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Michelle L Munro, Christian Soeller
The ventricular cardiomyocytes of adult mammals contain invaginations of the plasma membrane known as transverse (t)-tubules. These regular structures are essential for the synchronisation of excitation-contraction (EC) coupling throughout the cell, which is a vital process for cardiac function. T-tubules form a close association with the sarcoplasmic reticulum (SR) to form junctions, where several key proteins involved in EC coupling are localised, including the SR calcium release channels-the ryanodine receptors (RyR)...
January 6, 2017: Journal of Muscle Research and Cell Motility
Keita Kanzaki, Daiki Watanabe, Mai Kuratani, Takashi Yamada, Satoshi Matsunaga, Masanobu Wada
The aim of this study was to examine the in vivo effects of eccentric contraction (ECC) on calpain-dependent proteolysis of Ca(2+)-regulatory proteins and force production in fast-twitch skeletal muscles. Rat extensor digitorum longus muscles were exposed to 200-repeated ECC in situ and excised immediately (recovery 0) or 3 days (recovery 3) after cessation of ECC. Calpain inhibitor (CI)-treated rats were intraperitoneally injected with MDL-28170 before ECC and during 3 days of recovery. Tetanic force was markedly reduced at recovery 0 and remained reduced at recovery 3...
December 15, 2016: Journal of Applied Physiology
(no author information available yet)
No abstract text is available yet for this article.
December 1, 2016: Journal of Cell Science
Michelle L Munro, Isuru D Jayasinghe, Qiongling Wang, Ann Quick, Wei Wang, David Baddeley, Xander H T Wehrens, Christian Soeller
Signalling nanodomains requiring close contact between the plasma membrane and internal compartments, known as 'junctions', are fast communication hubs within excitable cells such as neurones and muscle. Here, we have examined two transgenic murine models probing the role of junctophilin-2, a membrane-tethering protein crucial for the formation and molecular organisation of sub-microscopic junctions in ventricular muscle cells of the heart. Quantitative single-molecule localisation microscopy showed that junctions in animals producing above-normal levels of junctophilin-2 were enlarged, allowing the re-organisation of the primary functional protein within it, the ryanodine receptor (RyR; in this paper, we use RyR to refer to the myocardial isoform RyR2)...
December 1, 2016: Journal of Cell Science
Yoshihiro Ujihara, Satoshi Mohri, Yuki Katanosaka
The Na(+)/Ca(2+) exchanger 1 (NCX1) is an essential Ca(2+) efflux system in cardiomyocytes. Although NCX1 is distributed throughout the sarcolemma, a subpopulation of NCX1 is localized to transverse (T)-tubules. There is growing evidence that T-tubule disorganization is a causal event that shifts the transition from hypertrophy to heart failure (HF). However, the detailed molecular mechanisms have not been clarified. Previously, we showed that induced NCX1 expression in pressure-overloaded hearts attenuates defective excitation-contraction coupling and HF progression...
October 24, 2016: Biochemical and Biophysical Research Communications
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...
December 15, 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...
December 2016: Current Opinion in Neurology
Ann P Quick, Qiongling Wang, Leonne E Philippen, Giselle Barreto-Torres, David Y Chiang, David Beavers, Guoliang Wang, Maha Khalid, Julia O Reynolds, Hannah M Campbell, Jordan Showell, Mark D McCauley, Arjen Scholten, Xander H T Wehrens
RATIONALE: Junctional membrane complexes (JMCs) 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 SPEG (striated muscle preferentially expressed protein kinase) remains unclear. OBJECTIVE: To determine the role of SPEG in healthy and failing adult hearts. METHODS AND RESULTS: Proteomic analysis of immunoprecipitated JMC proteins ryanodine receptor type 2 and junctophilin-2 (JPH2) followed by mass spectrometry identified the serine-threonine kinase SPEG as the only novel binding partner for both proteins...
January 6, 2017: 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...
November 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...
June 23, 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
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