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Robinson CV, Rohacs T, Hansen SB. Tools for Understanding Nanoscale Lipid Regulation of Ion Channels. Trends Biochem Sci 2019; 44:795-806. [PMID: 31060927 PMCID: PMC6729126 DOI: 10.1016/j.tibs.2019.04.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 03/23/2019] [Accepted: 04/01/2019] [Indexed: 11/17/2022]
Abstract
Anionic phospholipids are minor but prominent components of the plasma membrane that are necessary for ion channel function. Their persistence in bulk membranes, in particular phosphatidylinositol 4,5-bisphosphate (PIP2), initially suggested they act as channel cofactors. However, recent technologies have established an emerging system of nanoscale signaling to ion channels based on lipid compartmentalization (clustering), direct lipid binding, and local lipid dynamics that allow cells to harness lipid heterogeneity to gate ion channels. The new tools to study lipid binding are set to transform our view of the membrane and answer important questions surrounding ion channel-delimited processes such as mechanosensation.
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Affiliation(s)
- Carol V Robinson
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, UK
| | - Tibor Rohacs
- Department of Pharmacology, Physiology and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Scott B Hansen
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL 33458, USA; Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA.
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Molecular determinants of homo- and heteromeric interactions of Junctophilin-1 at triads in adult skeletal muscle fibers. Proc Natl Acad Sci U S A 2019; 116:15716-15724. [PMID: 31315980 DOI: 10.1073/pnas.1820980116] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In adult skeletal muscles, 2 junctophilin isoforms (JPH1 and JPH2) tether the sarcoplasmic reticulum (SR) to transverse tubule (T-tubule) membranes, generating stable membrane contact sites known as triads. JPHs are anchored to the membrane of the SR by a C-terminal transmembrane domain (TMD) and bind the T-tubule membrane through their cytosolic N-terminal region, which contains 8 lipid-binding (MORN) motifs. By combining expression of GFP-JPH1 deletion mutants in skeletal muscle fibers with in vitro biochemical experiments, we investigated the molecular determinants of JPH1 recruitment at triads in adult skeletal muscle fibers. We found that MORN motifs bind PI(4,5)P2 in the sarcolemma, but do not mediate the selective localization of JPH1 at the T-tubule compartment of triads. On the contrary, fusion proteins containing only the TMD of JPH1 were able to localize at the junctional SR compartment of the triad. Bimolecular fluorescence complementation experiments indicated that the TMD of JPH1 can form dimers, suggesting that the observed localization at triads may result from dimerization with the TMDs of resident JPH1. A second domain, capable of mediating homo- and heterodimeric interactions between JPH1 and JPH2 was identified in the cytosolic region. FRAP experiments revealed that removal of either one of these 2 domains in JPH1 decreases the association of the resulting mutant proteins with triads. Altogether, these results suggest that the ability to establish homo- and heterodimeric interactions with resident JPHs may support the recruitment and stability of newly synthesized JPHs at triads in adult skeletal muscle fibers.
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Okamura Y, Kawanabe A, Kawai T. Voltage-Sensing Phosphatases: Biophysics, Physiology, and Molecular Engineering. Physiol Rev 2019; 98:2097-2131. [PMID: 30067160 DOI: 10.1152/physrev.00056.2017] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Voltage-sensing phosphatase (VSP) contains a voltage sensor domain (VSD) similar to that in voltage-gated ion channels, and a phosphoinositide phosphatase region similar to phosphatase and tensin homolog deleted on chromosome 10 (PTEN). The VSP gene is conserved from unicellular organisms to higher vertebrates. Membrane depolarization induces electrical driven conformational rearrangement in the VSD, which is translated into catalytic enzyme activity. Biophysical and structural characterization has revealed details of the mechanisms underlying the molecular functions of VSP. Coupling between the VSD and the enzyme is tight, such that enzyme activity is tuned in a graded fashion to the membrane voltage. Upon VSP activation, multiple species of phosphoinositides are simultaneously altered, and the profile of enzyme activity depends on the history of the membrane potential. VSPs have been the obvious candidate link between membrane potential and phosphoinositide regulation. However, patterns of voltage change regulating VSP in native cells remain largely unknown. This review addresses the current understanding of the biophysical biochemical properties of VSP and provides new insight into the proposed functions of VSP.
