The GDNF target Vsnl1 marks the ureteric tip.

Glial cell line-derived neurotrophic factor (GDNF) is indispensable for ureteric budding and branching. If applied exogenously, GDNF promotes ectopic ureteric buds from the Wolffian duct. Although several downstream effectors of GDNF are known, the identification of early response genes is incomplete. Here, microarray screening detected several GDNF-regulated genes in the Wolffian duct, including Visinin like 1 (Vsnl1), which encodes a neuronal calcium-sensor protein. We observed renal Vsnl1 expression exclusively in the ureteric epithelium, but not in Gdnf-null kidneys. In the tissue culture of Gdnf-deficient kidney primordium, exogenous GDNF and alternative bud inducers (FGF7 and follistatin) restored Vsnl1 expression. Hence, Vsnl1 characterizes the tip of the ureteric bud epithelium regardless of the inducer. In the tips, Vsnl1 showed a mosaic expression pattern that was mutually exclusive with ß-catenin transcriptional activation. Vsnl1 was downregulated in both ß-catenin-stabilized and ß-catenin-deficient kidneys. Moreover, in a mouse collecting duct cell line, Vsnl1 compromised ß-catenin stability, suggesting a counteracting relationship between Vsnl1 and ß-catenin. In summary, Vsnl1 marks ureteric bud tips in embryonic kidneys, and its mosaic pattern demonstrates a heterogeneity of cell types that may be critical for normal ureteric branching.

Involvement of VILIP-1 (visinin-like protein) and opposite roles of cyclic AMP and GMP signaling in in vitro cell migration of murine skin squamous cell carcinoma.

VILIP-1 (visinin-like protein 1) is downregulated in various human squamous cell carcinoma (SCC). In a mouse skin SCC model VILIP-1 expression is reduced in aggressive tumor cells, accompanied by reduced cAMP levels. Overexpression of VILIP-1 in aggressive SCC cells led to enhanced cAMP production, in turn causing a reduction in invasive properties. Moreover, in primary neurons and neuronal tumor lines VILIP-1 enhanced cGMP signaling. Here, we set out to determine whether and how cAMP and cGMP signaling contribute to the VILIP-1 effect on enhanced SCC model cell migration, and thus most likely invasiveness in vivo. We found stronger increase in cGMP levels in aggressive, VILIP-1-negative SCC cells following stimulation of guanylyl cyclases NPR-A and -B with the natriuretic peptides ANP and CNP, respectively. Incubation with ANP or 8Br-cGMP to increase cGMP levels further enhanced the migration capacity of aggressive cells, whereas cell adhesion was unaffected. Increased cGMP was caused by elevated expression levels of NPR-A and -B. However, the expression level of VILIP-1 did not affect cGMP signaling and guanylyl cyclase expression in SCC. In contrast, VILIP-1 led to reduced migration of aggressive SCC cells depending on cAMP levels as shown by use of adenylyl cyclase (AC) inhibitor 2',3'-dideoxyadenosine. Involvement of cAMP-effectors PKA and EPAC play a role downstream of AC activation. VILIP-1-positive and -negative cells did not differ in mRNA expression of ACs, but an effect on enhanced protein expression and membrane localization of ACs was shown to underlie enhancement of cAMP production and, thus, reduction in cell migration by VILIP-1.

Promoter regulation of the visinin-like subfamily of neuronal calcium sensor proteins by nuclear respiratory factor-1.

VILIP-1 (gene name VSNL1), a member of the neuronal Ca(2+) sensor protein family, acts as a tumor suppressor gene by inhibiting cell proliferation, adhesion, and invasiveness. VILIP-1 expression is down-regulated in several types of human cancer. In human non-small cell lung cancer, we found that down-regulation was due to epigenetic changes. Consequently, in this study we analyzed the VSNL1 promoter and its regulation. Serial truncation of the proximal 2-kb VSNL1 promoter (VP-1998) from its 5' terminus disclosed that the last 3' terminal 100-bp promoter fragment maintained similar promoter activity as compared with VP-1998 and therefore was referred to as VSNL1 minimal promoter. When the 5' terminal 50 bp were deleted from the minimal promoter, the activity was dramatically decreased, suggesting that the deleted 50 bp contained a potential cis-acting element crucial for promoter activity. Deletion and site-directed mutagenesis combined with in silico transcription factor binding analysis of VSNL1 promoter identified nuclear respiratory factor (NRF)-1/alpha-PAL as a major player in regulating VSNL1 minimal promoter activity. The function of NRF-1 was further confirmed using dominant-negative NRF-1 overexpression and NRF-1 small interfering RNA knockdown. Electrophoretic mobility shift assay and chromatin immunoprecipitation provided evidence for direct NRF-1 binding to the VSNL1 promoter. Methylation of the NRF-1-binding site was found to be able to regulate VSNL1 promoter activity. Our results further indicated that NRF-1 could be a regulatory factor for gene expression of the other visinin-like subfamily members including HPCAL4, HPCAL1, HPCA, and NCALD.

