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Yang Y, Valencia LA, Lu CH, Nakamoto ML, Tsai CT, Liu C, Yang H, Zhang W, Jahed Z, Lee WR, Santoro F, Liou J, Wu JC, Cui B. Membrane Curvature Promotes ER-PM Contact Formation via Junctophilin-EHD Interactions. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.29.601287. [PMID: 38979311 PMCID: PMC11230412 DOI: 10.1101/2024.06.29.601287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
Contact sites between the endoplasmic reticulum (ER) and the plasma membrane (PM) play a crucial role in governing calcium regulation and lipid homeostasis. Despite their significance, the factors regulating their spatial distribution on the PM remain elusive. Inspired by observations in cardiomyocytes, where ER-PM contact sites concentrate on tubular PM invaginations known as transverse tubules (T-tubules), we hypothesize that the PM curvature plays a role in ER-PM contact formation. Through precise control of PM invaginations, we show that PM curvatures locally induce the formation of ER-PM contacts in cardiomyocytes. Intriguingly, the junctophilin family of ER-PM tethering proteins, specifically expressed in excitable cells, is the key player in this process, while the ubiquitously expressed extended synaptotagmin 2 does not show a preference for PM curvature. At the mechanistic level, we find that the low complexity region (LCR) and the MORN motifs of junctophilins can independently bind to the PM, but both the LCR and MORN motifs are required for targeting PM curvatures. By examining the junctophilin interactome, we identify a family of curvature-sensing proteins, Eps15-homology domain containing proteins (EHDs), that interact with the MORN_LCR motifs and facilitate junctophilins' preferential tethering to curved PM. These findings highlight the pivotal role of PM curvature in the formation of ER-PM contacts in cardiomyocytes and unveil a novel mechanism for the spatial regulation of ER-PM contacts through PM curvature modulation.
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Affiliation(s)
- Yang Yang
- Department of Chemistry, Stanford University, Stanford, CA, USA
- Wu-Tsai Neuroscience Institute and ChEM-H Institute, Stanford University; Stanford, CA, USA
| | - Luis A Valencia
- Department of Chemistry, Stanford University, Stanford, CA, USA
- Wu-Tsai Neuroscience Institute and ChEM-H Institute, Stanford University; Stanford, CA, USA
| | - Chih-Hao Lu
- Department of Chemistry, Stanford University, Stanford, CA, USA
- Wu-Tsai Neuroscience Institute and ChEM-H Institute, Stanford University; Stanford, CA, USA
| | - Melissa L Nakamoto
- Department of Chemistry, Stanford University, Stanford, CA, USA
- Wu-Tsai Neuroscience Institute and ChEM-H Institute, Stanford University; Stanford, CA, USA
| | - Ching-Ting Tsai
- Department of Chemistry, Stanford University, Stanford, CA, USA
- Wu-Tsai Neuroscience Institute and ChEM-H Institute, Stanford University; Stanford, CA, USA
| | - Chun Liu
- Stanford Cardiovascular Institute, Stanford University, Stanford, CA, USA
- Present address: Department of Physiology and Medicine, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Huaxiao Yang
- Stanford Cardiovascular Institute, Stanford University, Stanford, CA, USA
- Present address: Department of Biomedical Engineering, University of North Texas, Denton, TX, USA
| | - Wei Zhang
- Department of Chemistry, Stanford University, Stanford, CA, USA
- Wu-Tsai Neuroscience Institute and ChEM-H Institute, Stanford University; Stanford, CA, USA
| | - Zeinab Jahed
- Department of Chemistry, Stanford University, Stanford, CA, USA
- Present address: Department of Nanoengineering, Jacobs School of Engineering, University of California, San Diego, CA, USA
| | - Wan-Ru Lee
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Francesca Santoro
- Tissue Electronics, Istituto Italiano di Tecnologia, 80125 Naples, Italy
- Faculty of Electrical Engineering and IT, RWTH, Aachen 52074, Germany
- Institute of Biological Information Processing-Bioelectronics, IBI-3, Forschungszentrum, Juelich 52428, Germany
| | - Jen Liou
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Joseph C Wu
- Stanford Cardiovascular Institute, Stanford University, Stanford, CA, USA
- Department of Medicine (Division of Cardiology), Stanford University, Stanford, CA, USA
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - Bianxiao Cui
- Department of Chemistry, Stanford University, Stanford, CA, USA
