Fibin regulates cardiomyocyte hypertrophy and causes protein-aggregate-associated cardiomyopathy in vivo

Despite the identification of numerous molecular pathways modulating cardiac hypertrophy its pathogenesis is not completely understood. In this study we define an unexpected role for Fibin ("fin bud initiation factor homolog") in cardiomyocyte hypertrophy. Via gene expression profiling in hypertrophic murine hearts after transverse aortic constriction we found a significant induction of Fibin. Moreover, Fibin was upregulated in another mouse model of cardiac hypertrophy (calcineurin-transgenics) as well as in patients with dilated cardiomyopathy. Immunoflourescence microscopy revealed subcellular localization of Fibin at the sarcomeric z-disc. Overexpression of Fibin in neonatal rat ventricular cardiomyocytes revealed a strong anti-hypertrophic effect through inhibiting both, NFAT- and SRF-dependent signalling. In contrast, transgenic mice with cardiac-restricted overexpression of Fibin developed dilated cardiomyopathy, accompanied by induction of hypertrophy-associated genes. Moreover, Fibin overexpression accelerated the progression to heart failure in the presence of prohypertrophic stimuli such as pressure overload and calcineurin overexpression. Histological and ultrastructural analyses surprisingly showed large protein aggregates containing Fibin. On the molecular level, aggregate formation was accompanied by an induction of the unfolded protein response subsequent UPR-mediated apoptosis and autophagy. Taken together, we identified Fibin as a novel potent negative regulator of cardiomyocyte hypertrophy in vitro. Yet, heart-specific Fibin overexpression in vivo causes development of a protein-aggregate-associated cardiomyopathy. Because of close similarities to myofibrillar myopathies, Fibin represents a candidate gene for cardiomyopathy and Fibin transgenic mice may provide additional mechanistic insight into aggregate formation in these diseases.

Exploring the Involvement of Gut Microbiota in Cancer Therapy-Induced Cardiotoxicity

Trillions of microbes in the human intestinal tract, including bacteria, viruses, fungi, and protozoa, are collectively referred to as the gut microbiome. Recent technological developments have led to a significant increase in our understanding of the human microbiome. It has been discovered that the microbiome affects both health and the progression of diseases, including cancer and heart disease. Several studies have indicated that the gut microbiota may serve as a potential target in cancer therapy modulation, by enhancing the effectiveness of chemotherapy and/or immunotherapy. Moreover, altered microbiome composition has been linked to the long-term effects of cancer therapy; for example, the deleterious effects of chemotherapy on microbial diversity can, in turn, lead to acute dysbiosis and serious gastrointestinal toxicity. Specifically, the relationship between the microbiome and cardiac diseases in cancer patients following therapy is poorly understood. In this article, we provide a summary of the role of the microbiome in cancer treatment, while also speculating on a potential connection between treatment-related microbial changes and cardiotoxicity. Through a brief review of the literature, we further explore which bacterial families or genera were differentially affected in cancer treatment and cardiac disease. A deeper understanding of the link between the gut microbiome and cardiotoxicity caused by cancer treatment may help lower the risk of this critical and potentially fatal side effect.

Dataset of ileum bacterial diversity in mice after heart failure due to pressure overload

We recently reported the correlation of gut bacterial diversity with heart failure using a mouse model of heart failure due to pressure overload induced by transverse aortic constriction (TAC). We found that gut the bacterial diversity is significantly altered and is directly correlated to the severity of heart failure (Heart Failure Severity Closely Correlates with Intestinal Dysbiosis and Subsequent Metabolomic Alterations (Spehlmann, 2022). In addition, stool samples that were collected for the gut microbial diversity analysis, we dissected ileum from the mice after 42 days of TAC. The total DNA was extracted to identify the bacterial diversity resided in ileum using 16S rRNA gene amplicon shotgun sequencing and downstream bioinformatics analysis to determine if it is correlated to the heart failure.

Restoration of Cardiomyogenesis in Aged Mouse Hearts by Voluntary Exercise

BACKGROUND

The human heart has limited capacity to generate new cardiomyocytes and this capacity declines with age. Because loss of cardiomyocytes may contribute to heart failure, it is crucial to explore stimuli of endogenous cardiac regeneration to favorably shift the balance between loss of cardiomyocytes and the birth of new cardiomyocytes in the aged heart. We have previously shown that cardiomyogenesis can be activated by exercise in the young adult mouse heart. Whether exercise also induces cardiomyogenesis in aged hearts, however, is still unknown. Here, we aim to investigate the effect of exercise on the generation of new cardiomyocytes in the aged heart.

