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Hall DD, Takeshima H, Song LS. Structure, Function, and Regulation of the Junctophilin Family. Annu Rev Physiol 2024; 86:123-147. [PMID: 37931168 PMCID: PMC10922073 DOI: 10.1146/annurev-physiol-042022-014926] [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] [Indexed: 11/08/2023]
Abstract
In both excitable and nonexcitable cells, diverse physiological processes are linked to different calcium microdomains within nanoscale junctions that form between the plasma membrane and endo-sarcoplasmic reticula. It is now appreciated that the junctophilin protein family is responsible for establishing, maintaining, and modulating the structure and function of these junctions. We review foundational findings from more than two decades of research that have uncovered how junctophilin-organized ultrastructural domains regulate evolutionarily conserved biological processes. We discuss what is known about the junctophilin family of proteins. Our goal is to summarize the current knowledge of junctophilin domain structure, function, and regulation and to highlight emerging avenues of research that help our understanding of the transcriptional, translational, and post-translational regulation of this gene family and its roles in health and during disease.
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Affiliation(s)
- Duane D Hall
- Department of Internal Medicine, Division of Cardiovascular Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA; ,
| | - Hiroshi Takeshima
- Department of Biological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Long-Sheng Song
- Department of Internal Medicine, Division of Cardiovascular Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA; ,
- Department of Biochemistry and Molecular Biology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
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Johari M, Topf A, Folland C, Duff J, Dofash L, Marti P, Robertson T, Vilchez JJ, Cairns A, Harris E, Marini-Bettolo C, Ravenscroft G, Straub V. Loss-of-function variants in JPH1 cause congenital myopathy with prominent facial involvement. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.02.10.24302480. [PMID: 38370827 PMCID: PMC10871378 DOI: 10.1101/2024.02.10.24302480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Background Weakness of facial, ocular, and axial muscles is a common clinical presentation in congenital myopathies caused by pathogenic variants in genes encoding triad proteins. Abnormalities in triad structure and function resulting in disturbed excitation-contraction coupling and Ca 2+ homeostasis can contribute to disease pathology. Methods We analysed exome and genome sequencing data from three unrelated individuals with congenital myopathy characterised by striking facial, ocular, and bulbar involvement. We collected deep phenotypic data from the affected individuals. We analysed the RNA-seq data of one proband and performed gene expression outlier analysis in 129 samples. Results The three probands had remarkably similar clinical presentation with prominent facial, ocular, and bulbar features. Disease onset was in the neonatal period with hypotonia, poor feeding, cleft palate and talipes. Muscle weakness was generalised but most prominent in the lower limbs with facial weakness also present. All patients had myopathic facies, bilateral ptosis, ophthalmoplegia and fatiguability. While muscle biopsy on light microscopy did not show any obvious morphological abnormalities, ultrastructural analysis showed slightly reduced triads, and structurally abnormal sarcoplasmic reticulum. DNA sequencing identified three unique homozygous loss of function variants in JPH1 , encoding junctophilin-1 in the three families; a stop-gain (c.354C>A; p.Tyr118*) and two frameshift (c.373del p.Asp125Thrfs*30 and c.1738del; p.Leu580Trpfs*16) variants. Muscle RNA-seq showed strong downregulation of JPH1 in the F3 proband. Conclusions Junctophilin-1 is critical to the formation of skeletal muscle triad junctions by connecting the sarcoplasmic reticulum and T-tubules. Our findings suggest that loss of JPH1 results in a congenital myopathy with prominent facial, bulbar and ocular involvement. Key message This study identified novel homozygous loss-of-function variants in the JPH1 gene, linking them to a unique form of congenital myopathy characterised by severe facial and ocular symptoms. Our research sheds light on the critical impact on junctophilin-1 function in skeletal muscle triad junction formation and the consequences of its disruption resulting in a myopathic phenotype. What is already known on this topic Previous studies have shown that pathogenic variants in genes encoding triad proteins lead to various myopathic phenotypes, with clinical presentations often involving muscle weakness and myopathic facies. The triad structure is essential for excitation-contraction (EC) coupling and calcium homeostasis and is a key element in muscle physiology. What this study adds and how this study might affect research practice or policy This study establishes that homozygous loss-of-function mutations in JPH1 cause a congenital myopathy predominantly affecting facial and ocular muscles. This study also provides clinical insights that may aid the clinicians in diagnosing similar genetically unresolved cases.
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Kanazawa Y, Takahashi T, Nagano M, Koinuma S, Shigeyoshi Y. The Effects of Aging on Sarcoplasmic Reticulum-Related Factors in the Skeletal Muscle of Mice. Int J Mol Sci 2024; 25:2148. [PMID: 38396828 PMCID: PMC10889371 DOI: 10.3390/ijms25042148] [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: 12/30/2023] [Revised: 02/04/2024] [Accepted: 02/06/2024] [Indexed: 02/25/2024] Open
Abstract
The pathogenesis of sarcopenia includes the dysfunction of calcium homeostasis associated with the sarcoplasmic reticulum; however, the localization in sarcoplasmic reticulum-related factors and differences by myofiber type remain unclear. Here, we investigated the effects of aging on sarcoplasmic reticulum-related factors in the soleus (slow-twitch) and gastrocnemius (fast-twitch) muscles of 3- and 24-month-old male C57BL/6J mice. There were no notable differences in the skeletal muscle weight of these 3- and 24-month-old mice. The expression of Atp2a1, Atp2a2, Sln, and Pln increased with age in the gastrocnemius muscles, but not in the soleus muscles. Subsequently, immunohistochemical analysis revealed ectopic sarcoplasmic reticulum calcium ion ATPase (SERCA) 1 and SERCA2a immunoreactivity only in the gastrocnemius muscles of old mice. Histochemical and transmission electron microscope analysis identified tubular aggregate (TA), an aggregation of the sarcoplasmic reticulum, in the gastrocnemius muscles of old mice. Dihydropyridine receptor α1, ryanodine receptor 1, junctophilin (JPH) 1, and JPH2, which contribute to sarcoplasmic reticulum function, were also localized in or around the TA. Furthermore, JPH1 and JPH2 co-localized with matrix metalloproteinase (MMP) 2 around the TA. These results suggest that sarcoplasmic reticulum-related factors are localized in or around TAs that occur in fast-twitch muscle with aging, but some of them might be degraded by MMP2.
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Affiliation(s)
- Yuji Kanazawa
- Department of Physical Therapy, Hokuriku University, Kanazawa 920-1180, Ishikawa, Japan
- Department of Anatomy and Neurobiology, Faculty of Medicine, Kindai University, Osakasayama 589-8511, Osaka, Japan; (M.N.); (S.K.); (Y.S.)
| | - Tatsuo Takahashi
- Department of Clinical Pharmacology, Hokuriku University, Kanazawa 920-1181, Ishikawa, Japan;
| | - Mamoru Nagano
- Department of Anatomy and Neurobiology, Faculty of Medicine, Kindai University, Osakasayama 589-8511, Osaka, Japan; (M.N.); (S.K.); (Y.S.)
| | - Satoshi Koinuma
- Department of Anatomy and Neurobiology, Faculty of Medicine, Kindai University, Osakasayama 589-8511, Osaka, Japan; (M.N.); (S.K.); (Y.S.)
| | - Yasufumi Shigeyoshi
- Department of Anatomy and Neurobiology, Faculty of Medicine, Kindai University, Osakasayama 589-8511, Osaka, Japan; (M.N.); (S.K.); (Y.S.)
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Dixon RE, Trimmer JS. Endoplasmic Reticulum-Plasma Membrane Junctions as Sites of Depolarization-Induced Ca 2+ Signaling in Excitable Cells. Annu Rev Physiol 2023; 85:217-243. [PMID: 36202100 PMCID: PMC9918718 DOI: 10.1146/annurev-physiol-032122-104610] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Membrane contact sites between endoplasmic reticulum (ER) and plasma membrane (PM), or ER-PM junctions, are found in all eukaryotic cells. In excitable cells they play unique roles in organizing diverse forms of Ca2+ signaling as triggered by membrane depolarization. ER-PM junctions underlie crucial physiological processes such as excitation-contraction coupling, smooth muscle contraction and relaxation, and various forms of activity-dependent signaling and plasticity in neurons. In many cases the structure and molecular composition of ER-PM junctions in excitable cells comprise important regulatory feedback loops linking depolarization-induced Ca2+ signaling at these sites to the regulation of membrane potential. Here, we describe recent findings on physiological roles and molecular composition of native ER-PM junctions in excitable cells. We focus on recent studies that provide new insights into canonical forms of depolarization-induced Ca2+ signaling occurring at junctional triads and dyads of striated muscle, as well as the diversity of ER-PM junctions in these cells and in smooth muscle and neurons.
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Affiliation(s)
- Rose E Dixon
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, California, USA;
| | - James S Trimmer
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, California, USA;
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Protasi F, Girolami B, Roccabianca S, Rossi D. Store-operated calcium entry: From physiology to tubular aggregate myopathy. Curr Opin Pharmacol 2023; 68:102347. [PMID: 36608411 DOI: 10.1016/j.coph.2022.102347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 11/30/2022] [Accepted: 12/04/2022] [Indexed: 01/06/2023]
Abstract
Store-Operated Ca2+ entry (SOCE) is recognized as a key mechanism in muscle physiology necessary to refill intracellular Ca2+ stores during sustained muscle activity. For many years the cell structures expected to mediate SOCE in skeletal muscle fibres remained unknown. Recently, the identification of Ca2+ Entry Units (CEUs) in exercised muscle fibres opened new insights into the role of extracellular Ca2+ in muscle contraction and, more generally, in intracellular Ca2+ homeostasis. Accordingly, intracellular Ca2+ unbalance due to alterations in SOCE strictly correlates with muscle disfunction and disease. Mutations in proteins involved in SOCE (STIM1, ORAI1, and CASQ1) have been linked to tubular aggregate myopathy (TAM), a disease that causes muscle weakness and myalgia and is characterized by a typical accumulation of highly ordered and packed membrane tubules originated from the sarcoplasmic reticulum (SR). Achieving a full understanding of the molecular pathways activated by alterations in Ca2+ entry mechanisms is a necessary step to design effective therapies for human SOCE-related disorders.
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Affiliation(s)
- Feliciano Protasi
- CAST, Center for Advanced Studies and Technology; University G. d'Annunzio of Chieti-Pescara, I-66100, Italy; DMSI, Department of Medicine and Aging Sciences; University G. d'Annunzio of Chieti-Pescara, I-66100, Italy
| | - Barbara Girolami
- CAST, Center for Advanced Studies and Technology; University G. d'Annunzio of Chieti-Pescara, I-66100, Italy; DMSI, Department of Medicine and Aging Sciences; University G. d'Annunzio of Chieti-Pescara, I-66100, Italy
| | - Sara Roccabianca
- DMMS, Department of Molecular and Developmental Medicine; University of Siena, I-53100, Siena Italy
| | - Daniela Rossi
- DMMS, Department of Molecular and Developmental Medicine; University of Siena, I-53100, Siena Italy.
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Chivet M, McCluskey M, Nicot AS, Brocard J, Beaufils M, Giovannini D, Giannesini B, Poreau B, Brocard J, Humbert S, Saudou F, Fauré J, Marty I. Huntingtin regulates calcium fluxes in skeletal muscle. J Gen Physiol 2022; 155:213700. [PMID: 36409218 PMCID: PMC9682417 DOI: 10.1085/jgp.202213103] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 09/09/2022] [Accepted: 09/03/2022] [Indexed: 11/22/2022] Open
Abstract
The expression of the Huntingtin protein, well known for its involvement in the neurodegenerative Huntington's disease, has been confirmed in skeletal muscle. The impact of HTT deficiency was studied in human skeletal muscle cell lines and in a mouse model with inducible and muscle-specific HTT deletion. Characterization of calcium fluxes in the knock-out cell lines demonstrated a reduction in excitation-contraction (EC) coupling, related to an alteration in the coupling between the dihydropyridine receptor and the ryanodine receptor, and an increase in the amount of calcium stored within the sarcoplasmic reticulum, linked to the hyperactivity of store-operated calcium entry (SOCE). Immunoprecipitation experiments demonstrated an association of HTT with junctophilin 1 (JPH1) and stromal interaction molecule 1 (STIM1), both providing clues on the functional effects of HTT deletion on calcium fluxes. Characterization of muscle strength and muscle anatomy of the muscle-specific HTT-KO mice demonstrated that HTT deletion induced moderate muscle weakness and mild muscle atrophy associated with histological abnormalities, similar to the phenotype observed in tubular aggregate myopathy. Altogether, this study points toward the hypotheses of the involvement of HTT in EC coupling via its interaction with JPH1, and on SOCE via its interaction with JPH1 and/or STIM1.
