Crucial Role of ROCK2-Mediated Phosphorylation and Upregulation of FHOD3 in the Pathogenesis of Angiotensin II-Induced Cardiac Hypertrophy

FHOD-1 and profilin protect sarcomeres against contraction-induced deformation> in C. elegans

Formin HOmology Domain 2-containing (FHOD) proteins are a subfamily of actin-organizing formins important for striated muscle development in many animals. We showed previously that absence of the sole FHOD protein, FHOD-1, from Caenorhabditis elegans results in thin body wall muscles with misshapen dense bodies that serve as sarcomere Z-lines. We demonstrate here that mutations predicted to specifically disrupt actin polymerization by FHOD-1 similarly disrupt muscle development, and that FHOD-1 cooperates with profilin PFN-3 for dense body morphogenesis, and with profilins PFN-2 and PFN-3 to promote body wall muscle growth. We further demonstrate that dense bodies in worms lacking FHOD-1 or PFN-2/PFN-3 are less stable than in wild-type animals, having a higher proportion of dynamic protein, and becoming distorted by prolonged muscle contraction. We also observe accumulation of actin and actin depolymerization factor/cofilin homologue UNC-60B in body wall muscle of these mutants. Such accumulations may indicate targeted disassembly of thin filaments dislodged from unstable dense bodies, possibly accounting for the abnormally slow growth and reduced body wall muscle strength in fhod-1 mutants. Overall, these results implicate FHOD protein-mediated actin assembly in forming stable sarcomere Z-lines, and identify profilin as a new contributor to FHOD activity in striated muscle development.

Formin-like 1β phosphorylation at S1086 is necessary for secretory polarized traffic of exosomes at the immune synapse in Jurkat T lymphocytes

We analyzed here how formin-like 1 β (FMNL1β), an actin cytoskeleton-regulatory protein, regulates microtubule-organizing center (MTOC) and multivesicular bodies (MVB) polarization and exosome secretion at an immune synapse (IS) model in a phosphorylation-dependent manner. IS formation was associated with transient recruitment of FMNL1β to the IS, which was independent of protein kinase C δ (PKCδ). Simultaneous RNA interference of all FMNL1 isoforms prevented MTOC/MVB polarization and exosome secretion, which were restored by FMNL1βWT expression. However, expression of the non-phosphorylatable mutant FMNL1βS1086A did not restore neither MTOC/MVB polarization nor exosome secretion to control levels, supporting the crucial role of S1086 phosphorylation in MTOC/MVB polarization and exosome secretion. In contrast, the phosphomimetic mutant, FMNL1βS1086D, restored MTOC/MVB polarization and exosome secretion. Conversely, FMNL1βS1086D mutant did not recover the deficient MTOC/MVB polarization occurring in PKCδ-interfered clones, indicating that S1086 FMNL1β phosphorylation alone is not sufficient for MTOC/MVB polarization and exosome secretion. FMNL1 interference inhibited the depletion of F-actin at the central region of the immune synapse (cIS), which is necessary for MTOC/MVB polarization. FMNL1βWT and FMNL1βS1086D, but not FMNL1βS1086A expression, restored F-actin depletion at the cIS. Thus, actin cytoskeleton reorganization at the IS underlies the effects of all these FMNL1β variants on polarized secretory traffic. FMNL1 was found in the IS made by primary T lymphocytes, both in T cell receptor (TCR) and chimeric antigen receptor (CAR)-evoked synapses. Taken together, these results point out a crucial role of S1086 phosphorylation in FMNL1β activation, leading to cortical actin reorganization and subsequent control of MTOC/MVB polarization and exosome secretion.

Methylation and phosphorylation of formin homology domain proteins (Fhod1 and Fhod3) by protein arginine methyltransferase 7 (PRMT7) and Rho kinase (ROCK1)

