dependent kinase)-like ER kinase (PERK)/eukaryotic translation initiation factor 2α (p-eIF2α) and inositol-requiring protein 1 (IRE1)/x-box binding protein 1 (Xbp1) pathways but not via activating transcription factor 6 (ATF6). Collectively, results from the study demonstrate that COPII-dependent ER export plays a vital role in insulin biogenesis, ER homeostasis, and β-cell survival.
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Affiliation(s)
- Jingye Fang
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Ming Liu
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Xuebao Zhang
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Takeshi Sakamoto
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Douglas J Taatjes
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Bhanu P Jena
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Fei Sun
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - James Woods
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Tim Bryson
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Anjaneyulu Kowluru
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Kezhong Zhang
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
| | - Xuequn Chen
- Department of Physiology (J.F., B.P.J., F.S., J.W., T.B., X.C.) and Center for Molecular Medicine and Genetics (X.Z., K.Z.), School of Medicine, Department of Physics and Astronomy (T.S.), College of Liberal Arts and Sciences, and Department of Pharmaceutical Sciences (A.K.), Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, and John D. Dingell VA Medical Center (A.K.), Detroit, Michigan 48201; Department of Internal Medicine (M.L.), University of Michigan, Ann Arbor, Michigan 48109; and Department of Pathology (D.J.T.), Microscopy Imaging Center, University of Vermont College of Medicine, Burlington, Vermont 05405
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16
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Abstract
Congenital hyperinsulinism (CHI) is a complex heterogeneous condition in which insulin secretion from pancreatic β-cells is unregulated and inappropriate for the level of blood glucose. The inappropriate insulin secretion drives glucose into the insulin-sensitive tissues, such as the muscle, liver and adipose tissue, leading to severe hyperinsulinaemic hypoglycaemia (HH). At a molecular level, genetic abnormalities in nine different genes (ABCC8, KCNJ11, GLUD1, GCK, HNF4A, HNF1A, SLC16A1, UCP2 and HADH) have been identified which cause CHI. Autosomal recessive and dominant mutations in ABCC8/KCNJ11 are the commonest cause of medically unresponsive CHI. Mutations in GLUD1 and HADH lead to leucine-induced HH, and these two genes encode the key enzymes glutamate dehydrogenase and short chain 3-hydroxyacyl-CoA dehydrogenase which play a key role in amino acid and fatty acid regulation of insulin secretion respectively. Genetic abnormalities in HNF4A and HNF1A lead to a dual phenotype of HH in the newborn period and maturity onset-diabetes later in life. This state of the art review provides an update on the molecular basis of CHI.
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Affiliation(s)
- Sofia A Rahman
- Genetics and Genomic MedicineUCL Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UKDepartment of Paediatric EndocrinologyGreat Ormond Street Hospital for Children NHS, 30 Guilford Street, London WC1N 1EH, UK
| | - Azizun Nessa
- Genetics and Genomic MedicineUCL Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UKDepartment of Paediatric EndocrinologyGreat Ormond Street Hospital for Children NHS, 30 Guilford Street, London WC1N 1EH, UK
| | - Khalid Hussain
- Genetics and Genomic MedicineUCL Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UKDepartment of Paediatric EndocrinologyGreat Ormond Street Hospital for Children NHS, 30 Guilford Street, London WC1N 1EH, UK Genetics and Genomic MedicineUCL Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UKDepartment of Paediatric EndocrinologyGreat Ormond Street Hospital for Children NHS, 30 Guilford Street, London WC1N 1EH, UK
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17
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Zhou J, Li W, Xie Q, Hou Y, Zhan S, Yang X, Xu X, Cai J, Huang Z. Effects of simvastatin on glucose metabolism in mouse MIN6 cells. J Diabetes Res 2014; 2014:376570. [PMID: 24995341 PMCID: PMC4065655 DOI: 10.1155/2014/376570] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2014] [Accepted: 04/16/2014] [Indexed: 01/14/2023] Open
Abstract