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Affiliation(s)
- Mathilde Chivet
- CHU Grenoble Alpes, Grenoble Institut Neurosciences, INSERM, U1216, Université Grenoble Alpes, Grenoble, France
| | - Maximilian McCluskey
- CHU Grenoble Alpes, Grenoble Institut Neurosciences, INSERM, U1216, Université Grenoble Alpes, Grenoble, France
| | - Anne Sophie Nicot
- CHU Grenoble Alpes, Grenoble Institut Neurosciences, INSERM, U1216, Université Grenoble Alpes, Grenoble, France
| | - Julie Brocard
- CHU Grenoble Alpes, Grenoble Institut Neurosciences, INSERM, U1216, Université Grenoble Alpes, Grenoble, France
| | - Mathilde Beaufils
- CHU Grenoble Alpes, Grenoble Institut Neurosciences, INSERM, U1216, Université Grenoble Alpes, Grenoble, France
| | - Diane Giovannini
- CHU Grenoble Alpes, Grenoble Institut Neurosciences, INSERM, U1216, Université Grenoble Alpes, Grenoble, France
| | - Benoit Giannesini
- Centre National de la Recherche Scientifique, Centre de Résonance Magnétique Biologique et Médicale, Aix Marseille University, Marseille, France
| | - Brice Poreau
- CHU Grenoble Alpes, Grenoble Institut Neurosciences, INSERM, U1216, Université Grenoble Alpes, Grenoble, France
| | - Jacques Brocard
- CHU Grenoble Alpes, Grenoble Institut Neurosciences, INSERM, U1216, Université Grenoble Alpes, Grenoble, France
| | - Sandrine Humbert
- CHU Grenoble Alpes, Grenoble Institut Neurosciences, INSERM, U1216, Université Grenoble Alpes, Grenoble, France
| | - Frédéric Saudou
- CHU Grenoble Alpes, Grenoble Institut Neurosciences, INSERM, U1216, Université Grenoble Alpes, Grenoble, France
| | - Julien Fauré
- CHU Grenoble Alpes, Grenoble Institut Neurosciences, INSERM, U1216, Université Grenoble Alpes, Grenoble, France
| | - Isabelle Marty
- CHU Grenoble Alpes, Grenoble Institut Neurosciences, INSERM, U1216, Université Grenoble Alpes, Grenoble, France,Correspondence to Isabelle Marty:
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Bolaños P, Calderón JC. Excitation-contraction coupling in mammalian skeletal muscle: Blending old and last-decade research. Front Physiol 2022; 13:989796. [PMID: 36117698 PMCID: PMC9478590 DOI: 10.3389/fphys.2022.989796] [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: 07/08/2022] [Accepted: 08/08/2022] [Indexed: 11/13/2022] Open
Abstract
The excitation–contraction coupling (ECC) in skeletal muscle refers to the Ca2+-mediated link between the membrane excitation and the mechanical contraction. The initiation and propagation of an action potential through the membranous system of the sarcolemma and the tubular network lead to the activation of the Ca2+-release units (CRU): tightly coupled dihydropyridine and ryanodine (RyR) receptors. The RyR gating allows a rapid, massive, and highly regulated release of Ca2+ from the sarcoplasmic reticulum (SR). The release from triadic places generates a sarcomeric gradient of Ca2+ concentrations ([Ca2+]) depending on the distance of a subcellular region from the CRU. Upon release, the diffusing Ca2+ has multiple fates: binds to troponin C thus activating the contractile machinery, binds to classical sarcoplasmic Ca2+ buffers such as parvalbumin, adenosine triphosphate and, experimentally, fluorescent dyes, enters the mitochondria and the SR, or is recycled through the Na+/Ca2+ exchanger and store-operated Ca2+ entry (SOCE) mechanisms. To commemorate the 7th decade after being coined, we comprehensively and critically reviewed “old”, historical landmarks and well-established concepts, and blended them with recent advances to have a complete, quantitative-focused landscape of the ECC. We discuss the: 1) elucidation of the CRU structures at near-atomic resolution and its implications for functional coupling; 2) reliable quantification of peak sarcoplasmic [Ca2+] using fast, low affinity Ca2+ dyes and the relative contributions of the Ca2+-binding mechanisms to the whole concert of Ca2+ fluxes inside the fibre; 3) articulation of this novel quantitative information with the unveiled structural details of the molecular machinery involved in mitochondrial Ca2+ handing to understand how and how much Ca2+ enters the mitochondria; 4) presence of the SOCE machinery and its different modes of activation, which awaits understanding of its magnitude and relevance in situ; 5) pharmacology of the ECC, and 6) emerging topics such as the use and potential applications of super-resolution and induced pluripotent stem cells (iPSC) in ECC. Blending the old with the new works better!
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Affiliation(s)
- Pura Bolaños
- Laboratory of Cellular Physiology, Centre of Biophysics and Biochemistry, Venezuelan Institute for Scientific Research (IVIC), Caracas, Venezuela
| | - Juan C. Calderón
- Physiology and Biochemistry Research Group-PHYSIS, Faculty of Medicine, University of Antioquia, Medellín, Colombia
- *Correspondence: Juan C. Calderón,
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Budayeva HG, Sengupta-Ghosh A, Phu L, Moffat JG, Ayalon G, Kirkpatrick DS. Phosphoproteome Profiling of the Receptor Tyrosine Kinase MuSK Identifies Tyrosine Phosphorylation of Rab GTPases. Mol Cell Proteomics 2022; 21:100221. [PMID: 35227894 PMCID: PMC8972003 DOI: 10.1016/j.mcpro.2022.100221] [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: 06/23/2021] [Revised: 02/22/2022] [Accepted: 02/24/2022] [Indexed: 11/16/2022] Open
Abstract
Muscle-specific receptor tyrosine kinase (MuSK) agonist antibodies were developed 2 decades ago to explore the benefits of receptor activation at the neuromuscular junction. Unlike agrin, the endogenous agonist of MuSK, agonist antibodies function independently of its coreceptor low-density lipoprotein receptor–related protein 4 to delay the onset of muscle denervation in mouse models of ALS. Here, we performed dose–response and time-course experiments on myotubes to systematically compare site-specific phosphorylation downstream of each agonist. Remarkably, both agonists elicited similar intracellular responses at known and newly identified MuSK signaling components. Among these was inducible tyrosine phosphorylation of multiple Rab GTPases that was blocked by MuSK inhibition. Importantly, mutation of this site in Rab10 disrupts association with its effector proteins, molecule interacting with CasL 1/3. Together, these data provide in-depth characterization of MuSK signaling, describe two novel MuSK inhibitors, and expose phosphorylation of Rab GTPases downstream of receptor tyrosine kinase activation in myotubes. Different agonists of muscle-specific kinase (MuSK) elicit similar phosphoprofiles. MuSK activation induces tyrosine phosphorylation of several Rab GTPases. MuSK inhibitors diminish receptor signaling, including phosphorylation on Rab10 Y6. Mutation of Rab10 Y6 disrupts its association with Mical adaptor proteins.
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Affiliation(s)
- Hanna G Budayeva
- Microchemistry, Proteomics, and Lipidomics Department, Genentech, Inc, South San Francisco, California, USA.
| | | | - Lilian Phu
- Microchemistry, Proteomics, and Lipidomics Department, Genentech, Inc, South San Francisco, California, USA
| | - John G Moffat
- Biochemical and Cellular Pharmacology and Computational Drug Design, Genentech, Inc, South San Francisco, California, USA
| | - Gai Ayalon
- Neuroscience Department, Genentech, Inc, South San Francisco, California, USA
| | - Donald S Kirkpatrick
- Microchemistry, Proteomics, and Lipidomics Department, Genentech, Inc, South San Francisco, California, USA.
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Rossi D, Pierantozzi E, Amadsun DO, Buonocore S, Rubino EM, Sorrentino V. The Sarcoplasmic Reticulum of Skeletal Muscle Cells: A Labyrinth of Membrane Contact Sites. Biomolecules 2022; 12:488. [PMID: 35454077 PMCID: PMC9026860 DOI: 10.3390/biom12040488] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/14/2022] [Accepted: 03/18/2022] [Indexed: 12/17/2022] Open
Abstract
The sarcoplasmic reticulum of skeletal muscle cells is a highly ordered structure consisting of an intricate network of tubules and cisternae specialized for regulating Ca2+ homeostasis in the context of muscle contraction. The sarcoplasmic reticulum contains several proteins, some of which support Ca2+ storage and release, while others regulate the formation and maintenance of this highly convoluted organelle and mediate the interaction with other components of the muscle fiber. In this review, some of the main issues concerning the biology of the sarcoplasmic reticulum will be described and discussed; particular attention will be addressed to the structure and function of the two domains of the sarcoplasmic reticulum supporting the excitation-contraction coupling and Ca2+-uptake mechanisms.
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Affiliation(s)
- Daniela Rossi
- Department of Molecular and Developmental Medicine, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy; (E.P.); (D.O.A.); (S.B.); (E.M.R.); (V.S.)
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Perni S. The Builders of the Junction: Roles of Junctophilin1 and Junctophilin2 in the Assembly of the Sarcoplasmic Reticulum–Plasma Membrane Junctions in Striated Muscle. Biomolecules 2022; 12:biom12010109. [PMID: 35053257 PMCID: PMC8774113 DOI: 10.3390/biom12010109] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 01/06/2022] [Accepted: 01/07/2022] [Indexed: 02/06/2023] Open
Abstract
Contraction of striated muscle is triggered by a massive release of calcium from the sarcoplasmic reticulum (SR) into the cytoplasm. This intracellular calcium release is initiated by membrane depolarization, which is sensed by voltage-gated calcium channels CaV1.1 (in skeletal muscle) and CaV1.2 (in cardiac muscle) in the plasma membrane (PM), which in turn activate the calcium-releasing channel ryanodine receptor (RyR) embedded in the SR membrane. This cross-communication between channels in the PM and in the SR happens at specialized regions, the SR-PM junctions, where these two compartments come in close proximity. Junctophilin1 and Junctophilin2 are responsible for the formation and stabilization of SR-PM junctions in striated muscle and actively participate in the recruitment of the two essential players in intracellular calcium release, CaV and RyR. This short review focuses on the roles of junctophilins1 and 2 in the formation and organization of SR-PM junctions in skeletal and cardiac muscle and on the functional consequences of the absence or malfunction of these proteins in striated muscle in light of recently published data and recent advancements in protein structure prediction.
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Affiliation(s)
- Stefano Perni
- Department of Physiology and Biophysics, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045, USA
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11
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Lilliu E, Koenig S, Koenig X, Frieden M. Store-Operated Calcium Entry in Skeletal Muscle: What Makes It Different? Cells 2021; 10:cells10092356. [PMID: 34572005 PMCID: PMC8468011 DOI: 10.3390/cells10092356] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 09/03/2021] [Accepted: 09/04/2021] [Indexed: 01/26/2023] Open
Abstract
Current knowledge on store-operated Ca2+ entry (SOCE) regarding its localization, kinetics, and regulation is mostly derived from studies performed in non-excitable cells. After a long time of relative disinterest in skeletal muscle SOCE, this mechanism is now recognized as an essential contributor to muscle physiology, as highlighted by the muscle pathologies that are associated with mutations in the SOCE molecules STIM1 and Orai1. This review mainly focuses on the peculiar aspects of skeletal muscle SOCE that differentiate it from its counterpart found in non-excitable cells. This includes questions about SOCE localization and the movement of respective proteins in the highly organized skeletal muscle fibers, as well as the diversity of expressed STIM isoforms and their differential expression between muscle fiber types. The emerging evidence of a phasic SOCE, which is activated during EC coupling, and its physiological implication is described as well. The specific issues related to the use of SOCE modulators in skeletal muscles are discussed. This review highlights the complexity of SOCE activation and its regulation in skeletal muscle, with an emphasis on the most recent findings and the aim to reach a current picture of this mesmerizing phenomenon.
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Affiliation(s)
- Elena Lilliu
- Center for Physiology and Pharmacology, Department of Neurophysiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria;
| | - Stéphane Koenig
- Department of Cell Physiology and Metabolism, University of Geneva, 1201 Geneva, Switzerland;
| | - Xaver Koenig
- Center for Physiology and Pharmacology, Department of Neurophysiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria;
- Correspondence: (X.K.); (M.F.)
| | - Maud Frieden
- Department of Cell Physiology and Metabolism, University of Geneva, 1201 Geneva, Switzerland;
- Correspondence: (X.K.); (M.F.)
