1
|
Khodabukus A, Prabhu NK, Roberts T, Buldo M, Detwiler A, Fralish ZD, Kondash ME, Truskey GA, Koves TR, Bursac N. Bioengineered Model of Human LGMD2B Skeletal Muscle Reveals Roles of Intracellular Calcium Overload in Contractile and Metabolic Dysfunction in Dysferlinopathy. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024:e2400188. [PMID: 38887849 DOI: 10.1002/advs.202400188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 03/19/2024] [Indexed: 06/20/2024]
Abstract
Dysferlin is a multi-functional protein that regulates membrane resealing, calcium homeostasis, and lipid metabolism in skeletal muscle. Genetic loss of dysferlin results in limb girdle muscular dystrophy 2B/2R (LGMD2B/2R) and other dysferlinopathies - rare untreatable muscle diseases that lead to permanent loss of ambulation in humans. The mild disease severity in dysferlin-deficient mice and diverse genotype-phenotype relationships in LGMD2B patients have prompted the development of new in vitro models for personalized studies of dysferlinopathy. Here the first 3-D tissue-engineered hiPSC-derived skeletal muscle ("myobundle") model of LGMD2B is described that exhibits compromised contractile function, calcium-handling, and membrane repair, and transcriptomic changes indicative of impaired oxidative metabolism and mitochondrial dysfunction. In response to the fatty acid (FA) challenge, LGMD2B myobundles display mitochondrial deficits and intracellular lipid droplet (LD) accumulation. Treatment with the ryanodine receptor (RyR) inhibitor dantrolene or the dissociative glucocorticoid vamorolone restores LGMD2B contractility, improves membrane repair, and reduces LD accumulation. Lastly, it is demonstrated that chemically induced chronic RyR leak in healthy myobundles phenocopies LGMD2B contractile and metabolic deficit, but not the loss of membrane repair capacity. Together, these results implicate intramyocellular Ca2+ leak as a critical driver of dysferlinopathic phenotype and validate the myobundle system as a platform to study LGMD2B pathogenesis.
Collapse
Affiliation(s)
- Alastair Khodabukus
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Neel K Prabhu
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Taylor Roberts
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Meghan Buldo
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Amber Detwiler
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Zachary D Fralish
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Megan E Kondash
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - George A Truskey
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Timothy R Koves
- Duke Molecular Physiology Institute, Duke University, Durham, NC, 27708, USA
| | - Nenad Bursac
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| |
Collapse
|
2
|
Muriel J, Lukyanenko V, Kwiatkowski TA, Li Y, Bhattacharya S, Banford KK, Garman D, Bulgart HR, Sutton RB, Weisleder N, Bloch RJ. Nanodysferlins support membrane repair and binding to TRIM72/MG53 but do not localize to t-tubules or stabilize Ca 2+ signaling. Mol Ther Methods Clin Dev 2024; 32:101257. [PMID: 38779337 PMCID: PMC11109471 DOI: 10.1016/j.omtm.2024.101257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Accepted: 04/22/2024] [Indexed: 05/25/2024]
Abstract
Mutations in the DYSF gene, encoding the protein dysferlin, lead to several forms of muscular dystrophy. In healthy skeletal muscle, dysferlin concentrates in the transverse tubules and is involved in repairing the sarcolemma and stabilizing Ca2+ signaling after membrane disruption. The DYSF gene encodes 7-8 C2 domains, several Fer and Dysf domains, and a C-terminal transmembrane sequence. Because its coding sequence is too large to package in adeno-associated virus, the full-length sequence is not amenable to current gene delivery methods. Thus, we have examined smaller versions of dysferlin, termed "nanodysferlins," designed to eliminate several C2 domains, specifically C2 domains D, E, and F; B, D, and E; and B, D, E, and F. We also generated a variant by replacing eight amino acids in C2G in the nanodysferlin missing domains D through F. We electroporated dysferlin-null A/J mouse myofibers with Venus fusion constructs of these variants, or as untagged nanodysferlins together with GFP, to mark transfected fibers We found that, although these nanodysferlins failed to concentrate in transverse tubules, three of them supported membrane repair after laser wounding while all four bound the membrane repair protein, TRIM72/MG53, similar to WT dysferlin. By contrast, they failed to suppress Ca2+ waves after myofibers were injured by mild hypoosmotic shock. Our results suggest that the internal C2 domains of dysferlin are required for normal t-tubule localization and Ca2+ signaling and that membrane repair does not require these C2 domains.