METHODS

Aged (20-month-old) mice were subjected to an 8-week voluntary running protocol, and age-matched sedentary animals served as controls. Cardiomyogenesis in aged hearts was assessed on the basis of ¹⁵N-thymidine incorporation and multi-isotope imaging mass spectrometry. We analyzed 1793 cardiomyocytes from 5 aged sedentary mice and compared these with 2002 cardiomyocytes from 5 aged exercised mice, followed by advanced histology and imaging to account for ploidy and nucleation status of the cell. RNA sequencing and subsequent bioinformatic analyses were performed to investigate transcriptional changes induced by exercise specifically in aged hearts in comparison with young hearts.

RESULTS

Cardiomyogenesis was observed at a significantly higher frequency in exercised compared with sedentary aged hearts on the basis of the detection of mononucleated/diploid ¹⁵N-thymidine-labeled cardiomyocytes. No mononucleated/diploid ¹⁵N-thymidine-labeled cardiomyocyte was detected in sedentary aged mice. The annual rate of mononucleated/diploid ¹⁵N-thymidine-labeled cardiomyocytes in aged exercised mice was 2.3% per year. This compares with our previously reported annual rate of 7.5% in young exercised mice and 1.63% in young sedentary mice. Transcriptional profiling of young and aged exercised murine hearts and their sedentary controls revealed that exercise induces pathways related to circadian rhythm, irrespective of age. One known oscillating transcript, however, that was exclusively upregulated in aged exercised hearts, was isoform 1.4 of regulator of calcineurin, whose regulation and functional role were explored further.

CONCLUSIONS

Our data demonstrate that voluntary running in part restores cardiomyogenesis in aged mice and suggest that pathways associated with circadian rhythm may play a role in physiologically stimulated cardiomyogenesis.

Heart Failure Severity Closely Correlates with Intestinal Dysbiosis and Subsequent Metabolomic Alterations

Growing evidence suggests an altered gut microbiome in patients with heart failure (HF). However, the exact interrelationship between microbiota, HF, and its consequences on the metabolome are still unknown. We thus aimed here to decipher the association between the severity and progression of HF and the gut microbiome composition and circulating metabolites. Using a mouse model of transverse aortic constriction (TAC), gut bacterial diversity was found to be significantly lower in mice as early as day 7 post-TAC compared to Sham controls (p = 0.03), with a gradual progressive decrease in alpha-diversity on days 7, 14, and 42 (p = 0.014, p = 0.0016, p = 0.0021) compared to day 0, which coincided with compensated hypertrophy, maladaptive hypertrophy, and overtly failing hearts, respectively. Strikingly, segregated analysis based on the severity of the cardiac dysfunction (EF < 40% vs. EF 40−55%) manifested marked differences in the abundance and the grouping of several taxa. Multivariate analysis of plasma metabolites and bacterial diversity produced a strong correlation of metabolic alterations, such as reduced short-chain fatty acids and an increase in primary bile acids, with a differential abundance of distinct bacteria in HF. In conclusion, we showed that HF begets HF, likely via a vicious cycle of an altered microbiome and metabolic products.

Comprehensive plasma and tissue profiling reveals systemic metabolic alterations in cardiac hypertrophy and failure

AIMS

Heart failure is characterized by structural and metabolic cardiac remodelling. The aim of the present study is to expand our understanding of the complex metabolic alterations in the transition from pathological hypertrophy to heart failure and exploit the results from a translational perspective.

