المؤلفون: Kai C. Wollert, Michelle A. Sargent, Hanna Osinska, Jeffery D. Molkentin, Jeffrey Robbins, Joerg Heineke, Allen J. York

المصدر: Journal of Molecular and Cellular Cardiology. 48:1080-1087

مصطلحات موضوعية: Cardiomyopathy, Dilated, medicine.medical_specialty, Programmed cell death, Necrosis, Cardiomyopathy, Mice, Transgenic, Biology, Models, Biological, complex mixtures, Article, Mice, Internal medicine, medicine, Animals, cardiovascular diseases, Molecular Biology, Mice, Knockout, Cell Death, Calcineurin, Myocardium, Heart, Dilated cardiomyopathy, musculoskeletal system, medicine.disease, Cardiovascular physiology, Transplantation, Disease Models, Animal, Endocrinology, Gene Expression Regulation, Echocardiography, cardiovascular system, Calcium, Myocardial fibrosis, medicine.symptom, Cardiology and Cardiovascular Medicine

الوصف: Dilated cardiomyopathy (DCM) is a relatively common disease with a poor prognosis. Given that the only meaningful treatment for DCM is cardiac transplantation, investigators have explored the underlying molecular mechanisms of this disease in the hopes of identifying novel therapeutic targets. One such target is the serine-threonine phosphatase calcineurin, a Ca2+-activated signaling factor that is known to regulate the cardiac hypertrophic program, although its role in DCM is currently unknown. In order to address this issue, we crossed muscle lim protein (MLP) knock-out mice-a murine model of DCM-with calcineurin A beta ko mice, which lack the stress responsive isoform of calcineurin that critically regulates the cardiac hypertrophic response. Interestingly, the majority (73%) of the MLP/calcineurin A beta double knock-out mice died within 20 days of birth with signs of cardiomyopathy. Ultrastructural examination revealed enhanced cardiomyocyte apoptosis and necrosis in the postnatal myocardium of these mice. The MLP/calcineurin A beta double knock-out mice that survived until adulthood showed reduced left ventricular function, enhanced apoptotic and necrotic cardiomyocyte death and augmented myocardial fibrosis compared to various control groups. Antithetically, mild overexpression of activated calcineurin in the mouse heart improved function and adverse remodeling in MLP knock-out mice. Collectively, these results reveal an important and previously unrecognized protective function of endogenous myocardial calcineurin in a mouse model of dilated cardiomyopathy.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::03a8528d994006920245a5d0532d11b4Test
https://doi.org/10.1016/j.yjmcc.2009.10.012Test

المؤلفون: Jason R. Waggoner, Evangelia G. Kranias, Jeffrey Robbins, Kobra Haghighi, Kenneth S. Ginsburg, Bryan Mitton, Donald M. Bers

المصدر: American Journal of Physiology-Heart and Circulatory Physiology. 296:H698-H703

مصطلحات موضوعية: medicine.medical_specialty, SERCA, Physiology, Heart Ventricles, Genetic Vectors, Biology, Sodium-Calcium Exchanger, Adenoviridae, Sarcoplasmic Reticulum Calcium-Transporting ATPases, Contractility, Mice, Transduction, Genetic, Caffeine, Physiology (medical), Calcium-binding protein, Internal medicine, medicine, Animals, Myocyte, Myocytes, Cardiac, Calcium Signaling, Phosphorylation, Cells, Cultured, Calcium signaling, Sodium-calcium exchanger, Endoplasmic reticulum, Calcium-Binding Proteins, Isoproterenol, Biological Transport, Articles, Adrenergic beta-Agonists, musculoskeletal system, Myocardial Contraction, Up-Regulation, Phospholamban, Sarcoplasmic Reticulum, Endocrinology, cardiovascular system, Calcium, Rabbits, Cardiology and Cardiovascular Medicine, tissues, circulatory and respiratory physiology