The aim of this study was to investigate the effects of simvastatin on insulin secretion in mouse MIN6 cells and the possible mechanism. MIN6 cells were, respectively, treated with 0 μ M, 2 μ M, 5 μ M, and 10 μ M simvastatin for 48 h. Radio immunoassay was performed to measure the effect of simvastatin on insulin secretion in MIN6 cells. Luciferase method was used to examine the content of ATP in MIN6 cells. Real-time PCR and western blotting were performed to measure the mRNA and protein levels of inward rectifier potassium channel 6.2 (Kir6.2), voltage-dependent calcium channel 1.2 (Cav1.2), and glucose transporter-2 (GLUT2), respectively. ATP-sensitive potassium current and L-type calcium current were recorded by whole-cell patch-clamp technique. The results showed that high concentrations of simvastatin (5 μ M and 10 μ M) significantly reduced the synthesis and secretion of insulin compared to control groups in MIN6 cells (P < 0.05). ATP content in simvastatin-treated cells was lower than in control cells (P < 0.05). Compared with control group, the mRNA and protein expression of Kir6.2 increased with treatment of simvastatin (P < 0.05), and mRNA and protein expression of Cav1.2 and GLUT2 decreased in response to simvastatin (P < 0.05). Moreover, simvastatin increased the ATP-sensitive potassium current and reduced the L-type calcium current. These results suggest that simvastatin inhibits the synthesis and secretion of insulin through a reduction in saccharometabolism in MIN6 cells.
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Affiliation(s)
- Jieqiong Zhou
- Department of Cardiology, The First Affiliated Hospital of Xiamen University, 55 Zhenhai Road, Xiamen 361003, China
| | - Weihua Li
- Department of Cardiology, The First Affiliated Hospital of Xiamen University, 55 Zhenhai Road, Xiamen 361003, China
| | - Qiang Xie
- Department of Cardiology, The First Affiliated Hospital of Xiamen University, 55 Zhenhai Road, Xiamen 361003, China
| | - Yuxi Hou
- Department of Cardiology, The First Affiliated Hospital of Xiamen University, 55 Zhenhai Road, Xiamen 361003, China
| | - Shaopeng Zhan
- Department of Cardiology, The First Affiliated Hospital of Xiamen University, 55 Zhenhai Road, Xiamen 361003, China
| | - Xi Yang
- Department of Cardiology, The First Affiliated Hospital of Xiamen University, 55 Zhenhai Road, Xiamen 361003, China
| | - Xiaofeng Xu
- Department of Cardiology, The First Affiliated Hospital of Xiamen University, 55 Zhenhai Road, Xiamen 361003, China
| | - Jun Cai
- Department of Cardiology, Chaoyang Hospital, Capital Medical University, 8th Gongtinanlu Road, Chaoyang District, Beijing 100020, China
- *Jun Cai: and
| | - Zhengrong Huang
- Department of Cardiology, The First Affiliated Hospital of Xiamen University, 55 Zhenhai Road, Xiamen 361003, China
- *Zhengrong Huang:
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18
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Martin GM, Chen PC, Devaraneni P, Shyng SL. Pharmacological rescue of trafficking-impaired ATP-sensitive potassium channels. Front Physiol 2013; 4:386. [PMID: 24399968 PMCID: PMC3870925 DOI: 10.3389/fphys.2013.00386] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 12/09/2013] [Indexed: 12/25/2022] Open
Abstract
ATP-sensitive potassium (KATP) channels link cell metabolism to membrane excitability and are involved in a wide range of physiological processes including hormone secretion, control of vascular tone, and protection of cardiac and neuronal cells against ischemic injuries. In pancreatic β-cells, KATP channels play a key role in glucose-stimulated insulin secretion, and gain or loss of channel function results in neonatal diabetes or congenital hyperinsulinism, respectively. The β-cell KATP channel is formed by co-assembly of four Kir6.2 inwardly rectifying potassium channel subunits encoded by KCNJ11 and four sulfonylurea receptor 1 subunits encoded by ABCC8. Many mutations in ABCC8 or KCNJ11 cause loss of channel function, thus, congenital hyperinsulinism by hampering channel biogenesis and hence trafficking to the cell surface. The trafficking defects caused by a subset of these mutations can be corrected by sulfonylureas, KATP channel antagonists that have long been used to treat type 2 diabetes. More recently, carbamazepine, an anticonvulsant that is thought to target primarily voltage-gated sodium channels has been shown to correct KATP channel trafficking defects. This article reviews studies to date aimed at understanding the mechanisms by which mutations impair channel biogenesis and trafficking and the mechanisms by which pharmacological ligands overcome channel trafficking defects. Insight into channel structure-function relationships and therapeutic implications from these studies are discussed.
