scholarly journals Phosphatidylinositol-4,5-Bisphosphate Binding to Amphiphysin-II Modulates T-Tubule Remodeling: Implications for Heart Failure

2021 ◽  
Vol 12 ◽  
Author(s):  
Junlan Zhou ◽  
Neha Singh ◽  
Chloe Monnier ◽  
William Marszalec ◽  
Li Gao ◽  
...  
Keyword(s):  
Heart Failure ◽  
Binding Sites ◽  
Ventricular Myocytes ◽  
Structural Protein ◽  
Tubule Formation ◽  
Spontaneously Hypertensive ◽  
Time To Peak ◽  
Short Loop ◽  
Normal Rat ◽  
And Function

BIN1 (amphyphysin-II) is a structural protein involved in T-tubule (TT) formation and phosphatidylinositol-4,5-bisphosphate (PIP2) is responsible for localization of BIN1 to sarcolemma. The goal of this study was to determine if PIP2-mediated targeting of BIN1 to sarcolemma is compromised during the development of heart failure (HF) and is responsible for TT remodeling. Immunohistochemistry showed co-localization of BIN1, Cav1.2, PIP2, and phospholipase-Cβ1 (PLCβ1) in TTs in normal rat and human ventricular myocytes. PIP2 levels were reduced in spontaneously hypertensive rats during HF progression compared to age-matched controls. A PIP Strip assay of two native mouse cardiac-specific isoforms of BIN1 including the longest (cardiac BIN1 #4) and shortest (cardiac BIN1 #1) isoforms as well human skeletal BIN1 showed that all bound PIP2. In addition, overexpression of all three BIN1 isoforms caused tubule formation in HL-1 cells. A triple-lysine motif in a short loop segment between two helices was mutated and replaced by negative charges which abolished tubule formation, suggesting a possible location for PIP2 interaction aside from known consensus binding sites. Pharmacological PIP2 depletion in rat ventricular myocytes caused TT loss and was associated with changes in Ca2+ release typically found in myocytes during HF, including a higher variability in release along the cell length and a slowing in rise time, time to peak, and decay time in treated myocytes. These results demonstrate that depletion of PIP2 can lead to TT disruption and suggest that PIP2 interaction with cardiac BIN1 is required for TT maintenance and function.

scholarly journals Gut Microbiota Profile Identifies Transition From Compensated Cardiac Hypertrophy to Heart Failure in Hypertensive Rats

Hypertension ◽  
2020 ◽  
Vol 76 (5) ◽  
pp. 1545-1554
Author(s):  
Elena Gutiérrez-Calabrés ◽  
Adriana Ortega-Hernández ◽  
Javier Modrego ◽  
Rubén Gómez-Gordo ◽  
Alicia Caro-Vadillo ◽  
...  
Keyword(s):  
Heart Failure ◽  
Gut Microbiota ◽  
Spontaneously Hypertensive Rat ◽  
Spontaneously Hypertensive ◽  
Metabolic Functions ◽  
Hypertensive Rat ◽  
Spontaneously Hypertensive Heart Failure ◽  
Wistar Kyoto ◽  
And Function ◽  
Gut Microbial Community

Microcirculatory alterations displayed by patients with heart failure (HF) induce structural and functional intestinal changes that may affect normal gut microbial community. At the same time, gut microbiota can influence pathological mechanisms implicated in HF progression. However, it is unknown whether gut microbiota dysbiosis can precede the development of cardiac alterations in HF or it is only a mere consequence. Our aim was to investigate the potential relationship between gut microbiota composition and HF development by comparing spontaneously hypertensive heart failure and spontaneously hypertensive rat models. Gut microbiota from spontaneously hypertensive heart failure, spontaneously hypertensive rat, and normotensive Wistar Kyoto rats at 9 and 19 months of age was analyzed by sequencing the 16S ribosomal RNA gene, and KEGG metabolic pathways associated to 16S profiles were predicted. Beta diversity, Firmicutes / Bacteroidetes ratio, taxonomic abundances, and potential metabolic functions of gut microbiota were significantly different in spontaneously hypertensive heart failure with respect to spontaneously hypertensive rat before (9 months) and after (19 months) cardiac differences were presented. Nine-month-old spontaneously hypertensive heart failure showed a significant increase in the genera Paraprevotella, Oscillospira, Prevotella 9, Faecalitalea, Faecalibacterium, Ruminiclostridium 6, Phascolarctobacterium, Butyrivibrio, Parasutterella, and Parabacteroides compared with both Wistar Kyoto and spontaneously hypertensive rat, while Ruminiclostridium 9 , Oscillibacter , Ruminiclostridium , Mucispirillum, Intestinimonas , and Akkermansia were diminished. Of them, Akkermansia, Prevotella 9 , Paraprevotella , and Phascolarctobaterium were associated to changes in cardiac structure and function. Our results demonstrate an association between specific changes in gut microbiota and the development of HF in a hypertensive model of HF and further support the intervention to restore gut microbiota as an innovative therapeutic strategy for preventing HF.