الوصف: Phospholamban has been suggested to be a key regulator of cardiac sarcoplasmic reticulum (SR) Ca cycling and contractility and a potential therapeutic target in restoring the depressed Ca cycling in failing hearts. Our understanding of the function of phospholamban stems primarily from studies in genetically altered mouse models. To evaluate the significance of this protein in larger mammalian species, which exhibit Ca cycling properties similar to humans, we overexpressed phospholamban in adult rabbit cardiomyocytes. Adenoviral-mediated gene transfer, at high multiplicities of infection, resulted in an insignificant 1.22-fold overexpression of phospholamban. There were no effects on twitch Ca-transient amplitude or decay under basal or isoproterenol-stimulated conditions. Furthermore, the SR Ca load and Na/Ca exchanger function were not altered. These apparent differences between phospholamban overexpression in rabbit compared with previous findings in the mouse may be due to a significantly higher (1.5-fold) endogenous phospholamban-to-sarco(endo)plasmic reticulum Ca-ATPase (SERCA) 2a ratio and potential functional saturation of SERCA2a by phospholamban in rabbit cardiomyocytes. The findings suggest that important species-dependent differences in phospholamban regulation of SERCA2a occur. In larger mammals, a higher fraction of SERCA2a pumps are regulated by phospholamban, and this may influence therapeutic strategies to enhance cardiac contractility and functional cardiac reserve.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::d9664d304d561cf3f4954b779da8dd89Test
https://doi.org/10.1152/ajpheart.00272.2008Test

المؤلفون: R. John Solaro, Lori A. Walker, Aaron C. Hinken, David L. Geenen, Sarah B. Scruggs, Pieter P. de Tombe, Peter M. Buttrick, Jeffrey Robbins, Ariyaporn Thawornkaiwong

المصدر: Journal of Biological Chemistry. 284:5097-5106

مصطلحات موضوعية: Sarcomeres, Myofilament, medicine.medical_specialty, Myosin Light Chains, Heart Diseases, Heart Ventricles, Mice, Transgenic, macromolecular substances, Biology, Biochemistry, Sarcomere, Mice, Internal medicine, Troponin I, Myosin, Cyclic AMP, medicine, Animals, Protein phosphorylation, Phosphorylation, Protein kinase A, Molecular Biology, Protein Synthesis, Post-Translational Modification, and Degradation, Myocardium, Stroke Volume, Cell Biology, musculoskeletal system, Cyclic AMP-Dependent Protein Kinases, Myocardial Contraction, Actin Cytoskeleton, Endocrinology, Calcium, Carrier Proteins, Myofibril

الوصف: There is little direct evidence on the role of myosin regulatory light chain phosphorylation in ejecting hearts. In studies reported here we determined the effects of regulatory light chain (RLC) phosphorylation on in situ cardiac systolic mechanics and in vitro myofibrillar mechanics. We compared data obtained from control nontransgenic mice (NTG) with a transgenic mouse model expressing a cardiac specific nonphosphorylatable RLC (TG-RLC(P-). We also determined whether the depression in RLC phosphorylation affected phosphorylation of other sarcomeric proteins. TG-RLC(P-) demonstrated decreases in base-line load-independent measures of contractility and power and an increase in ejection duration together with a depression in phosphorylation of myosin-binding protein-C (MyBP-C) and troponin I (TnI). Although TG-RLC(P-) displayed a significantly reduced response to beta(1)-adrenergic stimulation, MyBP-C and TnI were phosphorylated to a similar level in TG-RLC(P-) and NTG, suggesting cAMP-dependent protein kinase signaling to these proteins was not disrupted. A major finding was that NTG controls were significantly phosphorylated at RLC serine 15 following beta(1)-adrenergic stimulation, a mechanism prevented in TG-RLC(P-), thus providing a biochemical difference in beta(1)-adrenergic responsiveness at the level of the sarcomere. Our measurements of Ca(2+) tension and Ca(2+)-ATPase rate relations in detergent-extracted fiber bundles from LV trabeculae demonstrated a relative decrease in maximum Ca(2+)-activated tension and tension cost in TG-RLC(P-) fibers, with no change in Ca(2+) sensitivity. Our data indicate that RLC phosphorylation is critical for normal ejection and response to beta(1)-adrenergic stimulation. Our data also indicate that the lack of RLC phosphorylation promotes compensatory changes in MyBP-C and TnI phosphorylation, which when normalized do not restore function.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::f9f7de7d75da1d585af98ddbdc05330eTest
https://doi.org/10.1074/jbc.m807414200Test

