Increased expression and phosphorylation of focal adhesion kinase correlates with dysfunction in the volume-overloaded human heart

STAT4 and COL1A2 are potential diagnostic biomarkers and therapeutic targets for heart failure comorbided with depression

BACKGROUND

Heart failure (HF) and depression are common disorders that markedly compromise quality of life and impose a great financial burden on the society. Although increasing evidence has supported the closely linkage between the two disorders, the comorbidity mechanisms remain to be fully illuminated. We performed a bioinformatics network analysis to understand potential diagnostic biomarkers and therapeutic targets for HF comorbided with depression.

METHODS

We downloaded the datasets of HF and depression from the Gene Expression Omnibus (GEO) database and constructed co-expression networks by Weighted Gene Co-Expression Network Analysis (WGCNA) to identify key modules. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were performed on the common genes existing in the HF and depression related modules. Then, we employed the STRING database to construct the protein-protein interaction (PPI) network and detected the hub genes in the network. Finally, we validated the expression difference of hub genes from additional datasets of HF and depression.

RESULTS

Functional enrichment analysis indicated that platelet activation, chemokine signaling and focal adhesion were probably involved in HF comorbided with depression. PPI network construction indicated that HF comorbided with depression is likely related to 5 hub genes, including STAT4, CD83, CX3CR1, COL1A2, and SH2D1B. In validated datasets, STAT4 and COL1A2 were especially involved in the comorbidity of HF and depression.

CONCLUSION

Our work indicated a total of 5 hub genes including STAT4, CD83, CX3CR1, COL1A2, and SH2D1B, in which STAT4 and COL1A2 especially underlie the comorbidity mechanisms of HF and depression. These shared pathways might provide new targets for further mechanistic studies of the pathogenesis and treatment of HF and depression.

Cardiomyogenic Differentiation Potential of Human Dilated Myocardium-Derived Mesenchymal Stem/Stromal Cells: The Impact of HDAC Inhibitor SAHA and Biomimetic Matrices

Dilated cardiomyopathy (DCM) is the most common type of nonischemic cardiomyopathy characterized by left ventricular or biventricular dilation and impaired contraction leading to heart failure and even patients’ death. Therefore, it is important to search for new cardiac tissue regenerating tools. Human mesenchymal stem/stromal cells (hmMSCs) were isolated from post-surgery healthy and DCM myocardial biopsies and their differentiation to the cardiomyogenic direction has been investigated in vitro. Dilated hmMSCs were slightly bigger in size, grew slower, but had almost the same levels of MSC-typical surface markers as healthy hmMSCs. Histone deacetylase (HDAC) activity in dilated hmMSCs was 1.5-fold higher than in healthy ones, which was suppressed by class I and II HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) showing activation of cardiomyogenic differentiation-related genes alpha-cardiac actin (ACTC1) and cardiac troponin T (TNNT2). Both types of hmMSCs cultivated on collagen I hydrogels with hyaluronic acid (HA) or 2-methacryloyloxyethyl phosphorylcholine (MPC) and exposed to SAHA significantly downregulated focal adhesion kinase (PTK2) and activated ACTC1 and TNNT2. Longitudinal cultivation of dilated hmMSC also upregulated alpha-cardiac actin. Thus, HDAC inhibitor SAHA, in combination with collagen I-based hydrogels, can tilt the dilated myocardium hmMSC toward cardiomyogenic direction in vitro with further possible therapeutic application in vivo.

Identifying disrupted pathways by tracking altered modules in type 2 DM-related heart failure

BACKGROUND

This study aimed to screen disrupted pathways in type 2 diabetes mellitus (T2DM) heart failure by systematically tracking the altered modules of reweighted protein-protein interaction (PPI) networks.

METHODS

We implemented systematic identification and comparison of modules across non-T2DM and T2DM heart failure subjects by integrating gene expression data and PPI networks. The PPI networks of non-T2DM heart failure and T2DM heart failure were constructed and reweighted by means of Spearman's correlation coefficient (SCC). Subsequently, a clique-merging algorithm was used to explore the modules in the PPI network, followed by the identification of disrupted modules based on a maximum-weight bipartite matching and sorting in descending order. Finally, pathway enrichment analyses were conducted for genes in disrupted modules to determine the biological pathways in T2DM heart failure.