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Affiliation(s)
- Gregory M Martin
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University Portland, OR, USA
| | - Pei-Chun Chen
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University Portland, OR, USA
| | - Prasanna Devaraneni
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University Portland, OR, USA
| | - Show-Ling Shyng
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University Portland, OR, USA
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19
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Martínez-Mármol R, Pérez-Verdaguer M, Roig SR, Vallejo-Gracia A, Gotsi P, Serrano-Albarrás A, Bahamonde MI, Ferrer-Montiel A, Fernández-Ballester G, Comes N, Felipe A. A non-canonical di-acidic signal at the C-terminus of Kv1.3 determines anterograde trafficking and surface expression. J Cell Sci 2013; 126:5681-91. [PMID: 24144698 DOI: 10.1242/jcs.134825] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Impairment of Kv1.3 expression at the cell membrane in leukocytes and sensory neuron contributes to the pathophysiology of autoimmune diseases and sensory syndromes. Molecular mechanisms underlying Kv1.3 channel trafficking to the plasma membrane remain elusive. We report a novel non-canonical di-acidic signal (E483/484) at the C-terminus of Kv1.3 essential for anterograde transport and surface expression. Notably, homologous motifs are conserved in neuronal Kv1 and Shaker channels. Biochemical analysis revealed interactions with the Sec24 subunit of the coat protein complex II. Disruption of this complex retains the channel at the endoplasmic reticulum. A molecular model of the Kv1.3-Sec24a complex suggests salt-bridges between the di-acidic E483/484 motif in Kv1.3 and the di-basic R750/752 sequence in Sec24. These findings identify a previously unrecognized motif of Kv channels essential for their expression on the cell surface. Our results contribute to our understanding of how Kv1 channels target to the cell membrane, and provide new therapeutic strategies for the treatment of pathological conditions.
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Affiliation(s)
- Ramón Martínez-Mármol
- Molecular Physiology Laboratory, Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Av. Diagonal 643, E-08028 Barcelona, Spain
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20
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Wang T, Cheng Y, Dou Y, Goonesekara C, David JP, Steele DF, Huang C, Fedida D. Trafficking of an endogenous potassium channel in adult ventricular myocytes. Am J Physiol Cell Physiol 2012; 303:C963-76. [PMID: 22914645 DOI: 10.1152/ajpcell.00217.2012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The roles of several small GTPases in the expression of an endogenous potassium current, I(to,f), in adult rat ventricular myocytes have been investigated. The results indicate that forward trafficking of newly synthesized Kv4.2, which underlies I(to,f) in these cells, requires both Rab1 and Sar1 function. Expression of a Rab1 dominant negative (DN) reduced I(to,f) current density by roughly one-half relative to control, mCherry-transfected myocytes. Similarly, expression of a Sar1DN nearly halved I(to,f) current density. Rab11 is not essential to trafficking of Kv4.2, as expression of a Rab11DN had no effect on I(to,f) over the time frames investigated here. In a process dependent on intact endoplasmic reticulum (ER)-to-Golgi transport, however, overexpression of wild-type Rab11 resulted in a doubling of I(to,f) density; block of ER-to-Golgi traffic by Brefeldin A completely abrogated the effect. Also implicated in the trafficking of Kv4.2 are Rab5 and Rab4. Rab5DN expression increased endogenous I(to,f) by two- to threefold, nonadditively with inhibition of dynamin-dependent endocytosis. And, in a phenomenon similar to that previously reported for myoblast-expressed Kv1.5, Rab4DN expression roughly doubled endogenous peak transient currents. Colocalization experiments confirmed the involvement of Rab4 in postinternalization trafficking of Kv4.2. There was little role evident for the lysosome in the degradation of internalized Kv4.2, as overexpression of neither wild-type nor DN isoforms of Rab7 had any effect on I(to,f). Instead, degradation may depend largely on the proteasome; the proteasome inhibitor MG132 significantly increased I(to,f) density.