المؤلفون: Natosha L. Finley, Hanna Osinska, Jeffrey Robbins, Paul R. Rosevear, Raisa Klevitsky, Sakthivel Sadayappan, Jack W. Howarth, John N. Lorenz

المصدر: The FASEB Journal. 22:1246-1257

مصطلحات موضوعية: Gene isoform, medicine.medical_specialty, Contraction (grammar), Molecular Sequence Data, chemistry.chemical_element, Mice, Transgenic, Stimulation, macromolecular substances, Calcium, Biochemistry, Article, Contractility, Mice, Internal medicine, Troponin I, Genetics, medicine, Animals, Humans, Magnesium, Myocytes, Cardiac, Amino Acid Sequence, Phosphorylation, Molecular Biology, Adenosine Triphosphatases, Myocardium, Heart, musculoskeletal system, Endocrinology, chemistry, cardiovascular system, PRKCE, Biotechnology

الوصف: Cardiac troponin I (cTnI) phosphorylation modulates myocardial contractility and relaxation during beta-adrenergic stimulation. cTnI differs from the skeletal isoform in that it has a cardiac specific N' extension of 32 residues (N' extension). The role of the acidic N' region in modulating cardiac contractility has not been fully defined. To test the hypothesis that the acidic N' region of cTnI helps regulate myocardial function, we generated cardiac-specific transgenic mice in which residues 2-11 (cTnI(Delta2-11)) were deleted. The hearts displayed significantly decreased contraction and relaxation under basal and beta-adrenergic stress compared to nontransgenic hearts, with a reduction in maximal Ca(2+)-dependent force and maximal Ca(2+)-activated Mg(2+)-ATPase activity. However, Ca(2+) sensitivity of force development and cTnI-Ser(23/24) phosphorylation were not affected. Chemical shift mapping shows that both cTnI and cTnI(Delta2-11) interact with the N lobe of cardiac troponin C (cTnC) and that phosphorylation at Ser(23/24) weakens these interactions. These observations suggest that residues 2-11 of cTnI, comprising the acidic N' region, do not play a direct role in the calcium-induced transition in the cardiac regulatory or N lobe of cTnC. We hypothesized that phosphorylation at Ser(23/24) induces a large conformational change positioning the conserved acidic N region to compete with actin for the inhibitory region of cTnI. Consistent with this hypothesis, deletion of the conserved acidic N' region results in a decrease in myocardial contractility in the cTnI(Delta2-11) mice demonstrating the importance of acidic N' region in regulating myocardial contractility and mediating the response of the heart to beta-AR stimulation.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::5f7a37c824d960f481e31904facacf2eTest
https://doi.org/10.1096/fj.07-9458comTest

المؤلفون: Karen B. Young, Evangelia G. Kranias, Michael J Gerst, James Gulick, Jeffrey Robbins, Qiujing Song, Guoxiang Chu, Ingrid L. Grupp

المصدر: The FASEB Journal. 18:974-976

مصطلحات موضوعية: Genetically modified mouse, endocrine system, medicine.medical_specialty, Contraction (grammar), Fluorescent Antibody Technique, Mice, Transgenic, Stimulation, Calcium-Transporting ATPases, Biology, Biochemistry, Sarcoplasmic Reticulum Calcium-Transporting ATPases, Mice, Isometric Contraction, Internal medicine, Genetics, medicine, Animals, Muscle, Skeletal, Molecular Biology, Calcium metabolism, Ryanodine receptor, Calcium-Binding Proteins, Isoproterenol, Cardiac muscle, Skeletal muscle, musculoskeletal system, Phospholamban, Sarcoplasmic Reticulum, Muscle Fibers, Slow-Twitch, Endocrinology, medicine.anatomical_structure, cardiovascular system, Calcium, Biotechnology