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Piggott CA, Wu Z, Nurrish S, Xu S, Kaplan JM, Chisholm AD, Jin Y. Caenorhabditis elegans junctophilin has tissue-specific functions and regulates neurotransmission with extended-synaptotagmin. Genetics 2021; 218:iyab063. [PMID: 33871019 PMCID: PMC8864756 DOI: 10.1093/genetics/iyab063] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 04/12/2021] [Indexed: 02/06/2023] Open
Abstract
The junctophilin family of proteins tether together plasma membrane (PM) and endoplasmic reticulum (ER) membranes, and couple PM- and ER-localized calcium channels. Understanding in vivo functions of junctophilins is of great interest for dissecting the physiological roles of ER-PM contact sites. Here, we show that the sole Caenorhabditis elegans junctophilin JPH-1 localizes to discrete membrane contact sites in neurons and muscles and has important tissue-specific functions. jph-1 null mutants display slow growth and development due to weaker contraction of pharyngeal muscles, leading to reduced feeding. In the body wall muscle, JPH-1 colocalizes with the PM-localized EGL-19 voltage-gated calcium channel and ER-localized UNC-68 RyR calcium channel, and is required for animal movement. In neurons, JPH-1 colocalizes with the membrane contact site protein Extended-SYnaptoTagmin 2 (ESYT-2) in the soma, and is present near presynaptic release sites. Interestingly, jph-1 and esyt-2 null mutants display mutual suppression in their response to aldicarb, suggesting that JPH-1 and ESYT-2 have antagonistic roles in neuromuscular synaptic transmission. Additionally, we find an unexpected cell nonautonomous effect of jph-1 in axon regrowth after injury. Genetic double mutant analysis suggests that jph-1 functions in overlapping pathways with two PM-localized voltage-gated calcium channels, egl-19 and unc-2, and with unc-68 for animal health and development. Finally, we show that jph-1 regulates the colocalization of EGL-19 and UNC-68 and that unc-68 is required for JPH-1 localization to ER-PM puncta. Our data demonstrate important roles for junctophilin in cellular physiology, and also provide insights into how junctophilin functions together with other calcium channels in vivo.
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Affiliation(s)
- Christopher A Piggott
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Zilu Wu
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Stephen Nurrish
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Suhong Xu
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Joshua M Kaplan
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Andrew D Chisholm
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Yishi Jin
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
- Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, CA 92093, USA
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13
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Targeting JP2: A New Treatment for Pulmonary Hypertension. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2021; 2021:2003446. [PMID: 34394822 PMCID: PMC8363443 DOI: 10.1155/2021/2003446] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 07/21/2021] [Accepted: 07/27/2021] [Indexed: 12/16/2022]
Abstract
Pulmonary hypertension (PH) is a disease with a complex etiology and high mortality rate. Abnormal pulmonary vasoconstriction and pulmonary vascular remodeling lead to an increase in mean pulmonary arterial blood pressure for which, and there is currently no cure. Junctophilin-2 (JP2) is beneficial for the assembly of junctional membrane complexes, the structural basis for excitation-contraction coupling that tethers the plasma membrane to the sarcoplasmic reticulum/endoplasmic reticulum and is involved in maintaining intracellular calcium concentration homeostasis and normal muscle contraction function. Recent studies have shown that JP2 maintains normal contraction and relaxation of vascular smooth muscle. In some experimental studies of drug treatments for PH, JP2 expression was increased, which improved pulmonary vascular remodeling and right ventricular function. Based on JP2 research to date, this paper summarizes the current understanding of JP2 protein structure, function, and related heart diseases and mechanisms and analyzes the feasibility and possible therapeutic strategies for targeting JP2 in PH.
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Piggott CA, Jin Y. Junctophilins: Key Membrane Tethers in Muscles and Neurons. Front Mol Neurosci 2021; 14:709390. [PMID: 34305529 PMCID: PMC8295595 DOI: 10.3389/fnmol.2021.709390] [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: 05/13/2021] [Accepted: 06/15/2021] [Indexed: 12/26/2022] Open
Abstract
Contacts between the endoplasmic reticulum (ER) and plasma membrane (PM) contain specialized tethering proteins that bind both ER and PM membranes. In excitable cells, ER–PM contacts play an important role in calcium signaling and transferring lipids. Junctophilins are a conserved family of ER–PM tethering proteins. They are predominantly expressed in muscles and neurons and known to simultaneously bind both ER- and PM-localized ion channels. Since their discovery two decades ago, functional studies using junctophilin-deficient animals have provided a deep understanding of their roles in muscles and neurons, including excitation-contraction coupling, store-operated calcium entry (SOCE), and afterhyperpolarization (AHP). In this review, we highlight key findings from mouse, fly, and worm that support evolutionary conservation of junctophilins.
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Affiliation(s)
- Christopher A Piggott
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, San Diego, CA, United States
| | - Yishi Jin
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, San Diego, CA, United States
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15
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Romer SH, Metzger S, Peraza K, Wright MC, Jobe DS, Song LS, Rich MM, Foy BD, Talmadge RJ, Voss AA. A mouse model of Huntington's disease shows altered ultrastructure of transverse tubules in skeletal muscle fibers. J Gen Physiol 2021; 153:211860. [PMID: 33683318 PMCID: PMC7931643 DOI: 10.1085/jgp.202012637] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 11/05/2020] [Accepted: 01/26/2021] [Indexed: 12/12/2022] Open
Abstract
Huntington’s disease (HD) is a fatal and progressive condition with severe debilitating motor defects and muscle weakness. Although classically recognized as a neurodegenerative disorder, there is increasing evidence of cell autonomous toxicity in skeletal muscle. We recently demonstrated that skeletal muscle fibers from the R6/2 model mouse of HD have a decrease in specific membrane capacitance, suggesting a loss of transverse tubule (t-tubule) membrane in R6/2 muscle. A previous report also indicated that Cav1.1 current was reduced in R6/2 skeletal muscle, suggesting defects in excitation–contraction (EC) coupling. Thus, we hypothesized that a loss and/or disruption of the skeletal muscle t-tubule system contributes to changes in EC coupling in R6/2 skeletal muscle. We used live-cell imaging with multiphoton confocal microscopy and transmission electron microscopy to assess the t-tubule architecture in late-stage R6/2 muscle and found no significant differences in the t-tubule system density, regularity, or integrity. However, electron microscopy images revealed that the cross-sectional area of t-tubules at the triad were 25% smaller in R6/2 compared with age-matched control skeletal muscle. Computer simulation revealed that the resulting decrease in the R6/2 t-tubule luminal conductance contributed to, but did not fully explain, the reduced R6/2 membrane capacitance. Analyses of bridging integrator-1 (Bin1), which plays a primary role in t-tubule formation, revealed decreased Bin1 protein levels and aberrant splicing of Bin1 mRNA in R6/2 muscle. Additionally, the distance between the t-tubule and sarcoplasmic reticulum was wider in R6/2 compared with control muscle, which was associated with a decrease in junctophilin 1 and 2 mRNA levels. Altogether, these findings can help explain dysregulated EC coupling and motor impairment in Huntington’s disease.
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Affiliation(s)
- Shannon H Romer
- Department of Biological Sciences, Wright State University, Dayton, OH.,Odyssey Systems, Environmental Health Effects Laboratory, Navy Medical Research Unit, Dayton, Wright-Patterson Air Force Base, Dayton, OH
| | - Sabrina Metzger
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, OH
| | - Kristiana Peraza
- Department of Biological Sciences, California State Polytechnic University, Pomona, Pomona, CA
| | - Matthew C Wright
- Department of Biological Sciences, California State Polytechnic University, Pomona, Pomona, CA
| | - D Scott Jobe
- Department of Biological Sciences, Wright State University, Dayton, OH
| | - Long-Sheng Song
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA
| | - Mark M Rich
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, OH
| | - Brent D Foy
- Department of Physics, Wright State University, Dayton, OH
| | - Robert J Talmadge
- Department of Biological Sciences, California State Polytechnic University, Pomona, Pomona, CA
| | - Andrew A Voss
- Department of Biological Sciences, Wright State University, Dayton, OH
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16
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Berlansky S, Humer C, Sallinger M, Frischauf I. More Than Just Simple Interaction between STIM and Orai Proteins: CRAC Channel Function Enabled by a Network of Interactions with Regulatory Proteins. Int J Mol Sci 2021; 22:E471. [PMID: 33466526 PMCID: PMC7796502 DOI: 10.3390/ijms22010471] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 12/29/2020] [Accepted: 12/29/2020] [Indexed: 12/27/2022] Open
Abstract
The calcium-release-activated calcium (CRAC) channel, activated by the release of Ca2+ from the endoplasmic reticulum (ER), is critical for Ca2+ homeostasis and active signal transduction in a plethora of cell types. Spurred by the long-sought decryption of the molecular nature of the CRAC channel, considerable scientific effort has been devoted to gaining insights into functional and structural mechanisms underlying this signalling cascade. Key players in CRAC channel function are the Stromal interaction molecule 1 (STIM1) and Orai1. STIM1 proteins span through the membrane of the ER, are competent in sensing luminal Ca2+ concentration, and in turn, are responsible for relaying the signal of Ca2+ store-depletion to pore-forming Orai1 proteins in the plasma membrane. A direct interaction of STIM1 and Orai1 allows for the re-entry of Ca2+ from the extracellular space. Although much is already known about the structure, function, and interaction of STIM1 and Orai1, there is growing evidence that CRAC under physiological conditions is dependent on additional proteins to function properly. Several auxiliary proteins have been shown to regulate CRAC channel activity by means of direct interactions with STIM1 and/or Orai1, promoting or hindering Ca2+ influx in a mechanistically diverse manner. Various proteins have also been identified to exert a modulatory role on the CRAC signalling cascade although inherently lacking an affinity for both STIM1 and Orai1. Apart from ubiquitously expressed representatives, a subset of such regulatory mechanisms seems to allow for a cell-type-specific control of CRAC channel function, considering the rather restricted expression patterns of the specific proteins. Given the high functional and clinical relevance of both generic and cell-type-specific interacting networks, the following review shall provide a comprehensive summary of regulators of the multilayered CRAC channel signalling cascade. It also includes proteins expressed in a narrow spectrum of cells and tissues that are often disregarded in other reviews of similar topics.
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Affiliation(s)
| | | | | | - Irene Frischauf
- Institute of Biophysics, Johannes Kepler University, 4020 Linz, Austria; (S.B.); (C.H.); (M.S.)
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17
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Woo JS, Jeong SY, Park JH, Choi JH, Lee EH. Calsequestrin: a well-known but curious protein in skeletal muscle. Exp Mol Med 2020; 52:1908-1925. [PMID: 33288873 PMCID: PMC8080761 DOI: 10.1038/s12276-020-00535-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 10/14/2020] [Accepted: 10/19/2020] [Indexed: 12/23/2022] Open
Abstract
Calsequestrin (CASQ) was discovered in rabbit skeletal muscle tissues in 1971 and has been considered simply a passive Ca2+-buffering protein in the sarcoplasmic reticulum (SR) that provides Ca2+ ions for various Ca2+ signals. For the past three decades, physiologists, biochemists, and structural biologists have examined the roles of the skeletal muscle type of CASQ (CASQ1) in skeletal muscle and revealed that CASQ1 has various important functions as (1) a major Ca2+-buffering protein to maintain the SR with a suitable amount of Ca2+ at each moment, (2) a dynamic Ca2+ sensor in the SR that regulates Ca2+ release from the SR to the cytosol, (3) a structural regulator for the proper formation of terminal cisternae, (4) a reverse-directional regulator of extracellular Ca2+ entries, and (5) a cause of human skeletal muscle diseases. This review is focused on understanding these functions of CASQ1 in the physiological or pathophysiological status of skeletal muscle.
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Affiliation(s)
- Jin Seok Woo
- Department of Physiology, David Geffen School of Medicine, UCLA, Los Angeles, CA, 10833, USA
| | - Seung Yeon Jeong
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul, 06591, Korea
- Department of Biomedicine & Health Sciences, Graduate School, The Catholic University of Korea, Seoul, 06591, Korea
| | - Ji Hee Park
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul, 06591, Korea
- Department of Biomedicine & Health Sciences, Graduate School, The Catholic University of Korea, Seoul, 06591, Korea
| | - Jun Hee Choi
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul, 06591, Korea
- Department of Biomedicine & Health Sciences, Graduate School, The Catholic University of Korea, Seoul, 06591, Korea
| | - Eun Hui Lee
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul, 06591, Korea.
- Department of Biomedicine & Health Sciences, Graduate School, The Catholic University of Korea, Seoul, 06591, Korea.