Cytosolic calcium transients in myocytes isolated from rats with ischemic heart failure

1993 ◽  
Vol 265 (6) ◽  
pp. H1953-H1964 ◽  
Author(s):  
J. M. Capasso ◽  
P. Li ◽  
P. Anversa
Keyword(s):  
Heart Failure ◽  
Mechanical Performance ◽  
Ventricular Myocytes ◽  
Diastolic Pressure ◽  
Cytosolic Calcium ◽  
Left Ventricular ◽  
Ischemic Heart ◽  
Ischemic Heart Failure ◽  
Time To Peak ◽  
Left And Right

Mechanical performance and cytosolic Ca2+ dynamics were characterized in myocytes isolated from left and right ventricles of rats with ischemic heart failure. Seven days after coronary artery narrowing (CAN) in rats filling pressures were elevated, whereas systolic pressures and ejection of blood were depressed. Left ventricular myocytes increased 18% in length and 19% in width, whereas right myocytes expanded longitudinally by 23% and transversely by 24%. Contractile behavior of myocytes displayed reductions in myocyte shortening and velocity of shortening, despite prolongation of time to peak shortening. Diastolic Ca2+ increased by 32 and 39% in left and right myocytes of CAN animals, whereas peak systolic Ca2+ in left ventricular myocytes was depressed (22%). Time to peak Ca2+ was prolonged by 68% in left myocytes. Moreover, time required for peak Ca2+ to return to diastolic levels was prolonged in left myocytes. Regression analysis revealed correlations between end-diastolic pressure and diastolic Ca2+ and peak developed pressure and systolic Ca2+. Thus ischemic heart failure finds its cellular basis in a depression in myocyte contractility that may in turn be due to alterations in cytosolic Ca2+ handling.

scholarly journals Decreased Ca2+ extrusion via Na+/Ca2+ exchange in epicardial left ventricular myocytes during compensated hypertrophy

2005 ◽  
Vol 288 (5) ◽  
pp. H2431-H2438 ◽  
Author(s):  
Mark R. Fowler ◽  
James R. Naz ◽  
Mark D. Graham ◽  
Gilles Bru-Mercier ◽  
Simon M. Harrison ◽  
...  
Keyword(s):  
Time Course ◽  
Ventricular Myocytes ◽  
Major Change ◽  
Left Ventricular ◽  
Spontaneously Hypertensive ◽  
Cellular Hypertrophy ◽  
Time To Peak ◽  
Intracellular Ca ◽  
The Face ◽  
Wistar Kyoto

Hypertension-induced cardiac hypertrophy alters the amplitude and time course of the systolic Ca2+ transient of subepicardial and subendocardial ventricular myocytes. The present study was designed to elucidate the mechanisms underlying these changes. Myocytes were isolated from the left ventricular subepicardium and subendocardium of 20-wk-old spontaneously hypertensive rats (SHR) and age-matched normotensive Wistar-Kyoto rats (WKY; control). We monitored intracellular Ca2+ using fluo 3 or fura 2; caffeine (20 mmol/l) was used to release Ca2+ from the sarcoplasmic reticulum (SR), and Ni2+ (10 mM) was used to inhibit Na+/Ca2+ exchange (NCX) function. SHR myocytes were significantly larger than those from WKY hearts, consistent with cellular hypertrophy. Subepicardial myocytes from SHR hearts showed larger Ca2+ transient amplitude and SR Ca2+ content and less Ca2+ extrusion via NCX compared with subepicardial WKY myocytes. These parameters did not change in subendocardial myocytes. The time course of decline of the Ca2+ transient was the same in all groups of cells, but its time to peak was shorter in subepicardial cells than in subendocardial cells in WKY and SHR and was slightly prolonged in subendocardial SHR cells compared with WKY subendocardial myocytes. It is concluded that the major change in Ca2+ cycling during compensated hypertrophy in SHR is a decrease in NCX activity in subepicardial cells; this increases SR Ca2+ content and hence Ca2+ transient amplitude, thus helping to maintain the strength of contraction in the face of an increased afterload.

scholarly journals Caveolin-3 KO disrupts t-tubule structure and decreases t-tubular ICa density in mouse ventricular myocytes