الوصف: The relative amount of sarcoplasmic reticulum Ca2+-ATPase (SERCA2a) and its crucial inhibitor phospholamban (PLN) are closely regulated and play a pivotal role in maintaining muscle function. The functional importance of PLN has been intensively investigated in cardiac muscle. However, little is known about the role of PLN in the slow-twitch skeletal muscle, which expresses a significantly lower level of PLN but a similar level of SERCA2a compared with cardiac muscle. Thus, to define the physiological significance of PLN in slow-twitch skeletal muscle, we generated transgenic mice with PLN-specific overexpression in soleus, which is largely composed of slow-muscle fibers. The PLN protein levels and the PLN/SERCA2a ratio in transgenic soleus were comparable with those in cardiac muscle. Assessment of isometric-twitch contractions indicated that PLN overexpression was associated with depressed rates of contraction and relaxation, which were not linked to reduced SERCA2a abundance, although the levels of other key Ca2+-handling proteins, including ryanodine receptor, FKBP12, and L-type Ca2+ channel, were significantly decreased. However, isoproterenol stimulation reversed the inhibitory effects of PLN on the transgenic soleus twitch kinetics. Furthermore, the PLN-overexpressing soleus had smaller muscle size, mass, and cross-sectional area compared with wild-types. Interestingly, the percentage of slow fibers was increased in PLN-overexpressing soleus. Taken together, these findings indicate that increased PLN expression in slow-twitch skeletal muscle is associated with impaired contractile function and muscle remodeling.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::6c7371dde9960fa1cba900e5ae6d4576Test
https://doi.org/10.1096/fj.03-1058fjeTest

المؤلفون: Jeffrey Robbins, John J. McAuliffe

المصدر: Pediatric Research. 29:580-585

مصطلحات موضوعية: Heart Defects, Congenital, medicine.medical_specialty, Molecular Sequence Data, Gene Expression, Blood Pressure, Biology, Polymerase Chain Reaction, Fetal Heart, Troponin T, Pregnancy, Internal medicine, Gene expression, medicine, Animals, Pressure overload, Fetus, Sheep, Base Sequence, Alternative splicing, Cardiac muscle, DNA, musculoskeletal system, Troponin, Endocrinology, medicine.anatomical_structure, Great vessels, Pediatrics, Perinatology and Child Health, biology.protein, Female

الوصف: The effects of cardiac hypertrophy in adult animals on the expression of a number of genes are well established. There is, however, a paucity of information about the effect of pressure overload on the expression of genes coding for the contractile proteins in the prenatal developing heart. The prenatal cardiac muscle can increase cell number in response to stress, whereas the adult heart increases cell mass. Thus, the response of the fetal heart to pressure overload cannot be assumed to be identical to that of adult myocardium. We studied the effect of banding the great vessels of fetal sheep hearts on the expression of troponin T (TNT). In other vertebrates, TNT mRNA is generated by alternative splicing of a primary transcript. Thus, both the levels and patterns of TNT isoforms generated by alternative splicing in the heart could be influenced by pressure overload. The techniques of cDNA library screening and polymerase chain reaction were used to define the influence of in utero banding of the great vessels on TNT expression. The data indicate that there is a single dominant isoform of TNT expressed from mid-gestation to adult life in sheep. The pattern of TNT isoform expression in the sheep heart proved to be unique among all animals studied to date.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::312dbc9614630d0699398b7819598650Test
https://doi.org/10.1203/00006450-199106010-00012Test

المؤلفون: Jeffrey Robbins, So ichiro Yasuda, Joseph M. Metzger, Sakthivel Sadayappan, Pierre Coutu

المصدر: Circulation research. 101(4)