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18
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Protasi F, Pietrangelo L, Boncompagni S. Calcium entry units (CEUs): perspectives in skeletal muscle function and disease. J Muscle Res Cell Motil 2020; 42:233-249. [PMID: 32812118 PMCID: PMC8332569 DOI: 10.1007/s10974-020-09586-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 08/03/2020] [Indexed: 12/28/2022]
Abstract
In the last decades the term Store-operated Ca2+ entry (SOCE) has been used in the scientific literature to describe an ubiquitous cellular mechanism that allows recovery of calcium (Ca2+) from the extracellular space. SOCE is triggered by a reduction of Ca2+ content (i.e. depletion) in intracellular stores, i.e. endoplasmic or sarcoplasmic reticulum (ER and SR). In skeletal muscle the mechanism is primarily mediated by a physical interaction between stromal interaction molecule-1 (STIM1), a Ca2+ sensor located in the SR membrane, and ORAI1, a Ca2+-permeable channel of external membranes, located in transverse tubules (TTs), the invaginations of the plasma membrane (PM) deputed to propagation of action potentials. It is generally accepted that in skeletal muscle SOCE is important to limit muscle fatigue during repetitive stimulation. We recently discovered that exercise promotes the assembly of new intracellular junctions that contains colocalized STIM1 and ORAI1, and that the presence of these new junctions increases Ca2+ entry via ORAI1, while improving fatigue resistance during repetitive stimulation. Based on these findings we named these new junctions Ca2+ Entry Units (CEUs). CEUs are dynamic organelles that assemble during muscle activity and disassemble during recovery thanks to the plasticity of the SR (containing STIM1) and the elongation/retraction of TTs (bearing ORAI1). Interestingly, similar structures described as SR stacks were previously reported in different mouse models carrying mutations in proteins involved in Ca2+ handling (calsequestrin-null mice; triadin and junctin null mice, etc.) or associated to microtubules (MAP6 knockout mice). Mutations in Stim1 and Orai1 (and calsequestrin-1) genes have been associated to tubular aggregate myopathy (TAM), a muscular disease characterized by: (a) muscle pain, cramping, or weakness that begins in childhood and worsens over time, and (b) the presence of large accumulations of ordered SR tubes (tubular aggregates, TAs) that do not contain myofibrils, mitochondria, nor TTs. Interestingly, TAs are also present in fast twitch muscle fibers of ageing mice. Several important issues remain un-answered: (a) the molecular mechanisms and signals that trigger the remodeling of membranes and the functional activation of SOCE during exercise are unclear; and (b) how dysfunctional SOCE and/or mutations in Stim1, Orai1 and calsequestrin (Casq1) genes lead to the formation of tubular aggregates (TAs) in aging and disease deserve investigation.
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Affiliation(s)
- Feliciano Protasi
- CAST, Center for Advanced Studies and Technology, University G. d'Annunzio of Chieti-Pescara, 66100, Chieti, Italy.
- DMSI, Department of Medicine and Aging Sciences, University G. d'Annunzio of Chieti-Pescara, 66100, Chieti, Italy.
| | - Laura Pietrangelo
- CAST, Center for Advanced Studies and Technology, University G. d'Annunzio of Chieti-Pescara, 66100, Chieti, Italy
- DMSI, Department of Medicine and Aging Sciences, University G. d'Annunzio of Chieti-Pescara, 66100, Chieti, Italy
| | - Simona Boncompagni
- CAST, Center for Advanced Studies and Technology, University G. d'Annunzio of Chieti-Pescara, 66100, Chieti, Italy
- DNICS, Department of Neuroscience, Imaging and Clinical Sciences, University G. d'Annunzio of Chieti-Pescara, 66100, Chieti, Italy
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19
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Öztürk Z, O’Kane CJ, Pérez-Moreno JJ. Axonal Endoplasmic Reticulum Dynamics and Its Roles in Neurodegeneration. Front Neurosci 2020; 14:48. [PMID: 32116502 PMCID: PMC7025499 DOI: 10.3389/fnins.2020.00048] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 01/13/2020] [Indexed: 12/13/2022] Open
Abstract
The physical continuity of axons over long cellular distances poses challenges for their maintenance. One organelle that faces this challenge is endoplasmic reticulum (ER); unlike other intracellular organelles, this forms a physically continuous network throughout the cell, with a single membrane and a single lumen. In axons, ER is mainly smooth, forming a tubular network with occasional sheets or cisternae and low amounts of rough ER. It has many potential roles: lipid biosynthesis, glucose homeostasis, a Ca2+ store, protein export, and contacting and regulating other organelles. This tubular network structure is determined by ER-shaping proteins, mutations in some of which are causative for neurodegenerative disorders such as hereditary spastic paraplegia (HSP). While axonal ER shares many features with the tubular ER network in other contexts, these features must be adapted to the long and narrow dimensions of axons. ER appears to be physically continuous throughout axons, over distances that are enormous on a subcellular scale. It is therefore a potential channel for long-distance or regional communication within neurons, independent of action potentials or physical transport of cargos, but involving its physiological roles such as Ca2+ or organelle homeostasis. Despite its apparent stability, axonal ER is highly dynamic, showing features like anterograde and retrograde transport, potentially reflecting continuous fusion and breakage of the network. Here we discuss the transport processes that must contribute to this dynamic behavior of ER. We also discuss the model that these processes underpin a homeostatic process that ensures both enough ER to maintain continuity of the network and repair breaks in it, but not too much ER that might disrupt local cellular physiology. Finally, we discuss how failure of ER organization in axons could lead to axon degenerative diseases, and how a requirement for ER continuity could make distal axons most susceptible to degeneration in conditions that disrupt ER continuity.
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Affiliation(s)
| | - Cahir J. O’Kane
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
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20
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Wang LY, Shen H, Yang Q, Min J, Wang Q, Xi W, Yin L, Le SG, Zhang YF, Xiao J, Wang ZN, Ji GY. LncRNA-LINC00472 contributes to the pathogenesis of atrial fibrillation (Af) by reducing expression of JP2 and RyR2 via miR-24. Biomed Pharmacother 2019; 120:109364. [DOI: 10.1016/j.biopha.2019.109364] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 07/31/2019] [Accepted: 08/14/2019] [Indexed: 12/31/2022] Open
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21
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Jiang J, Tang M, Huang Z, Chen L. Junctophilins emerge as novel therapeutic targets. J Cell Physiol 2019; 234:16933-16943. [DOI: 10.1002/jcp.28405] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 01/25/2019] [Accepted: 01/30/2019] [Indexed: 12/24/2022]
Affiliation(s)
- Jinyong Jiang
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, Hunan Province Cooperative Innovation Center for Molecular Target New Drugs Study University of South China Hengyang China
| | - Mingzhu Tang
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, Hunan Province Cooperative Innovation Center for Molecular Target New Drugs Study University of South China Hengyang China
| | - Zhen Huang
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, Hunan Province Cooperative Innovation Center for Molecular Target New Drugs Study University of South China Hengyang China
| | - Linxi Chen
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, Hunan Province Cooperative Innovation Center for Molecular Target New Drugs Study University of South China Hengyang China
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22
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Saito A, Imaizumi K. Unfolded Protein Response-Dependent Communication and Contact among Endoplasmic Reticulum, Mitochondria, and Plasma Membrane. Int J Mol Sci 2018; 19:ijms19103215. [PMID: 30340324 PMCID: PMC6213962 DOI: 10.3390/ijms19103215] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 10/10/2018] [Accepted: 10/13/2018] [Indexed: 12/20/2022] Open
Abstract
The function of the endoplasmic reticulum (ER) can be impaired by changes to the extra- and intracellular environment, such as disruption of calcium homeostasis, expression of mutated proteins, and oxidative stress. In response to disruptions to ER homeostasis, eukaryotic cells activate canonical branches of signal transduction cascades, collectively termed the unfolded protein response (UPR). The UPR functions to remove or recover the activity of misfolded proteins that accumulated in the ER and to avoid irreversible cellular damage. Additionally, the UPR plays unique physiological roles in the regulation of diverse cellular events, including cell differentiation and development and lipid biosynthesis. Recent studies have shown that these important cellular events are also regulated by contact and communication among organelles. These reports suggest strong involvement among the UPR, organelle communication, and regulation of cellular homeostasis. However, the precise mechanisms for the formation of contact sites and the regulation of ER dynamics by the UPR remain unresolved. In this review, we summarize the current understanding of how the UPR regulates morphological changes to the ER and the formation of contact sites between the ER and other organelles. We also review how UPR-dependent connections between the ER and other organelles affect cellular and physiological functions.
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Affiliation(s)
- Atsushi Saito
- Department of Stress Protein Processing, Institute of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
| | - Kazunori Imaizumi
- Department of Biochemistry, Institute of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
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23
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Cho CH, Lee KJ, Lee EH. With the greatest care, stromal interaction molecule (STIM) proteins verify what skeletal muscle is doing. BMB Rep 2018; 51:378-387. [PMID: 29898810 PMCID: PMC6130827 DOI: 10.5483/bmbrep.2018.51.8.128] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Indexed: 12/11/2022] Open
Abstract
Skeletal muscle contracts or relaxes to maintain the body position and locomotion. For the contraction and relaxation of skeletal muscle, Ca2+ in the cytosol of skeletal muscle fibers acts as a switch to turn on and off a series of contractile proteins. The cytosolic Ca2+ level in skeletal muscle fibers is governed mainly by movements of Ca2+ between the cytosol and the sarcoplasmic reticulum (SR). Store-operated Ca2+ entry (SOCE), a Ca2+ entryway from the extracellular space to the cytosol, has gained a significant amount of attention from muscle physiologists. Orai1 and stromal interaction molecule 1 (STIM1) are the main protein identities of SOCE. This mini-review focuses on the roles of STIM proteins and SOCE in the physiological and pathophysiological functions of skeletal muscle and in their correlations with recently identified proteins, as well as historical proteins that are known to mediate skeletal muscle function.
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Affiliation(s)
- Chung-Hyun Cho
- Department of Pharmacology, College of Medicine, Seoul National University, Seoul 08826, Korea
| | - Keon Jin Lee
- Department of Physiology, College of Medicine, The Catholic University of Korea; Department of Biomedicine & Health Sciences, Graduate School, The Catholic University of Korea, Seoul 06591, Korea
| | - Eun Hui Lee
- Department of Physiology, College of Medicine, The Catholic University of Korea; Department of Biomedicine & Health Sciences, Graduate School, The Catholic University of Korea, Seoul 06591, Korea
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24
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Fan HK, Luo TX, Zhao WD, Mu YH, Yang Y, Guo WJ, Tu HY, Zhang Q. Functional interaction of Junctophilin 2 with small- conductance Ca 2+ -activated potassium channel subtype 2(SK2) in mouse cardiac myocytes. Acta Physiol (Oxf) 2018; 222. [PMID: 29055091 PMCID: PMC6084295 DOI: 10.1111/apha.12986] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Revised: 10/15/2017] [Accepted: 10/15/2017] [Indexed: 12/17/2022]
Abstract
Aim Junctophilins (JPs), a protein family of the junctional membrane complex, maintain the close conjunction between cell surface and intracellular membranes in striate muscle cells mediating the crosstalk between extracellular Ca2+ entry and intracellular Ca2+ release. The small‐conductance Ca2+‐activated K+ channels are activated by the intracellular calcium and play an essential role in the cardiac action potential profile. Molecular mechanisms of regulation of the SK channels are still uncertain. Here, we sought to determine whether there is a functional interaction of junctophilin type 2 (JP2) with the SK channels and whether JP2 gene silencing might modulate the function of SK channels in cardiac myocytes. Methods Association of JP2 with SK2 channel in mouse heart tissue as well as HEK293 cells was studied using in vivo and in vitro approaches. siRNA knockdown of JP2 gene was assessed by real‐time PCR. The expression of proteins was analysed by Western blotting. Ca2+‐activated K+ current (IK,Ca) in infected adult mouse cardiac myocytes was recorded using whole‐cell voltage‐clamp technique. The intracellular Ca2+ transient was measured using an IonOptix photometry system. Results We showed for the first time that JP2 associates with the SK2 channel in native cardiac tissue. JP2, via the membrane occupation and recognition nexus (MORN motifs) in its N‐terminus, directly interacted with SK2 channels. A colocalization of the SK2 channel with its interaction protein of JP2 was found in the cardiac myocytes. Moreover, we demonstrated that JP2 is necessary for the proper cell surface expression of the SK2 channel in HEK293. Functional experiments indicated that knockdown of JP2 caused a significant decrease in the density of IK,Ca and reduced the amplitude of the Ca2+ transient in infected cardiomyocytes. Conclusion The present data provide evidence that the functional interaction between JP2 and SK2 channels is present in the native mouse heart tissue. Junctophilin 2, as junctional membrane complex (JMC) protein, is an important regulator of the cardiac SK channels.