Collapse
Affiliation(s)
- Joaquin Muriel
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Valeriy Lukyanenko
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Thomas A. Kwiatkowski
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Yi Li
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Sayak Bhattacharya
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Kassidy K. Banford
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Daniel Garman
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Hannah R. Bulgart
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Roger B. Sutton
- Department of Cell Physiology and Molecular Biophysics, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Noah Weisleder
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Robert J. Bloch
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| |
Collapse
|
3
|
Poudel BH, Fletcher S, Wilton SD, Aung-Htut M. Limb Girdle Muscular Dystrophy Type 2B (LGMD2B): Diagnosis and Therapeutic Possibilities. Int J Mol Sci 2024; 25:5572. [PMID: 38891760 PMCID: PMC11171558 DOI: 10.3390/ijms25115572] [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: 04/18/2024] [Revised: 05/11/2024] [Accepted: 05/16/2024] [Indexed: 06/21/2024] Open
Abstract
Dysferlin is a large transmembrane protein involved in critical cellular processes including membrane repair and vesicle fusion. Mutations in the dysferlin gene (DYSF) can result in rare forms of muscular dystrophy; Miyoshi myopathy; limb girdle muscular dystrophy type 2B (LGMD2B); and distal myopathy. These conditions are collectively known as dysferlinopathies and are caused by more than 600 mutations that have been identified across the DYSF gene to date. In this review, we discuss the key molecular and clinical features of LGMD2B, the causative gene DYSF, and the associated dysferlin protein structure. We also provide an update on current approaches to LGMD2B diagnosis and advances in drug development, including splice switching antisense oligonucleotides. We give a brief update on clinical trials involving adeno-associated viral gene therapy and the current progress on CRISPR/Cas9 mediated therapy for LGMD2B, and then conclude by discussing the prospects of antisense oligomer-based intervention to treat selected mutations causing dysferlinopathies.
Collapse
Affiliation(s)
- Bal Hari Poudel
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, WA 6150, Australia; (B.H.P.); (S.F.); (S.D.W.)
- Perron Institute for Neurological and Translational Science, The University of Western Australia, Perth, WA 6009, Australia
- Central Department of Biotechnology, Tribhuvan University, Kirtipur, Kathmandu 44618, Nepal
| | - Sue Fletcher
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, WA 6150, Australia; (B.H.P.); (S.F.); (S.D.W.)
| | - Steve D. Wilton
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, WA 6150, Australia; (B.H.P.); (S.F.); (S.D.W.)
- Perron Institute for Neurological and Translational Science, The University of Western Australia, Perth, WA 6009, Australia
| | - May Aung-Htut
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, WA 6150, Australia; (B.H.P.); (S.F.); (S.D.W.)
- Perron Institute for Neurological and Translational Science, The University of Western Australia, Perth, WA 6009, Australia
| |
Collapse
|
4
|
Quinn CJ, Cartwright EJ, Trafford AW, Dibb KM. On the role of dysferlin in striated muscle: membrane repair, t-tubules and Ca 2+ handling. J Physiol 2024; 602:1893-1910. [PMID: 38615232 DOI: 10.1113/jp285103] [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: 06/27/2023] [Accepted: 03/05/2024] [Indexed: 04/15/2024] Open
Abstract
Dysferlin is a 237 kDa membrane-associated protein characterised by multiple C2 domains with a diverse role in skeletal and cardiac muscle physiology. Mutations in DYSF are known to cause various types of human muscular dystrophies, known collectively as dysferlinopathies, with some patients developing cardiomyopathy. A myriad of in vitro membrane repair studies suggest that dysferlin plays an integral role in the membrane repair complex in skeletal muscle. In comparison, less is known about dysferlin in the heart, but mounting evidence suggests that dysferlin's role is similar in both muscle types. Recent findings have shown that dysferlin regulates Ca2+ handling in striated muscle via multiple mechanisms and that this becomes more important in conditions of stress. Maintenance of the transverse (t)-tubule network and the tight coordination of excitation-contraction coupling are essential for muscle contractility. Dysferlin regulates the maintenance and repair of t-tubules, and it is suspected that dysferlin regulates t-tubules and sarcolemmal repair through a similar mechanism. This review focuses on the emerging complexity of dysferlin's activity in striated muscle. Such insights will progress our understanding of the proteins and pathways that regulate basic heart and skeletal muscle function and help guide research into striated muscle pathology, especially that which arises due to dysferlin dysfunction.