2018 ◽  
Vol 315 (5) ◽  
pp. H1101-H1111 ◽  
Author(s):  
Simon M. Bryant ◽  
Cherrie H. T. Kong ◽  
Judy J. Watson ◽  
Hanne C. Gadeberg ◽  
David M. Roth ◽  
...  
Keyword(s):  
Cardiac Hypertrophy ◽  
Ventricular Myocytes ◽  
Wild Type ◽  
Tubule Formation ◽  
Membrane Area ◽  
Cellular Hypertrophy ◽  
Channel Expression ◽  
T Tubules ◽  
And Function

Caveolin-3 (Cav-3) is a protein that has been implicated in t-tubule formation and function in cardiac ventricular myocytes. In cardiac hypertrophy and failure, Cav-3 expression decreases, t-tubule structure is disrupted, and excitation-contraction coupling is impaired. However, the extent to which the decrease in Cav-3 expression underlies these changes is unclear. We therefore investigated the structure and function of myocytes isolated from the hearts of Cav-3 knockout (KO) mice. These mice showed cardiac dilatation and decreased ejection fraction in vivo compared with wild-type control mice. Isolated KO myocytes showed cellular hypertrophy, altered t-tubule structure, and decreased L-type Ca2+ channel current ( ICa) density. This decrease in density occurred predominantly in the t-tubules, with no change in total ICa, and was therefore a consequence of the increase in membrane area. Cav-3 KO had no effect on L-type Ca2+ channel expression, and C3SD peptide, which mimics the scaffolding domain of Cav-3, had no effect on ICa in KO myocytes. However, inhibition of PKA using H-89 decreased ICa at the surface and t-tubule membranes in both KO and wild-type myocytes. Cav-3 KO had no significant effect on Na+/Ca2+ exchanger current or Ca2+ release. These data suggest that Cav-3 KO causes cellular hypertrophy, thereby decreasing t-tubular ICa density. NEW & NOTEWORTHY Caveolin-3 (Cav-3) is a protein that inhibits hypertrophic pathways, has been implicated in the formation and function of cardiac t-tubules, and shows decreased expression in heart failure. This study demonstrates that Cav-3 knockout mice show cardiac dysfunction in vivo, while isolated ventricular myocytes show cellular hypertrophy, changes in t-tubule structure, and decreased t-tubular L-type Ca2+ current density, suggesting that decreased Cav-3 expression contributes to these changes in cardiac hypertrophy and failure.

Abstract 15023: Junctophilin-2 (JPH2) Interactome in Ventricular Myocytes is Subcellular Compartment-dependent and Subject to Remodeling During Hypertrophy Leading to Heart Failure

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Tytus Bernas ◽  
Rengasayee Veeraraghavan ◽  
Wilson T Zachary ◽  
Soltisz Andrew ◽  
Min Jiang ◽  
...  
Keyword(s):  
Heart Failure ◽  
Connexin 43 ◽  
Ventricular Myocytes ◽  
Subcellular Location ◽  
Spatial Relationships ◽  
Structured Illumination ◽  
Structured Illumination Microscopy ◽  
Subcellular Compartment ◽  
Spontaneously Hypertensive ◽  
Intracellular Ca

Introduction: Junctions between sarco/endoplasmic reticulum (SR/ER) and sarcolemma (SL), where Ca-induced Ca release (CICR) takes place, are important for myocardial contractility. JPH2 is the major SR/SL tether in cardiomyocytes. Hypothesis: JPH2 interacts with diverse proteins depending on its subcellular location. Furthermore, JPH2's distribution and relations with its interactors are subject to remodeling in diseased state. Methods: We studied spontaneously hypertensive rats: 2-3 months (SY, healthy) and ≥ 20 months (SO, in heart failure). We used immunoprecipitation (IP) and global unbiased search (proteomics) to identify JPH2's interactors in cardiomyocytes. We used high-resolution structured illumination microscopy (SIM) followed by deconvolution and object-based segmentation in 3 dimension (OBS3D) to quantify spatial relationships between JPH2 and interactors. Results: Based on proteomics JPH2's interactors are involved in: SR/ER function, vesicular transport, sub-sarcolemma scaffold, ion transporters/channels, intercalated disc (ICD) organization and mitochondrial function. We quantified spatial relationships between JPH2 and 6 interactors representing distinct subcellular compartments: RyR2 (junctional SR), Cav1.2 (t-tubules), dystrophin (peripheral SL), caveolin-3 (caveolae), connexin-43 (ICD), and prohibitin-1 (mitochondria). In SY myocytes, JPH2 clusters are organized along the z-lines and peripheral SL, consistent with close and reciprocal association in JPH2/RyR2 and JPH2/dystrophin. In SO myocytes, JPH2 is dispersed from z-lines but stays close to peripheral SL and clusters to ICD. This leads to reduced proximity between JPH2 and Cav1.2 or RyR2, but closer proximity to connexin-43. Conclusions: In failing heart, a portion of JPH2 shifts from t-tubule/SR junctions (where CICR occurs) to ICDs (where store-operated Ca entry 'SOCE' occurs), likely contributing to dysregulation of intracellular Ca handling.

