The emergence of plasma membrane calcium pump as a novel therapeutic target for heart disease.

The plasma membrane calcium/calmodulin dependent ATPase (PMCA) is a calcium-extruding enzymatic pump important in the control of intracellular calcium concentration. PMCA is the only system for calcium extrusion in the majority of cells. In excitable cells such as cardiomyocytes however, PMCA has been shown to play only a minor role in calcium homeostasis. In these cells the main mechanism of calcium extrusion is the sodium calcium exchanger. However, increasing evidence points to an important role for PMCA in signal transduction; in particular in the nitric oxide signalling pathway. In this review we will discuss recent advances that support a key role for PMCA in signal transduction and the potential for therapeutic targeting of this molecule in the treatment of cardiac diseases

The sarcolemmal calcium pump, alpha-1 syntrophin, and neuronal nitric-oxide synthase are parts of a macromolecular protein complex.

The main role of the plasma membrane Ca2+/calmodulin-dependent ATPase (PMCA) is in the removal of Ca2+ from the cytosol. Recently, we and others have suggested a new function for PMCA as a modulator of signal transduction pathways. This paper shows the physical interaction between PMCA (isoforms 1 and 4) and alpha-1 syntrophin and proposes a ternary complex of interaction between endogenous PMCA, alpha-1 syntrophin, and NOS-1 in cardiac cells. We have identified that the linker region between the pleckstrin homology 2 (PH2) and the syntrophin unique (SU) domains, corresponding to amino acids 399-447 of alpha-1 syntrophin, is crucial for interaction with PMCA1 and -4. The PH2 and the SU domains alone failed to interact with PMCA. The functionality of the interaction was demonstrated by investigating the inhibition of neuronal nitric-oxide synthase-1 (NOS-1); PMCA is a negative regulator of NOS-1-dependent NO production, and overexpression of alpha-1 syntrophin and PMCA4 resulted in strongly increased inhibition of NO production. Analysis of the expression levels of alpha-1 syntrophin protein in the heart, skeletal muscle, brain, uterus, kidney, or liver of PMCA4-/- mice, did not reveal any differences when compared with those found in the same tissues of wild-type mice. These results suggest that PMCA4 is tethered to the syntrophin complex as a regulator of NOS-1, but its absence does not cause collapse of the complex, contrary to what has been reported for other proteins within the complex, such as dystrophin. In conclusion, the present data demonstrate for the first time the localization of PMCA1b and -4b to the syntrophin.dystrophin complex in the heart and provide a specific molecular mechanism of interaction as well as functionality

Inhibition of nuclear import of calcineurin prevents myocardial hypertrophy.

The time that transcription factors remain nuclear is a major determinant for transcriptional activity. It has recently been demonstrated that the phosphatase calcineurin is translocated to the nucleus with the transcription factor nuclear factor of activated T cells (NF-AT). This study identifies a nuclear localization sequence (NLS) and a nuclear export signal (NES) in the sequence of calcineurin. Furthermore we identified the nuclear cargo protein importinbeta(1) to be responsible for nuclear translocation of calcineurin. Inhibition of the calcineurin/importin interaction by a competitive peptide (KQECKIKYSERV), which mimicked the calcineurin NLS, prevented nuclear entry of calcineurin. A noninhibitory control peptide did not interfere with the calcineurin/importin binding. Using this approach, we were able to prevent the development of myocardial hypertrophy. In angiotensin II-stimulated cardiomyocytes, [(3)H]-leucine incorporation (159%+/-9 versus 111%+/-11; P<0.01) and cell size were suppressed significantly by the NLS peptide compared with a control peptide. The NLS peptide inhibited calcineurin/NF-AT transcriptional activity (227%+/-11 versus 133%+/-8; P<0.01), whereas calcineurin phosphatase activity was unaffected (298%+/-9 versus 270%+/-11; P=NS). We conclude that calcineurin is not only capable of dephosphorylating NF-AT, thus enabling its nuclear import, but the presence of calcineurin in the nucleus is also important for full NF-AT transcriptional activity

The sarcolemmal calcium pump inhibits the calcineurin/nuclear factor of activated T-cell pathway via interaction with the calcineurin A catalytic subunit.

The calcineurin/nuclear factor of activated T-cell (NFAT) pathway represents a crucial transducer of cellular function. There is increasing evidence placing the sarcolemmal calcium pump, or plasma membrane calcium/calmodulin ATPase pump (PMCA), as a potential modulator of signal transduction pathways. We demonstrate a novel interaction between PMCA and the calcium/calmodulin-dependent phosphatase, calcineurin, in mammalian cells. The interaction domains were located to the catalytic domain of PMCA4b and the catalytic domain of the calcineurin A subunit. Endogenous calcineurin activity, assessed by measuring the transcriptional activity of its best characterized substrate, NFAT, was significantly inhibited by 60% in the presence of ectopic PMCA4b. This inhibition was notably reversed by the co-expression of the PMCA4b interaction domain, demonstrating the functional significance of this interaction. PMCA4b was, however, unable to confer its inhibitory effect in the presence of a calcium/calmodulin-independent constitutively active mutant calcineurin A suggesting a calcium/calmodulin-dependent mechanism. The modulatory function of PMCA4b is further supported by the observation that endogenous calcineurin moves from the cytoplasm to the plasma membrane when PMCA4b is overexpressed. We suggest recruitment by PMCA4b of calcineurin to a low calcium environment as a possible explanation for these findings. In summary, our results offer strong evidence for a novel functional interaction between PMCA and calcineurin, suggesting a role for PMCA as a negative modulator of calcineurin-mediated signaling pathways in mammalian cells. This study reinforces the emerging role of PMCA as a molecular organizer and regulator of signaling transduction pathways