Collapse
Affiliation(s)
- C J Quinn
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, School of Medical Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, 3.14 Core Technology Facility, Manchester, UK
| | - E J Cartwright
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, School of Medical Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, 3.14 Core Technology Facility, Manchester, UK
| | - A W Trafford
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, School of Medical Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, 3.14 Core Technology Facility, Manchester, UK
| | - K M Dibb
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, School of Medical Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, 3.14 Core Technology Facility, Manchester, UK
| |
Collapse
|
5
|
Hesami H, Ghasemi S, Houshmand G, Nilipour Y, Hesami M, Biglari A, Nafissi S, Maleki M, Kalayinia S. A novel homozygous variant (c.5876T > C: p. Leu1959Pro) in DYSF segregates with limb-girdle muscular dystrophy: a case report. BMC Musculoskelet Disord 2024; 25:241. [PMID: 38539162 PMCID: PMC10967161 DOI: 10.1186/s12891-024-07354-9] [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: 08/23/2023] [Accepted: 03/12/2024] [Indexed: 04/02/2024] Open
Abstract
BACKGROUND Limb girdle muscular dystrophies (LGMDs) constitute a heterogeneous group of neuromuscular disorders with a very variable clinical presentation and overlapping traits. The clinical symptoms of LGMD typically appear in adolescence or early adulthood. Genetic variation in the dysferlin gene (DYSF) has been associated with LGMD. METHODS We characterized a recessive LGMD in a young adult from consanguineous Irani families using whole-exome sequencing (WES) technology. Sanger sequencing was performed to verify the identified variant. Computational modeling and protein-protein docking were used to investigate the impact of the variant on the structure and function of the DYSF protein. RESULTS By WES, we identified a novel homozygous missense variant in DYSF (NM_003494.4: c.5876T > C: p. Leu1959Pro) previously been associated with LGMD phenotypes. CONCLUSIONS The identification and validation of new pathogenic DYSF variant in the present study further highlight the importance of this gene in LGMD.
Collapse
Affiliation(s)
- Hamed Hesami
- Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Serwa Ghasemi
- Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Golnaz Houshmand
- Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Yalda Nilipour
- Pediatric Pathology Research Center, Research Institute for Children's Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran
- Neuromuscular Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Mahshid Hesami
- Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Alireza Biglari
- School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Shahriar Nafissi
- Neuromuscular Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Majid Maleki
- Cardiogenetic Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Samira Kalayinia
- Cardiogenetic Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran.
| |
Collapse
|
6
|
Bouchard C, Tremblay JP. Portrait of Dysferlinopathy: Diagnosis and Development of Therapy. J Clin Med 2023; 12:6011. [PMID: 37762951 PMCID: PMC10531777 DOI: 10.3390/jcm12186011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 09/13/2023] [Accepted: 09/14/2023] [Indexed: 09/29/2023] Open
Abstract
Dysferlinopathy is a disease caused by a dysferlin deficiency due to mutations in the DYSF gene. Dysferlin is a membrane protein in the sarcolemma and is involved in different functions, such as membrane repair and vesicle fusion, T-tubule development and maintenance, Ca2+ signalling, and the regulation of various molecules. Miyoshi Myopathy type 1 (MMD1) and Limb-Girdle Muscular Dystrophy 2B/R2 (LGMD2B/LGMDR2) are two possible clinical presentations, yet the same mutations can cause both presentations in the same family. They are therefore grouped under the name dysferlinopathy. Onset is typically during the teenage years or young adulthood and is characterized by a loss of Achilles tendon reflexes and difficulty in standing on tiptoes or climbing stairs, followed by a slow progressive loss of strength in limb muscles. The MRI pattern of patient muscles and their biopsies show various fibre sizes, necrotic and regenerative fibres, and fat and connective tissue accumulation. Recent tools were developed for diagnosis and research, especially to evaluate the evolution of the patient condition and to prevent misdiagnosis caused by similarities with polymyositis and Charcot-Marie-Tooth disease. The specific characteristic of dysferlinopathy is dysferlin deficiency. Recently, mouse models with patient mutations were developed to study genetic approaches to treat dysferlinopathy. The research fields for dysferlinopathy therapy include symptomatic treatments, as well as antisense-mediated exon skipping, myoblast transplantation, and gene editing.