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Affiliation(s)
- Tiantian Wang
- Dept. of Anesthesiology, Pharmacology and Therapeutics, Univ. of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada V6T 1Z3.
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21
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Balse E, Steele DF, Abriel H, Coulombe A, Fedida D, Hatem SN. Dynamic of Ion Channel Expression at the Plasma Membrane of Cardiomyocytes. Physiol Rev 2012; 92:1317-58. [DOI: 10.1152/physrev.00041.2011] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cardiac myocytes are characterized by distinct structural and functional entities involved in the generation and transmission of the action potential and the excitation-contraction coupling process. Key to their function is the specific organization of ion channels and transporters to and within distinct membrane domains, which supports the anisotropic propagation of the depolarization wave. This review addresses the current knowledge on the molecular actors regulating the distinct trafficking and targeting mechanisms of ion channels in the highly polarized cardiac myocyte. In addition to ubiquitous mechanisms shared by other excitable cells, cardiac myocytes show unique specialization, illustrated by the molecular organization of myocyte-myocyte contacts, e.g., the intercalated disc and the gap junction. Many factors contribute to the specialization of the cardiac sarcolemma and the functional expression of cardiac ion channels, including various anchoring proteins, motors, small GTPases, membrane lipids, and cholesterol. The discovery of genetic defects in some of these actors, leading to complex cardiac disorders, emphasizes the importance of trafficking and targeting of ion channels to cardiac function. A major challenge in the field is to understand how these and other actors work together in intact myocytes to fine-tune ion channel expression and control cardiac excitability.
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Affiliation(s)
- Elise Balse
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - David F. Steele
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - Hugues Abriel
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - Alain Coulombe
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - David Fedida
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - Stéphane N. Hatem
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
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22
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Georges A, Bonneau J, Bonnefont-Rousselot D, Champigneulle J, Rabès JP, Abifadel M, Aparicio T, Guenedet JC, Bruckert E, Boileau C, Morali A, Varret M, Aggerbeck LP, Samson-Bouma ME. Molecular analysis and intestinal expression of SAR1 genes and proteins in Anderson's disease (Chylomicron retention disease). Orphanet J Rare Dis 2011; 6:1. [PMID: 21235735 PMCID: PMC3029219 DOI: 10.1186/1750-1172-6-1] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Accepted: 01/14/2011] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Anderson's disease (AD) or chylomicron retention disease (CMRD) is a very rare hereditary lipid malabsorption syndrome. In order to discover novel mutations in the SAR1B gene and to evaluate the expression, as compared to healthy subjects, of the Sar1 gene and protein paralogues in the intestine, we investigated three previously undescribed individuals with the disease. METHODS The SAR1B, SAR1A and PCSK9 genes were sequenced. The expression of the SAR1B and SAR1A genes in intestinal biopsies of both normal individuals and patients was measured by RTqPCR. Immunohistochemistry using antibodies to recombinant Sar1 protein was used to evaluate the expression and localization of the Sar1 paralogues in the duodenal biopsies. RESULTS Two patients had a novel SAR1B mutation (p.Asp48ThrfsX17). The third patient, who had a previously described SAR1B mutation (p.Leu28ArgfsX7), also had a p.Leu21dup variant of the PCSK9 gene. The expression of the SAR1B gene in duodenal biopsies from an AD/CMRD patient was significantly decreased whereas the expression of the SAR1A gene was significantly increased, as compared to healthy individuals. The Sar1 proteins were present in decreased amounts in enterocytes in duodenal biopsies from the patients as compared to those from healthy subjects. CONCLUSIONS Although the proteins encoded by the SAR1A and SAR1B genes are 90% identical, the increased expression of the SAR1A gene in AD/CMRD does not appear to compensate for the lack of the SAR1B protein. The PCSK9 variant, although reported to be associated with low levels of cholesterol, does not appear to exert any additional effect in this patient. The results provide further insight into the tissue-specific nature of AD/CMRD.