Quality of life assessment in patients undergoing trans-catheter aortic valve implantation using MacNew Questionnaire

The MacNew questionnaire is a disease-specific quality of life measure that has been used in patients with myocardial infarction and heart failure. We aimed to investigate the impact of transcatheter aortic valve implantation (TAVI) on health-related quality of life (HRQoL) using MacNew Questionnaire and identify predictors associated with a change in its score. This was a prospective multi-center study performed across 5 National Health Service hospitals in the United Kingdom performing TAVI between 2016 and 2018. HRQoL was assessed using MacNew Questionnaire, Euro Quality of Life-5D-5L, and Short Form 36 questionnaires collected at baseline, 3-, 6- and 12 months after the procedure. Out of 225 recruited patients, 19 did not have TAVI and 4 withdrew their consent, and hence 202 patients were included. HRQoL was assessed in 181, 161, and 147 patients at 3, 6, and 12 months, respectively. Using MacNew, there was a significant improvement in all domains of HRQoL as early as 3 months after TAVI which was sustained up to 12 months with improved discrimination of change in HRQoL compared with other scales. Poor mobility at baseline and history of myocardial infarction were independent predictors of reduced improvement in HRQoL at 3 months. HRQoL increased in all subgroups of patients including frail ones. In conclusion, the MacNew assessment tool performed well in a representative TAVI cohort and could be used as an alternative disease-specific method for assessing HRQoL change after TAVI

Serum metabolomics reveals many novel metabolic markers of heart failure, including pseudouridine and 2-oxoglutarate

There is intense interest in the identification of novel biomarkers which improve the diagnosis of heart failure. Serum samples from 52 patients with systolic heart failure (EF&lt; 40% plus signs and symptoms of failure) and 57 controls were analyzed by gas chromatography - time of flight - mass spectrometry and the raw data reduced to 272 statistically robust metabolite peaks. 38 peaks showed a significant difference between case and control (p &lt;5 × 10-5). Two such metabolites were pseudouridine, a modified nucleotide present in t- and rRNA and a marker of cell turnover, as well as the tricarboxylic acid cycle intermediate 2-oxoglutarate. Furthermore, 3 further new compounds were also excellent discriminators between patients and controls: 2-hydroxy, 2-methylpropanoic acid, erythritol and 2,4,6-trihydroxypyrimidine. Although renal disease may be associated with heart failure, and metabolites associated with renal disease and other markers were also elevated (e.g. urea, creatinine and uric acid), there was no correlation within the patient group between these metabolites and our heart failure biomarkers, indicating that these were indeed biomarkers of heart failure and not renal disease per se. These findings demonstrate the power of data-driven metabolomics approaches to identify such markers of disease. © Springer Science+Business Media, LLC 2007

Cost-effectiveness of transcatheter edge-to-edge repair in secondary mitral regurgitation

Background: Transcatheter edge-to-edge mitral valve repair (TMVr) improves symptoms and survival for patients with heart failure with reduced left ventricular ejection fraction (HFrEF) and severe secondary mitral regurgitation despite guideline-recommended medical therapy (GRMT). Whether TMVr is cost-effective from a UK National Health Service (NHS) perspective is unknown. Methods: We used patient-level data from the Cardiovascular Outcomes Assessment of the MitraClip Percutaneous Therapy for Heart Failure Patients with Functional Mitral Regurgitation (COAPT) trial to perform a cost-effectiveness analysis of TMVr +GRMT versus GRMT alone from an NHS perspective. Costs for the TMVr procedure were based on standard English tariffs and device costs. Subsequent costs were estimated based on data acquired during the trial. Health utilities were estimated using the Short-Form 6-Dimension Health Survey. Results: Costs for the index procedural hospitalisation were £18 781, of which £16 218 were for the TMVr device. Over 2-year follow-up, TMVr reduced subsequent costs compared with GRMT (£10 944 vs £14 932, p=0.006), driven mainly by reductions in heart failure hospitalisations; nonetheless, total 2-year costs remained higher with TMVr (£29 165 vs £14 932, p&lt;0.001). When survival, health utilities and costs were projected over a lifetime, TMVr was projected to increase life expectancy by 1.57 years and quality-adjusted life expectancy by 1.12 quality-adjusted life-years (QALYs) at an incremental cost of £21 980, resulting in an incremental cost-effectiveness ratio (ICER) of £23 270 per QALY gained (after discounting). If the benefits of TMVr observed in the first 2 years were maintained without attenuation, the ICER improved to £12 494 per QALY. Conclusions: For patients with HFrEF and severe secondary mitral regurgitation similar to those enrolled in COAPT, TMVr increases life expectancy and quality-adjusted life expectancy compared with GRMT at an ICER that represents good value from an NHS perspective