Protein post-translational modifications (PTMs) can regulate biological processes by altering an amino acid's bulkiness, charge, and hydrogen bonding interactions. Common modifications include phosphorylation, methylation, acetylation, and ubiquitylation. Although a primary focus of studying PTMs is understanding the effects of a single amino acid modification, the possibility of additional modifications increases the complexity. For example, substrate recognition motifs for arginine methyltransferases and some serine/threonine kinases overlap, leading to potential enzymatic crosstalk. In this study we have shown that the human family of formin homology domain-containing proteins (Fhods) contain a substrate recognition motif specific for human protein arginine methyltransferase 7 (PRMT7). In particular, PRMT7 methylates two arginine residues in the diaphanous autoinhibitory domain (DAD) of the family of Fhod proteins: R1588 and/or R1590 of Fhod3 isoform 4. Additionally, we confirmed that S1589 and S1595 in the DAD domain of Fhod3 can be phosphorylated by Rho/ROCK1 kinase. Significantly, we have determined that if S1589 is phosphorylated then PRMT7 cannot subsequently methylate R1588 or R1590. In contrast, if R1588 or R1590 of Fhod3 is methylated then ROCK1 phosphorylation activity is only slightly affected. Finally, we show that the interaction of the N-terminal DID domain can also inhibit the methylation of the DAD domain. Taken together these results suggest that the family of Fhod proteins, potential in vivo substrates for PRMT7, might be regulated by a combination of methylation and phosphorylation.

FHOD-1/profilin-mediated actin assembly protects sarcomeres against contraction-induced deformation in C. elegans

Formin HOmology Domain 2-containing (FHOD) proteins are a subfamily of actin-organizing formins important for striated muscle development in many animals. We showed previously that absence of the sole FHOD protein, FHOD-1, from C. elegans results in thin body-wall muscles with misshapen dense bodies that serve as sarcomere Z-lines. We demonstrate here that actin polymerization by FHOD-1 is required for its function in muscle development, and that FHOD-1 cooperates with profilin PFN-3 for dense body morphogenesis, and profilins PFN-2 and PFN-3 to promote body-wall muscle growth. We further demonstrate dense bodies in fhod-1 and pfn-3 mutants are less stable than in wild type animals, having a higher proportion of dynamic protein, and becoming distorted by prolonged muscle contraction. We also observe accumulation of actin depolymerization factor/cofilin homolog UNC-60B in body-wall muscle of these mutants. Such accumulations may indicate targeted disassembly of thin filaments dislodged from unstable dense bodies, and may account for the abnormally slow growth and reduced strength of body-wall muscle in fhod-1 mutants. Overall, these results show the importance of FHOD protein-mediated actin assembly to forming stable sarcomere Z-lines, and identify profilin as a new contributor to FHOD activity in striated muscle development.

Coptisine inhibits neointimal hyperplasia through attenuating Pak1/Pak2 signaling in vascular smooth muscle cells without retardation of re-endothelialization

BACKGROUND AND AIMS

Vascular injury-induced endothelium-denudation and profound vascular smooth muscle cells (VSMCs) proliferation and dis-regulated apoptosis lead to post-angioplasty restenosis. Coptisine (CTS), an isoquinoline alkaloid, has multiple beneficial effects on the cardiovascular system. Recent studies identified it selectively inhibits VSMCs proliferation. However, its effects on neointimal hyperplasia, re-endothelialization, and the underlying mechanisms are still unclear.

METHODS

Cell viability was assayed by 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and cell counting kit-8 (CCK-8). Cell proliferation and apoptosis were measured by flow cytometry and immunofluorescence of Ki67 and TUNEL. Quantitative phosphoproteomics (QPP) was employed to screen CTS-responsive phosphor-sites in the key regulators of cell proliferation and apoptosis. Neointimal hyperplasia was induced by balloon injury of rat left carotid artery (LCA). Adenoviral gene transfer was conducted in both cultured cells and LCA. Re-endothelialization was evaluated by Evan's blue staining of LCA.

RESULTS

1) CTS had strong anti-proliferative and pro-apoptotic effects in cultured rat VSMCs, with the EC50 4∼10-folds lower than that in endothelial cells (ECs). 2) Rats administered with CTS, either locally to LCA's periadventitial space or orally, demonstrated a potently inhibited balloon injury-induced neointimal hyperplasia, but had no delaying effect on re-endothelialization. 3) The QPP results revealed that the phosphorylation levels of Pak1S144/S203, Pak2S20/S197, Erk1T202/Y204, Erk2T185/Y187, and BadS136 were significantly decreased in VSMCs by CTS. 4) Adenoviral expression of phosphomimetic mutants Pak1D144/D203/Pak2D20/D197 enhanced Pak1/2 activities, stimulated the downstream pErk1T202/Y204/pErk2T185/Y187/pErk3S189/pBadS136, attenuated CTS-mediated inhibition of VSMCs proliferation and promotion of apoptosis in vitro, and potentiated neointimal hyperplasia in vivo. 5) Adenoviral expression of phosphoresistant mutants Pak1A144/A203/Pak2A20/A197 inactivated Pak1/2 and totally simulated the inhibitory effects of CTS on platelet-derived growth factor (PDGF)-stimulated VSMCs proliferation and PDGF-inhibited apoptosis in vitro and neointimal hyperplasia in vivo. 6) LCA injury significantly enhanced the endogenous phosphorylation levels of all but pBadS136. CTS markedly attenuated all the enhanced levels.