METHODS AND RESULTS

Mice were subjected to transverse aortic constriction (TAC) or sham surgery and sacrificed 2 weeks, 4 weeks, or 6 weeks after the procedure. Samples from plasma, liver, skeletal muscle, and heart were collected and analysed using metabolomics. Cardiac samples were also analysed by transcriptional profiling. Progressive alterations of key cardiac metabolic pathways and gene expression patterns indicated impaired mitochondrial function and a metabolic switch during transition to heart failure. Similar to the heart, liver, and skeletal muscle revealed significant metabolic alterations such as depletion of essential fatty acids and glycerolipids in late stages of heart failure. Circulating metabolites, particularly fatty acids, reflected cardiac metabolic defects, and deteriorating heart function. For example, inverse correlation was found between plasma and the heart levels of triacylglycerol (C18:1, C18:2, C18:3), and sphingomyelin (d18:1, C23:0) already at an early stage of heart failure. Interestingly, combining metabolic and transcriptional data from cardiac tissue revealed that decreased carnitine shuttling and transportation preceded mitochondrial dysfunction. We, thus, studied the therapeutic potential of OCTN2 (Organic Cation/Carnitine Transporter 2), an important factor for carnitine transportation. Cardiac overexpression of OCTN2 using an adeno-associated viral vector significantly improved ejection fraction and reduced interstitial fibrosis in mice subjected to TAC.

CONCLUSION

Comprehensive plasma and tissue profiling reveals systemic metabolic alterations in heart failure, which can be used for identification of novel biomarkers and potential therapeutic targets.

Abstract 800: HECT Domain Containing-3 (HECTD3) is a Novel Regulator of Cardiac Hypertrophy and Inflammation

Objective: In this study, using a Yeast two-hybrid screen, we identified the HECT domain-containing E3 ubiquitin ligase 3 (HECTD3) as one of the novel cardiac binding partners of SUMO2. Present study thus focusses on deciphering the cardiac function of HECTD3.

Methods and Results: HECTD3-SUMO2 interaction was further validated by co-immunoprecipitation analysis. Interesting, adenovirus-mediated overexpression of HECTD3 in neonatal rat ventricular cardiomyocytes (NRVCMs) resulted in downregulation of endogenous as well as overexpressed SUMO2. Proteasome inhibitor MG132 treatment however inhibited HECTD3-mediated SUMO2 downregulation, suggesting SUMO2 as a likely substrate of HECTD3 in ubiquitin-proteasome system dependent protein degradation. To get further insights into cardiac substrates of HECTD3, we performed mass-spectrometry analysis of NRVCM protein lysate. Interestingly, several proteins from interferon signaling, including signal transducer and activator of transcription-1 (STAT1), were significantly downregulated by HECTD3 overexpression. Functional dissection of HECTD3-SUMO2-STAT1 interaction revealed attenuation of cellular hypertrophy and LPS mediated activation of inflammatory cascade in NRVCMs. Importantly, in vitro findings were consistent in vivo , where, AAV-9 mediated overexpression of HECTD3 substantially reduced cardiac hypertrophy and fibrosis, inhibited activation of STAT1-mediated downstream signaling, and attenuated infiltration of inflammatory cells to the heart after transverse-aortic constriction or Angiotensin II treatment.

Conclusions: In conclusion, we describe here a novel cardioprotective mechanism involving the ubiquitin ligase HECTD3, which exerts anti-hypertrophic and anti-inflammatory effects via dual regulation of SUMO2 and its sumoylation target STAT1. This “dual pathway” inhibition may be exploited for the prevention and/or therapy of cardiac hypertrophy and heart failure.

Sumoylation-independent activation of Calcineurin-NFAT-signaling via SUMO2 mediates cardiomyocyte hypertrophy

The objective of this study was to identify unknown modulators of Calcineurin (Cn)-NFAT signaling. Measurement of NFAT reporter driven luciferase activity was therefore utilized to screen a human cardiac cDNA-library (~10⁷ primary clones) in C2C12 cells through serial dilutions until single clones could be identified. This extensive screening strategy culminated in the identification of SUMO2 as a most efficient Cn-NFAT activator. SUMO2-mediated activation of Cn-NFAT signaling in cardiomyocytes translated into a hypertrophic phenotype. Prohypertrophic effects were also observed in mice expressing SUMO2 in the heart using AAV9 (Adeno-associated virus), complementing the in vitro findings. In addition, increased SUMO2-mediated sumoylation in human cardiomyopathy patients and in mouse models of cardiomyopathy were observed. To decipher the underlying mechanism, we generated a sumoylation-deficient SUMO2 mutant (ΔGG). Surprisingly, ΔGG replicated Cn-NFAT-activation and the prohypertrophic effects of native SUMO2, both in vitro and in vivo, suggesting a sumoylation-independent mechanism. Finally, we discerned a direct interaction between SUMO2 and CnA, which promotes CnA nuclear localization. In conclusion, we identified SUMO2 as a novel activator of Cn-NFAT signaling in cardiomyocytes. In broader terms, these findings reveal an unexpected role for SUMO2 in cardiac hypertrophy and cardiomyopathy, which may open the possibility for therapeutic manipulation of this pathway.