مصطلحات موضوعية: Myofilament, medicine.medical_specialty, Cell Membrane Permeability, Physiology, Mice, Transgenic, macromolecular substances, Adenoviridae, Membrane Potentials, Contractility, Rats, Sprague-Dawley, Mice, Internal medicine, Isometric Contraction, Troponin I, medicine, Myocyte, Animals, Myocytes, Cardiac, cardiovascular diseases, Cells, Cultured, biology, Chemistry, Genetic transfer, Cardiac myocyte, Calcium-Binding Proteins, Molecular Mimicry, Gene Transfer Techniques, musculoskeletal system, Troponin, Myocardial Contraction, Phospholamban, Rats, Endocrinology, cardiovascular system, biology.protein, Calcium, Cardiology and Cardiovascular Medicine

الوصف: Elucidating the relative roles of cardiac troponin I (cTnI) and phospholamban (PLN) in β-adrenergic–mediated hastening of cardiac relaxation has been challenging and controversial. To test the hypothesis that β-adrenergic phosphorylation of cTnI has a prominent role in accelerating cardiac myocyte relaxation performance we used transgenic (Tg) mice bearing near complete replacement of native cTnI with a β-adrenergic phospho-mimetic of cTnI whereby tandem serine codons 23/24 were converted to aspartic acids (cTnI S23/24D). Adult cardiac myocytes were isolated and contractility determined at physiological temperature under unloaded and loaded conditions using micro-carbon fibers. At baseline, cTnI S23/24D myocytes had significantly faster relaxation times relative to controls, and isoproterenol stimulation (Iso) had only a small effect to further speed relaxation in cTnI S23/24D myocytes (delta Iso: 7.2 ms) relative to the maximum Iso effect (31.2 ms) in control. The Ca 2+ transient decay rate was similarly accelerated by Iso in Tg and nontransgenic (Ntg) myocytes. Gene transfer of cTnI S23/24D to myocytes in primary culture showed comparable findings. Gene transfer of cTnI with both serines 23/24 converted to alanines (cTnI S23/24A), or gene transfer of slow skeletal TnI, both of which lack PKA phosphorylation sites, significantly blunted Iso-mediated enhanced relaxation compared with controls. Gene transfer of wild-type cTnI had no effect on relaxation. These findings support a key role of cTnI in myocyte relaxation and highlight a direct contribution of the myofilaments in modulating the dynamics of myocardial performance.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::97675e65f0002fba5afebd6843522582Test
https://pubmed.ncbi.nlm.nih.gov/17702976Test

المؤلفون: Jeffrey Robbins, Jeanne James, James Scott Pattison, Jason R. Waggoner, Hanna Osinska, Lisa J. Martin, Evangelia G. Kranias, James Gulick, Raisa Klevitsky

المصدر: Transgenic research. 17(2)

مصطلحات موضوعية: Cardiac function curve, Genetically modified mouse, Male, medicine.medical_specialty, Transgene, Molecular Sequence Data, chemistry.chemical_element, Gene Expression, Biology, Calcium, Article, Animals, Genetically Modified, Immunoenzyme Techniques, Microscopy, Electron, Transmission, Internal medicine, Calcium-binding protein, Receptors, Adrenergic, beta, Genetics, medicine, Animals, Amino Acid Sequence, RNA, Messenger, Cells, Cultured, DNA Primers, Reverse Transcriptase Polymerase Chain Reaction, Calcium-Binding Proteins, Skeletal muscle, Heart, medicine.disease, musculoskeletal system, Phospholamban, Sarcoplasmic Reticulum, Endocrinology, medicine.anatomical_structure, chemistry, Echocardiography, Heart failure, cardiovascular system, Animal Science and Zoology, Female, Rabbits, Agronomy and Crop Science, Biotechnology