CONCLUSIONS

These results indicate that CTS is a promising medicine for prevention of post-angioplasty restenosis without adverse impact on re-endothelialization. CTS-directed suppression of pPak1S144/S203/pPak2S20/S197 and the subsequent effects on downstream pErk1T202/Y204/pErk2T185/Y187/pErk3S189 and pBadS136 underline its mechanisms of inhibition of VSMCs proliferation and stimulation of apoptosis. Therefore, the phosphor-sites of Pak1S144/S203/Pak2S20/S197 constitute a potential drug-screening target for fighting neointimal hyperplasia restenosis.

Transforming growth factor-β and bone morphogenetic protein signaling pathways in pathological cardiac hypertrophy

Pathological cardiac hypertrophy (referred to as cardiac hypertrophy) is a maladaptive response of the heart to a variety of pathological stimuli, and cardiac hypertrophy is an independent risk factor for heart failure and sudden death. Currently, the treatments for cardiac hypertrophy are limited to improving symptoms and have little effect. Elucidation of the developmental process of cardiac hypertrophy at the molecular level and the identification of new targets for the treatment of cardiac hypertrophy are crucial. In this review, we summarize the research on multiple active substances related to the pathogenesis of cardiac hypertrophy and the signaling pathways involved and focus on the role of transforming growth factor-β (TGF-β) and bone morphogenetic protein (BMP) signaling in the development of cardiac hypertrophy and the identification of potential targets for molecular intervention. We aim to identify important signaling molecules with clinical value and hope to help promote the precise treatment of cardiac hypertrophy and thus improve patient outcomes.

Novel signaling axis of FHOD1-RNF213-Col1α/Col3α in the pathogenesis of hypertension-induced tunica media thickening

Hypertension-induced tunica media thickening (TMT) is the most important fundamental for the subsequent complications like stroke and cardiovascular diseases. Pathogenically, TMT originates from both vascular smooth muscle cells (VSMCs) hypertrophy due to synthesizing more amount of intracellular contractile proteins and excess secretion of extracellular matrix. However, what key molecules are involved in the pathogenesis of TMT is unknown. We hypothesize that formin homology 2 domain-containing protein 1 (FHOD1), an amply expressed mediator for assembly of thin actin filament in VSMCs, is a key regulator for the pathogenesis of TMT. In this study, we found that FHOD1 expression and its phosphorylation/activation were both upregulated in the arteries of three kinds of hypertensive rats. Ang-II induced actin filament formation and hypertrophy through activation and upregulation of FHOD1 in VSMCs. Active FHOD1-mediated actin filament assembly and secretions of collagen-1α/collagen-3α played crucial roles in Ang-II-induced VSMCs hypertrophy in vitro and hypertensive TMT in vivo. Proteomics demonstrated that activated FL-FHOD1 or its C-terminal diaphanous-autoregulatory domain significantly upregulated RNF213 (ring finger protein 213), a 591-kDa cytosolic E3 ubiquitin ligase with its loss-of-functional mutations being a susceptibility gene for Moyamoya disease which has prominent tunica media thinning in both intracranial and systemic arteries. Mechanistically, activated FHOD1 upregulated its downstream effector RNF213 independently of its classical pathway of decreasing G-actin/F-actin ratio, transcription, and translation, but dependently on its C-terminus-mediated stabilization of RNF213 protein. FHOD1-RNF213 signaling dramatically promoted collagen-1α/collagen-3α syntheses in VSMCs. Our results discovered a novel signaling axis of FHOD1-RNF213-collagen-1α/collagen-3α and its key role in the pathogenesis of hypertensive TMT.