Abstract 93: The Role of the Stretch-responsive Genes Mlf1 and Rnd1 for Cardiac Physiology and Pathophysiology

Cardiac remodeling is a typical change in function and morphology of the heart in response to pathological biomechanical stress. Despite substantial research in this area several underlying mechanisms remain unclear. We thus devised a screening experiment of dynamic stretch of neonatal cardiomyocytes (NRVCM) which revealed several genes which have not yet been implicated in cardiac remodeling before. In further analyses we focused on Mlf1 and Rnd1 , both showing significant expression in heart as well as in skeletal and liver. Conformational qRT-PCR revealed upregulation of Rnd1 mRNA (5.94x) after 24 h of stretch. Mlf1 mRNA was significantly downregulated (qRT-PCR 0.34x). Stimulation with phenylephrine (PE) induced Rnd1 mRNA (3.98x), while Mlf1 mRNA levels remained unchanged. Furthermore, in line with the in vitro results we found upregulation of Rnd1 (2.1x, p<0.001) and downregulation of the cardiac Mlf1 expression (var. 1 0.45x, var. 2 0.36x, both p<0.001) in mice after transverse aortic constriction.

Adenoviral overexpression of Mlf1 in NRVCM induced the fetal gene program (e.g., nppa , nppb ). However, a significant decrease in cell size was found. We noticed the consistent findings after stretch or PE-stimulation. Rnd1 overexpression also led to induction of nppa , nppb and Rcan1.4, but caused an increase in cell size.

To analyze whether Mlf1 and Rnd1 also influenced cell proliferation, we analyzed Mlf1/Rnd1-infected cells for the expression of proliferation markers Ki67 and phosphohistone H3 (PHH3). Mlf1 overexpression led to an increase in Ki67+ cells of about 5.92 fold, and in PHH3+ cells of 2.48 fold (p<0.001), Rnd1 overexpression showed an increase in Ki67+ cells of about 6.9 fold and in PHH3+ cells of 5,25 fold (p<0.001).

Taken together, we could identify two stretch-sensitive genes which influence the process of cardiac hypertrophy and cell proliferation. Current work focuses on a knockdown of both genes in vivo and on the identification of potential protein-protein interactions to complete the characterization of Mlf1 and Rnd1.

Abstract 393: The Intercalated Disc Protein Myozap: A Novel Player in Cardiac Proteinopathy

Background: A growing number of cardiac muscle diseases are characterized by depositions of misfolded proteins, including cardiac amyloidosis and desmin-releated cardiomyopathy (DRM). The continued presence and chronic accumulation of misfolded or unfolded proteins can lead to aggregation and/or the formation of soluble peptides that are proteotoxic. This in turn leads to compromised protein quality control and precipitates a downward spiral of the cell’s ability to maintain homeostasis and may eventually result in cell death. We recently identified massive protein aggregates in the hearts of transgenic mice overexpressing the intercalated disc (ID) protein myozap (Myozap-tg). We now sought to investigate the precise composition of these aggregates and the role of Myozap in other proteinopathies such as DRM.

Methods and Results: We employed multi-dimensional proteomics, transcriptomics, confocal microscopy, and molecular biology approaches to decipher the underlying causes and consequences of protein aggregate formation in Myozap-tg mice. Transcriptome profiling of these mice revealed striking upregulation of autophagy, protein synthesis, and pro-inflammatory pathways, whereas protein degradation pathways were down-regulated. Surprisingly, proteomics analyses revealed Desmin and α-crystallin B (CryAB) as the major constituents of the aggregates, which was further validated by confocal microscopy. Moreover, we identified the presence of toxic preamyloid oligomers in Myozap-tg mouse hearts, a hallmark in many protein aggregation-based diseases including DRM. Most interestingly, we also observed co-localization of Myozap with protein aggregates observed in both transgenic mouse hearts overexpressing mutant Desmin (D7) and mutant CryAB (R120G), as well as in human DRM patients.