Loss of Long-Term Potentiation at Hippocampal Output Synapses in Experimental Temporal Lobe Epilepsy.

Patients suffering from temporal lobe epilepsy (TLE) show severe problems in hippocampus dependent memory consolidation. Memory consolidation strongly depends on an intact dialog between the hippocampus and neocortical structures. Deficits in hippocampal signal transmission are known to provoke disturbances in memory formation. In the present study, we investigate changes of synaptic plasticity at hippocampal output structures in an experimental animal model of TLE. In pilocarpine-treated rats, we found suppressed long-term potentiation (LTP) in hippocampal and parahippocampal regions such as the subiculum and the entorhinal cortex (EC). Subsequently we focused on the subiculum, serving as the major relay station between the hippocampus proper and downstream structures. In control animals, subicular pyramidal cells express different forms of LTP depending on their intrinsic firing pattern. In line with our extracellular recordings, we could show that LTP could only be induced in a minority of subicular pyramidal neurons. We demonstrate that a well-characterized cAMP-dependent signaling pathway involved in presynaptic forms of LTP is perturbed in pilocarpine-treated animals. Our findings suggest that in TLE, disturbances of synaptic plasticity may influence the information flow between the hippocampus and the neocortex.

Visinin-like proteins (VSNLs): interaction partners and emerging functions in signal transduction of a subfamily of neuronal Ca2+ -sensor proteins.

The visinin-like protein (VSNL) subfamily, including VILIP-1 (the founder protein), VILIP-2, VILIP-3, hippocalcin, and neurocalcin delta, constitute a highly homologous subfamily of neuronal calcium sensor (NCS) proteins. Comparative studies have shown that VSNLs are expressed predominantly in the brain with restricted expression patterns in various subsets of neurons but are also found in peripheral organs. In addition, the proteins display differences in their calcium affinities, in their membrane-binding kinetics, and in the intracellular targets to which they associate after calcium binding. Even though the proteins use a similar calcium-myristoyl switch mechanism to translocate to cellular membranes, they show calcium-dependent localization to various subcellular compartments when expressed in the same neuron. These distinct calcium-myristoyl switch properties might be explained by specificity for defined phospholipids and membrane-bound targets; this enables VSNLs to modulate various cellular signal transduction pathways, including cyclic nucleotide and MAPK signaling. An emerging theme is the direct or indirect effect of VSNLs on gene expression and their interaction with components of membrane trafficking complexes, with a possible role in membrane trafficking of different receptors and ion channels, such as glutamate receptors of the kainate and AMPA subtype, nicotinic acetylcholine receptors, and Ca(2+)-channels. One hypothesis is that the highly homologous VSNLs have evolved to fulfil specialized functions in membrane trafficking and thereby affect neuronal signaling and differentiation in defined subsets of neurons. VSNLs are involved in differentiation processes showing a tumor-invasion-suppressor function in peripheral organs. Finally, VSNLs play neuroprotective and neurotoxic roles and have been implicated in neurodegenerative diseases.

Nicotine-induced Ca2+-myristoyl switch of neuronal Ca2+ sensor VILIP-1 in hippocampal neurons: a possible crosstalk mechanism for nicotinic receptors.