الوصف: There has been considerable interest in pursuing phospholamban as a putative therapeutic target for overcoming depressed calcium handling in human heart failure. Studies predominantly done in mice have shown that phospholamban is a key regulator of sarcoplasmic reticulum calcium cycling and cardiac function. However, mice differ significantly from humans in how they regulate calcium, whereas rabbits better recapitulate human cardiac function and calcium handling. To investigate phospholamban's role in the rabbit heart, transgenic rabbits that overexpressed wild-type phospholamban in the ventricular cardiomyocytes and slow-twitch skeletal muscles were generated. Rabbits expressing high levels of phospholamban were not viable due to severe skeletal muscle wasting, the onset of cardiac pathology and early death. A viable transgenic line exhibited a 30% increase in PLN protein levels in the heart. These animals showed isolated foci of cardiac pathology, but cardiac function as well as the response to beta-adrenergic stimulation were normal. SR-calcium uptake measurements showed that the transgenic hearts had the expected reduced affinity for calcium. The data show that phospholamban-overexpressing transgenic rabbits differ markedly in phenotype from analogous transgenic mice in that rabbits are quite sensitive to alterations in phospholamban levels. Exceeding a relatively narrow window of phospholamban expression results in significant morbidity and early death.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::3f4bd3cb5f8dbc8cd69b98984e99b393Test
https://pubmed.ncbi.nlm.nih.gov/17882530Test

المؤلفون: Rosalvo T. H. Fogaça, Beata M. Wolska, Grace M. Arteaga, James R. Peña, Fernando Augusto Lavezzo Dias, Lori A. Walker, Kalpana Vijayan, John S. Walker, Yunbo Ke, Atsushi Sanbe, Jeffrey Robbins

المصدر: Journal of molecular and cellular cardiology. 41(2)

مصطلحات موضوعية: Genetically modified mouse, Cardiac function curve, medicine.medical_specialty, Myosin Light Chains, Stimulation, Blood Pressure, Mice, Transgenic, macromolecular substances, Biology, Contractility, Mice, Internal medicine, Myosin, medicine, Myocyte, Animals, Myocytes, Cardiac, Phosphorylation, Molecular Biology, Myosin-Light-Chain Kinase, Myocardium, Cardiac muscle, musculoskeletal system, Myocardial Contraction, medicine.anatomical_structure, Endocrinology, Calcium, Cardiology and Cardiovascular Medicine, Protein Processing, Post-Translational

الوصف: Although it has been suggested that in cardiac muscle the phosphorylation level of myosin regulatory light chain (RLC) correlates with frequency of stimulation, its significance in the modulation of the force-frequency and pressure-frequency relationships remains unclear. We examined the role of RLC phosphorylation on the force-frequency relation (papillary muscles), the pressure-frequency relation (Langendorff perfused hearts) and shortening-frequency relation (isolated cardiac myocytes) in nontransgenic (NTG) and transgenic mouse hearts expressing a nonphosphorylatable RLC protein (RLC(P-)). At 22 degrees C, NTG and RLC(P-) muscles showed a negative force-frequency relation. At 32 degrees C, at frequencies above 1 Hz, both groups showed a flat force-frequency relation. There was a small increase in RLC phosphorylation in NTG muscles when the frequency of stimulation was increased from 0.2 Hz to 4.0 Hz. However, the level of RLC phosphorylation in these isolated muscles was significantly lower compared to samples taken from NTG intact hearts. In perfused hearts, there was no difference in the slope of pressure-frequency relationship between groups, but the RLC(P-) group consistently developed a reduced systolic pressure and demonstrated a decreased contractility. There was no difference in the level of RLC phosphorylation in hearts paced at 300 and 600 bpm. In RLC(P-) hearts, the level of TnI phosphorylation was reduced compared to NTG. There was no change in the expression of PLB between groups, but expression of SERCA2 was increased in hearts from RLC(P-) compared to NTG. In isolated cardiac myocytes, there was no change in shortening-frequency relationship between groups. Moreover, there was no change in Ca(2+) transient parameters in cells from NTG and RLC(P-) hearts. Our data demonstrate that in cardiac muscle RLC phosphorylation is not an essential determinant of force- and pressure-frequency relations but the absence of RLC phosphorylation decreases contractility in force/pressure developing preparations.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::96457104669cfae488f74b73a6f29b9cTest
https://pubmed.ncbi.nlm.nih.gov/16806259Test