Melusin is a muscle specific signaling protein, required for compensatory hypertrophy response in pressure-overloaded heart. The role of Melusin in heart function has been established both by loss ...and gain of function experiments in murine models. With the aim of verifying the hypothesis of a potential role of the Melusin encoding gene, ITGB1BP2, in the modification of the clinical phenotype of human cardiomyopathies, we screened the ITGB1BP2 gene looking for genetic variations possibly associated to the pathological phenotype in three selected groups of patients affected by hypertension and dilated or hypertrophic cardiomyopathy
We analyzed ITGB1BP2 by direct sequencing of the 11 coding exons and intron flanking sequences in 928 subjects, including 656 hypertensive or cardiopathic patients and 272 healthy individuals.
Only three nucleotide variations were found in patients of three distinct families: a C>T missense substitution at position 37 of exon 1 causing an amino acid change from His-13 to Tyr in the protein primary sequence, a duplication (IVS6+12_18dupTTTTGAG) near the 5'donor splice site of intron 6, and a silent 843C>T substitution in exon 11.
The three variations of the ITGB1BP2 gene have been detected in families of patients affected either by hypertension or primary hypertrophic cardiomyopathy; however, a clear genotype/phenotype correlation was not evident. Preliminary functional results and bioinformatic analysis seem to exclude a role for IVS6+12_18dupTTTTGAG and 843C>T in affecting splicing mechanism.Our analysis revealed an extremely low number of variations in the ITGB1BP2 gene in nearly 1000 hypertensive/cardiopathic and healthy individuals, thus suggesting a high degree of conservation of the melusin gene within the populations analyzed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Melusin is a muscle specific protein required for heart hypertrophy in response to mechanical overload. Here we describe a protein 63% homologous to melusin, named chp-1, expressed in all tissues ...tested, including muscles, and highly conserved from invertebrates to human. Both proteins are characterized in their N-terminal half by a tandemly repeated zinc binding 60 amino acid domain with a motif of uniquely spaced cysteine and histidine residues. These motives are highly conserved from plants to mammals and have been recently named CHORD (for cysteine and histidine rich domain) domains. At the C-terminal end melusin contains a calcium binding stretch of 30 acidic amino acid residues which is absent in chp-1. While invertebrate genome contains only one gene coding for a chp-1 homolog, two genes coding for CHORD containing proteins (chp-1 and melusin) are present in vertebrates. Sequence analysis suggests that the muscle specific CHORD containing protein melusin originated by a gene duplication event during early chordate evolution.
The failing heart is characterized by complex tissue remodelling involving increased cardiomyocyte death, and impairment of sarcomere function, metabolic activity, endothelial and vascular function, ...together with increased inflammation and interstitial fibrosis. For years, therapeutic approaches for heart failure (HF) relied on vasodilators and diuretics which relieve cardiac workload and HF symptoms. The introduction in the clinic of drugs interfering with beta-adrenergic and angiotensin signalling have ameliorated survival by interfering with the intimate mechanism of cardiac compensation. Current therapy, though, still has a limited capacity to restore muscle function fully, and the development of novel therapeutic targets is still an important medical need. Recent progress in understanding the molecular basis of myocardial dysfunction in HF is paving the way for development of new treatments capable of restoring muscle function and targeting specific pathological subsets of LV dysfunction. These include potentiating cardiomyocyte contractility, increasing cardiomyocyte survival and adaptive hypertrophy, increasing oxygen and nutrition supply by sustaining vessel formation, and reducing ventricular stiffness by favourable extracellular matrix remodelling. Here, we consider drugs such as omecamtiv mecarbil, nitroxyl donors, cyclosporin A, SERCA2a (sarcoplasmic/endoplasmic Ca(2 +) ATPase 2a), neuregulin, and bromocriptine, all of which are currently in clinical trials as potential HF therapies, and discuss novel molecular targets with potential therapeutic impact that are in the pre-clinical phases of investigation. Finally, we consider conceptual changes in basic science approaches to improve their translation into successful clinical applications.
The ability of cardiomyocytes to detect mechanical and humoral stimuli is critical for adaptation of the myocardium in response to new conditions and for sustaining the increased workload during ...stress. While certain stimuli mediate a beneficial adaptation to stress conditions, others result in maladaptive remodelling, ultimately leading to heart failure. Specific signalling pathways activating either adaptive or maladaptive cardiac remodelling have been identified. Paradoxically, however, in a number of cases, the transduction pathways involved in such opposing responses engage the same signalling proteins. A notable example is the Raf–MEK1/2–ERK1/2 signalling pathway that can control both adaptive and maladaptive remodelling. ERK1/2 signalling requires a signalosome complex where a scaffold protein drives the assembly of these three kinases into a linear pathway to facilitate their sequential phosphorylation, ultimately targeting specific effector molecules. Interestingly, a number of different Raf–MEK1/2–ERK1/2 scaffold proteins have been identified, and their role in determining the adaptive or maladaptive cardiac remodelling is a promising field of investigation for the development of therapeutic strategies capable of selectively potentiating the adaptive response.
The mechanical stress imposed by hemodynamic overload on heart walls is a primary event in triggering the cardiac hypertrophic response. Integrins, a class of membrane receptors, are major players in ...transmitting the mechanical force across the plasma membrane and sensing the mechanical load in cardiomyocytes. In fact, integrins, together with a number of associated cytoskeletal proteins, connect the sarcomeric contractile apparatus to the extracellular matrix across the plasma membrane and trigger intracellular signaling pathways activating the cardiomyocyte hypertrophy program. In this review, we will discuss the role of the muscle-specific integrin isoform beta1D and of associated proteins such as FAK, melusin, vinculin, zyxin, VASP, and migfilin that are the most upstream elements ("initiators") activated by mechanical strain. These molecules trigger a coordinated downstream signaling cascade involving proteins such as AKT, RAS, and MAPKs that execute the biochemical program leading to cardiomyocyte hypertrophy. Better understanding of the functional role of the initiator elements is of key importance to developing novel strategies to control cardiac hypertrophy and prevent heart failure.