Collapse
Affiliation(s)
- Camille Bouchard
- Département de Médecine Moléculaire, Université Laval, Québec, QC G1V 0A6, Canada;
- Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec, QC G1E 6W2, Canada
| | - Jacques P. Tremblay
- Département de Médecine Moléculaire, Université Laval, Québec, QC G1V 0A6, Canada;
- Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec, QC G1E 6W2, Canada
| |
Collapse
|
7
|
Kwok E, Otto SC, Khuu P, Carpenter AP, Codding SJ, Reardon PN, Vanegas J, Kumar TM, Kuykendall CJ, Mehl RA, Baio J, Johnson CP. The Dysferlin C2A Domain Binds PI(4,5)P2 and Penetrates Membranes. J Mol Biol 2023; 435:168193. [PMID: 37406927 PMCID: PMC10699586 DOI: 10.1016/j.jmb.2023.168193] [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: 02/06/2023] [Revised: 06/22/2023] [Accepted: 06/27/2023] [Indexed: 07/07/2023]
Abstract
Dysferlin is a large membrane protein found most prominently in striated muscle. Loss of dysferlin activity is associated with reduced exocytosis, abnormal intracellular Ca2+ and the muscle diseases limb-girdle muscular dystrophy and Miyoshi myopathy. The cytosolic region of dysferlin consists of seven C2 domains with mutations in the C2A domain at the N-terminus resulting in pathology. Despite the importance of Ca2+ and membrane binding activities of the C2A domain for dysferlin function, the mechanism of the domain remains poorly characterized. In this study we find that the C2A domain preferentially binds membranes containing PI(4,5)P2 through an interaction mediated by residues Y23, K32, K33, and R77 on the concave face of the domain. We also found that subsequent to membrane binding, the C2A domain inserts residues on the Ca2+ binding loops into the membrane. Analysis of solution NMR measurements indicate that the domain inhabits two distinct structural states, with Ca2+ shifting the population between states towards a more rigid structure with greater affinity for PI(4,5)P2. Based on our results, we propose a mechanism where Ca2+ converts C2A from a structurally dynamic, low PI(4,5)P2 affinity state to a high affinity state that targets dysferlin to PI(4,5)P2 enriched membranes through interaction with Tyr23, K32, K33, and R77. Binding also involves changes in lipid packing and insertion by the third Ca2+ binding loop of the C2 domain into the membrane, which would contribute to dysferlin function in exocytosis and Ca2+ regulation.
Collapse
Affiliation(s)
- Ethiene Kwok
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, USA
| | - Shauna C Otto
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, USA
| | - Patricia Khuu
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, USA
| | - Andrew P Carpenter
- Department of Chemical Engineering, Oregon State University, Corvallis, OR 97331, USA
| | - Sara J Codding
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, USA
| | | | - Juan Vanegas
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, USA
| | - Tanushri M Kumar
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, USA
| | - Chapman J Kuykendall
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, USA
| | - Ryan A Mehl
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, USA
| | - Joe Baio
- Department of Chemical Engineering, Oregon State University, Corvallis, OR 97331, USA
| | - Colin P Johnson
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, USA.
| |
Collapse
|
8
|
Sun C, Xie Z, Cong L, Xu Y, Liu Z. An in-frame pseudoexon activation caused by a novel deep-intronic variant in the dysferlin gene. Ann Clin Transl Neurol 2023; 10:292-296. [PMID: 36542547 PMCID: PMC9930419 DOI: 10.1002/acn3.51716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 11/23/2022] [Accepted: 11/23/2022] [Indexed: 12/24/2022] Open
Abstract
The precise detection and interpretation of pathogenic DYSF variants are sometimes challenging, largely due to rare deep-intronic splice-altering variants. Here, we report on the genetic diagnosis of a male patient with dysferlinopathy. He remained genetically unsolved after routine exonic detection approaches that only detected a novel heterozygous frameshift variant (c.407dup, p.Thr137Tyrfs*11) in DYSF exon 5. Via muscle-derived DYSF mRNA studies, we identified a novel deep-intronic DYSF variant in the other allele (c.1397 + 649C > T), which causing in-frame alterations in DYSF mRNA and protein structure and confirmed his genetic diagnosis of dysferlinopathy. Our study emphasizes the potential role of undetected deep-intronic splice-altering variants in monogenic diseases.