Visinin-like protein (VILIP-1) belongs to the neuronal Ca2+ sensor family of EF-hand Ca2+-binding proteins that regulate a variety of Ca2+-dependent signal transduction processes in neurons. It is an interaction partner of alpha4beta2 nicotinic acetylcholine receptor (nAChR) and increases surface expression level and agonist sensitivity of the receptor in oocytes. Nicotine stimulation of nicotinic receptors has been reported to lead to an increase in intracellular Ca2+ concentration by Ca2+-permeable nAChRs, which in turn might lead to activation of VILIP-1, by a mechanism described as the Ca2+-myristoyl switch. It has been postulated that this will lead to co-localization of the proteins at cell membranes, where VILIP-1 can influence functional activity of alpha4-containing nAChRs. In order to test this hypothesis we have investigated whether a nicotine-induced and reversible Ca2+-myristoyl switch of VILIP-1 exists in primary hippocampal neurons and whether pharmacological agents, such as antagonist specific for distinct nAChRs, can interfere with the Ca2+-dependent membrane localization of VILIP-1. Here we report, that only alpha7- but not alpha4-containing nAChRs are able to elicit a Ca2+-dependent and reversible membrane-translocation of VILIP-1 in interneurons as revealed by employing the specific receptor antagonists dihydro-beta-erythroidine and methylallylaconitine. The nAChRs are associated with processes of synaptic plasticity in hippocampal neurons and they have been implicated in the pathology of CNS disorders, including Alzheimer's disease and schizophrenia. VILIP-1 might provide a novel functional crosstalk between alpha4- and alpha7-containing nAChRs.

Inhibition of the Interaction Between Group I Metabotropic Glutamate Receptors and PDZ-Domain Proteins Prevents Hippocampal Long-Term Depression, but Not Long-Term Potentiation.

The group I metabotropic glutamate (mGlu) receptor subtypes, mGlu1 and mGlu5, strongly regulate hippocampal synaptic plasticity. Both harbor PSD-95/discs-large/ZO-1 (PDZ) motifs at their extreme carboxyl terminals, which allow interaction with the PDZ domain of Tamalin, regulate the cell surface expression of group I mGlu receptors, and may modulate their coupling to signaling proteins. We investigated the functional role of this interaction in hippocampal long-term depression (LTD). Acute intracerebral treatment of adult rats with a cell-permeable PDZ-blocking peptide (pep-mGluR-STL), designed to competitively inhibit the interaction between Tamalin and group 1 mGlu receptors, prevented expression of LTD in the hippocampal CA1 region without affecting long-term potentiation (LTP) or basal synaptic transmission. Pep-mGluR-STL prevented facilitation by the group I mGlu receptor agonist, (S)-3,5-Dihydroxyphenylglycine (DHPG), and the mGlu5 agonist, (R,S)-2-chloro-5-Hydroxyphenylglycine (CHPG), of short-term depression (STD) into LTD, suggesting that Tamalin preferentially acts by mediating signaling through mGlu5. These data support that Tamalin is essential for the persistent expression of LTD and that it subserves the effective signaling of group 1 mGlu receptors.

Implication of neuronal Ca2+ -sensor protein VILIP-1 in the glutamate hypothesis of schizophrenia.

Post mortem studies in the hippocampus of schizophrenia patients revealed increased expression of neuronal Ca(2+)-sensor VILIP-1 (visinin-like protein) and enhanced co-localization with alpha4beta2 nAChR in interneurons. To study the pathological role of VILIP-1, particularly in interneurons, in the context of the glutamate hypothesis of schizophrenia, we have used ketamine-treated rats, a NMDA receptor hypofunction model, and hippocampal cultures as model systems for schizophrenia. Treatment with ketamine leads to enhanced VILIP-1 expression in interneurons in rat hippocampal CA1 region. In cultures glutamate treatment led to an increase in VILIP-1-positive interneurons, which is not dependent on NMDA receptor but metabotropic glutamate receptor activation. VILIP-1 mainly co-localizes with the interneuron marker calretinin, mGluR1alpha and the VILIP-1 interaction partner alpha4beta2 nAChR in hippocampal slices. Overexpression of VILIP-1 leads to enhanced nAChR-dependent inhibitory postsynaptic current (IPSC) generation by interneurons. This novel molecular link between the pathological role of mGluRs, VILIP-1 and its interaction partner alpha4beta2 nAChR by converging pathological glutamatergic and nicotinergic transmission may underlie cognitive impairments in schizophrenia.

C-Type natriuretic peptide modulates pre- and postsynaptic properties in hippocampal area CA1 in vitro.