RESULTS

By comparing the modules of non-T2DM heart failure and T2DM heart failure, 804 disrupted modules were explored. The genes in disrupted modules were significantly enriched in 39 categories (p < 1.00E-06). Of these, the most significant pathways were the focal adhesion, vascular endothelial growth factor (VEGF) signaling, and mitogen-activated protein kinase (MAPK) signaling pathways.

CONCLUSION

The identified disrupted pathways - focal adhesion, VEGF signaling, and MAPK signaling - might play important roles in the progression of T2DM heart failure.

The integrin adhesome: from genes and proteins to human disease

The adhesive interactions of cells with their environment through the integrin family of transmembrane receptors have key roles in regulating multiple aspects of cellular physiology, including cell proliferation, viability, differentiation and migration. Consequently, failure to establish functional cell adhesions, and thus the assembly of associated cytoplasmic scaffolding and signalling networks, can have severe pathological effects. The roles of specific constituents of integrin-mediated adhesions, which are collectively known as the 'integrin adhesome', in diverse pathological states are becoming clear. Indeed, the prominence of mutations in specific adhesome molecules in various human diseases is now appreciated, and experimental as well as in silico approaches provide insights into the molecular mechanisms underlying these pathological conditions.

Differential patterns of replacement and reactive fibrosis in pressure and volume overload are related to the propensity for ischaemia and involve resistin

Pathological left ventricle (LV) hypertrophy (LVH) results in reactive and replacement fibrosis. Volume overload LVH (VOH) is less profibrotic than pressure overload LVH (POH). Studies attribute subendocardial fibrosis in POH to ischaemia, and reduced fibrosis in VOH to collagen degradation favouring dilatation. However, the mechanical origin of the relative lack of fibrosis in VOH is incompletely understood. We hypothesized that reduced ischaemia propensity in VOH compared to POH accounted for the reduced replacement fibrosis, along with reduced reactive fibrosis. Rats with POH (ascending aortic banding) evolved into either compensated-concentric POH (POH-CLVH) or dilated cardiomyopathy (POH-DCM); they were compared to VOH (aorta-caval fistula). We quantified LV fibrosis, structural and haemodynamic factors of ischaemia propensity, and the activation of profibrotic pathways. Fibrosis in POH-DCM was severe, subendocardial and subepicardial, in contrast with subendocardial fibrosis in POH-CLVH and nearly no fibrosis in VOH. The propensity for ischaemia was more important in POH versus VOH, explaining different patterns of replacement fibrosis. LV collagen synthesis and maturation, and matrix metalloproteinase-2 expression, were more important in POH. The angiotensin II-transforming growth-factor β axis was enhanced in POH, and connective tissue growth factor (CTGF) was overexpressed in all types of LVH. LV resistin expression was markedly elevated in POH, mildly elevated in VOH and independently reflected chronic ischaemic injury after myocardial infarction. In vitro, resistin is induced by angiotensin II and induces CTGF in cardiomyocytes. Based on these findings, we conclude that a reduced ischaemia propensity and attenuated upstream reactive fibrotic pathways account for the attenuated fibrosis in VOH versus POH.