FHODs: Nuclear tethered formins for nuclear mechanotransduction

In this review, we discuss FHOD formins with a focus on recent studies that reveal a new role for them as critical links for nuclear mechanotransduction. The FHOD family in vertebrates comprises two structurally related proteins, FHOD1 and FHOD3. Their similar biochemical properties suggest overlapping and redundant functions. FHOD1 is widely expressed, FHOD3 less so, with highest expression in skeletal (FHOD1) and cardiac (FHOD3) muscle where specific splice isoforms are expressed. Unlike other formins, FHODs have strong F-actin bundling activity and relatively weak actin polymerization activity. These activities are regulated by phosphorylation by ROCK and Src kinases; bundling is additionally regulated by ERK1/2 kinases. FHODs are unique among formins in their association with the nuclear envelope through direct, high affinity binding to the outer nuclear membrane proteins nesprin-1G and nesprin-2G. Recent crystallographic structures reveal an interaction between a conserved motif in one of the spectrin repeats (SRs) of nesprin-1G/2G and a site adjacent to the regulatory domain in the amino terminus of FHODs. Nesprins are components of the LINC (linker of nucleoskeleton and cytoskeleton) complex that spans both nuclear membranes and mediates bidirectional transmission of mechanical forces between the nucleus and the cytoskeleton. FHODs interact near the actin-binding calponin homology (CH) domains of nesprin-1G/2G enabling a branched connection to actin filaments that presumably strengthens the interaction. At the cellular level, the tethering of FHODs to the outer nuclear membrane mechanically couples perinuclear actin arrays to the nucleus to move and position it in fibroblasts, cardiomyocytes, and potentially other cells. FHODs also function in adhesion maturation during cell migration and in the generation of sarcomeres, activities distant from the nucleus but that are still influenced by it. Human genetic studies have identified multiple FHOD3 variants linked to dilated and hypertrophic cardiomyopathies, with many mutations mapping to "hot spots" in FHOD3 domains. We discuss how FHOD1/3's role in reinforcing the LINC complex and connecting to perinuclear actin contributes to functions of mechanically active tissues such as striated muscle.

Detrimental Role of PDZ-RhoGEF in Pathological Cardiac Hypertrophy

BACKGROUND

Postsynaptic density 95/disk-large/ZO-1 Rho guanine nucleotide exchange factor (PDZ-RhoGEF, PRG) functions as a RhoGEF for activated Gα13 and transmits activation signals to downstream signaling pathways in various pathological processes. Although the prohypertrophic effect of activated Gα13 (guanine nucleotide binding protein alpha 13; a heterotrimeric G protein) is well-established, the role of PDZ-RhoGEF in pathological cardiac hypertrophy is still obscure.

METHODS

Genetically engineered mice and neonatal rat ventricular myocytes were generated to investigate the function of PRG in pathological myocardial hypertrophy. The prohypertrophic stimuli-induced alternations in the morphology and intracellular signaling were measured in myocardium and neonatal rat ventricular myocytes. Furthermore, multiple molecular methodologies were used to identify the precise molecular mechanisms underlying PDZ-RhoGEF function.

RESULTS

Increased PDZ-RhoGEF expression was documented in both hypertrophied hearts and neonatal rat ventricular myocytes. Upon prohypertrophic stimuli, the PDZ-RhoGEF-deficient hearts displayed alleviated cardiomyocyte enlargement and attenuated collagen deposition with improved cardiac function, whereas the adverse hypertrophic responses in hearts and neonatal rat ventricular myocytes were markedly exaggerated by PDZ-RhoGEF overexpression. Mechanistically, RhoA (ras homolog family member A)-dependent signaling pathways may function as the downstream effectors of PDZ-RhoGEF in hypertrophic remodeling, as confirmed by rescue experiments using a RhoA inhibitor and dominant-negative RhoA. Furthermore, PDZ-RhoGEF is associated with activated Gα13 and contributes to Gα13-mediated activation of RhoA-dependent signaling.

CONCLUSIONS

Our data provide the first evidence that PDZ-RhoGEF promotes pathological cardiac hypertrophy by linking activated Gα13 to RhoA-dependent signaling pathways. Therefore, PDZ-RhoGEF has the potential to be a diagnostic marker or therapeutic target for pathological cardiac hypertrophy.

Actin-Binding Proteins in Cardiac Hypertrophy

The heart reacts to a large number of pathological stimuli through cardiac hypertrophy, which finally can lead to heart failure. However, the molecular mechanisms of cardiac hypertrophy remain elusive. Actin participates in the formation of highly differentiated myofibrils under the regulation of actin-binding proteins (ABPs), which provides a structural basis for the contractile function and morphological change in cardiomyocytes. Previous studies have shown that the functional abnormality of ABPs can contribute to cardiac hypertrophy. Here, we review the function of various actin-binding proteins associated with the development of cardiac hypertrophy, which provides more references for the prevention and treatment of cardiomyopathy.