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Affiliation(s)
- H. K. Fan
- Department of Physiology; School of Medicine; Zhengzhou University; Zhengzhou China
| | - T. X. Luo
- Department of Physiology; School of Medicine; Zhengzhou University; Zhengzhou China
| | - W. D. Zhao
- Faculty of Medicine; KU Leuven; Leuven Belgium
| | - Y. H. Mu
- Department of Pathophysiology; School of Medicine; Xinxiang Medical College; Xinxiang China
| | - Y. Yang
- Department of Physiology; School of Medicine; Zhengzhou University; Zhengzhou China
| | - W. J. Guo
- Department of Physiology; School of Medicine; Zhengzhou University; Zhengzhou China
| | - H. Y. Tu
- Department of Physiology; School of Medicine; Zhengzhou University; Zhengzhou China
| | - Q. Zhang
- Department of Physiology; School of Medicine; Zhengzhou University; Zhengzhou China
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25
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Calpena E, López Del Amo V, Chakraborty M, Llamusí B, Artero R, Espinós C, Galindo MI. The Drosophila junctophilin gene is functionally equivalent to its four mammalian counterparts and is a modifier of a Huntingtin poly-Q expansion and the Notch pathway. Dis Model Mech 2018; 11:dmm.029082. [PMID: 29208631 PMCID: PMC5818072 DOI: 10.1242/dmm.029082] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 11/08/2017] [Indexed: 12/13/2022] Open
Abstract
Members of the Junctophilin (JPH) protein family have emerged as key actors in all excitable cells, with crucial implications for human pathophysiology. In mammals, this family consists of four members (JPH1-JPH4) that are differentially expressed throughout excitable cells. The analysis of knockout mice lacking JPH subtypes has demonstrated their essential contribution to physiological functions in skeletal and cardiac muscles and in neurons. Moreover, mutations in the human JPH2 gene are associated with hypertrophic and dilated cardiomyopathies; mutations in JPH3 are responsible for the neurodegenerative Huntington's disease-like-2 (HDL2), whereas JPH1 acts as a genetic modifier in Charcot–Marie–Tooth 2K peripheral neuropathy. Drosophila melanogaster has a single junctophilin (jp) gene, as is the case in all invertebrates, which might retain equivalent functions of the four homologous JPH genes present in mammalian genomes. Therefore, owing to the lack of putatively redundant genes, a jpDrosophila model could provide an excellent platform to model the Junctophilin-related diseases, to discover the ancestral functions of the JPH proteins and to reveal new pathways. By up- and downregulation of Jp in a tissue-specific manner in Drosophila, we show that altering its levels of expression produces a phenotypic spectrum characterized by muscular deficits, dilated cardiomyopathy and neuronal alterations. Importantly, our study has demonstrated that Jp modifies the neuronal degeneration in a Drosophila model of Huntington's disease, and it has allowed us to uncover an unsuspected functional relationship with the Notch pathway. Therefore, this Drosophila model has revealed new aspects of Junctophilin function that can be relevant for the disease mechanisms of their human counterparts. Summary: This work reveals that the Drosophila Junctophilin protein has similar functions to its mammalian homologues and uncovers new interactions of potential biomedical interest with Huntingtin and Notch signalling.
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Affiliation(s)
- Eduardo Calpena
- Program in Molecular Mechanisms of Disease, Centro de Investigación Príncipe Felipe (CIPF), c/ Eduardo Primo Yúfera no. 3, 46012 Valencia, Spain
| | - Víctor López Del Amo
- Program in Molecular Mechanisms of Disease, Centro de Investigación Príncipe Felipe (CIPF), c/ Eduardo Primo Yúfera no. 3, 46012 Valencia, Spain
| | - Mouli Chakraborty
- Translational Genomics Group, Incliva Health Research Institute, Avda. Menendez Pelayo 4 acc 46010, Valencia, Spain.,Department of Genetics and Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED), Universitat de València, c/ Dr Moliner 50, 46100 Burjasot, Spain
| | - Beatriz Llamusí
- Translational Genomics Group, Incliva Health Research Institute, Avda. Menendez Pelayo 4 acc 46010, Valencia, Spain.,Department of Genetics and Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED), Universitat de València, c/ Dr Moliner 50, 46100 Burjasot, Spain
| | - Rubén Artero
- Translational Genomics Group, Incliva Health Research Institute, Avda. Menendez Pelayo 4 acc 46010, Valencia, Spain.,Department of Genetics and Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED), Universitat de València, c/ Dr Moliner 50, 46100 Burjasot, Spain
| | - Carmen Espinós
- Program in Molecular Mechanisms of Disease, Centro de Investigación Príncipe Felipe (CIPF), c/ Eduardo Primo Yúfera no. 3, 46012 Valencia, Spain.,UPV-CIPF Joint Unit Disease Mechanisms and Nanomedicine, 46012 Valencia, Spain
| | - Máximo I Galindo
- Program in Molecular Mechanisms of Disease, Centro de Investigación Príncipe Felipe (CIPF), c/ Eduardo Primo Yúfera no. 3, 46012 Valencia, Spain .,UPV-CIPF Joint Unit Disease Mechanisms and Nanomedicine, 46012 Valencia, Spain.,Instituto Interuniversitario de Investigación de Reconocimiento Molecular y Desarrollo Tecnológico (IDM), Universitat Politècnica de València, Universitat de València, 46022 Valencia, Spain
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Oh MR, Lee KJ, Huang M, Kim JO, Kim DH, Cho CH, Lee EH. STIM2 regulates both intracellular Ca 2+ distribution and Ca 2+ movement in skeletal myotubes. Sci Rep 2017; 7:17936. [PMID: 29263348 PMCID: PMC5738411 DOI: 10.1038/s41598-017-18256-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 12/08/2017] [Indexed: 01/09/2023] Open
Abstract
Stromal interaction molecule 1 (STIM1) along with Orai1 mediates extracellular Ca2+ entry into the cytosol through a store-operated Ca2+ entry (SOCE) mechanism in various tissues including skeletal muscle. However, the role(s) of STIM2, a homolog of STIM1, in skeletal muscle has not been well addressed. The present study, first, was focused on searching for STIM2-binding proteins from among proteins mediating skeletal muscle functions. This study used a binding assay, quadrupole time-of-flight mass spectrometry, and co-immunoprecipitation assay with bona-fide STIM2- and SERCA1a-expressing rabbit skeletal muscle. The region for amino acids from 453 to 729 of STIM2 binds to sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 1a (SERCA1a). Next, oxalate-supported 45Ca2+-uptake experiments and various single-myotube Ca2+ imaging experiments using STIM2-knockdown mouse primary skeletal myotubes have suggested that STIM2 attenuates SERCA1a activity during skeletal muscle contraction, which contributes to the intracellular Ca2+ distribution between the cytosol and the SR at rest. In addition, STIM2 regulates Ca2+ movement through RyR1 during skeletal muscle contraction as well as SOCE. Therefore, via regulation of SERCA1a activity, STIM2 regulates both intracellular Ca2+ distribution and Ca2+ movement in skeletal muscle, which makes it both similar to, yet different from, STIM1.
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Affiliation(s)
- Mi Ri Oh
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul, 06591, Republic of Korea
| | - Keon Jin Lee
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul, 06591, Republic of Korea
| | - Mei Huang
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul, 06591, Republic of Korea
| | - Jin Ock Kim
- School of Life Sciences, GIST, Gwangju, 61005, Republic of Korea
| | - Do Han Kim
- School of Life Sciences, GIST, Gwangju, 61005, Republic of Korea
| | - Chung-Hyun Cho
- Department of Pharmacology, College of Medicine, Seoul National University, Seoul, 08826, Republic of Korea
| | - Eun Hui Lee
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul, 06591, Republic of Korea.
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A focus on extracellular Ca 2+ entry into skeletal muscle. Exp Mol Med 2017; 49:e378. [PMID: 28912570 PMCID: PMC5628281 DOI: 10.1038/emm.2017.208] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 06/16/2017] [Accepted: 06/28/2017] [Indexed: 01/06/2023] Open
Abstract
The main task of skeletal muscle is contraction and relaxation for body movement and posture maintenance. During contraction and relaxation, Ca2+ in the cytosol has a critical role in activating and deactivating a series of contractile proteins. In skeletal muscle, the cytosolic Ca2+ level is mainly determined by Ca2+ movements between the cytosol and the sarcoplasmic reticulum. The importance of Ca2+ entry from extracellular spaces to the cytosol has gained significant attention over the past decade. Store-operated Ca2+ entry with a low amplitude and relatively slow kinetics is a main extracellular Ca2+ entryway into skeletal muscle. Herein, recent studies on extracellular Ca2+ entry into skeletal muscle are reviewed along with descriptions of the proteins that are related to extracellular Ca2+ entry and their influences on skeletal muscle function and disease.
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Hu X, Kuang Y, Li L, Tang H, Shi Q, Shu X, Zhang Y, Chan FKL, Tao Q, He C. Epigenomic and Functional Characterization of Junctophilin 3 (JPH3) as a Novel Tumor Suppressor Being Frequently Inactivated by Promoter CpG Methylation in Digestive Cancers. Am J Cancer Res 2017; 7:2150-2163. [PMID: 28656064 PMCID: PMC5485426 DOI: 10.7150/thno.18185] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 04/04/2017] [Indexed: 12/28/2022] Open
Abstract
Junctophilin (JPH) proteins stabilize junctional membrane complexes between plasma membrane and endoplasmic reticulum, also implicated in some human diseases. JPH3 mutations are linked to Huntington's disease-like 2 syndrome. Through epigenomic study of a colon cancer cell line pair (HCT116 and DKO), we identified JPH3 as a methylated novel tumor suppressor gene (TSG) candidate at 16q24. We further studied its epigenetic alterations and functions in digestive tumorigenesis. JPH3 expression at the RNA level was found to be frequently silenced or reduced in colorectal and gastric cancers due to its promoter CpG methylation, which is associated with tumor progression and poor survival of digestive cancer patients. Ectopic expression of JPH3 inhibited tumor cell growth in vitro and in vivo. JPH3 expression upregulated the cytosolic Ca2+ levels, and unfolded protein response gene expression upon endoplasmic reticulum stress. JPH3 also induced calpain activation and subsequent mitochondrial membrane depolarization and cell apoptosis. Thus, JPH3 was identified as a novel TSG methylated in colorectal and gastric tumors which promotes mitochondrial-mediated apoptosis, also as a potential metastasis and survival biomarker for digestive cancers.
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Chang CL, Chen YJ, Liou J. ER-plasma membrane junctions: Why and how do we study them? BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:1494-1506. [PMID: 28554772 DOI: 10.1016/j.bbamcr.2017.05.018] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 05/09/2017] [Accepted: 05/17/2017] [Indexed: 12/17/2022]
Abstract
Endoplasmic reticulum (ER)-plasma membrane (PM) junctions are membrane microdomains important for communication between the ER and the PM. ER-PM junctions were first reported in muscle cells in 1957, but mostly ignored in non-excitable cells due to their scarcity and lack of functional significance. In 2005, the discovery of stromal interaction molecule 1 (STIM1) mediating a universal Ca2+ feedback mechanism at ER-PM junctions in mammalian cells led to a resurgence of research interests toward ER-PM junctions. In the past decade, several major advancements have been made in this emerging topic in cell biology, including the generation of tools for labeling ER-PM junctions and the unraveling of mechanisms underlying regulation and functions of ER-PM junctions. This review summarizes early studies, recently developed tools, and current advances in the characterization and understanding of ER-PM junctions. This article is part of a Special Issue entitled: Membrane Contact Sites edited by Christian Ungermann and Benoit Kornmann.
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Affiliation(s)
- Chi-Lun Chang
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Yu-Ju Chen
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jen Liou
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390, USA.
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Organization of junctional sarcoplasmic reticulum proteins in skeletal muscle fibers. J Muscle Res Cell Motil 2015; 36:501-15. [DOI: 10.1007/s10974-015-9421-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 09/08/2015] [Indexed: 01/24/2023]
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Nanoscale patterning of STIM1 and Orai1 during store-operated Ca2+ entry. Proc Natl Acad Sci U S A 2015; 112:E5533-42. [PMID: 26351694 DOI: 10.1073/pnas.1515606112] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Stromal interacting molecule (STIM) and Orai proteins constitute the core machinery of store-operated calcium entry. We used transmission and freeze-fracture electron microscopy to visualize STIM1 and Orai1 at endoplasmic reticulum (ER)-plasma membrane (PM) junctions in HEK 293 cells. Compared with control cells, thin sections of STIM1-transfected cells possessed far more ER elements, which took the form of complex stackable cisternae and labyrinthine structures adjoining the PM at junctional couplings (JCs). JC formation required STIM1 expression but not store depletion, induced here by thapsigargin (TG). Extended molecules, indicative of STIM1, decorated the cytoplasmic surface of ER, bridged a 12-nm ER-PM gap, and showed clear rearrangement into small clusters following TG treatment. Freeze-fracture replicas of the PM of Orai1-transfected cells showed extensive domains packed with characteristic "particles"; TG treatment led to aggregation of these particles into sharply delimited "puncta" positioned upon raised membrane subdomains. The size and spacing of Orai1 channels were consistent with the Orai crystal structure, and stoichiometry was unchanged by store depletion, coexpression with STIM1, or an Orai1 mutation (L273D) affecting STIM1 association. Although the arrangement of Orai1 channels in puncta was substantially unstructured, a portion of channels were spaced at ∼15 nm. Monte Carlo analysis supported a nonrandom distribution for a portion of channels spaced at ∼15 nm. These images offer dramatic, direct views of STIM1 aggregation and Orai1 clustering in store-depleted cells and provide evidence for the interaction of a single Orai1 channel with small clusters of STIM1 molecules.