Melusin is a muscle-specific protein which interacts with β1 integrin cytoplasmic domain and acts as chaperone protein. Its overexpression induces improved resistance to cardiac overload delaying ...left ventricle dilation and reducing the occurrence of heart failure. Here, we investigated possible protective effect of melusin overexpression against acute ischemia/reperfusion (I/R) injury with or without Postconditioning cardioprotective maneuvers. Melusin transgenic (Mel-TG) mice hearts were subjected to 30-min global ischemia followed by 60-min reperfusion. Interestingly, infarct size was reduced in Mel-TG mice hearts compared to wild-type (WT) hearts (40.3 ± 3.5 % Mel-TG vs. 59.5 ± 3.8 % WT hearts;
n
= 11 animals/group;
P
< 0.05). The melusin protective effect was also demonstrated by measuring LDH release, which was 50 % lower in Mel-TG compared to WT. Mel-TG hearts had a higher baseline level of AKT, ERK1/2 and GSK3β phosphorylation, and displayed increased phospho-kinases level after I/R compared to WT mice. Post-ischemic Mel-TG hearts displayed also increased levels of the anti-apoptotic factor phospho-BAD. Importantly, pharmacological inhibition of PI3K/AKT (Wortmannin) and ERK1/2 (U0126) pathways abrogated the melusin protective effect. Notably, HSP90, a chaperone known to protect heart from I/R injury, showed high levels of expression in the heart of Mel-TG mice suggesting a possible collaboration of this molecule with AKT/ERK/GSK3β pathways in the melusin-induced protection. Postconditioning, known to activate AKT/ERK/GSK3β pathways, significantly reduced IS and LDH release in WT hearts, but had no additive protective effects in Mel-TG hearts. These findings implicate melusin as an enhancer of AKT and ERK pathways and as a novel player in cardioprotection from I/R injury.
Myocardial hypertrophy is a response of cardiac muscle to altered conditions of haemodynamic overload caused by a large number of physiological and pathological conditions. Traditionally, it has been ...considered a beneficial mechanism. However, sustained hypertrophy has been associated with a significant increase in the risk of cardiovascular disease and mortality. Actually, many researchers are trying to understand whether left ventricular hypertrophy is a 'good' mechanism to stimulate or a 'bad' process to prevent. In this review we investigate the most common biochemical signaling pathways involved in the hypertrophic response to identify the precise role, either 'adaptive' or 'maladaptive', of each molecular pathway. Delinealing intracellular signaling pathways involved in the different aspects of cardiac hypertrophy will permit future improvements in the signaling that controls beneficial growth.
Extracellular signal-regulated kinase 1/2 (ERK1/2) signalling is a key pathway in cardiomyocyte hypertrophy and survival in response to many different stress stimuli. We have previously characterized ...melusin as a muscle-specific chaperone protein capable of ERK1/2 signalling activation in the heart. Here, we show that in the heart, melusin forms a supramolecular complex with the proto-oncogene c-Raf, MEK1/2 (also known as MAPKK1/2) and ERK1/2 and that melusin-bound mitogen-activated protein kinases (MAPKs) are activated by pressure overload. Moreover, we demonstrate that both focal adhesion kinase (FAK) and IQ motif-containing GTPase activating protein 1 (IQGAP1), a scaffold protein for the ERK1/2 signalling cascade, are part of the melusin complex and are required for ERK1/2 activation in response to pressure overload. Finally, analysis of isolated neonatal cardiomyocytes indicates that both FAK and IQGAP1 regulate melusin-dependent cardiomyocyte hypertrophy and survival through ERK1/2 activation.
Aims
The Raf-MEK1/2-ERK1/2 (ERK1/2-extracellular signal-regulated kinases 1/2) signalling cascade is crucial in triggering cardiac responses to different stress stimuli. Scaffold proteins are key ...elements in coordinating signalling molecules for their appropriate spatiotemporal activation. Here, we investigated the role of IQ motif-containing GTPase-activating protein 1 (IQGAP1), a scaffold for the ERK1/2 cascade, in heart function and remodelling in response to pressure overload.
Methods and results
IQGAP1-null mice have unaltered basal heart function. When subjected to pressure overload, IQGAP1-null mice initially develop a compensatory hypertrophy indistinguishable from that of wild-type (WT) mice. However, upon a prolonged stimulus, the hypertrophic response develops towards a thinning of left ventricular walls, chamber dilation, and a decrease in contractility, in an accelerated fashion compared with WT mice. This unfavourable cardiac remodelling is characterized by blunted reactivation of the foetal gene programme, impaired cardiomyocyte hypertrophy, and increased cardiomyocyte apoptosis. Analysis of signalling pathways revealed two temporally distinct waves of both ERK1/2 and AKT phosphorylation peaking, respectively, at 10 min and 4 days after aortic banding in WT hearts. IQGAP1-null mice show strongly impaired phosphorylation of MEK1/2-ERK1/2 and AKT following 4 days of pressure overload, but normal activation of these kinases after 10 min. Pull-down experiments indicated that IQGAP1 is able to bind the three components of the ERK cascade, namely c-Raf, MEK1/2, and ERK1/2, as well as AKT in the heart.
Conclusion
These data demonstrate, for the first time, a key role for the scaffold protein IQGAP1 in integrating hypertrophy and survival signals in the heart and regulating long-term left ventricle remodelling upon pressure overload.
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