Formins in Human Disease

Almost 25 years have passed since a mutation of a formin gene, DIAPH1, was identified as being responsible for a human inherited disorder: a form of sensorineural hearing loss. Since then, our knowledge of the links between formins and disease has deepened considerably. Mutations of DIAPH1 and six other formin genes (DAAM2, DIAPH2, DIAPH3, FMN2, INF2 and FHOD3) have been identified as the genetic cause of a variety of inherited human disorders, including intellectual disability, renal disease, peripheral neuropathy, thrombocytopenia, primary ovarian insufficiency, hearing loss and cardiomyopathy. In addition, alterations in formin genes have been associated with a variety of pathological conditions, including developmental defects affecting the heart, nervous system and kidney, aging-related diseases, and cancer. This review summarizes the most recent discoveries about the involvement of formin alterations in monogenic disorders and other human pathological conditions, especially cancer, with which they have been associated. In vitro results and experiments in modified animal models are discussed. Finally, we outline the directions for future research in this field.

Genome-wide analysis of genetic diversity and artificial selection in Large White pigs in Russia

Breeding practices adopted at different farms are aimed at maximizing the profitability of pig farming. In this work, we have analyzed the genetic diversity of Large White pigs in Russia. We compared genomes of historic and modern Large White Russian breeds using 271 pig samples. We have identified 120 candidate regions associated with the differentiation of modern and historic pigs and analyzed genomic differences between the modern farms. The identified genes were associated with height, fitness, conformation, reproductive performance, and meat quality.

ROCK Inhibition as Potential Target for Treatment of Pulmonary Hypertension

Pulmonary hypertension (PH) is a cardiovascular disease caused by extensive vascular remodeling in the lungs, which ultimately leads to death in consequence of right ventricle (RV) failure. While current drugs for PH therapy address the sustained vasoconstriction, no agent effectively targets vascular cell proliferation and tissue inflammation. Rho-associated protein kinases (ROCKs) emerged in the last few decades as promising targets for PH therapy, since ROCK inhibitors demonstrated significant anti-remodeling and anti-inflammatory effects. In this review, current aspects of ROCK inhibition therapy are discussed in relation to the treatment of PH and RV dysfunction, from cell biology to preclinical and clinical studies.

Disruption of actin dynamics regulated by Rho effector mDia1 attenuates pressure overload-induced cardiac hypertrophic responses and exacerbates dysfunction

AIMS

Cardiac hypertrophy is a compensatory response to pressure overload, leading to heart failure. Recent studies have demonstrated that Rho is immediately activated in left ventricles after pressure overload and that Rho signalling plays crucial regulatory roles in actin cytoskeleton rearrangement during cardiac hypertrophic responses. However, the mechanisms by which Rho and its downstream proteins control actin dynamics during hypertrophic responses remain not fully understood. In this study, we identified the pivotal roles of mammalian homologue of Drosophila diaphanous (mDia) 1, a Rho-effector molecule, in pressure overload-induced ventricular hypertrophy.

METHODS AND RESULTS

Male wild-type (WT) and mDia1-knockout (mDia1KO) mice (10-12 weeks old) were subjected to a transverse aortic constriction (TAC) or sham operation. The heart weight/tibia length ratio, cardiomyocyte cross-sectional area, left ventricular wall thickness, and expression of hypertrophy-specific genes were significantly decreased in mDia1KO mice 3 weeks after TAC, and the mortality rate was higher at 12 weeks. Echocardiography indicated that mDia1 deletion increased the severity of heart failure 8 weeks after TAC. Importantly, we could not observe apparent defects in cardiac hypertrophic responses in mDia3-knockout mice. Microarray analysis revealed that mDia1 was involved in the induction of hypertrophy-related genes, including immediate early genes, in pressure overloaded hearts. Loss of mDia1 attenuated activation of the mechanotransduction pathway in TAC-operated mice hearts. We also found that mDia1 was involved in stretch-induced activation of the mechanotransduction pathway and gene expression of c-fos in neonatal rat ventricular cardiomyocytes (NRVMs). mDia1 regulated the filamentous/globular (F/G)-actin ratio in response to pressure overload in mice. Additionally, increases in nuclear myocardin-related transcription factors and serum response factor were perturbed in response to pressure overload in mDia1KO mice and to mechanical stretch in mDia1 depleted NRVMs.

CONCLUSION

mDia1, through actin dynamics, is involved in compensatory cardiac hypertrophy in response to pressure overload.