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Demonbreun AR, Swanson KE, Rossi AE, Deveaux HK, Earley JU, Allen MV, Arya P, Bhattacharyya S, Band H, Pytel P, McNally EM. Eps 15 Homology Domain (EHD)-1 Remodels Transverse Tubules in Skeletal Muscle. PLoS One 2015; 10:e0136679. [PMID: 26325203 PMCID: PMC4556691 DOI: 10.1371/journal.pone.0136679] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 08/06/2015] [Indexed: 11/19/2022] Open
Abstract
We previously showed that Eps15 homology domain-containing 1 (EHD1) interacts with ferlin proteins to regulate endocytic recycling. Myoblasts from Ehd1-null mice were found to have defective recycling, myoblast fusion, and consequently smaller muscles. When expressed in C2C12 cells, an ATPase dead-EHD1 was found to interfere with BIN1/amphiphysin 2. We now extended those findings by examining Ehd1-heterozygous mice since these mice survive to maturity in normal Mendelian numbers and provide a ready source of mature muscle. We found that heterozygosity of EHD1 was sufficient to produce ectopic and excessive T-tubules, including large intracellular aggregates that contained BIN1. The disorganized T-tubule structures in Ehd1-heterozygous muscle were accompanied by marked elevation of the T-tubule-associated protein DHPR and reduction of the triad linker protein junctophilin 2, reflecting defective triads. Consistent with this, Ehd1-heterozygous muscle had reduced force production. Introduction of ATPase dead-EHD1 into mature muscle fibers was sufficient to induce ectopic T-tubule formation, seen as large BIN1 positive structures throughout the muscle. Ehd1-heterozygous mice were found to have strikingly elevated serum creatine kinase and smaller myofibers, but did not display findings of muscular dystrophy. These data indicate that EHD1 regulates the maintenance of T-tubules through its interaction with BIN1 and links T-tubules defects with elevated creatine kinase and myopathy.
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Affiliation(s)
- Alexis R. Demonbreun
- Center for Genetic Medicine, Northwestern University, Chicago, IL, United States of America
- * E-mail:
| | - Kaitlin E. Swanson
- Department of Pathology, The University of Chicago, Chicago, IL, United States of America
| | - Ann E. Rossi
- Department of Medicine, The University of Chicago, Chicago, IL, United States of America
| | - H. Kieran Deveaux
- Department of Medicine, The University of Chicago, Chicago, IL, United States of America
| | - Judy U. Earley
- Center for Genetic Medicine, Northwestern University, Chicago, IL, United States of America
| | - Madison V. Allen
- Center for Genetic Medicine, Northwestern University, Chicago, IL, United States of America
| | - Priyanka Arya
- Department of Genetics, Cell Biology & Anatomy, University of Nebraska Medical Center, Omaha, NE, United States of America
| | - Sohinee Bhattacharyya
- Department of Pathology & Microbiology, Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, United States of America
| | - Hamid Band
- Department of Pathology & Microbiology, Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, United States of America
| | - Peter Pytel
- Department of Pathology, The University of Chicago, Chicago, IL, United States of America
| | - Elizabeth M. McNally
- Center for Genetic Medicine, Northwestern University, Chicago, IL, United States of America
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Walters TJ, Garg K, Corona BT. Activity attenuates skeletal muscle fiber damage after ischemia and reperfusion. Muscle Nerve 2015; 52:640-8. [PMID: 25641705 DOI: 10.1002/mus.24581] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Revised: 01/09/2015] [Accepted: 01/16/2015] [Indexed: 01/21/2023]
Abstract
INTRODUCTION In this investigation we aimed to determine whether: (1) physical activity protects rat skeletal muscle from ischemia/reperfusion (I/R) injury; and (2) continued activity after I/R improves the rate of healing. METHODS Rats were divided into sedentary or active (voluntary wheel running) groups. Active rats ran for 4 weeks before I/R or 4 weeks before plus 4 weeks after I/R. RESULTS Activity before I/R resulted in 73.2% less muscle damage (Evans blue dye inclusion). Sedentary and active rats had a similar decline in neural-evoked (∼ 99%) and directly stimulated (∼ 70%) in vivo muscle torque, and a similar reduction in junctophilin 1. Active rats produced 19% and 15% greater neural-evoked torque compared with sedentary rats at 14 and 28 days postinjury, respectively, although the rate of recovery appeared similar. CONCLUSIONS Activity protects against long-term muscle damage, but not short-term neural injury or excitation-contraction uncoupling. Continued activity neither accelerates nor hinders the rate of functional recovery.
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Affiliation(s)
- Thomas J Walters
- Extremity Trauma and Regenerative Medicine Research Program, United States Army Institute of Surgical Research, 3698 Chambers Pass, Fort Sam Houston, Texas, 78234-6315, USA
| | - Koyal Garg
- Extremity Trauma and Regenerative Medicine Research Program, United States Army Institute of Surgical Research, 3698 Chambers Pass, Fort Sam Houston, Texas, 78234-6315, USA
| | - Benjamin T Corona
- Extremity Trauma and Regenerative Medicine Research Program, United States Army Institute of Surgical Research, 3698 Chambers Pass, Fort Sam Houston, Texas, 78234-6315, USA
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Zhu H, Zhang H, Jin F, Fang M, Huang M, Yang CS, Chen T, Fu L, Pan Z. Elevated Orai1 expression mediates tumor-promoting intracellular Ca2+ oscillations in human esophageal squamous cell carcinoma. Oncotarget 2015; 5:3455-71. [PMID: 24797725 PMCID: PMC4116495 DOI: 10.18632/oncotarget.1903] [Citation(s) in RCA: 114] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Effective treatment as well as prognostic biomarker for malignant esophageal squamous cell carcinoma (ESCC) is urgently needed. The present study was aimed at identifying oncogenic genes involving dysregulated intracellular Ca2+ signaling, which is known to function importantly in cellular proliferation and migration. Tumors from patients with ESCC were found to display elevated expression of Orai1, a store-operated Ca2+ entry (SOCE) channel, and the high expression of Orai1 was associated with poor overall and recurrence-free survival. In contrast to the quiescent nature of non-tumorigenic epithelial cells, human ESCC cells exhibited strikingly hyperactive in intracellular Ca2+ oscillations, which were sensitive to treatments with Orai1 channel blockers and to orai1 silencing. Moreover, pharmacologic inhibition of Orai1 activity or reduction of Orai1 expression suppressed proliferation and migration of ESCC in vitro and slowed tumor formation and growth in in vivo xenografted mice. Combined, these findings provide the first evidence to imply Orai1 as a novel biomarker for ESCC prognostic stratification and also highlight Orai1-mediated Ca2+ signaling pathway as a potential target for treatment of this deadly disease.
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Affiliation(s)
- Hua Zhu
- Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH; Department of Surgery, The Ohio State University Wexner Medical Center, Columbus, OH
| | | | | | | | | | | | | | - Liwu Fu
- Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China
| | - Zui Pan
- Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH; Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, OH
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Takeshima H, Hoshijima M, Song LS. Ca²⁺ microdomains organized by junctophilins. Cell Calcium 2015; 58:349-56. [PMID: 25659516 PMCID: PMC5159448 DOI: 10.1016/j.ceca.2015.01.007] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 01/15/2015] [Accepted: 01/16/2015] [Indexed: 11/21/2022]
Abstract
Excitable cells typically possess junctional membrane complexes (JMCs) constructed by the plasma membrane and the endo/sarcoplasmic reticulum (ER/SR) for channel crosstalk. These JMCs are termed triads in skeletal muscle, dyads in cardiac muscle, peripheral couplings in smooth and developing striated muscles, and subsurface cisterns in neurons. Junctophilin subtypes contribute to the formation and maintenance of JMCs by serving as a physical bridge between the plasma membrane and ER/SR membrane in different cell types. In muscle cells, junctophilin deficiency prevents JMC formation and functional crosstalk between cell-surface Ca2+ channels and ER/SR Ca2+ release channels. Human genetic mutations in junctophilin subtypes are linked to congenital hypertrophic cardiomyopathy and neurodegenerative diseases. Furthermore, growing evidence suggests that dysregulation of junctophilins induces pathological alterations in skeletal and cardiac muscle.
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Affiliation(s)
- Hiroshi Takeshima
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan.
| | - Masahiko Hoshijima
- Department of Medicine and Center for Research in Biological Systems, University of California, San Diego, CA 92093, USA.
| | - Long-Sheng Song
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA.
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Abstract
Ca(2+) release from intracellular stores and influx from extracellular reservoir regulate a wide range of physiological functions including muscle contraction and rhythmic heartbeat. One of the most ubiquitous pathways involved in controlled Ca(2+) influx into cells is store-operated Ca(2+) entry (SOCE), which is activated by the reduction of Ca(2+) concentration in the lumen of endoplasmic or sarcoplasmic reticulum (ER/SR). Although SOCE is pronounced in non-excitable cells, accumulating evidences highlight its presence and important roles in skeletal muscle and heart. Recent discovery of STIM proteins as ER/SR Ca(2+) sensors and Orai proteins as Ca(2+) channel pore forming unit expedited the mechanistic understanding of this pathway. This review focuses on current advances of SOCE components, regulation and physiologic and pathophysiologic roles in muscles. The specific property and the dysfunction of this pathway in muscle diseases, and new directions for future research in this rapidly growing field are discussed.
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Affiliation(s)
- Zui Pan
- Department of Internal Medicine-Cardiovascular Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Marco Brotto
- Muscle Biology Research Group-MUBIG, Schools of Nursing & Medicine, University of Missouri-Kansas City, MO, USA
| | - Jianjie Ma
- Department of Surgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, USA
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Pla-Martín D, Calpena E, Lupo V, Márquez C, Rivas E, Sivera R, Sevilla T, Palau F, Espinós C. Junctophilin-1 is a modifier gene of GDAP1-related Charcot-Marie-Tooth disease. Hum Mol Genet 2014; 24:213-29. [PMID: 25168384 DOI: 10.1093/hmg/ddu440] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Mutations in the GDAP1 gene cause different forms of Charcot-Marie-Tooth (CMT) disease, and the primary clinical expression of this disease is markedly variable in the dominant inheritance form (CMT type 2K; CMT2K), in which carriers of the GDAP1 p.R120W mutation can display a wide range of clinical severity. We investigated the JPH1 gene as a genetic modifier of clinical expression variability because junctophilin-1 (JPH1) is a good positional and functional candidate. We demonstrated that the JPH1-GDAP1 cluster forms a paralogon and is conserved in vertebrates. Moreover, both proteins play a role in Ca(2+) homeostasis, and we demonstrated that JPH1 is able to restore the store-operated Ca(2+) entry (SOCE) activity in GDAP1-silenced cells. After the mutational screening of JPH1 in a series of 24 CMT2K subjects who harbour the GDAP1 p.R120W mutation, we characterized the JPH1 p.R213P mutation in one patient with a more severe clinical picture. JPH1(p.R213P) cannot rescue the SOCE response in GDAP1-silenced cells. We observed that JPH1 colocalizes with STIM1, which is the activator of SOCE, in endoplasmic reticulum-plasma membrane puncta structures during Ca(2+) release in a GDAP1-dependent manner. However, when GDAP1(p.R120W) is expressed, JPH1 seems to be retained in mitochondria. We also established that the combination of GDAP1(p.R120W) and JPH1(p.R213P) dramatically reduces SOCE activity, mimicking the effect observed in GDAP1 knock-down cells. In summary, we conclude that JPH1 and GDAP1 share a common pathway and depend on each other; therefore, JPH1 can contribute to the phenotypical consequences of GDAP1 mutations.