Tools for protein posttranslational modifications analysis: FAK, a case study

Recent advances in mass spectrometry have resulted in an exponential increase in annotation of posttranslational modifications (PTMs). Just in the Swiss-Prot Knowledgebase, there are 89,931 of a total of 27 characterized PTM types reported experimentally. A single protein can be dynamically modified during its lifetime for regulation of its function. Considering a PTM can occur at different levels and the number of different PTMs described, the number of possibilities for a single protein is unthinkable. Narrowing the study to a single PTM can be rather unmerited considering that most proteins are heavily modified. Currently crosstalk between PTMs is plentifully reported in the literature. The example of amino acids serine and threonine on one hand and lysine on the other hand, as targets of different modifications, demand a more global analysis approach of a protein. Besides the direct competition for the same amino acid, a PTM can directly or indirectly influence other PTMs in the same protein molecule by for example steric hindrance due to close proximity between the modifications or creation of a binding site such as an SH2 binding domain for protein recruitment and further modifications. Given the complexity of PTMs a number of tools have been developed to archive, analyze, and visualize modifications. VISUALPROT is presented here to demonstrate the usefulness of visualizing all annotated protein features such as amino acid content, domains, amino acid modification sites and single amino acid polymorphisms in a single image. VISUALPROT application is demonstrated for the protein focal adhesion kinase (FAK) as an example. FAK is a highly phosphorylated cytoplasmatic tyrosine kinase comprising different domains and regions. FAK is crucial for integrating signals from integrins and receptor tyrosine kinases in processes such as cell survival, proliferation, and motility.

Focal adhesion kinase governs cardiac concentric hypertrophic growth by activating the AKT and mTOR pathways

The heart responds to sustained overload by hypertrophic growth in which the myocytes distinctly thicken or elongate on increases in systolic or diastolic stress. Though potentially adaptive, hypertrophy itself may predispose to cardiac dysfunction in pathological settings. The mechanisms underlying the diverse morphology and outcomes of hypertrophy are uncertain. Here we used a focal adhesion kinase (FAK) cardiac-specific transgenic mice model (FAK-Tg) to explore the function of this non-receptor tyrosine kinase on the regulation of myocyte growth. FAK-Tg mice displayed a phenocopy of concentric cardiac hypertrophy, reflecting the relative thickening of the individual myocytes. Moreover, FAK-Tg mice showed structural, functional and molecular features of a compensated hypertrophic growth, and preserved responses to chronic pressure overload. Mechanistically, FAK overexpression resulted in enhanced myocardial FAK activity, which was proven by treatment with a selective FAK inhibitor to be required for the cardiac hypertrophy in this model. Our results indicate that upregulation of FAK does not affect the activity of Src/ERK1/2 pathway, but stimulated signaling by a cascade that encompasses PI3K, AKT, mTOR, S6K and rpS6. Moreover, inhibition of the mTOR complex by rapamycin extinguished the cardiac hypertrophy of the transgenic FAK mice. These findings uncover a unique role for FAK in regulating the signaling mechanisms that governs the selective myocyte growth in width, likely controlling the activity of PI3K/AKT/mTOR pathway, and suggest that FAK activation could be important for the adaptive response to increases in cardiac afterload. This article is part of a Special Issue entitled "Local Signaling in Myocytes".

Focal adhesion kinase -- the basis of local hypertrophic signaling domains

Focal adhesion kinase (FAK), a broadly expressed non-receptor tyrosine kinase which transduces signals from integrins, growth and hormonal factors, is a key player in many fundamental biological processes and functions, including cell adhesion, migration, proliferation and survival. The involvement of FAK in this range of functions supports its role in important aspects of organismal development and disease, such as central nervous system and cardiovascular development, cancer, cardiac hypertrophy and tissue fibrosis. Many functions of FAK are correlated with its tyrosine kinase activity, which is temporally and spatially controlled by complex intra-molecular autoinhibitory conformation and inter-molecular interactions with protein and lipid partners. The inactivation of FAK in mice results in embryonic lethality attributed to the lack of proper development and function of the heart. Accordingly, embryonic FAK myocyte-specific knockout mice display lethal cardiac defects such as thin ventricle wall and ventricular septum defects. Emerging data also support a role for FAK in the reactive hypertrophy and failure of adult hearts. Moreover, the mechanisms that regulate FAK in differentiated cardiac myocytes to biomechanical stress and soluble factors are beginning to be revealed and are discussed here together with data that connect FAK to its downstream effectors. This article is part of a Special Issue entitled "Local Signaling in Myocytes".