Piperlongumine attenuates angiotensin-II-induced cardiac hypertrophy and fibrosis by inhibiting Akt-FoxO1 signalling

BACKGROUND

Cardiac hypertrophy and fibrosis are closely related to cardiac dysfunction, especially diastolic dysfunction. Limited medications can be used to simultaneously delay cardiac hypertrophy and fibrosis in clinical practice. Piperlongumine (PLG) is an amide alkaloid extracted from Piper longum and has been shown to have multiple biological effects, including anticancer and antioxidant effects. However, the role of PLG in cardiac hypertrophy and fibrosis is not clear.

PURPOSE

The aim of this study was to reveal the role of PLG in cardiac hypertrophy and fibrosis and the associated mechanism.

METHODS

Cardiac hypertrophy and fibrosis were induced by angiotensin II (Ang II) in vivo and in vitro. The effect of PLG in vivo, in vitro and its mechanism were investigated by proliferation and apoptosis assays, western blot, real-time PCR, immunofluorescence, histochemistry, echocardiography, flow cytometry and chromatin immunoprecipitation.

RESULTS

Proliferation and apoptosis assays showed that 2.5 μM PLG slightly inhibited proliferation and did not promote apoptosis. Treatment with 5 mg/kg PLG obviously inhibited Ang II-induced cardiac hypertrophy and fibrosis in vivo. In vitro studies of neonatal rat cardiomyocytes (NRCMs) showed that the anti-hypertrophic effect of PLG was mediated by reducing the phosphorylation of Akt and thereby preserving the level of Forkhead box transcription factor O1 (FoxO1), since knockdown of FoxO1 by siRNA reversed the protective effect of PLG on NRCMs. In addition, PLG significantly decreased the Ang II-induced expression of profibrotic proteins in neonatal cardiac fibroblasts by reducing the expression of Krüppel-like factor 4 (KLF4) and the recruitment of KLF4 to the promoter regions of transforming growth factor-β and connective tissue growth factor.

CONCLUSION

We demonstrate the cardioprotective effects of PLG in both cardiac hypertrophy and fibrosis and the potential value of PLG for developing novel medications for pathological cardiac hypertrophy and heart failure.

FHOD formin and SRF promote post-embryonic striated muscle growth through separate pathways in C. elegans

Previous work with cultured cells has shown transcription of muscle genes by serum response factor (SRF) can be stimulated by actin polymerization driven by proteins of the formin family. However, it is not clear if endogenous formins similarly promote SRF-dependent transcription during muscle development in vivo. We tested whether formin activity promotes SRF-dependent transcription in striated muscle in the simple animal model, Caenorhabditis elegans. Our lab has shown FHOD-1 is the only formin that directly promotes sarcomere formation in the worm's striated muscle. We show here FHOD-1 and SRF homolog UNC-120 both support muscle growth and also muscle myosin II heavy chain A expression. However, while a hypomorphic unc-120 allele blunts expression of a set of striated muscle genes, these genes are largely upregulated or unchanged by absence of FHOD-1. Instead, pharmacological inhibition of the proteasome restores myosin protein levels in worms lacking FHOD-1, suggesting elevated proteolysis accounts for their myosin deficit. Interestingly, proteasome inhibition does not restore normal muscle growth to fhod-1(Δ) mutants, suggesting formin contributes to muscle growth by some alternative mechanism. Overall, we find SRF does not depend on formin to promote muscle gene transcription in a simple in vivo system.

FHOD3 promotes carcinogenesis by regulating RhoA/ROCK1/LIMK1 signaling pathway in medulloblastoma

PURPOSE

Medulloblastoma (MB) is a malignant brain disease in young children. The overall survival of MB patients is disappointing due to absence of effective therapeutics and this could be attributed to the lack of molecular mechanism underlying MB. FHOD3 was an important gene during cardio-genesis and was reported to promote cell migration in cancer. However, its role in MB is not clear to date.

METHODS

RT-qPCR and IHC analysis were used to determine expression of FHOD3. Survival curve was drawn by K-M analysis. FHOD3 was knocked down by RNAi technology. The effects of FHOD3 on medulloblastoma cells were determined by CCK-8 assay, colony formation assay, transwell assay and FACs analysis.

RESULTS

FHOD3 expression increased by 1.5 fold in tumor tissues compared to the control and IHC analysis further confirmed strong expression of FHOD3 in medulloblastoma tissues. Then higher FHOD3 expression was associated with shorter survival time in MB patients (13.0 months versus 43.8 months). In medulloblastoma cells such as Daoy and D283med, FHOD3 also displayed abundant expression. When FHOD3 was knocked down, the ability of cell proliferation and colony formation was reduced over greatly. The capability of cell migration and invasion was also inhibited significantly. However, cell apoptotic rate increased significantly reversely. Mechanistically, the phosphorylation level of RhoA, ROCK1, and LIMK1 was decreased when FHOD3 was knocked down but increased reversely when FHOD3 was over-expressed in Daoy cells.