The cGMP producing natriuretic peptide receptor B (NPR-B) and its ligand C-type natriuretic peptide (CNP) are widely distributed in the brain and are highly expressed in the hippocampal regions CA1-CA3. To date only limited functional data is available concerning the physiological effects of the peptide hormone in the hippocampus. Therefore, we were interested in how bath application of the peptide hormone might influence synaptic plasticity following high frequency stimulation (HFS). We found that CNP application decreased the population spike (PS) amplitude after HFS, thereby affecting long-term potentiation (LTP) in acute hippocampal slices. To investigate the molecular consequences of CNP application leading to a decrease in PS amplitude, we further analyzed the impact of the hormone on the number of presynaptic synapsin I clusters and number of postsynaptic AMPA receptor subunit GluR1 clusters as well as their co-localization in a primary hippocampal cell culture system. The observed pre-and postsynaptic effects after CNP stimulation of the cGMP pathway in hippocampal cell cultures may underlie the effect of the peptide hormone on LTP.

Visinin-like protein-1 is a potent inhibitor of cell adhesion and migration in squamous carcinoma cells.

Tumor cell invasion is a highly integrated and complex process comprising several biologically distinct functions such as cell adhesion, motility, proteolysis, etc. Visinin-like protein-1 (VILIP-1), a member of the neuronal EF-hand calcium-sensor protein family, plays a role in regulating tumor cell invasiveness of mouse squamous cell carcinoma (SCC). VILIP-1 enhances cyclic adenosine monophosphate levels through PKA induction. However, the mechanism by which VILIP-1 reduces cell invasiveness is not well understood. In this study, we show that VILIP-1 decreased cell adhesion and migration/invasiveness of highly invasive mouse SCC cells. Forced expression of VILIP-1 reduced cell adhesion to fibronectin in parallel to downregulating alphav and alpha5 integrin subunit levels. VILIP-1 overexpression also led to decreased migration ability. Conversely, short hairpin RNA-mediated VILIP-1 knock-down of SCC cells' characterized by little or no invasiveness, correlated with increased adhesion to fibronectin and enhanced expression of alphav and alpha5 integrin subunits together with increased cell migration. Function-blocking assays with inhibitory anti-alpha5 and anti-alphav integrin antibodies showed that both subunits contributed to cell adhesion, migration, and invasiveness of highly invasive SCC cell lines. These results point to a critical role of VILIP-1 in regulating cell adhesion and migration by downregulation of fibronectin receptor expression. Decreased or absent VILIP-1 expression in SCC cell subpopulations may lead to a more advanced malignant phenotype characterized by changes in adhesive ability and increased cell motility, suggestive of a tumor suppressor function.

The darker side of Ca2+ signaling by neuronal Ca2+-sensor proteins: from Alzheimer's disease to cancer.

Neuronal Ca2+-sensor (NCS) proteins constitute a subfamily of closely related EF-hand Ca2+-binding proteins that are expressed mainly in neurons or retinal photoreceptor cells. A variety of different neuronal functions have been attributed to these proteins. However, important new discoveries indicate that these proteins also have key roles in pathological processes of disease. Thus, a 'darker side' of NCS protein signaling has become evident in some CNS disorders, such as Alzheimer's disease and schizophrenia, and in cancer. In this article, I will provide an overview of the current, and rapidly expanding, knowledge of how this important family of proteins might be involved in various major CNS diseases, the proposed role of NCS proteins in pathophysiological signaling and the development of pharmacological tools and novel research strategies.

Overexpression of the calcium sensor visinin-like protein-1 leads to a cAMP-mediated decrease of in vivo and in vitro growth and invasiveness of squamous cell carcinoma cells.

Visinin-like protein-1 (VILIP-1) is a member of the neuronal EF-hand Ca(2+)-sensor protein family. VILIP-1 is expressed in the central nervous system where it plays a crucial role in regulating cAMP levels, cell signaling, and differentiation. Screening of mouse skin tumor cell lines for differentially expressed genes showed high-level VILIP-1 expression in less aggressive squamous cell carcinoma (SCC) and papilloma cell lines. Conversely, expression was markedly decreased or lost in invasive SCC and spindle cell carcinoma cell lines. In addition, immunohistochemistry of normal skin and primary tumors showed that VILIP-1 is expressed in basal cells of the normal intrafollicular epidermis as well as in basal cells of papillomas. The expression was decreased in low-grade SCCs and disappeared in most high-grade SCCs. When two high-grade carcinoma cell lines were transfected with VILIP1-cDNA, the VILIP-1 transfectants had significantly higher cAMP levels than the respective vector alone-transfected lines. VILIP-1-transfected cells were less invasive (both in vivo and in vitro) than the control transfectants. Reduced invasiveness and elevation of cAMP levels were accompanied by decreased MMP-9, as well as decreased RhoA activity. These results indicate that VILIP-1 plays an important role in regulating tumor cell invasiveness and that its loss could aid in enhancing the advanced malignant phenotype.