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Affiliation(s)
- David Pla-Martín
- Program in Rare and Genetic Diseases and IBV/CSIC Associated Unit, Centro de Investigación Príncipe Felipe (CIPF), Valencia 46012, Spain Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Valencia 46012, Spain
| | - Eduardo Calpena
- Program in Rare and Genetic Diseases and IBV/CSIC Associated Unit, Centro de Investigación Príncipe Felipe (CIPF), Valencia 46012, Spain Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Valencia 46012, Spain
| | - Vincenzo Lupo
- Program in Rare and Genetic Diseases and IBV/CSIC Associated Unit, Centro de Investigación Príncipe Felipe (CIPF), Valencia 46012, Spain Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Valencia 46012, Spain
| | | | - Eloy Rivas
- Department of Pathology, Hospital Universitario Virgen del Rocío, Seville 41013, Spain
| | - Rafael Sivera
- Department of Neurology, Hospital Universitari i Politècnic La Fe and Instituto de Investigación Sanitario (IIS)-La Fe, Valencia 46026, Spain Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Valencia 46026, Spain
| | - Teresa Sevilla
- Department of Neurology, Hospital Universitari i Politècnic La Fe and Instituto de Investigación Sanitario (IIS)-La Fe, Valencia 46026, Spain Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Valencia 46026, Spain Department of Medicine and
| | - Francesc Palau
- Program in Rare and Genetic Diseases and IBV/CSIC Associated Unit, Centro de Investigación Príncipe Felipe (CIPF), Valencia 46012, Spain Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Valencia 46012, Spain University of Castilla-La Mancha School of Medicine, Ciudad Real 13071, Spain
| | - Carmen Espinós
- Program in Rare and Genetic Diseases and IBV/CSIC Associated Unit, Centro de Investigación Príncipe Felipe (CIPF), Valencia 46012, Spain Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Valencia 46012, Spain Department of Genetics, Universitat de València, Valencia 46010, Spain and
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38
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Prinz WA. Bridging the gap: membrane contact sites in signaling, metabolism, and organelle dynamics. ACTA ACUST UNITED AC 2014; 205:759-69. [PMID: 24958771 PMCID: PMC4068136 DOI: 10.1083/jcb.201401126] [Citation(s) in RCA: 296] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Regions of close apposition between two organelles, often referred to as membrane contact sites (MCSs), mostly form between the endoplasmic reticulum and a second organelle, although contacts between mitochondria and other organelles have also begun to be characterized. Although these contact sites have been noted since cells first began to be visualized with electron microscopy, the functions of most of these domains long remained unclear. The last few years have witnessed a dramatic increase in our understanding of MCSs, revealing the critical roles they play in intracellular signaling, metabolism, the trafficking of metabolites, and organelle inheritance, division, and transport.
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Affiliation(s)
- William A Prinz
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
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39
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Baumann CW, Rogers RG, Gahlot N, Ingalls CP. Eccentric contractions disrupt FKBP12 content in mouse skeletal muscle. Physiol Rep 2014; 2:2/7/e12081. [PMID: 25347864 PMCID: PMC4187567 DOI: 10.14814/phy2.12081] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Strength deficits associated with eccentric contraction‐induced muscle injury stem, in part, from impaired voltage‐gated sarcoplasmic reticulum (SR) Ca2+ release. FKBP12 is a 12‐kD immunophilin known to bind to the SR Ca2+ release channel (ryanodine receptor, RyR1) and plays an important role in excitation‐contraction coupling. To assess the effects of eccentric contractions on FKBP12 content, we measured anterior crural muscle (tibialis anterior [TA], extensor digitorum longus [EDL], extensor hallucis longus muscles) strength and FKBP12 content in pellet and supernatant fractions after centrifugation via immunoblotting from mice before and after a single bout of either 150 eccentric or concentric contractions. There were no changes in peak isometric torque or FKBP12 content in TA muscles after concentric contractions. However, FKBP12 content was reduced in the pelleted fraction immediately after eccentric contractions, and increased in the soluble protein fraction 3 day after injury induction. FKBP12 content was correlated (P = 0.025; R2= 0.38) to strength deficits immediately after injury induction. In summary, eccentric contraction‐induced muscle injury is associated with significant alterations in FKBP12 content after injury, and is correlated with changes in peak isometric torque. Eccentric contraction‐induced muscle injury is associated with immediate and prolonged strength deficits that stem in part from impaired sarcoplasmic reticulum (SR) calcium release. The content of FKBP12, a 12‐kD immunophilin known to bind to the SR calcium release channel and influence SR calcium release, is reduced in mouse skeletal muscle immediately after injury induction and is significantly associated with strength deficits.
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Affiliation(s)
- Cory W Baumann
- Department of Kinesiology and Health, Muscle Biology Laboratory, Georgia State University, Atlanta, 30302, Georgia
| | - Russell G Rogers
- Department of Kinesiology and Health, Muscle Biology Laboratory, Georgia State University, Atlanta, 30302, Georgia
| | - Nidhi Gahlot
- Department of Kinesiology and Health, Muscle Biology Laboratory, Georgia State University, Atlanta, 30302, Georgia
| | - Christopher P Ingalls
- Department of Kinesiology and Health, Muscle Biology Laboratory, Georgia State University, Atlanta, 30302, Georgia
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40
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Landstrom AP, Beavers DL, Wehrens XHT. The junctophilin family of proteins: from bench to bedside. Trends Mol Med 2014; 20:353-62. [PMID: 24636942 PMCID: PMC4041816 DOI: 10.1016/j.molmed.2014.02.004] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 02/10/2014] [Accepted: 02/14/2014] [Indexed: 12/25/2022]
Abstract
Excitable tissues rely on junctional membrane complexes to couple cell surface signals to intracellular channels. The junctophilins have emerged as a family of proteins critical in coordinating the maturation and maintenance of this cellular ultrastructure. Within skeletal and cardiac muscle, junctophilin 1 and junctophilin 2, respectively, couple sarcolemmal and intracellular calcium channels. In neuronal tissue, junctophilin 3 and junctophilin 4 may have an emerging role in coupling membrane neurotransmitter receptors and intracellular calcium channels. These important physiological roles are highlighted by the pathophysiology which results when these proteins are perturbed, and a growing body of literature has associated junctophilins with the pathogenesis of human disease.
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Affiliation(s)
- Andrew P Landstrom
- Department of Pediatrics, Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX 77030, USA
| | - David L Beavers
- Department of Molecular Physiology and Biophysics, Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX 77030, USA
| | - Xander H T Wehrens
- Department of Molecular Physiology and Biophysics, Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX 77030, USA; Department of Medicine (Cardiology), Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX 77030, USA.
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41
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Zhou X, Lin P, Yamazaki D, Park KH, Komazaki S, Chen SRW, Takeshima H, Ma J. Trimeric intracellular cation channels and sarcoplasmic/endoplasmic reticulum calcium homeostasis. Circ Res 2014; 114:706-16. [PMID: 24526676 DOI: 10.1161/circresaha.114.301816] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Trimeric intracellular cation channels (TRIC) represents a novel class of trimeric intracellular cation channels. Two TRIC isoforms have been identified in both the human and the mouse genomes: TRIC-A, a subtype predominantly expressed in the sarcoplasmic reticulum (SR) of muscle cells, and TRIC-B, a ubiquitous subtype expressed in the endoplasmic reticulum (ER) of all tissues. Genetic ablation of either TRIC-A or TRIC-B leads to compromised K(+) permeation and Ca(2+) release across the SR/ER membrane, supporting the hypothesis that TRIC channels provide a counter balancing K(+) flux that reduces SR/ER membrane depolarization for maintenance of the electrochemical gradient that drives SR/ER Ca(2+) release. TRIC-A and TRIC-B seem to have differential functions in Ca(2+) signaling in excitable and nonexcitable cells. Tric-a(-/-) mice display defective Ca(2+) sparks and spontaneous transient outward currents in arterial smooth muscle and develop hypertension, in addition to skeletal muscle dysfunction. Knockout of TRIC-B results in abnormal IP3 receptor-mediated Ca(2+) release in airway epithelial cells, respiratory defects, and neonatal lethality. Double knockout mice lacking both TRIC-A and TRIC-B show embryonic lethality as a result of cardiac arrest. Such an aggravated lethality indicates that TRIC-A and TRIC-B share complementary physiological functions in Ca(2+) signaling in embryonic cardiomyocytes. Tric-a(-/-) and Tric-b(+/-) mice are viable and susceptible to stress-induced heart failure. Recent evidence suggests that TRIC-A directly modulates the function of the cardiac ryanodine receptor 2 Ca(2+) release channel, which in turn controls store-overload-induced Ca(2+) release from the SR. Thus, the TRIC channels, in addition to providing a countercurrent for SR/ER Ca(2+) release, may also function as accessory proteins that directly modulate the ryanodine receptor/IP3 receptor channel functions.
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Affiliation(s)
- Xinyu Zhou
- From the Department of Surgery, Davis Heart and Lung Research Institute, Wexner Medical Center, The Ohio State University, Columbus (X.Z., P.L., K.H.P., J.M.); Department of Biological Chemistry, Kyoto University Graduate School of Pharmaceutical Sciences, Kyoto, Japan (D.Y., H.T.); Department of Anatomy, Saitama Medical University, Saitama, Japan (S.K.); and Departments of Physiology and Pharmacology, and Biochemistry and Molecular Biology, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada (W.C.)
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42
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Giurisato E, Gamberucci A, Ulivieri C, Marruganti S, Rossi E, Giacomello E, Randazzo D, Sorrentino V. The KSR2-calcineurin complex regulates STIM1-ORAI1 dynamics and store-operated calcium entry (SOCE). Mol Biol Cell 2014; 25:1769-81. [PMID: 24672054 PMCID: PMC4038503 DOI: 10.1091/mbc.e13-05-0292] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Store-operated calcium entry (SOCE) is the predominant Ca(2+) entry mechanism in nonexcitable cells and controls a variety of physiological and pathological processes. Although significant progress has been made in identifying the components required for SOCE, the molecular mechanisms underlying it are elusive. The present study provides evidence for a direct involvement of kinase suppressor of Ras 2 (KSR2) in SOCE. Using lymphocytes and fibroblasts from ksr2(-/-) mice and shKSR2-depleted cells, we find that KSR2 is critical for the elevation of cytosolic Ca(2+) concentration. Specifically, our results show that although it is dispensable for Ca(2+)-store depletion, KSR2 is required for optimal calcium entry. We observe that KSR2 deficiency affects stromal interaction molecule 1 (STIM1)/ORAI1 puncta formation, which is correlated with cytoskeleton disorganization. Of interest, we find that KSR2-associated calcineurin is crucial for SOCE. Blocking calcineurin activity impairs STIM1/ORAI1 puncta-like formation and cytoskeleton organization. In addition, we observe that calcineurin activity and its role in SOCE are both KSR2 dependent.
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Affiliation(s)
- E Giurisato
- Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy
| | - A Gamberucci
- Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy
| | - C Ulivieri
- Department of Life Sciences, University of Siena, 53100 Siena, Italy
| | - S Marruganti
- Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy
| | - E Rossi
- Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy
| | - E Giacomello
- Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy
| | - D Randazzo
- Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy
| | - V Sorrentino
- Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy
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43
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Bolaños P, Guillen A, Gámez A, Caputo C. Quantifying SOCE fluorescence measurements in mammalian muscle fibres. The effects of ryanodine and osmotic shocks. J Muscle Res Cell Motil 2013; 34:379-93. [PMID: 24129906 DOI: 10.1007/s10974-013-9360-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Accepted: 09/18/2013] [Indexed: 11/28/2022]
Abstract
We have quantified Ca(2+) entry through store operated calcium channels in mice muscle fibres, measuring the rates of change of myoplasmic [Ca(2+)], d[Ca(2+)](myo)/dt, and of Ca(2+) removal, d[Ca(2+)](Removal)/dt, turning store operated calcium entry (SOCE) ON, and OFF, by switching on or off external Ca(2+). In depleted fibres, poisoned with 10 μM cyclopiazonic acid SOCE influx was about 3 μM/s. Ryanodine (50 μM) caused a robust, nifedipine (50 μM) independent, increase in SOCE activation to 8.6 μM/s. Decreasing medium osmolarity from 300 to 220 mOsm/L, decreased SOCE to 0.9 μM/s, while increasing osmolarity from 220 to 400 mOsm/L potentiated SOCE to 43.6 μM/s. Ryanodine inhibited the effects of hypotonicity. Experiments using 2-aminoethoxydiphenyl borate, nifedipine, or Mn(2+) quenching, strongly suggest that the increased [Ca(2+)](myo) by ryanodine or hypertonic shock is mediated by potentiated SOCE activation. The Ca(2+) response decay, quantified by d[Ca(2+)](Removal)/dt, indicates a robust residual Ca(2+) removal mechanism in sarco-endoplasmic reticulum calcium ATPase poisoned fibres. SOCE high sensitivity to osmotic shocks, or to ryanodine receptor (RyR) binding, suggests its high dependency on the structural relationship between its molecular constituents, Orai1 and stromal interaction molecule and the sarcoplasmic reticulum and plasma membranes, in the triadic junctional region, where RyRs, are conspicuously present. This study demonstrates that SOCE machinery is highly sensitive to structural changes caused by binding of an agonist to its receptor or by imposed osmotical volume changes.