- Wu-Tsai Neuroscience Institute and ChEM-H Institute, Stanford University; Stanford, CA, 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: 11] [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: 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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Hakui H, Kioka H, Miyashita Y, Nishimura S, Matsuoka K, Kato H, Tsukamoto O, Kuramoto Y, Takuwa A, Takahashi Y, Saito S, Ohta K, Asanuma H, Fu HY, Shinomiya H, Yamada N, Ohtani T, Sawa Y, Kitakaze M, Takashima S, Sakata Y, Asano Y. Loss-of-function mutations in the co-chaperone protein BAG5 cause dilated cardiomyopathy requiring heart transplantation. Sci Transl Med 2022; 14:eabf3274. [PMID: 35044787 DOI: 10.1126/scitranslmed.abf3274] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Dilated cardiomyopathy (DCM) is a major cause of heart failure, characterized by ventricular dilatation and systolic dysfunction. Familial DCM is reportedly caused by mutations in more than 50 genes, requiring precise disease stratification based on genetic information. However, the underlying genetic causes of 60 to 80% of familial DCM cases remain unknown. Here, we identified that homozygous truncating mutations in the gene encoding Bcl-2-associated athanogene (BAG) co-chaperone 5 (BAG5) caused inherited DCM in five patients among four unrelated families with complete penetrance. BAG5 acts as a nucleotide exchange factor for heat shock cognate 71 kDa protein (HSC70), promoting adenosine diphosphate release and activating HSC70-mediated protein folding. Bag5 mutant knock-in mice exhibited ventricular dilatation, arrhythmogenicity, and poor prognosis under catecholamine stimulation, recapitulating the human DCM phenotype, and administration of an adeno-associated virus 9 vector carrying the wild-type BAG5 gene could fully ameliorate these DCM phenotypes. Immunocytochemical analysis revealed that BAG5 localized to junctional membrane complexes (JMCs), critical microdomains for calcium handling. Bag5-mutant mouse cardiomyocytes exhibited decreased abundance of functional JMC proteins under catecholamine stimulation, disrupted JMC structure, and calcium handling abnormalities. We also identified heterozygous truncating mutations in three patients with tachycardia-induced cardiomyopathy, a reversible DCM subtype associated with abnormal calcium homeostasis. Our study suggests that loss-of-function mutations in BAG5 can cause DCM, that BAG5 may be a target for genetic testing in cases of DCM, and that gene therapy may potentially be a treatment for this disease.
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Affiliation(s)
- Hideyuki Hakui
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Hidetaka Kioka
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Yohei Miyashita
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Shunsuke Nishimura
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Ken Matsuoka
- Department of Medical Biochemistry, Osaka University Graduate School of Frontier Biosciences, Suita, Osaka 565-0871, Japan
| | - Hisakazu Kato
- Department of Medical Biochemistry, Osaka University Graduate School of Frontier Biosciences, Suita, Osaka 565-0871, Japan
| | - Osamu Tsukamoto
- Department of Medical Biochemistry, Osaka University Graduate School of Frontier Biosciences, Suita, Osaka 565-0871, Japan
| | - Yuki Kuramoto
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Ayako Takuwa
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Yusuke Takahashi
- Department of Molecular Pharmacology, National Cerebral and Cardiovascular Center, Suita, Osaka 564-8565, Japan
| | - Shigeyoshi Saito
- Department of Medical Physics and Engineering, Division of Health Sciences, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.,Department of Biomedical Imaging, National Cerebral and Cardiovascular Center, Suita, Osaka 564-8565, Japan
| | - Kunio Ohta
- Department of Pediatrics, School of Medicine, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Ishikawa 920-8640, Japan
| | - Hiroshi Asanuma
- Department of Internal Medicine, Meiji University of Integrative Medicine, Nantan, Kyoto 629-0392, Japan
| | - Hai Ying Fu
- Department of Clinical Medicine and Development, National Cerebral and Cardiovascular Center, Suita, Osaka 564-8565, Japan
| | - Haruki Shinomiya
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Noriaki Yamada
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Tomohito Ohtani
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Yoshiki Sawa
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Masafumi Kitakaze
- Department of Clinical Medicine and Development, National Cerebral and Cardiovascular Center, Suita, Osaka 564-8565, Japan
| | - Seiji Takashima
- Department of Medical Biochemistry, Osaka University Graduate School of Frontier Biosciences, Suita, Osaka 565-0871, Japan