Conclusion: The present study implies a new role for Myozap, which was previously reported to affect cardiac SRF signaling: (1) Myozap accumulates in various forms of experimental and human protein aggregation cardiomyopathy, suggesting involvement in protein homoestasis. (2) The fact that Myozap is now the third ID protein (after desmin and CryAB) to cause cardiac proteinopathy points to a general role of the ID in its molecular pathogenesis.

Abstract 181: Myozap Deficiency Promotes Adverse Remodeling And Cardiomyopathy In Response To Biomechanical Stress

Background: Myozap is a new addition to the list of intercalated disc (ID) proteins, which we previously identified using a bioinformatics screen. In vitro characterization of Myozap revealed that it activates Rho-dependent SRF signaling. Moreover, cardiac restricted overexpression of Myozap in mice resulted in protein aggregate-associated cardiomyopathy, whereas, knockdown of its ortholog in Zebrafish led to severe contractile dysfunction and cardiomyopathy. The objective of the current study was to elucidate the cardiac consequences of targeted deletion of Myozap in mice.

Methods and Results: We generated a Myozap null mutant (MZP-ko) by global deletion of Myozap in mice. Unchallenged MZP-ko mice did not exhibit a baseline cardiac phenotype. However, upon biomechanical stress due to TAC (transverse aortic constriction), deficiency for Myozap led to accelerated cardiac hypertrophy (significant increases in the heart to body weight, left ventricular to body weight ratios) and fibrosis, accompanied by “super”-induction of the hypertrophic gene program (ANF/BNP). Moreover, MZP-ko mice revealed a severe reduction of fractional shortening and signs heart failure (increased lung/body weights) as well as a markedly increased mortality in response to TAC). Additional molecular data exhibited a significant decrease in the levels of native and phosphorylated Connexin 43 after transverse aortic constriction (TAC) in MZP-ko mice compared to wildtype animals. Finally, we observed a downregulation of dysbindin, a novel interaction partner of Myozap and known inducer of ERK1/2 signaling in TAC operated MZP-ko mice. Consistently, activation of ERK1/2 in response to TAC was blunted compared to wild-type littermates.

Conclusions: We here show that myozap deficiency in vivo leads to a maladaptative response to increased biomechanical stress associated with cardiomyopathy, heart failure and cardiac death. Mechanistically, this phenotype can at least in part be explained by the interruption of the interaction between myozap and dysbindin with subsequent loss of ERK1/2 activation. Taken into a larger perspective, our data imply an essential role of the ID and its associated proteins in cardiac remodeling.

Mice with cardiac-restricted overexpression of Myozap are sensitized to biomechanical stress and develop a protein-aggregate-associated cardiomyopathy

The intercalated disc (ID) is a major component of the cell-cell contact structures of cardiomyocytes and has been recognized as a hot spot for cardiomyopathy. We have previously identified Myozap as a novel cardiac-enriched ID protein, which interacts with several other ID proteins and is involved in RhoA/SRF signaling in vitro. To now study its potential role in vivo we generated a mouse model with cardiac overexpression of Myozap. Transgenic (Tg) mice developed cardiomyopathy with hypertrophy and LV dilation. Consistently, these mice displayed upregulation of the hypertrophy-associated and SRF-dependent gene expression. Pressure overload (transverse aortic constriction, TAC) caused exaggerated cardiac hypertrophy, further loss of contractility and LV dilation. Similarly, a physiological stimulus (voluntary running) also led to significant LV dysfunction. On the ultrastructural level, Myozap-Tg mouse hearts exhibited massive protein aggregates composed of Myozap, desmoplakin and other ID proteins. This aggregate-associated pathology closely resembled the alterations observed in desmin-related cardiomyopathy. Interestingly, desmin was not detectable in the aggregates, yet was largely displaced from the ID. Molecular analyses revealed induction of autophagy and dysregulation of the unfolded protein response (UPR), associated with apoptosis. Taken together, cardiac overexpression of Myozap leads to cardiomyopathy, mediated, at least in part by induction of Rho-dependent SRF signaling in vivo. Surprisingly, this phenotype was also accompanied by protein aggregates in cardiomyocytes, UPR alteration, accelerated autophagy and apoptosis. Thus, this mouse model may also offer additional insight into the pathogenesis of protein-aggregate-associated cardiomyopathies and represents a new candidate gene itself.