CONCLUSIONS

FHOD3 was associated with overall survival time in medulloblastoma patients and was essential to cell proliferation, growth and survival in medulloblastoma and might regulates activation of RhoA/ROCK1/LIMK1 signaling pathway.

Glucagon-like peptide 1 reverses myocardial hypertrophy through cAMP/PKA/RhoA/ROCK2 signaling

Myocardial hypertrophy is a major pathological and physiological process during heart failure. Glucagon-like peptide 1 (GLP-1) is a glucagon incretin hormone released from the gut endocrine L-cells that has protective effects on various cardiovascular diseases, including hypertension, atherosclerosis, and myocardial hypertrophy. However, the protective mechanisms of GLP-1 in myocardial hypertrophy remain unclear. Here, we showed that the GLP-1 agonist liraglutide and dipeptidyl peptidase 4 inhibitor alogliptin decreased heart weight and cardiac muscle cell volume in spontaneously hypertensive rats (SHR). In H9C2 cell hypertensive models induced by angiotensin II, GLP-1 treatment reduced myocardial cell volume, inhibited the expressions of atrial natriuretic peptide, brain/B-type natriuretic peptide, β-myosin heavy chain, RhoA, and ROCK2, and decreased MLC and MYPT1 phosphorylation. When H9C2 cells were treated with H89, a PKA inhibitor, the inhibitory effect of GLP-1 disappeared, while the inhibitory role was enhanced under the treatment of Y-27632, a ROCK2 inhibitor. These results suggested that GLP-1 might reverse myocardial hypertrophy through the PKA/RhoA/ROCK2 signaling pathway.

Sexual dimorphism in cardiac transcriptome associated with a troponin C murine model of hypertrophic cardiomyopathy

Heart disease remains the number one killer of women in the US. Nonetheless, studies in women and female animal models continue to be underrepresented in cardiac research. Hypertrophic cardiomyopathy (HCM), the most commonly inherited cardiac disorder, has been tied to sarcomeric protein variants in both sexes. Among the susceptible genes, TNNC1-encoding cardiac troponin C (cTnC)-causes a substantial HCM phenotype in mice. Mice bearing an HCM-associated cTnC-A8V point mutation exhibited a significant decrease in stroke volume and left ventricular diameter and volume. Importantly, isovolumetric contraction time was significantly higher for female HCM mice. We utilized a transcriptomic approach to investigate the basis underlying the sexual dimorphism observed in the cardiac physiology of adult male and female HCM mice. RNA sequencing revealed several altered canonical pathways within the HCM mice versus WT groups including an increase in eukaryotic initiation factor 2 signaling, integrin-linked kinase signaling, actin nucleation by actin-related protein-Wiskott-Aldrich syndrome family protein complex, regulation of actin-based motility by Rho kinase, vitamin D receptor/retinoid X receptor activation, and glutathione redox reaction pathways. In contrast, valine degradation, tricarboxylic acid cycle II, methionine degradation, and inositol phosphate compound pathways were notably down-regulated in HCM mice. These down-regulated pathways may be reduced in response to altered energetics in the hypertrophied hearts and may represent conservation of energy as the heart is compensating to meet increased contractile demands. HCM male versus female mice followed similar trends of the canonical pathways altered between HCM and WT. In addition, seven of the differentially expressed genes in both WT and HCM male versus female comparisons swapped directions in fold-change between the sexes. These findings suggest a sexually-dimorphic HCM phenotype due to a sarcomeric mutation and pinpoint several key targetable pathways and genes that may provide the means to alleviate the more severe decline in female cardiac function.