| | - Yasushi Sakata
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Yoshihiro Asano
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
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Abstract
Junctophilins (JPHs) comprise a family of structural proteins that connect the plasma membrane to intracellular organelles such as the endo/sarcoplasmic reticulum. Tethering of these membrane structures results in the formation of highly organized subcellular junctions that play important signaling roles in all excitable cell types. There are four JPH isoforms, expressed primarily in muscle and neuronal cell types. Each JPH protein consists of 6 'membrane occupation and recognition nexus' (MORN) motifs, a joining region connecting these to another set of 2 MORN motifs, a putative alpha-helical region, a divergent region exhibiting low homology between JPH isoforms, and a carboxy-terminal transmembrane region anchoring into the ER/SR membrane. JPH isoforms play essential roles in developing and maintaining subcellular membrane junctions. Conversely, inherited mutations in JPH2 cause hypertrophic or dilated cardiomyopathy, while trinucleotide expansions in the JPH3 gene cause Huntington Disease-Like 2. Loss of JPH1 protein levels can cause skeletal myopathy, while loss of cardiac JPH2 levels causes heart failure and atrial fibrillation, among other disease. This review will provide a comprehensive overview of the JPH gene family, phylogeny, and evolutionary analysis of JPH genes and other MORN domain proteins. JPH biogenesis, membrane tethering, and binding partners will be discussed, as well as functional roles of JPH isoforms in excitable cells. Finally, potential roles of JPH isoform deficits in human disease pathogenesis will be reviewed.
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Affiliation(s)
- Stephan E Lehnart
- Cellular Biophysics and Translational Cardiology Section, Heart Research Center Göttingen, University Medical Center Göttingen, Department of Cardiology and Pneumology, Georg-August University Göttingen, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Göttingen, Germany
| | - Xander H T Wehrens
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, Texas, United States; Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), Pediatrics (Cardiology), Neuroscience, and Center for Space Medicine, Baylor College of Medicine, Houston, Texas, United States
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Calpain-2 specifically cleaves Junctophilin-2 at the same site as Calpain-1 but with less efficacy. Biochem J 2021; 478:3539-3553. [PMID: 34524407 PMCID: PMC8589432 DOI: 10.1042/bcj20210629] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 09/14/2021] [Accepted: 09/15/2021] [Indexed: 11/17/2022]
Abstract
Calpain proteolysis contributes to the pathogenesis of heart failure but the calpain isoforms responsible and their substrate specificities have not been rigorously defined. One substrate, Junctophilin-2 (JP2), is essential for maintaining junctional cardiac dyads and excitation-contraction coupling. We previously demonstrated that mouse JP2 is cleaved by calpain-1 (CAPN1) between Arginine 565 (R565) and Threonine 566 (T566). Recently, calpain-2 (CAPN2) was reported to cleave JP2 at a novel site between Glycine 482 (G482) and Threonine 483 (T483). We aimed to directly compare the contributions of each calpain isoform, their Ca2+ sensitivity, and their cleavage site selection for JP2. We find CAPN1, CAPN2 and their requisite CAPNS1 regulatory subunit are induced by pressure overload stress that is concurrent with JP2 cleavage. Using in vitro calpain cleavage assays, we demonstrate that CAPN1 and CAPN2 cleave JP2 into similar 75 kD N-terminal (JP2NT) and 25 kD C-terminal fragments (JP2CT) with CAPNS1 co-expression enhancing proteolysis. Deletion mutagenesis shows both CAPN1 and CAPN2 require R565/T566 but not G482/T483. When heterologously expressed, the JP2CT peptide corresponding to R565/T566 cleavage approximates the 25 kD species found during cardiac stress while the C-terminal peptide from potential cleavage at G482/T483 produces a 35 kD product. Similar results were obtained for human JP2. Finally, we show that CAPN1 has higher Ca2+ sensitivity and cleavage efficacy than CAPN2 on JP2 and other cardiac substrates including cTnT, cTnI and β2-spectrin. We conclude that CAPN2 cleaves JP2 at the same functionally conserved R565/T566 site as CAPN1 but with less efficacy and suggest heart failure may be targeted through specific inhibition of CAPN1.
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