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Affiliation(s)
- Yasushi Okamura
- Department of Physiology, Laboratory of Integrative Physiology, Graduate School of Medicine, Osaka University , Osaka , Japan ; and Graduate School of Frontier Biosciences, Osaka University , Osaka , Japan
| | - Akira Kawanabe
- Department of Physiology, Laboratory of Integrative Physiology, Graduate School of Medicine, Osaka University , Osaka , Japan ; and Graduate School of Frontier Biosciences, Osaka University , Osaka , Japan
| | - Takafumi Kawai
- Department of Physiology, Laboratory of Integrative Physiology, Graduate School of Medicine, Osaka University , Osaka , Japan ; and Graduate School of Frontier Biosciences, Osaka University , Osaka , Japan
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Hilgemann DW, Dai G, Collins A, Lariccia V, Magi S, Deisl C, Fine M. Lipid signaling to membrane proteins: From second messengers to membrane domains and adapter-free endocytosis. J Gen Physiol 2018; 150:211-224. [PMID: 29326133 PMCID: PMC5806671 DOI: 10.1085/jgp.201711875] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Hilgemann et al. explain how lipid signaling to membrane proteins involves a hierarchy of mechanisms from lipid binding to membrane domain coalescence. Lipids influence powerfully the function of ion channels and transporters in two well-documented ways. A few lipids act as bona fide second messengers by binding to specific sites that control channel and transporter gating. Other lipids act nonspecifically by modifying the physical environment of channels and transporters, in particular the protein–membrane interface. In this short review, we first consider lipid signaling from this traditional viewpoint, highlighting innumerable Journal of General Physiology publications that have contributed to our present understanding. We then switch to our own emerging view that much important lipid signaling occurs via the formation of membrane domains that influence the function of channels and transporters within them, promote selected protein–protein interactions, and control the turnover of surface membrane.
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Affiliation(s)
- Donald W Hilgemann
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Gucan Dai
- Department of Physiology and Biophysics, University of Washington, Seattle, WA
| | - Anthony Collins
- Saba University School of Medicine, The Bottom, Saba, Dutch Caribbean
| | - Vincenzo Lariccia
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche," Ancona, Italy
| | - Simona Magi
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche," Ancona, Italy
| | - Christine Deisl
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Michael Fine
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
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Bachmann C, Jungbluth H, Muntoni F, Manzur AY, Zorzato F, Treves S. Cellular, biochemical and molecular changes in muscles from patients with X-linked myotubular myopathy due to MTM1 mutations. Hum Mol Genet 2017; 26:320-332. [PMID: 28007904 DOI: 10.1093/hmg/ddw388] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 11/07/2016] [Indexed: 01/07/2023] Open
Abstract
Centronuclear myopathies are early-onset muscle diseases caused by mutations in several genes including MTM1, DNM2, BIN1, RYR1 and TTN. The most severe and often fatal X-linked form of myotubular myopathy (XLMTM) is caused by mutations in the gene encoding the ubiquitous lipid phosphatase myotubularin, an enzyme specifically dephosphorylating phosphatidylinositol-3-phosphate and phosphatidylinositol-3,5-bisphosphate. Because XLMTM patients have a predominantly muscle-specific phenotype a number of pathogenic mechanisms have been proposed, including a direct effect of the accumulated lipid on the skeletal muscle calcium channel ryanodine receptor 1, a negative effect on the structure of intracellular organelles and defective autophagy. Animal models knocked out for MTM1 show severe reduction of ryanodine receptor 1 mediated calcium release but, since knocking out genes in animal models does not necessarily replicate the human phenotype, we considered it important to study directly the effect of MTM1 mutations on patient muscle cells. The results of the present study show that at the level of myotubes MTM1 mutations do not dramatically affect calcium homeostasis and calcium release mediated through the ryanodine receptor 1, though they do affect myotube size and nuclear content. On the other hand, mature muscles such as those obtained from patient muscle biopsies exhibit a significant decrease in expression of the ryanodine receptor 1, a decrease in muscle-specific microRNAs and a considerable up-regulation of histone deacetylase-4. We hypothesize that the latter events consequent to the primary genetic mutation, are the cause of the severe decrease in muscle strength that characterizes these patients.
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Affiliation(s)
- Christoph Bachmann
- Departments of Biomedicine and Anesthesia, Basel University Hospital, Basel University, Basel, Switzerland
| | - Heinz Jungbluth
- Department of Paediatric Neurology, Neuromuscular Service, Evelina Children's Hospital, St Thomas' Hospital, London, UK.,Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King's College London, London, UK.,Randall Division of Cell and Molecular Biophysics, Muscle Signalling Section, King's College, London, UK
| | - Francesco Muntoni
- Dubowitz Neuromuscular Centre and MRC Centre for Neuromuscular Diseases, Institute of Child Health, London, UK
| | - Adnan Y Manzur
- Dubowitz Neuromuscular Centre and MRC Centre for Neuromuscular Diseases, Institute of Child Health, London, UK
| | - Francesco Zorzato
- Departments of Biomedicine and Anesthesia, Basel University Hospital, Basel University, Basel, Switzerland.,Department of Life Sciences, General Pathology section, University of Ferrara, Ferrara, Italy
| | - Susan Treves
- Departments of Biomedicine and Anesthesia, Basel University Hospital, Basel University, Basel, Switzerland.,Department of Life Sciences, General Pathology section, University of Ferrara, Ferrara, Italy
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Abstract
Phosphatases play key roles in normal physiology and diseases. Studying phosphatases has been both essential and challenging, and the application of conventional genetic and biochemical methods has led to crucial but still limited understanding of their mechanisms, substrates, and exclusive functions within highly intricate networks. With the advances in technologies such as cellular imaging and molecular and chemical biology in terms of sensitive tools and methods, the phosphatase field has thrived in the past years and has set new insights for cell signaling studies and for therapeutic development. In this review, we give an overview of the existing interdisciplinary tools for phosphatases, give examples on how they have been applied to increase our understanding of these enzymes, and suggest how they-and other tools yet barely used in the phosphatase field-might be adapted to address future questions and challenges.