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Affiliation(s)
- Amandine Georges
- Service de Médecine Infantile 3 et Génétique Clinique, INSERM U954, Hôpital d'Enfants Brabois, CHU Nancy, Vandoeuvre les Nancy, 54511, France
| | - Jessica Bonneau
- INSERM U781, Université Paris Descartes, Hôpital Necker Enfants Malades, Paris, 75015, France
| | - Dominique Bonnefont-Rousselot
- UF de Biochimie des Maladies Métaboliques, Service de Biochimie Métabolique, Groupe Hospitalier Pitié-Salpêtrière (AP-HP), and Département de Biologie Expérimentale, Métabolique et Clinique, EA 4466, Faculté des Sciences Pharmaceutiques et Biologiques, Université Paris Descartes, Paris, 75013, France
| | - Jacqueline Champigneulle
- Laboratoire d'Anatomie et de Cytologie Pathologiques, Hôpital de Brabois, Université Paris 13, Bobigny, 93000, France
| | - Jean P Rabès
- INSERM U781, Université Paris Descartes, Hôpital Necker Enfants Malades, Paris, 75015, France
- Service de Biochimie et Génétique Moléculaire, CHU A Paré, AP-HP et Faculté de Médecine (PIFO-UVSQ), Boulogne, 92104, France
| | - Marianne Abifadel
- INSERM U781, Université Paris Descartes, Hôpital Necker Enfants Malades, Paris, 75015, France
| | - Thomas Aparicio
- Service de Gastroentérologie, Hôpital Avicenne, 125 rue de Stalingrad, Université Paris 13, Bobigny, 93000, France
| | - Jean C Guenedet
- Laboratoire d'Anatomie et de Cytologie Pathologiques, Hôpital de Brabois, Université Paris 13, Bobigny, 93000, France
- Service de Microscopie Electronique, Hôpital de Brabois, CHU Nancy, Vandoeuvre les Nancy, 54511, France
| | - Eric Bruckert
- Service d'Endocrinologie-Métabolisme, Hôpital Pitié Salpêtrière, (AP-HP), Paris, 75013, France
| | - Catherine Boileau
- INSERM U781, Université Paris Descartes, Hôpital Necker Enfants Malades, Paris, 75015, France
- Service de Biochimie et Génétique Moléculaire, CHU A Paré, AP-HP et Faculté de Médecine (PIFO-UVSQ), Boulogne, 92104, France
| | - Alain Morali
- Service de Médecine Infantile 3 et Génétique Clinique, INSERM U954, Hôpital d'Enfants Brabois, CHU Nancy, Vandoeuvre les Nancy, 54511, France
| | - Mathilde Varret
- INSERM U781, Université Paris Descartes, Hôpital Necker Enfants Malades, Paris, 75015, France
| | | | - Marie E Samson-Bouma
- INSERM U781, Université Paris Descartes, Hôpital Necker Enfants Malades, Paris, 75015, France
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23
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Chen PC, Bruederle CE, Gaisano HY, Shyng SL. Syntaxin 1A regulates surface expression of beta-cell ATP-sensitive potassium channels. Am J Physiol Cell Physiol 2011; 300:C506-16. [PMID: 21209369 DOI: 10.1152/ajpcell.00429.2010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The pancreatic ATP-sensitive potassium (K(ATP)) channel consisting of four inwardly rectifying potassium channel 6.2 (Kir6.2) and four sulfonylurea receptor SUR1 subunits plays a key role in insulin secretion by linking glucose metabolism to membrane excitability. Syntaxin 1A (Syn-1A) is a plasma membrane protein important for membrane fusion during exocytosis of insulin granules. Here, we show that Syn-1A and K(ATP) channels endogenously expressed in the insulin-secreting cell INS-1 interact. Upregulation of Syn-1A by overexpression in INS-1 leads to a decrease, whereas downregulation of Syn-1A by small interfering RNA (siRNA) leads to an increase, in surface expression of K(ATP) channels. Using COSm6 cells as a heterologous expression system for mechanistic investigation, we found that Syn-1A interacts with SUR1 but not Kir6.2. Furthermore, Syn-1A decreases surface expression of K(ATP) channels via two mechanisms. One mechanism involves accelerated endocytosis of surface channels. The other involves decreased biogenesis and processing of channels in the early secretory pathway. This regulation is K(ATP) channel specific as Syn-1A has no effect on another inward rectifier potassium channel Kir3.1/3.4. Our results demonstrate that in addition to a previously documented role in modulating K(ATP) channel gating, Syn-1A also regulates K(ATP) channel expression in β-cells. We propose that physiological or pathological changes in Syn-1A expression may modulate insulin secretion by altering glucose-secretion coupling via changes in K(ATP) channel expression.