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Affiliation(s)
- Pura Bolaños
- Laboratorio de Fisiología Celular, Centro de Biofísica y Bioquímica, Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas, Venezuela,
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44
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Mosca B, Delbono O, Laura Messi M, Bergamelli L, Wang ZM, Vukcevic M, Lopez R, Treves S, Nishi M, Takeshima H, Paolini C, Martini M, Rispoli G, Protasi F, Zorzato F. Enhanced dihydropyridine receptor calcium channel activity restores muscle strength in JP45/CASQ1 double knockout mice. Nat Commun 2013; 4:1541. [PMID: 23443569 DOI: 10.1038/ncomms2496] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Accepted: 01/14/2013] [Indexed: 01/06/2023] Open
Abstract
Muscle strength declines with age in part due to a decline of Ca(2+) release from sarcoplasmic reticulum calcium stores. Skeletal muscle dihydropyridine receptors (Ca(v)1.1) initiate muscle contraction by activating ryanodine receptors in the sarcoplasmic reticulum. Ca(v)1.1 channel activity is enhanced by a retrograde stimulatory signal delivered by the ryanodine receptor. JP45 is a membrane protein interacting with Ca(v)1.1 and the sarcoplasmic reticulum Ca(2+) storage protein calsequestrin (CASQ1). Here we show that JP45 and CASQ1 strengthen skeletal muscle contraction by modulating Ca(v)1.1 channel activity. Using muscle fibres from JP45 and CASQ1 double knockout mice, we demonstrate that Ca(2+) transients evoked by tetanic stimulation are the result of massive Ca(2+) influx due to enhanced Ca(v)1.1 channel activity, which restores muscle strength in JP45/CASQ1 double knockout mice. We envision that JP45 and CASQ1 may be candidate targets for the development of new therapeutic strategies against decay of skeletal muscle strength caused by a decrease in sarcoplasmic reticulum Ca(2+) content.
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Affiliation(s)
- Barbara Mosca
- Department of Experimental and Diagnostic Medicine, General Pathology section, University of Ferrara, Via Borsari 46, Ferrara 44121, Italy
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45
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Morphogenesis of T-tubules in heart cells: the role of junctophilin-2. SCIENCE CHINA-LIFE SCIENCES 2013; 56:647-52. [PMID: 23749380 DOI: 10.1007/s11427-013-4490-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Accepted: 04/28/2013] [Indexed: 11/27/2022]
Abstract
The T-tubule (TT) system forms the structural basis for excitation-contraction coupling in heart and muscle cells. The morphogenesis of the TT system is a key step in the maturation of heart cells because it does not exist in neonatal cardiomyocytes. In the present study, we quantified the morphological changes in TTs during heart cell maturation and investigated the role of junctophilin-2 (JP2), a protein known to anchor the sarcoplasmic reticulum (SR) to TT, in changes to TT morphological parameters. Analysis of confocal images showed that the transverse elements of TTs increased, while longitudinal elements decreased during the maturation of TTs. Fourier transform analysis showed that the power of ∼2 μm spatial components increased with cardiomyocytes maturation. These changes were preceded by increased expression of JP2, and were reversed by JP2 knockdown. These findings indicate that JP2 is required for the morphogenesis of TTs during heart development.
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46
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Romero-Suarez S, Mo C, Touchberry C, Lara N, Baker K, Craig R, Brotto L, Andresen J, Wacker M, Kaja S, Abreu E, Dillmann W, Mestril R, Brotto M, Nosek T. Hyperthermia: from diagnostic and treatments to new discoveries. Recent Pat Biotechnol 2012; 6:172-183. [PMID: 23092438 PMCID: PMC8865757 DOI: 10.2174/1872208311206030172] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2012] [Revised: 07/30/2012] [Accepted: 08/04/2012] [Indexed: 06/01/2023]
Abstract
Hyperthermia is an important approach for the treatment of several diseases. Hyperthermia is also thought to induce hypertrophy of skeletal muscles in vitro and in vivo, and has been used as a therapeutic tool for millennia. In the first part of our work, we revise several relevant patents related to the utilization of hyperthermia for the treatment and diagnostic of human diseases. In the second part, we present exciting new data on the effects of forced and natural overexpression of HSP72, using murine in vitro (muscle cells) and ex vivo (primary skeletal muscles) models. These studies help to demonstrate that hyperthermia effects are orchestrated by tight coupling between gene expression, protein function, and intracellular Ca2+ signaling pathways with a key role for calcium-induced calcium release. We hope that the review of current patents along with previous unknown information on molecular signaling pathways that underlie the hypertrophy response to hyperthermia in skeletal muscles may trigger the curiosity of scientists worldwide to explore new inventions that fully utilize hyperthermia for the treatment of muscle diseases.
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Affiliation(s)
- Sandra Romero-Suarez
- University of Missouri-Kansas City, Muscle Biology Research Group-MUBIG, School of Nursing
| | - Chenglin Mo
- University of Missouri-Kansas City, Muscle Biology Research Group-MUBIG, School of Nursing
| | | | - Nuria Lara
- Department of Oral Biology, School of Dentistry
| | - Kendra Baker
- University of Missouri-Kansas City, Muscle Biology Research Group-MUBIG, School of Nursing
| | - Robin Craig
- University of Missouri-Kansas City, Muscle Biology Research Group-MUBIG, School of Nursing
| | - Leticia Brotto
- University of Missouri-Kansas City, Muscle Biology Research Group-MUBIG, School of Nursing
| | - Jon Andresen
- University of Missouri-Kansas City, Muscle Biology Research Group-MUBIG, School of Nursing
- School of Medicine
| | - Michael Wacker
- University of Missouri-Kansas City, Muscle Biology Research Group-MUBIG, School of Nursing
- School of Medicine
| | - Simon Kaja
- Vision Research Center and Department of Ophthalmology, School of Medicine
| | - Eduardo Abreu
- University of Missouri-Kansas City, Muscle Biology Research Group-MUBIG, School of Nursing
| | | | - Ruben Mestril
- Loyola University Chicago, Department of Cell and Molecular Physiology
| | - Marco Brotto
- University of Missouri-Kansas City, Muscle Biology Research Group-MUBIG, School of Nursing
- School of Medicine
| | - Thomas Nosek
- Case Western Reserve University, School of Medicine
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47
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Murphy RM, Dutka TL, Horvath D, Bell JR, Delbridge LM, Lamb GD. Ca2+-dependent proteolysis of junctophilin-1 and junctophilin-2 in skeletal and cardiac muscle. J Physiol 2012; 591:719-29. [PMID: 23148318 DOI: 10.1113/jphysiol.2012.243279] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Excessive increases in intracellular [Ca(2+)] in skeletal muscle fibres cause failure of excitation-contraction coupling by disrupting communication between the dihydropyridine receptors in the transverse tubular system and the Ca(2+) release channels (RyRs) in the sarcoplasmic reticulum (SR), but the exact mechanism is unknown. Previous work suggested a possible role of Ca(2+)-dependent proteolysis in this uncoupling process but found no proteolysis of the dihydropyridine receptors, RyRs or triadin. Junctophilin-1 (JP1; ∼90 kDa) stabilizes close apposition of the transverse tubular system and SR membranes in adult skeletal muscle; its C-terminal end is embedded in the SR and its N-terminal associates with the transverse tubular system membrane. Exposure of skeletal muscle homogenates to precisely set [Ca(2+)] revealed that JP1 undergoes Ca(2+)-dependent proteolysis over the physiological [Ca(2+)] range in tandem with autolytic activation of endogenous μ-calpain. Cleavage of JP1 occurs close to the C-terminal, yielding a ∼75 kDa diffusible fragment and a fixed ∼15 kDa fragment. Depolarization-induced force responses in rat skinned fibres were abolished following 1 min exposure to 40 μm Ca(2+), with accompanying loss of full-length JP1. Supraphysiological stimulation of rat skeletal muscle in vitro by repeated tetanic stimulation in 30 mm caffeine also produced marked proteolysis of JP1 (and not RyR1). In dystrophic mdx mice, JP1 proteolysis is seen in limb muscles at 4 and not at 10 weeks of age. Junctophilin-2 in cardiac and skeletal muscle also undergoes Ca(2+)-dependent proteolysis, and junctophilin-2 levels are reduced following cardiac ischaemia-reperfusion. Junctophilin proteolysis may contribute to skeletal muscle weakness and cardiac dysfunction in a range of circumstances.
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Affiliation(s)
- R M Murphy
- Department of Zoology, La Trobe University, Melbourne, Victoria 3086, Australia
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48
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Liang X, Mei Y, Huang X, Shen G, Zhu D, Yu Y, Wang J, Lou Y. Junctophilin 2 knockdown interfere with mitochondrium status in ESC-CMs and cardiogenesis of ES cells. J Cell Biochem 2012; 113:2884-94. [DOI: 10.1002/jcb.24164] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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49
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Woo JS, Cho CH, Lee KJ, Kim DH, Ma J, Lee EH. Hypertrophy in skeletal myotubes induced by junctophilin-2 mutant, Y141H, involves an increase in store-operated Ca2+ entry via Orai1. J Biol Chem 2012; 287:14336-48. [PMID: 22389502 DOI: 10.1074/jbc.m111.304808] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Junctophilins (JPs) play an important role in the formation of junctional membrane complexes (JMC) in striated muscle by physically linking the transverse-tubule and sarcoplasmic reticulum (SR) membranes. Researchers have found five JP2 mutants in humans with hypertrophic cardiomyopathy. Among these, Y141H and S165F are associated with severely altered Ca(2+) signaling in cardiomyocytes. We previously reported that S165F also induced both hypertrophy and altered intracellular Ca(2+) signaling in mouse skeletal myotubes. In the present study, we attempted to identify the dominant-negative role(s) of Y141H in primary mouse skeletal myotubes. Consistent with S165F, Y141H led to hypertrophy and altered Ca(2+) signaling (a decrease in the gain of excitation-contraction coupling and an increase in the resting level of myoplasmic Ca(2+)). However, unlike S165F, neither ryanodine receptor 1-mediated Ca(2+) release from the SR nor the phosphorylation of the mutated JP2 by protein kinase C was related to the altered Ca(2+) signaling by Y141H. Instead, abnormal JMC and increased SOCE via Orai1 were found, suggesting that the hypertrophy caused by Y141H progressed differently from S165F. Therefore JP2 can be linked to skeletal muscle hypertrophy via various Ca(2+) signaling pathways, and SOCE could be one of the causes of altered Ca(2+) signaling observed in muscle hypertrophy.
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Affiliation(s)
- Jin Seok Woo
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea
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50
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Pan Z, Zhao X, Brotto M. Fluorescence-based measurement of store-operated calcium entry in live cells: from cultured cancer cell to skeletal muscle fiber. J Vis Exp 2012:3415. [PMID: 22349010 PMCID: PMC3376931 DOI: 10.3791/3415] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Store operated Ca2+ entry (SOCE), earlier termed capacitative Ca2+ entry, is a tightly regulated mechanism for influx of extracellular Ca2+ into cells to replenish depleted endoplasmic reticulum (ER) or sarcoplasmic reticulum (SR) Ca2+ stores1,2. Since Ca2+ is a ubiquitous second messenger, it is not surprising to see that SOCE plays important roles in a variety of cellular processes, including proliferation, apoptosis, gene transcription and motility. Due to its wide occurrence in nearly all cell types, including epithelial cells and skeletal muscles, this pathway has received great interest3,4. However, the heterogeneity of SOCE characteristics in different cell types and the physiological function are still not clear5-7. The functional channel properties of SOCE can be revealed by patch-clamp studies, whereas a large body of knowledge about this pathway has been gained by fluorescence-based intracellular Ca2+ measurements because of its convenience and feasibility for high-throughput screening. The objective of this report is to summarize a few fluorescence-based methods to measure the activation of SOCE in monolayer cells, suspended cells and muscle fibers5,8-10. The most commonly used of these fluorescence methods is to directly monitor the dynamics of intracellular Ca2+ using the ratio of F340nm and F380nm (510 nm for emission wavelength) of the ratiometric Ca2+ indicator Fura-2. To isolate the activity of unidirectional SOCE from intracellular Ca2+ release and Ca2+ extrusion, a Mn2+ quenching assay is frequently used. Mn2+ is known to be able to permeate into cells via SOCE while it is impervious to the surface membrane extrusion processes or to ER uptake by Ca2+ pumps due to its very high affinity with Fura-2. As a result, the quenching of Fura-2 fluorescence induced by the entry of extracellular Mn2+ into the cells represents a measurement of activity of SOCE9. Ratiometric measurement and the Mn+2 quenching assays can be performed on a cuvette-based spectrofluorometer in a cell population mode or in a microscope-based system to visualize single cells. The advantage of single cell measurements is that individual cells subjected to gene manipulations can be selected using GFP or RFP reporters, allowing studies in genetically modified or mutated cells. The spatiotemporal characteristics of SOCE in structurally specialized skeletal muscle can be achieved in skinned muscle fibers by simultaneously monitoring the fluorescence of two low affinity Ca2+ indicators targeted to specific compartments of the muscle fiber, such as Fluo-5N in the SR and Rhod-5N in the transverse tubules9,11,12.
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Affiliation(s)
- Zui Pan
- Department of Physiology and Biophysics, Confocal Microscopy and Cell Imaging Core, Robert Wood Johnson Medical School.
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