Reversible translocation and activity-dependent localization of the calcium-myristoyl switch protein VILIP-1 to different membrane compartments in living hippocampal neurons.

Visinin-like protein-1 (VILIP-1) belongs to the family of neuronal calcium sensor (NCS) proteins, a neuronal subfamily of EF-hand [corrected] calcium-binding proteins that are myristoylated at their N termini. NCS proteins are discussed to play roles in calcium-dependent signal transduction of physiological and pathological processes in the CNS. The calcium-dependent membrane association, the so-called calcium-myristoyl switch, localizes NCS proteins to a distinct cellular signaling compartment and thus may be a critical mechanism for the coordinated regulation of signaling cascades. To study whether the biochemically defined calcium-myristoyl switch of NCS proteins can occur in living neuronal cells, the reversible and stimulus-dependent translocation of green fluorescent protein (GFP)-tagged VILIP-1 to subcellular targets was examined by fluorescence microscopy in transfected cell lines and hippocampal primary neurons. In transiently transfected NG108-15 and COS-7 cells, a translocation of diffusely distributed VILIP-1-GFP but not of myristoylation-deficient VILIP-1-GFP to the plasma membrane and to intracellular targets, such as Golgi membranes, occurred after raising the intracellular calcium concentration with a calcium ionophore. The observed calcium-dependent localization was completely reversed after depletion of intracellular calcium by EGTA. Interestingly, a fast and reversible translocation of VILIP-1-GFP and translocation of endogenous VILIP-1 to specialized membrane structures was also observed after a depolarizing stimulus or activation of glutamate receptors in hippocampal neurons. These results show for the first time the reversibility and stimulus-dependent occurrence of the calcium-myristoyl switch in living neurons, suggesting a physiological role as a signaling mechanism of NCS proteins, enabling them to activate specific targets localized in distinct membrane compartments.

Hippocampal expression of the calcium sensor protein visinin-like protein-1 in schizophrenia.

Hippocampal cytoarchitectural abnormalities may be part of the cerebral substrate of schizophrenia. Amongst the chemical components being abnormal in brains of schizophrenics are altered calcium concentrations and reduced expression of the neurotrophin receptor, trkB. We studied by immunohistochemical methods the distribution of visinin-like protein-1 (VILIP-1), which is a calcium sensor protein and at the same time a trkB mRNA binding protein, in hippocampi of nine schizophrenic patients and nine matched control subjects. In normal hippocampi VILIP-1 immunoreactivity was found in multiple pyramidal cells and interneurons. A portion of VILIP-1 immunoreactive interneurons co-express calretinin (60%) and parvalbumin (<10%). In schizophrenics fewer pyramidal cells but more interneurons were immunostained. Our data point to an involvement of the protein in the altered hippocampal circuitry in schizophrenia.

Brain region-specific changes in the expression of calcium sensor proteins after repeated applications of ketamine to rats.

We investigated the cellular distribution of three calcium sensor proteins, visinin-like protein-1 (VILIP-1), VILIP-3, and hippocalcin, in different rat brain areas after repeated administration of the non-competitive N-methyl-D-aspartate receptor antagonist ketamine. In comparison to controls we observed an increase in the density of VILIP-1 immunoreactive (IR) hippocampal interneurons and presubicular nerve cells in ketamine treated rats, whereas the density of VILIP-1 expressing cells was decreased in the Nuc. accumbens of these rats. No alterations were seen in the distribution patterns of VILIP-3. The density of hippocalcin-expressing neurons was increased in the cingulate cortex of drug-treated rats. Our experiments show that repeated injections of subanesthetic doses of ketamine induce subtle changes in the cellular distribution of calcium sensor proteins which in part resemble those recently described in postmortem brains of human schizophrenics [Bernstein, H.-G., Braunewell, K.-H., Spilker, C., Danos, P., Baumann, B., Funke, S., Diekmann, S., Gundelfinger, E.D. and Bogerts, B., NeuroReport, 13 (2002) 393-396].