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Affiliation(s)
- Pei-Chun Chen
- Dept. of Biochemistry and Molecular Biology, School of Medicine, Oregon Health & Science Univ., 3181 S. W. Sam Jackson Park Rd., Portland, OR 97239, USA
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24
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Chen L, Jeffries O, Rowe ICM, Liang Z, Knaus HG, Ruth P, Shipston MJ. Membrane trafficking of large conductance calcium-activated potassium channels is regulated by alternative splicing of a transplantable, acidic trafficking motif in the RCK1-RCK2 linker. J Biol Chem 2010; 285:23265-75. [PMID: 20479001 PMCID: PMC2906319 DOI: 10.1074/jbc.m110.139758] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2010] [Indexed: 01/26/2023] Open
Abstract
Trafficking of the pore-forming alpha-subunits of large conductance calcium- and voltage-activated potassium (BK) channels to the cell surface represents an important regulatory step in controlling BK channel function. Here, we identify multiple trafficking signals within the intracellular RCK1-RCK2 linker of the cytosolic C terminus of the channel that are required for efficient cell surface expression of the channel. In particular, an acidic cluster-like motif was essential for channel exit from the endoplasmic reticulum and subsequent cell surface expression. This motif could be transplanted onto a heterologous nonchannel protein to enhance cell surface expression by accelerating endoplasmic reticulum export. Importantly, we identified a human alternatively spliced BK channel variant, hSloDelta(579-664), in which these trafficking signals are excluded because of in-frame exon skipping. The hSloDelta(579-664) variant is expressed in multiple human tissues and cannot form functional channels at the cell surface even though it retains the putative RCK domains and downstream trafficking signals. Functionally, the hSloDelta(579-664) variant acts as a dominant negative subunit to suppress cell surface expression of BK channels. Thus alternative splicing of the intracellular RCK1-RCK2 linker plays a critical role in determining cell surface expression of BK channels by controlling the inclusion/exclusion of multiple trafficking motifs.
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Affiliation(s)
- Lie Chen
- From the
Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom
| | - Owen Jeffries
- From the
Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom
| | - Iain C. M. Rowe
- From the
Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom
| | - Zhi Liang
- From the
Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom
| | - Hans-Guenther Knaus
- the
Division for Molecular and Cellular Pharmacology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Medical University Innsbruck, Peter-Mayr Strasse 1, 6020 Innsbruck, Austria, and
| | - Peter Ruth
- Pharmacology and Toxicology, Institute of Pharmacy, University Tuebingen, 72076 Tuebingen, Germany
| | - Michael J. Shipston
- From the
Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom
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25
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McTaggart JS, Clark RH, Ashcroft FM. The role of the KATP channel in glucose homeostasis in health and disease: more than meets the islet. J Physiol 2010; 588:3201-9. [PMID: 20519313 DOI: 10.1113/jphysiol.2010.191767] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
ATP-sensitive potassium (K(ATP)) channels are critical for the maintenance of glucose homeostasis. They are essential for glucose-stimulated insulin secretion from pancreatic beta-cells, contribute to the mechanisms by which hypoglycaemia stimulates glucagon release from pancreatic alpha-cells, and are involved in glucose uptake into skeletal muscle, glucose production and release from the liver, and feeding behaviour. Not surprisingly, loss- or gain-of-function mutations in K(ATP) channel genes have profound effects, giving rise to congenital hyperinsulinaemia and neonatal diabetes respectively. This symposium review focuses on our current understanding of the role of the K(ATP) channel in glucose homeostasis in health and disease.
