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Julia O Reynolds, Ann P Quick, Qiongling Wang, David L Beavers, Leonne E Philippen, Jordan Showell, Giselle Barreto-Torres, Donna J Thuerauf, Shirin Doroudgar, Christopher C Glembotski, Xander H T Wehrens
BACKGROUND: Junctophilin-2 (JPH2) is the primary structural protein for the coupling of transverse (T)-tubule associated cardiac L-type Ca channels and type-2 ryanodine receptors on the sarcoplasmic reticulum within junctional membrane complexes (JMCs) in cardiomyocytes. Effective signaling between these channels ensures adequate Ca-induced Ca release required for normal cardiac contractility. Disruption of JMC subcellular domains, a common feature of failing hearts, has been attributed to JPH2 downregulation...
October 8, 2016: International Journal of Cardiology
Russell L Margolis, Dobrila D Rudnicki
PURPOSE OF REVIEW: Huntington's disease-like 2 (HDL2) is a rare, progressive, autosomal dominant neurodegenerative disorder that genetically, clinically, and pathologically closely resembles Huntington's disease. We review HDL2 pathogenic mechanisms and examine the implications of these mechanisms for Huntington's disease and related diseases. RECENT FINDINGS: HDL2 is caused by a CTG/CAG repeat expansion in junctophilin-3. Available data from cell and animal models and human brain suggest that HDL2 is a complex disease in which transcripts and proteins expressed bidirectionally from the junctophilin-3 locus contribute to pathogenesis through both gain-and loss-of-function mechanisms...
October 5, 2016: Current Opinion in Neurology
Ann P Quick, Qiongling Wang, Leonne E Philippen, Giselle Barreto-Torres, David Y Chiang, David L Beavers, Guoliang Wang, Maha Khalid, Julia O Reynolds, Hannah M Campbell, Jordan Showell, Mark D McCauley, Arjen Scholten, Xander H Wehrens
RATIONALE: Junctional membrane complexes (JMC) in myocytes are critical microdomains, in which excitation-contraction coupling occurs. Structural and functional disruption of JMCs underlies contractile dysfunction in failing hearts. However, the role of newly identified JMC protein striated muscle preferentially expressed gene (SPEG) remains unclear. OBJECTIVE: To determine the role of SPEG in healthy and failing adult hearts. MMethods and Results: Proteomic analysis of immunoprecipatated JMC-proteins ryanodine receptor type-2 (RyR2) and junctophilin-2 (JPH2) followed by mass spectrometry identified the serine-threonine kinase SPEG as the only novel binding partner for both proteins...
October 11, 2016: Circulation Research
Petra Cela, Marek Hampl, Katherine K Fu, Michaela Kunova Bosakova, Pavel Krejci, Joy M Richman, Marcela Buchtova
MORN5 (MORN repeat containing 5) is encoded by a locus positioned on chromosome 17 in the chicken genome. The MORN motif is found in multiple copies in several proteins including junctophilins or phosphatidylinositol phosphate kinase family and the MORN proteins themselves are found across the animal and plant kingdoms. MORN5 protein has a characteristic punctate pattern in the cytoplasm in immunofluorescence imaging. Previously, MORN5 was found among differentially expressed genes in a microarray profiling experiment of the chicken embryo head...
2016: Frontiers in Physiology
Shengcun Li, Lulu Zhang, Rui Ni, Ting Cao, Dong Zheng, Sidong Xiong, Peter A Greer, Guo-Chang Fan, Tianqing Peng
Diabetes and obesity are prevalent in westernized countries. In both conditions, excessive fatty acid uptake by cardiomyocytes induces cardiac lipotoxicity, an important mechanism contributing to diabetic cardiomyopathy. This study investigated the effect of calpain disruption on cardiac lipotoxicity. Cardiac-specific capns1 knockout mice and their wild-type littermates (male, age of 4weeks) were fed a high fat diet (HFD) or normal diet for 20weeks. HFD increased body weight, altered blood lipid profiles and impaired glucose tolerance comparably in both capns1 knockout mice and their wild-type littermates...
August 11, 2016: Biochimica et Biophysica Acta
L Li, Z-F Pan, X Huang, B-W Wu, T Li, M-X Kang, R-S Ge, X-Y Hu, Y-H Zhang, L-J Ge, D-Y Zhu, Y-L Wu, Y-J Lou
It is well accepted that junctophilin (JPHs) isoforms act as a physical bridge linking plasma membrane and endoplasmic reticulum (ER) for channel crosstalk in excitable cells. Our purpose is to investigate whether JPHs are involved in the proper communication between Ca(2+) influx and subsequent Ca(2+) amplification in pancreatic beta cells, thereby participating in regulating insulin secretion. The expression of JPH isoforms was examined in human and mouse pancreatic tissues, and JPH3 expression was found in both the beta cells...