A role for focal adhesion kinase in cardiac mitochondrial biogenesis induced by mechanical stress

We studied the implication of focal adhesion kinase (FAK) in cardiac mitochondrial biogenesis induced by mechanical stress. Prolonged stretching (2-12 h) of neonatal rat ventricular myocytes (NRVM) upregulated the main components of mitochondrial transcription cascade [peroxisome proliferator-activated receptor coactivator-1 (PGC-1α), nuclear respiratory factor (NRF-1), and mitochondrial transcription factor A]. Concomitantly, prolonged stretching enhanced mitochondrial biogenesis [copy number of mitochondrial DNA (mtDNA), content of the subunit IV of cytochrome oxidase, and mitochondrial staining-green fluorescence intensity of Mitotracker green] and induced the hypertrophic growth (cell size and atrial natriuretic peptide transcripts) of NRVM. Furthermore, the stretching of NRVM enhanced phosphorylation, nuclear localization, and association of FAK with PGC-1α. Recombinant FAK COOH-terminal, but not the NH(2)-terminal or kinase domain, precipitated PGC-1α from nuclear extracts of NRVM. Depletion of FAK by RNA interference suppressed the upregulation of PGC-1α and NRF-1 and markedly attenuated the enhanced mitochondrial biogenesis and hypertrophic growth of stretched NRVM. In the context of energy metabolism, FAK depletion became manifest by a reduction of ATP levels in stretched NRVM. Complementary studies in adult mice left ventricle demonstrated that pressure overload upregulated PGC-1α, NRF-1, and mtDNA. In vivo FAK silencing transiently attenuated the upregulation of PGC-1α, NRF-1, and mtDNA, as well as the left ventricular hypertrophy induced by pressure overload. In conclusion, activation of FAK signaling seems to be important for conferring enhanced mitochondrial biogenesis coupled to the hypertrophic growth of cardiomyocytes in response to mechanical stress, via control of mitochondrial transcription cascade.

FAK mediates the activation of cardiac fibroblasts induced by mechanical stress through regulation of the mTOR complex

AIMS

Cardiac fibroblasts are activated by mechanical stress, but the underlying mechanisms involved remain poorly understood. In this study, we investigated whether focal adhesion kinase (FAK) plays a role in the activation of cardiac fibroblasts in response to cyclic stretch.

METHODS AND RESULTS

Neonatal (NF-P3/80--third passage, 80% confluence) and adult (AF-P1/80--first passage, 80% confluence) rat cardiac fibroblasts were exposed to cyclic stretch (biaxial, 1 Hz), which enhanced FAK phosphorylation at Tyr397. Proliferation (anti-5-bromo-2'-deoxyuridine and anti-Ki67 nuclear labelling), differentiation into myofibroblasts (expression of alpha-smooth muscle actin--alpha-SMA), and the activity of matrix metalloproteinase-2 were equally enhanced in stretched NF-P3/80 and AF-P1/80. Treatment with the integrin inhibitor RGD peptide impaired FAK phosphorylation and increased apoptosis (TUNEL) in non-stretched and stretched NF-P3/80, whereas FAK silencing induced by small interfering RNA modestly enhanced apoptosis only in stretched cells. RGD peptide or FAK silencing suppressed the activation of NF-P3/80 invoked by cyclic stretch. In addition, NF-P3/80 depleted of FAK were defective in AKT Ser473, TSC-2 Thr1462, and S6 kinase Thr389 phosphorylation induced by cyclic stretch. The activation of NF-P3/80 invoked by cyclic stretch was prevented by pre-treatment with the mammalian target of rapamycin (mTOR) inhibitor rapamycin, whereas supplementation with the amino acid, leucine, activated S6K and rescued the stretch-induced activation of NF-P3/80 depleted of FAK.

CONCLUSIONS

These findings demonstrate a critical role for the mTOR complex, downstream from FAK, in mediating the activation of cardiac fibroblasts in response to mechanical stress.