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Affiliation(s)
- James S McTaggart
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, and OXION Centre for Ion Channel Studies, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
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26
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Manna PT, Smith AJ, Taneja TK, Howell GJ, Lippiat JD, Sivaprasadarao A. Constitutive endocytic recycling and protein kinase C-mediated lysosomal degradation control K(ATP) channel surface density. J Biol Chem 2010; 285:5963-73. [PMID: 20026601 PMCID: PMC2820821 DOI: 10.1074/jbc.m109.066902] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 12/07/2009] [Indexed: 11/06/2022] Open
Abstract
Pancreatic ATP-sensitive potassium (K(ATP)) channels control insulin secretion by coupling the excitability of the pancreatic beta-cell to glucose metabolism. Little is currently known about how the plasma membrane density of these channels is regulated. We therefore set out to examine in detail the endocytosis and recycling of these channels and how these processes are regulated. To achieve this goal, we expressed K(ATP) channels bearing an extracellular hemagglutinin epitope in human embryonic kidney cells and followed their fate along the endocytic pathway. Our results show that K(ATP) channels undergo multiple rounds of endocytosis and recycling. Further, activation of protein kinase C (PKC) with phorbol 12-myristate 13-acetate significantly decreases K(ATP) channel surface density by reducing channel recycling and diverting the channel to lysosomal degradation. These findings were recapitulated in the model pancreatic beta-cell line INS1e, where activation of PKC leads to a decrease in the surface density of native K(ATP) channels. Because sorting of internalized channels between lysosomal and recycling pathways could have opposite effects on the excitability of pancreatic beta-cells, we propose that PKC-regulated K(ATP) channel trafficking may play a role in the regulation of insulin secretion.
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Affiliation(s)
- Paul T. Manna
- From the Multidisciplinary Cardiovascular Research Centre, Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
| | - Andrew J. Smith
- From the Multidisciplinary Cardiovascular Research Centre, Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
| | - Tarvinder K. Taneja
- From the Multidisciplinary Cardiovascular Research Centre, Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
| | - Gareth J. Howell
- From the Multidisciplinary Cardiovascular Research Centre, Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
| | - Jonathan D. Lippiat
- From the Multidisciplinary Cardiovascular Research Centre, Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
| | - Asipu Sivaprasadarao
- From the Multidisciplinary Cardiovascular Research Centre, Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom
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27
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Bhalla-Gehi R, Penuela S, Churko JM, Shao Q, Laird DW. Pannexin1 and pannexin3 delivery, cell surface dynamics, and cytoskeletal interactions. J Biol Chem 2010; 285:9147-60. [PMID: 20086016 DOI: 10.1074/jbc.m109.082008] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Pannexins (Panx) are a class of integral membrane proteins that have been proposed to exhibit characteristics similar to those of connexin family members. In this study, we utilized Cx43-positive BICR-M1R(k) cells to stably express Panx1, Panx3, or Panx1-green fluorescent protein (GFP) to assess their trafficking, cell surface dynamics, and interplay with the cytoskeletal network. Expression of a Sar1 dominant negative mutant revealed that endoplasmic reticulum to Golgi transport of Panx1 and Panx3 was mediated via COPII-dependent vesicles. Distinct from Cx43-GFP, fluorescence recovery after photobleaching studies revealed that both Panx1-GFP and Panx3-GFP remained highly mobile at the cell surface. Unlike Cx43, Panx1-GFP exhibited no detectable interrelationship with microtubules. Conversely, cytochalasin B-induced disruption of microfilaments caused a severe loss of cell surface Panx1-GFP, a reduction in the recoverable fraction of Panx1-GFP that remained at the cell surface, and a decrease in Panx1-GFP vesicular transport. Furthermore, co-immunoprecipitation and co-sedimentation assays revealed actin as a novel binding partner of Panx1. Collectively, we conclude that although Panx1 and Panx3 share a common endoplasmic reticulum to Golgi secretory pathway to Cx43, their ultimate cell surface residency appears to be independent of cell contacts and the need for intact microtubules. Importantly, Panx1 has an interaction with actin microfilaments that regulates its cell surface localization and mobility.
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Affiliation(s)
- Ruchi Bhalla-Gehi
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario N6A 5C1, Canada
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