Effects of phosphate on vascular function under normal conditions and influence of the uraemic state

AIMS

Increased serum phosphorus levels are associated with cardiovascular disease in patients with chronic kidney disease (CKD) and in the general population. High phosphate levels may play a direct role in vascular dysfunction. We investigated here the effects of phosphate loading and of the phosphate binder sevelamer-HCl on vascular function.

METHODS AND RESULTS

CKD and non-CKD C57/BL6 mice were used to study the effects of CKD, phosphate, and sevelamer-HCl on vascular function and structure. In vitro, phosphate exhibited a direct vasoconstrictor effect on aortic rings. This effect was smaller in vessels from CKD than non-CKD mice and it was abolished by reactive oxygen species inhibitor dimethylthiourea. A high-phosphate diet (1.3%) increased phenylephrine-induced contraction and lowered acetylcholine-induced relaxation of aortic rings ex vivo, both in non-CKD and CKD mice. It also induced endothelial cell detachment. Sevelamer-HCl exposure in vitro normalized the endothelial dysfunction induced by 3.0 mM phosphate and restored endothelial integrity. Sevelamer-HCl treatment of CKD mice under normal diet (0.65% phosphate) improved the endothelial dysfunction, aortic systolic expansion rate, and pulse wave velocity, and it reduced the endothelial expression of adhesion molecules.

CONCLUSION

Changes in extracellular phosphorus concentrations may directly modulate vascular function and thereby modulate the vascular smooth muscle response to physiological or pathological stimuli in normal and CKD mice. Whether serum phosphorus lowering and/or dietary phosphate restriction can improve arterial function in humans remains to be established.

Adiponutrin functions as a nutritionally regulated lysophosphatidic acid acyltransferase

Numerous studies in humans link a nonsynonymous genetic polymorphism (I148M) in adiponutrin (ADPN) to various forms of fatty liver disease and liver cirrhosis. Despite its high clinical relevance, the molecular function of ADPN and the mechanism by which I148M variant affects hepatic metabolism are unclear. Here we show that ADPN promotes cellular lipid synthesis by converting lysophosphatidic acid (LPA) into phosphatidic acid. The ADPN-catalyzed LPA acyltransferase (LPAAT) reaction is specific for LPA and long-chain acyl-CoAs. Wild-type mice receiving a high-sucrose diet exhibit substantial upregulation of Adpn in the liver and a concomitant increase in LPAAT activity. In Adpn-deficient mice, this diet-induced increase in hepatic LPAAT activity is reduced. Notably, the I148M variant of human ADPN exhibits increased LPAAT activity leading to increased cellular lipid accumulation. This gain of function provides a plausible biochemical mechanism for the development of liver steatosis in subjects carrying the I148M variant.

Lactobacillus plantarum (VR1) isolated from an ayurvedic medicine (Kutajarista) ameliorates in vitro cellular damage caused by Aeromonas veronii

Background

Lactobacillus plantarum is considered as a safe and effective probiotic microorganism. Among various sources of isolation, traditionally fermented foods are considered to be rich in Lactobacillus spp., which can be exploited for their probiotic attribute. Antibacterial property of L. plantarum has been demonstrated against various enteric pathogens in both in vitro and in vivo systems. This study was aimed at characterizing L. plantarum isolated from Kutajarista, an ayurvedic fermented biomedicine, and assessing its antagonistic property against a common enteropathogen Aeromonas veronii.

Results

We report the isolation of L. plantarum (VR1) from Kutajarista, and efficacy of its cell free supernatant (CFS) in amelioration of cytotoxicity caused by Aeromonas veronii. On the part of probiotic attributes, VR1 was tolerant to pH 2, 0.3% bile salts and simulated gastric juice. Additionally, VR1 also exhibited adhesive property to human intestinal HT-29 cell line. Furthermore, CFS of VR1 was antibacterial to enteric pathogens like Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Aeromonas veronii and clinical isolates of P. aeruginosa and E. coli. Detailed study regarding the effect of VR1 CFS on A. veronii cytotoxicity showed a significant decrease in vacuole formation and detrimental cellular changes in Vero cells. On the other hand, A. veronii CFS caused disruption of tight junction proteins ZO-1 and actin in MDCK cell line, which was prevented by pre-incubation with CFS of VR1.