Expression of visinin-like protein-3 in mouse kidney.

In renal proximal brush borders the Na/Pi cotransporter NaPi-IIa is part of a heteromultimeric complex including the PDZ proteins PDZK1 and NHERF1, which interact with the C terminus of NaPi-IIa. In this study, a yeast two-hybrid screen against the N terminus of the Na/Pi cotransporter NaPi-IIa was performed. Thereby we identified visinin-like protein-3 (VILIP-3), a member of neuronal calcium sensors. In this study, expression and protein localization of VILIP-3 in the mouse kidney was performed by immunofluorescence and RT-PCR using laser-assisted microdissected nephron segments. VILIP-3 was found to be abundant in distal and collecting ducts where it partly colocalized with calbindin D28K. In addition VILIP-3 was observed in the brush borders of proximal tubular S1 and S3 segments of both superficial and deep nephrons.

The expression of Visinin-like 1 during mouse embryonic development.

Visinin like 1 (Vsnl1) encodes a calcium binding protein which is well conserved between species. It was originally found in the brain and its biological functions in central nervous system have been addressed in several studies. Low expression levels have also been found in some peripheral organs, but very little information is available regarding its physiological roles in non-neuronal tissues. Except for the kidney, the expression pattern of Vsnl1 mRNA and protein has not yet been addressed during embryogenesis. By in situ hybridization and immunolabeling we have extensively analyzed the expression pattern of Vsnl1 during murine development. Vsnl1 specifies the cardiac primordia and its expression becomes restricted to the atrial myocardium after heart looping. However, in the adult heart, Vsnl1 is expressed by all four cardiac chambers. It also serves as a specific marker for the cardiomyocyte-derived structures in the systemic and pulmonary circulation. Vsnl1 is dynamically expressed also by many other organs during development e.g. taste buds, cochlea, thyroid, tooth, salivary and adrenal gland. The stage specific expression pattern of Vsnl1 makes it a potentially useful marker particularly in studies of cardiac and vascular morphogenesis.

Divalent cations and redox conditions regulate the molecular structure and function of visinin-like protein-1.

The NCS protein Visinin-like Protein 1 (VILIP-1) transduces calcium signals in the brain and serves as an effector of the non-retinal receptor guanylyl cyclases (GCs) GC-A and GC-B, and nicotinic acetyl choline receptors (nAchR). Analysis of the quaternary structure of VILIP-1 in solution reveals the existence of monomeric and dimeric species, the relative contents of which are affected but not exclusively regulated by divalent metal ions and Redox conditions. Using small-angle X-ray scattering, we have investigated the low resolution structure of the calcium-bound VILIP-1 dimer under reducing conditions. Scattering profiles for samples with high monomeric and dimeric contents have been obtained. The dimerization interface involves residues from EF-hand regions EF3 and EF4.Using monolayer adsorption experiments, we show that myristoylated and unmyristoylated VILIP-1 can bind lipid membranes. The presence of calcium only marginally improves binding of the protein to the monolayer, suggesting that charged residues at the protein surface may play a role in the binding process.In the presence of calcium, VILIP-1 undergoes a conformational re-arrangement, exposing previously hidden surfaces for interaction with protein partners. We hypothesise a working model where dimeric VILIP-1 interacts with the membrane where it binds membrane-bound receptors in a calcium-dependent manner.

Visinin-like protein 1 regulates natriuretic peptide receptor B in the heart.

Accumulating evidence indicates that Visinin-like protein-1 (VILIP-1), a member of the family of neuronal calcium sensor proteins (NCS), modulates a variety of processes in extra-neuronal tissues. In this study, we describe VILIP-1 expression in the human heart, rat cardiomyocytes, and H9c2 cells, and demonstrate that VILIP-1 regulates the cell surface localization of natriuretic peptide receptor B (NPR-B). In preparations from failing hearts, we observed VILIP-1 downregulation and reduced NPR-B signalling. In conclusion, VILIP-1 deficiency may be responsible for the reduced efficiency of the natriuretic peptide system in cardiac hypertrophy and heart failure and may therefore serve as pharmacological target.