2016: Cell Death & Disease
Michael Frisk, Marianne Ruud, Emil K S Espe, Jan Magnus Aronsen, Åsmund T Røe, Lili Zhang, Per Andreas Norseng, Ole M Sejersted, Geir A Christensen, Ivar Sjaastad, William E Louch
AIMS: Invaginations of the cellular membrane called t-tubules are essential for maintaining efficient excitation-contraction coupling in ventricular cardiomyocytes. Disruption of t-tubule structure during heart failure has been linked to dyssynchronous, slowed Ca(2+) release and reduced power of the heartbeat. The underlying mechanism is, however, unknown. We presently investigated whether elevated ventricular wall stress triggers remodelling of t-tubule structure and function. METHODS AND RESULTS: MRI and blood pressure measurements were employed to examine regional wall stress across the left ventricle of sham-operated and failing, post-infarction rat hearts...
October 2016: Cardiovascular Research
Jin Seok Woo, Sonal Srikanth, Miyuki Nishi, Peipei Ping, Hiroshi Takeshima, Yousang Gwack
Orai1 and stromal interaction molecule 1 (STIM1) mediate store-operated Ca(2+) entry (SOCE) in immune cells. STIM1, an endoplasmic reticulum (ER) Ca(2+) sensor, detects store depletion and interacts with plasma membrane (PM)-resident Orai1 channels at the ER-PM junctions. However, the molecular composition of these junctions in T cells remains poorly understood. Here, we show that junctophilin-4 (JP4), a member of junctional proteins in excitable cells, is expressed in T cells and localized at the ER-PM junctions to regulate Ca(2+) signaling...
March 8, 2016: Proceedings of the National Academy of Sciences of the United States of America
Fiona K Baine, Amanda Krause, L Jacquie Greenberg
BACKGROUND: Huntington disease (HD) has most recently been estimated to affect between 10.6 and 13.7 per 100,000 individuals in European populations. However, prevalence is known to differ geographically. In South Africa, the only published estimates are from a survey performed in the 1970s, an era when the disease was believed to be rare or absent in black individuals and molecular confirmation was absent. The disease phenotype in South Africa is currently attributable to mutations in both the huntington and junctophilin-3 genes, which underlie the well-known HD and the rarer HD-like 2 (HDL2) respectively...
2016: Neuroepidemiology
Xingguang Liang, Dongsheng Hong, Yujie Huang, Yuefeng Rao, Kuifen Ma, Mingzhu Huang, Xingguo Zhang, Yijia Lou, Qingwei Zhao
Junctophilin2 (JP2) is a critical protein associated with cardiogenesis. Icariin (ICA) facilitated the directional differentiation of murine embryonic stem (ES) cells into cardiomyocytes. However, little is known about the effects of ICA on JP2 during cardiac differentiation. Here, we explored whether ICA has effects on the expression and Ca2+ related function of JP2 during cardiomyocyte differentiation of ES cells in vitro. Embryonid bodies (EBs) formed by hanging drop were treated with 10(-7) mol/L ICA from day 5 to promote the cardiac differentiation...
December 2015: Die Pharmazie
Ann P Quick, Andrew P Landstrom, Xander H T Wehrens
No abstract text is available yet for this article.
March 2016: Heart Rhythm: the Official Journal of the Heart Rhythm Society
Min Jiang, Mei Zhang, Maureen Howren, Yuhong Wang, Alex Tan, Ravi C Balijepalli, Jose F Huizar, Gea-Ny Tseng
BACKGROUND: In a canine model of premature ventricular contraction-induced cardiomyopathy (PVC-CM), Cav1.2 is downregulated and misplaced from transverse tubules (T tubules). Junctophilin-2 (JPH-2) is also downregulated. OBJECTIVES: The objectives of this study were to understand the role of JPH-2 in PVC-CM and to probe changes in other proteins involved in dyad structure and function. METHODS: We quantify T-tubule contents (di-8-ANEPPS fluorescence in live myocytes), examine myocyte ultrastructures (electron microscopy), probe JPH-2-interacting proteins (co-immunoprecipitation), quantify dyad and nondyad protein levels (immunoblotting), and examine subcellular distributions of dyad proteins (immunofluorescence/confocal microscopy)...
March 2016: Heart Rhythm: the Official Journal of the Heart Rhythm Society
Virginia Barone, Davide Randazzo, Valeria Del Re, Vincenzo Sorrentino, Daniela Rossi
The sarcoplasmic reticulum (SR) of striated muscles is specialized for releasing Ca(2+) following sarcolemma depolarization in order to activate muscle contraction. To this end, the SR forms a network of longitudinal tubules and cisternae that surrounds the myofibrils and, at the same time, participates to the assembly of the triadic junctional membrane complexes formed by the close apposition of one t-tubule, originated from the sarcolemma, and two SR terminal cisternae. Advancements in understanding the molecular basis of the SR structural organization have identified an interaction between sAnk1, a transmembrane protein located on the longitudinal SR (l-SR) tubules, and obscurin, a myofibrillar protein...