Conclusions

This is the first study to report isolation of L. plantarum (VR1) from Kutajarista and characterisation for its probiotic attributes. Our study demonstrates the antagonistic property of VR1 to A. veronii and effect of VR1 CFS in reduction of cellular damage caused by A. veronii in both Vero and MDCK cell lines.

Biochemical characterization of three putative ATPases from a new type IV secretion system of Aeromonas veronii plasmid pAC3249A

Background

Type four secretion systems (TFSS) are bacterial macromolecular transport systems responsible for transfer of various substrates such as proteins, DNA or protein-DNA complexes. TFSSs encode two or three ATPases generating energy for the secretion process. These enzymes exhibit highest sequence conservation among type four secretion components.

Results

Here, we report the biochemical characterization of three ATPases namely TraE, TraJ and TraK (VirB4, VirB11 and VirD4 homologs of the Agrobacterium tumefaciens transfer system, respectively) from the transfer system of Aeromonas veronii plasmid pAC3249A. ATPases were expressed as His-tag fusion proteins in E. coli and purified by affinity chromatography. ATP binding and ATP hydrolysis experiments were performed with the purified ATPases. TraE and TraK showed strong binding to TNP-ATP and TNP-CTP (fluorescent analogs of ATP and CTP respectively) whereas TraJ showed weak binding. The optimum temperature range for the three ATPases was between 42°C and 50°C. Highest ATP hydrolysis activity for all the ATPases was observed in the presence of Mg²⁺ and Mn²⁺. However, TraJ and TraK also showed activity in the presence of Co²⁺. TraJ exhibited the highest specific activity of all the three ATPases with v_max 118 ± 5.68 nmol/min/mg protein and K_M 0.58 ± 0.10 mM.

Conclusions

This is the first biochemical characterization of conjugative transport ATPases encoded by a conjugative plasmid from Aeromonas. Our study demonstrated that the three ATPases of a newly reported TFSS of A. veronii plasmid pAc3249A are functional in both ATP hydrolysis and ATP binding.

Analysis of mitochondrial DNA sequences in childhood encephalomyopathies reveals new disease-associated variants

Background

Mitochondrial encephalomyopathies are a heterogeneous group of clinical disorders generally caused due to mutations in either mitochondrial DNA (mtDNA) or nuclear genes encoding oxidative phosphorylation (OXPHOS). We analyzed the mtDNA sequences from a group of 23 pediatric patients with clinical and morphological features of mitochondrial encephalopathies and tried to establish a relationship of identified variants with the disease.

Methodology/Principle Findings

Complete mitochondrial genomes were amplified by PCR and sequenced by automated DNA sequencing. Sequencing data was analyzed by SeqScape software and also confirmed by BLASTn program. Nucleotide sequences were compared with the revised Cambridge reference sequence (CRS) and sequences present in mitochondrial databases. The data obtained shows that a number of known and novel mtDNA variants were associated with the disease. Most of the non-synonymous variants were heteroplasmic (A4136G, A9194G and T11916A) suggesting their possibility of being pathogenic in nature. Some of the missense variants although homoplasmic were showing changes in highly conserved amino acids (T3394C, T3866C, and G9804A) and were previously identified with diseased conditions. Similarly, two other variants found in tRNA genes (G5783A and C8309T) could alter the secondary structure of Cys-tRNA and Lys-tRNA. Most of the variants occurred in single cases; however, a few occurred in more than one case (e.g. G5783A and A10149T).

Conclusions and Significance

The mtDNA variants identified in this study could be the possible cause of mitochondrial encephalomyopathies with childhood onset in the patient group. Our study further strengthens the pathogenic score of known variants previously reported as provisionally pathogenic in mitochondrial diseases. The novel variants found in the present study can be potential candidates for further investigations to establish the relationship between their incidence and role in expressing the disease phenotype. This study will be useful in genetic diagnosis and counseling of mitochondrial diseases in India as well as worldwide.