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Affiliation(s)
- Sara Fahs
- European Molecular Biology Laboratory, Genome Biology
Unit, Meyerhofstrasse
1, 69117 Heidelberg, Germany
| | - Pablo Lujan
- European Molecular Biology Laboratory, Genome Biology
Unit, Meyerhofstrasse
1, 69117 Heidelberg, Germany
| | - Maja Köhn
- European Molecular Biology Laboratory, Genome Biology
Unit, Meyerhofstrasse
1, 69117 Heidelberg, Germany
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Maurocalcin phosphorylated at threonin 26 maintains its activity on ryanodine receptor-mediated Ca2+ release in intact muscle fibers. Proc Natl Acad Sci U S A 2016; 113:E4264-5. [PMID: 27422549 DOI: 10.1073/pnas.1608049113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Treves S, Jungbluth H, Voermans N, Muntoni F, Zorzato F. Ca 2+ handling abnormalities in early-onset muscle diseases: Novel concepts and perspectives. Semin Cell Dev Biol 2016; 64:201-212. [PMID: 27427513 DOI: 10.1016/j.semcdb.2016.07.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 07/14/2016] [Indexed: 12/17/2022]
Abstract
The physiological process by which Ca2+ is released from the sarcoplasmic reticulum is called excitation-contraction coupling; it is initiated by an action potential which travels deep into the muscle fiber where it is sensed by the dihydropyridine receptor, a voltage sensing L-type Ca2+channel localized on the transverse tubules. Voltage-induced conformational changes in the dihydropyridine receptor activate the ryanodine receptor Ca2+ release channel of the sarcoplasmic reticulum. The released Ca2+ binds to troponin C, enabling contractile thick-thin filament interactions. The Ca2+ is subsequently transported back into the sarcoplasmic reticulum by specialized Ca2+ pumps (SERCA), preparing the muscle for a new cycle of contraction. Although other proteins are involved in excitation-contraction coupling, the mechanism described above emphasizes the unique role played by the two Ca2+ channels (the dihydropyridine receptor and the ryanodine receptor), the SERCA Ca2+ pumps and the exquisite spatial organization of the membrane compartments endowed with the proteins responsible for this mechanism to function rapidly and efficiently. Research over the past two decades has uncovered the fine details of excitation-contraction coupling under normal conditions while advances in genomics have helped to identify mutations in novel genes in patients with neuromuscular disorders. While it is now clear that many patients with congenital muscle diseases carry mutations in genes encoding proteins directly involved in Ca2+ homeostasis, it has become apparent that mutations are also present in genes encoding for proteins not thought to be directly involved in Ca2+ regulation. Ongoing research in the field now focuses on understanding the functional effect of individual mutations, as well as understanding the role of proteins not specifically located in the sarcoplasmic reticulum which nevertheless are involved in Ca2+ regulation or excitation-contraction coupling. The principal challenge for the future is the identification of drug targets that can be pharmacologically manipulated by small molecules, with the ultimate aim to improve muscle function and quality of life of patients with congenital muscle disorders. The aim of this review is to give an overview of the most recent findings concerning Ca2+ dysregulation and its impact on muscle function in patients with congenital muscle disorders due to mutations in proteins involved in excitation-contraction coupling and more broadly on Ca2+ homeostasis.
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Affiliation(s)
- Susan Treves
- Departments of Biomedicine and Anesthesia, Basel University Hospital, 4031 Basel, Switzerland; Department of Life Sciences, General Pathology Section, University of Ferrara, 44100 Ferrara, Italy.