Cardiac fibroblasts require focal adhesion kinase for normal proliferation and migration

Migration and proliferation of cardiac fibroblasts (CFs) play an important role in the myocardial remodeling process. While many factors have been identified that regulate CF growth and migration, less is known about the signaling mechanisms involved in these processes. Here, we utilized Cre-LoxP technology to obtain focal adhesion kinase (FAK)-deficient adult mouse CFs and studied how FAK functioned in modulating cell adhesion, proliferation, and migration of these cells. Treatment of FAK(flox/flox) CFs with Ad/Cre virus caused over 70% reduction of FAK protein levels within a cell population. FAK-deficient CFs showed no changes in focal adhesions, cell morphology, or protein expression levels of vinculin, talin, or paxillin; proline-rich tyrosine kinase 2 (Pyk2) expression and activity were increased. Knockdown of FAK protein in CFs increased PDGF-BB-induced proliferation, while it reduced PDGF-BB-induced migration. Adhesion to fibronectin was not altered. To distinguish between the function of FAK and Pyk2, FAK function was inhibited via adenoviral-mediated overexpression of the natural FAK inhibitor FAK-related nonkinase (FRNK). Ad/FRNK had no effect on Pyk2 expression, inhibited the PDGF-BB-induced migration, but did not change the PDGF-BB-induced proliferation. FAK deficiency had only modest effects on increasing PDGF-BB activation of p38 and JNK MAPKs, with no alteration in the ERK response vs. control cells. These results demonstrate that FAK is required for the PDGF-BB-induced migratory response of adult mouse CFs and suggest that FAK could play an essential role in the wound-healing response that occurs in numerous cardiac pathologies.

Targeting focal adhesion kinase with small interfering RNA prevents and reverses load-induced cardiac hypertrophy in mice

Hypertrophy is a critical event in the onset of failure in chronically overloaded hearts. Focal adhesion kinase (FAK) has attracted particular attention as a mediator of hypertrophy induced by increased load. Here, we demonstrate increased expression and phosphorylation of FAK in the hypertrophic left ventricles (LVs) of aortic-banded mice. We used an RNA interference strategy to examine whether FAK signaling plays a role in the pathophysiology of load-induced LV hypertrophy and failure. Intrajugular delivery of specific small interfering RNA induced prolonged FAK silencing ( approximately 70%) in both normal and hypertrophic LVs. Myocardial FAK silencing was accompanied by prevention, as well as reversal, of load-induced left ventricular hypertrophy. The function of LVs was preserved and the survival rate was higher in banded mice treated with small interfering RNA targeted to FAK, despite the persistent pressure overload. Studies in cardiac myocytes and fibroblasts harvested from LVs confirmed the ability of the systemically administered specific small interfering RNA to silence FAK in both cell types. Further analysis indicated attenuation of cardiac myocyte hypertrophic growth and of the rise in the expression of beta-myosin heavy chain in overloaded LVs. Moreover, FAK silencing was demonstrated to attenuate the rise in the fibrosis, collagen content, and activity of matrix metalloproteinase-2 in overloaded LVs, as well as the rise of matrix metalloproteinase-2 protein expression in fibroblasts harvested from overloaded LVs. This study provides novel evidence that FAK may be involved in multiple aspects of the pathophysiology of cardiac hypertrophy and failure induced by pressure overload.

Proteinaceous cysteine protease inhibitors

Studies of proteinaceous cysteine protease inhibitors originated with the discovery of cystatins in the 1960s. Since that time, a rich and fascinating world of proteins that control and regulate a multitude of important physiological processes, ranging from the basics of protein turnover to development and brain function, has been uncovered. Failures in such important and complex systems inevitably lead to pathologies. Many threatening diseases such as cancer or neurological disorders, to mention only some, are attributed to deregulation of proteaseinhibitor balance. Moreover, important aspects of infection pathology and host defense rely on proteolysis and protease inhibition. Recent advances in the field of protease inhibitors have drawn attention to the possible use of this collected knowledge to control related pathological processes. This review attempts to familiarize the reader with proteinaceous cysteine protease inhibitors by providing an overview of current knowledge. The work primarily highlights biological processes in which the inhibitors are involved and focuses on pathologies resulting from aberrant protease-inhibitor balance, pointing out emerging possibilities for their correction.