December 2015: Journal of Muscle Research and Cell Motility
Alexis R Demonbreun, Kaitlin E Swanson, Ann E Rossi, H Kieran Deveaux, Judy U Earley, Madison V Allen, Priyanka Arya, Sohinee Bhattacharyya, Hamid Band, Peter Pytel, Elizabeth M McNally
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...
2015: PloS One
Amanda Krause, Claire Mitchell, Fahmida Essop, Susan Tager, James Temlett, Giovanni Stevanin, Christopher Ross, Dobrila Rudnicki, Russell Margolis
Huntington disease (HD) is a progressive autosomal dominant neurodegenerative disorder, characterized by abnormal movements, cognitive decline, and psychiatric symptoms, caused by a CAG repeat expansion in the huntingtin (HTT) gene on chromosome 4p. A CAG/CTG repeat expansion in the junctophilin-3 (JPH3) gene on chromosome 16q24.2 causes a Huntington disease-like phenotype (HDL2). All patients to date with HDL2 have some African ancestry. The present study aimed to characterize the genetic basis of the Huntington disease phenotype in South Africans and to investigate the possible origin of the JPH3 mutation...
October 2015: American Journal of Medical Genetics. Part B, Neuropsychiatric Genetics
Ang Guo, Duane Hall, Caimei Zhang, Tianqing Peng, Jordan D Miller, William Kutschke, Chad E Grueter, Frances L Johnson, Richard Z Lin, Long-Sheng Song
Junctophilin-2 (JP2), a membrane-binding protein that provides a structural bridge between the plasmalemma and sarcoplasmic reticulum, is essential for precise Ca(2+)-induced Ca(2+) release during excitation-contraction coupling in cardiomyocytes. In animal and human failing hearts, expression of JP2 is decreased markedly, but the molecular mechanisms underlying JP2 down-regulation remain incompletely defined. In mouse hearts, ischemia/reperfusion injury resulted in acute JP2 down-regulation, which was attenuated by pretreatment with the calpain inhibitor MDL-28170 or by transgenic overexpression of calpastatin, an endogenous calpain inhibitor...
July 17, 2015: Journal of Biological Chemistry
Yueqin Cai, Jue Tu, Shuizhen Pan, Jianping Jiang, Qiyang Shou, Yun Ling, Yunxiang Chen, Dejun Wang, Weiji Yang, Letian Shan, Minli Chen
ETHNOPHARMACOLOGICAL RELEVANCE: Rhizome and root of Smilax glabra Roxb (Liliaceae family) is a widely used traditional Chinese medicine (TCM) named Tu-fu-ling (TFL) for cardiac disease therapy. The TFL flavonoids (TFLF) has been extracted and proven to possess the anti-cardiac hypertrophy effect in our previous reports. Such effect could be mediated by the modulation of intracellular Ca(2+) flux in myocardial cells, in which junctophilin-2 (JP2) and ryanodine receptor 2 (RyR2) play an important role...
July 1, 2015: Journal of Ethnopharmacology
David J Crossman, Yufeng Hou, Isuru Jayasinghe, David Baddeley, Christian Soeller
Many biological questions require information at different spatial scales that include molecular, organelle, cell and tissue scales. Here we detail a method of multi-scale imaging of human cardiac tissue by correlatively combining nano-scale data of direct stochastic optical reconstruction microscopy (dSTORM) with cellular and tissue level data provided by confocal microscopy. By utilising conventional fluorescence dyes the same cellular structures can be imaged with both modalities. Human cardiac tissue was first imaged at the nanoscale to identify macro-molecular membrane complexes containing the cardiac muscle proteins junctophilin (JPH) and the ryanodine receptor (RyR)...
October 15, 2015: Methods: a Companion to Methods in Enzymology
Hiroshi Takeshima, Masahiko Hoshijima, Long-Sheng Song
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...
October 2015: Cell Calcium
Yufeng Hou, Isuru Jayasinghe, David J Crossman, David Baddeley, Christian Soeller
The contractile properties of cardiac myocytes depend on the calcium (Ca(2+)) released by clusters of ryanodine receptors (RyRs) throughout the myoplasm. Accurate quantification of the spatial distribution of RyRs has previously been challenging due to the comparatively low resolution in optical microscopy. We have combined single-molecule localisation microscopy (SMLM) in a super-resolution modality known as dSTORM with immunofluorescence staining of tissue sections of rat ventricles to resolve a wide, near-exponential size distribution of RyR clusters that lined on average ~57% of the perimeter of each myofibril...
March 2015: Journal of Molecular and Cellular Cardiology
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