Collapse
Affiliation(s)
- Chengyue Sun
- Department of Neurology, Peking University People's Hospital, Beijing, 100044, China
| | - Zhiying Xie
- Department of Neurology, Peking University First Hospital, Beijing, 100034, China
| | - Lu Cong
- Department of Neurology, Peking University People's Hospital, Beijing, 100044, China
| | - Yan Xu
- Department of Neurology, Peking University People's Hospital, Beijing, 100044, China
| | - Zunjing Liu
- Department of Neurology, Peking University People's Hospital, Beijing, 100044, China
| |
Collapse
|
9
|
Overduin M, Tran A, Eekels DM, Overduin F, Kervin TA. Transmembrane Membrane Readers form a Novel Class of Proteins That Include Peripheral Phosphoinositide Recognition Domains and Viral Spikes. MEMBRANES 2022; 12:1161. [PMID: 36422153 PMCID: PMC9692390 DOI: 10.3390/membranes12111161] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 11/11/2022] [Accepted: 11/15/2022] [Indexed: 06/16/2023]
Abstract
Membrane proteins are broadly classified as transmembrane (TM) or peripheral, with functions that pertain to only a single bilayer at a given time. Here, we explicate a class of proteins that contain both transmembrane and peripheral domains, which we dub transmembrane membrane readers (TMMRs). Their transmembrane and peripheral elements anchor them to one bilayer and reversibly attach them to another section of bilayer, respectively, positioning them to tether and fuse membranes while recognizing signals such as phosphoinositides (PIs) and modifying lipid chemistries in proximity to their transmembrane domains. Here, we analyze full-length models from AlphaFold2 and Rosetta, as well as structures from nuclear magnetic resonance (NMR) spectroscopy and X-ray crystallography, using the Membrane Optimal Docking Area (MODA) program to map their membrane-binding surfaces. Eukaryotic TMMRs include phospholipid-binding C1, C2, CRAL-TRIO, FYVE, GRAM, GTPase, MATH, PDZ, PH, PX, SMP, StART and WD domains within proteins including protrudin, sorting nexins and synaptotagmins. The spike proteins of SARS-CoV-2 as well as other viruses are also TMMRs, seeing as they are anchored into the viral membrane while mediating fusion with host cell membranes. As such, TMMRs have key roles in cell biology and membrane trafficking, and include drug targets for diseases such as COVID-19.
Collapse
Affiliation(s)
- Michael Overduin
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Anh Tran
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | | | - Finn Overduin
- Institute of Nutritional Science, University of Potsdam, 14476 Potsdam, Germany
| | - Troy A. Kervin
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| |
Collapse
|
10
|
Lukyanenko V, Muriel J, Garman D, Breydo L, Bloch RJ. Elevated Ca2+ at the triad junction underlies dysregulation of Ca2+ signaling in dysferlin-null skeletal muscle. Front Physiol 2022; 13:1032447. [PMID: 36406982 PMCID: PMC9669649 DOI: 10.3389/fphys.2022.1032447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 10/14/2022] [Indexed: 11/05/2022] Open
Abstract
Dysferlin-null A/J myofibers generate abnormal Ca2+ transients that are slightly reduced in amplitude compared to controls. These are further reduced in amplitude by hypoosmotic shock and often appear as Ca2+ waves (Lukyanenko et al., J. Physiol., 2017). Ca2+ waves are typically associated with Ca2+-induced Ca2+ release, or CICR, which can be myopathic. We tested the ability of a permeable Ca2+ chelator, BAPTA-AM, to inhibit CICR in injured dysferlin-null fibers and found that 10–50 nM BAPTA-AM suppressed all Ca2+ waves. The same concentrations of BAPTA-AM increased the amplitude of the Ca2+ transient in A/J fibers to wild type levels and protected transients against the loss of amplitude after hypoosmotic shock, as also seen in wild type fibers. Incubation with 10 nM BAPTA-AM led to intracellular BAPTA concentrations of ∼60 nM, as estimated with its fluorescent analog, Fluo-4AM. This should be sufficient to restore intracellular Ca2+ to levels seen in wild type muscle. Fluo-4AM was ∼10-fold less effective than BAPTA-AM, however, consistent with its lower affinity for Ca2+. EGTA, which has an affinity for Ca2+ similar to BAPTA, but with much slower kinetics of binding, was even less potent when introduced as the -AM derivative. By contrast, a dysferlin variant with GCaMP6fu in place of its C2A domain accumulated at triad junctions, like wild type dysferlin, and suppressed all abnormal Ca2+ signaling. GCaMP6fu introduced as a Venus chimera did not accumulate at junctions and failed to suppress abnormal Ca2+ signaling. Our results suggest that leak of Ca2+ into the triad junctional cleft underlies dysregulation of Ca2+ signaling in dysferlin-null myofibers, and that dysferlin’s C2A domain suppresses abnormal Ca2+ signaling and protects muscle against injury by binding Ca2+ in the cleft.
Collapse
Affiliation(s)
- Valeriy Lukyanenko
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Joaquin Muriel
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Daniel Garman
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
- Program in Biochemistry and Molecular Biology, University of Maryland, Baltimore, MD, United States
| | - Leonid Breydo
- Formulation Development, Regeneron Pharmaceuticals, Tarrytown, NY, United States
| | - Robert J. Bloch
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
- *Correspondence: Robert J. Bloch,
| |
Collapse
|