Altered Ca2+ dynamics in single cardiac myocytes from renovascular hypertensive rats

1991 ◽  
Vol 260 (2) ◽  
pp. C327-C337 ◽  
Author(s):  
R. L. Moore ◽  
R. V. Yelamarty ◽  
H. Misawa ◽  
R. C. Scaduto ◽  
D. G. Pawlush ◽  
...  
Keyword(s):  
Renovascular Hypertension ◽  
Binding Sites ◽  
Ventricular Myocytes ◽  
Indirect Evidence ◽  
Fold Increase ◽  
Myocardial Contraction ◽  
Left Ventricular ◽  
Left Renal Artery ◽  
Beta Adrenergic ◽  
Time To Peak

Several functional and biochemical characteristics of hypertrophied hearts isolated from rats with renovascular hypertension provide indirect evidence that cellular Ca2+ dynamics during myocardial contraction-relaxation are altered. In this study, intracellular Ca2+ concentration ([Ca2+]i) dynamics were examined in paced left ventricular (LV) myocytes isolated from rats with hypertension (HYP) induced by partial occlusion of the left renal artery and from normotensive rats (Sham). Characteristic myocardial changes produced by renovascular hypertension included a 40% increase in LV weight and a 3.6-fold increase in the fractional expression of the beta-heavy chain of myosin in isolated LV myocytes. In periods of mechanical quiescence between contractions, basal [Ca2+]i values were similar in Sham and HYP LV myocytes. During a contraction-relaxation cycle in HYP myocytes, peak [Ca2+]i, +d[Ca2+]i/dt, and -d[Ca2+]i/dt were reduced, whereas the time required for [Ca2+]i to rise from a basal value to a peak value (time-to-peak [Ca2+]i) was unaffected. In both Sham and HYP myocytes, the fall in [Ca2+]i from peak to basal values could be approximated by a monoexponential rate constant, kf. Values for kf were significantly smaller in HYP than in Sham myocytes. After treatment with 4 microM isoproterenol, peak [Ca2+]i, +[Ca2+]i/dt, -d[Ca2+]i/dt, and kf increased in both Sham and HYP myocytes. In contrast, basal [Ca2+]i and time-to-peak [Ca2+]i did not change. Thus, despite recent reports of inefficiencies of beta-adrenergic receptor coupling, there was no evidence of blunted beta-adrenergic responsiveness in HYP myocytes with respect to [Ca2+]i dynamics during contraction-relaxation. Finally, no Sham vs. HYP differences in the number of specific [3H]-PN200-110 binding sites per cell in quiescent, rod-shaped myocytes were detected, but a significant reduction in [3H]-PN200-110 binding sites in an enriched sarcolemmal membrane fraction isolated from HYP animals was observed. These observations are suggestive of a reduction in slow, Ca2+ channel surface density in HYP myocytes. The results of this study clearly indicate that [Ca2+]i dynamics during contraction-relaxation in single left ventricular myocytes are affected by residence in a chronic setting of renovascular hypertension. In addition, the prolonged [Ca2+]i removal phase observed in HYP myocytes can be restored toward normal by beta-adrenergic agonists.

Conformation of Ribosomes from Escherichia Coli

1974 ◽  
Vol 32 ◽  
pp. 210-211
Author(s):  
M. Boublik ◽  
W. Hellmann ◽  
F. Jenkins
Keyword(s):  
Binding Sites ◽  
Ribosomal Proteins ◽  
Fluorescent Dyes ◽  
Protein Biosynthesis ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Dimensional Structure ◽  
Complete Understanding ◽  
And Function

The present knowledge of the three-dimensional structure of ribosomes is far too limited to enable a complete understanding of the various roles which ribosomes play in protein biosynthesis. The spatial arrangement of proteins and ribonuclec acids in ribosomes can be analysed in many ways. Determination of binding sites for individual proteins on ribonuclec acid and locations of the mutual positions of proteins on the ribosome using labeling with fluorescent dyes, cross-linking reagents, neutron-diffraction or antibodies against ribosomal proteins seem to be most successful approaches. Structure and function of ribosomes can be correlated be depleting the complete ribosomes of some proteins to the functionally inactive core and by subsequent partial reconstitution in order to regain active ribosomal particles.

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