| | - Heinz Jungbluth
- Department of Paediatric Neurology, Neuromuscular Service, Evelina Children's Hospital, St. Thomas' Hospital, London, United Kingdom; Randall Division for Cell and Molecular Biophysics, Muscle Signalling Section, King's College, London, United Kingdom; Department of Basic and Clinical Neuroscience, IoPPN, King's College, London, United Kingdom
| | - Nicol Voermans
- Department of Neurology, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Francesco Muntoni
- Dubowitz Neuromuscular Centre, Institute of Child Health, University College London, United Kingdom
| | - Francesco Zorzato
- Departments of Biomedicine and Anesthesia, Basel University Hospital, 4031 Basel, Switzerland; Department of Life Sciences, General Pathology Section, University of Ferrara, 44100 Ferrara, Italy
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Hadley KB, Ryan AS, Forsyth S, Gautier S, Salem N. The Essentiality of Arachidonic Acid in Infant Development. Nutrients 2016; 8:216. [PMID: 27077882 PMCID: PMC4848685 DOI: 10.3390/nu8040216] [Citation(s) in RCA: 220] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Revised: 04/01/2016] [Accepted: 04/05/2016] [Indexed: 01/16/2023] Open
Abstract
Arachidonic acid (ARA, 20:4n-6) is an n-6 polyunsaturated 20-carbon fatty acid formed by the biosynthesis from linoleic acid (LA, 18:2n-6). This review considers the essential role that ARA plays in infant development. ARA is always present in human milk at a relatively fixed level and is accumulated in tissues throughout the body where it serves several important functions. Without the provision of preformed ARA in human milk or infant formula the growing infant cannot maintain ARA levels from synthetic pathways alone that are sufficient to meet metabolic demand. During late infancy and early childhood the amount of dietary ARA provided by solid foods is low. ARA serves as a precursor to leukotrienes, prostaglandins, and thromboxanes, collectively known as eicosanoids which are important for immunity and immune response. There is strong evidence based on animal and human studies that ARA is critical for infant growth, brain development, and health. These studies also demonstrate the importance of balancing the amounts of ARA and DHA as too much DHA may suppress the benefits provided by ARA. Both ARA and DHA have been added to infant formulas and follow-on formulas for more than two decades. The amounts and ratios of ARA and DHA needed in infant formula are discussed based on an in depth review of the available scientific evidence.
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Affiliation(s)
- Kevin B Hadley
- DSM Nutritional Products, 6480 Dobbin Road, Columbia, MD 21045, USA.
| | - Alan S Ryan
- Clinical Research Consulting, 9809 Halston Manor, Boynton Beach, FL 33473, USA.
| | - Stewart Forsyth
- School of Medicine, Dentistry & Nursing, University of Dundee, Ninewells Hospital and Medical School, Dundee, UK.
| | - Sheila Gautier
- DSM Nutritional Products, 6480 Dobbin Road, Columbia, MD 21045, USA.
| | - Norman Salem
- DSM Nutritional Products, 6480 Dobbin Road, Columbia, MD 21045, USA.
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Affiliation(s)
- Bernhard E Flucher
- Section of Physiology, Medical University Innsbruck, 6020 Innsbruck, Austria
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Phosphoinositides in Ca(2+) signaling and excitation-contraction coupling in skeletal muscle: an old player and newcomers. J Muscle Res Cell Motil 2015; 36:491-9. [PMID: 26377756 DOI: 10.1007/s10974-015-9422-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 09/09/2015] [Indexed: 10/23/2022]
Abstract
Since the postulate, 30 years ago, that phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P 2) as the precursor of inositol 1,4,5-trisphosphate (Ins(1,4,5)P 3) would be critical for skeletal muscle excitation-contraction (EC) coupling, the issue of whether phosphoinositides (PtdInsPs) may have something to do with Ca(2+) signaling in muscle raised limited interest, if any. In recent years however, the PtdInsP world has expanded considerably with new functions for PtdIns(4,5)P 2 but also with functions for the other members of the PtdInsP family. In this context, the discovery that genetic deficiency in a PtdInsP phosphatase has dramatic consequences on Ca(2+) homeostasis in skeletal muscle came unanticipated and opened up new perspectives in regards to how PtdInsPs modulate muscle Ca(2+) signaling under normal and disease conditions. This review intends to make an update of the established, the questioned, and the unknown regarding the role of PtdInsPs in skeletal muscle Ca(2+) homeostasis and EC coupling, with very specific emphasis given to Ca(2+) signals in differentiated skeletal muscle fibers.
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Adler EM. Of bipolar cell synapses, light-activated K+ channels, and substrate binding to DAT. ACTA ACUST UNITED AC 2015; 146:1-2. [PMID: 26123193 PMCID: PMC4485023 DOI: 10.1085/jgp.201511449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Berthier C, Kutchukian C, Bouvard C, Okamura Y, Jacquemond V. Depression of voltage-activated Ca 2+release in skeletal muscle by activation of a voltage-sensing phosphatase. J Biophys Biochem Cytol 2015. [DOI: 10.1083/jcb.2091oia66] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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14
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Adler EM. Of muscle modulation and the CFTR gate. J Gen Physiol 2015; 145:255. [PMID: 25825167 PMCID: PMC4380216 DOI: 10.1085/jgp.201511391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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