The scaffold-protein IQGAP1 enhances and spatially restricts the actin-nucleating activity of Diaphanous-related formin 1 (DIAPH1)

The actin cytoskeleton is a dynamic array of filaments that undergoes rapid remodeling to drive many cellular processes. An essential feature of filament remodeling is the spatio-temporal regulation of actin filament nucleation. One family of actin filament nucleators, the Diaphanous-related formins, is activated by the binding of small G-proteins such as RhoA. However, RhoA only partially activates formins, suggesting that additional factors are required to fully activate the formin. Here we identify one such factor, IQ motif containing GTPase activating protein-1 (IQGAP1), which enhances RhoA-mediated activation of the Diaphanous-related formin (DIAPH1) and targets DIAPH1 to the plasma membrane. We find that the inhibitory intramolecular interaction within DIAPH1 is disrupted by the sequential binding of RhoA and IQGAP1. Binding of RhoA and IQGAP1 robustly stimulates DIAPH1-mediated actin filament nucleation in vitro In contrast, the actin capping protein Flightless-I, in conjunction with RhoA, only weakly stimulates DIAPH1 activity. IQGAP1, but not Flightless-I, is required to recruit DIAPH1 to the plasma membrane where actin filaments are generated. These results indicate that IQGAP1 enhances RhoA-mediated activation of DIAPH1 in vivo Collectively these data support a model where the combined action of RhoA and an enhancer ensures the spatio-temporal regulation of actin nucleation to stimulate robust and localized actin filament production in vivo.

Morphological and Functional Characteristics of Animal Models of Myocardial Fibrosis Induced by Pressure Overload

Myocardial fibrosis is characterized by excessive deposition of myocardial interstitial collagen, abnormal distribution, and excessive proliferation of fibroblasts. According to the researches in recent years, myocardial fibrosis, as the pathological basis of various cardiovascular diseases, has been proven to be a core determinant in ventricular remodeling. Pressure load is one of the causes of myocardial fibrosis. In experimental models of pressure-overload-induced myocardial fibrosis, significant increase in left ventricular parameters such as interventricular septal thickness and left ventricular posterior wall thickness and the decrease of ejection fraction are some of the manifestations of cardiac damage. These morphological and functional changes have a serious impact on the maintenance of physiological functions. Therefore, establishing a suitable myocardial fibrosis model is the basis of its pathogenesis research. This paper will discuss the methods of establishing myocardial fibrosis model and compare the advantages and disadvantages of the models in order to provide a strong basis for establishing a myocardial fibrosis model.

Targeting ROCK signaling in health, malignant and non-malignant diseases

A Rho-associated coiled-coil kinase (ROCK) is identified as a critical downstream effector of GTPase RhoA which contains two isoforms, ROCK1 (also known as p160ROCK and ROKβ) and ROCK2 (also known as Rho-kinase and ROKα), the gene of which is placed on chromosomes 18 (18q11.1) and 2 (2p24), respectively. ROCKs have a principal function in the generation of actin-myosin contractility and regulation of actin cytoskeleton dynamics. They represent a chief role in regulating various cellular functions, such as apoptosis, growth, migration, and metabolism through modulation of cytoskeletal actin synthesis, and cellular contraction through phosphorylation of numerous downstream targets. Emerging evidence has indicated that ROCKs present a significant function in cardiac physiology. Of note, dysregulation of ROCKs involves in several cardiac pathological processes like cardiac hypertrophy, cardiac fibrosis, systemic blood pressure disorder, and pulmonary hypertension. Moreover, ROCKs, in addition to their role in regulating renal arteriolar contraction, glomerular blood flow, and filtration, can also play a role in controlling podocytes, tubular cells, and mesangial cell structure and function. Hyperactivity disorder and over-gene expression of Rho/ROCK have been indicated in different cancers. Furthermore, it seems that increasing the expression of mRNA or ROCK protein has an undesirable effect on patient survival and has a positive impact on the progression and worsening of disease prognosis. This review focuses on the physiological and pathological functions of ROCKs with a particular view on its possible value of ROCK inhibitors as a new therapy in cancers and non-cancer diseases.

Huoxue Qianyang decoction ameliorates cardiac remodeling in obese spontaneously hypertensive rats in association with ATF6-CHOP endoplasmic reticulum stress signaling pathway regulation

OBJECTIVE

Endoplasmic reticulum (ER) stress is involved in hypertension related cardiac remodeling. We aimed to evaluate the effects of Huoxue Qianyang (HXQY) decoction on cardiac remodeling in obese spontaneously hypertensive rats (SHRs), and explore its impacts on the activating transcription factor 6 (ATF6)-C/EBP homologous protein (CHOP) ER stress signaling pathway.

METHODS

Twenty-seven obese SHRs were randomly divided into Obese SHR, Obese SHR + HXQY and Obese SHR + Valsartan groups, and treated with the indicated drugs for 8 weeks. Nine age-matched male SHRs were used as controls. Systolic blood pressure (SBP), body weight (BW), and the left ventricular mass index (LVMI) were measured weekly or at end point. Then, angiotensin II (Ang II), fasting glucose (FPG) and fasting insulin (FIN), total cholesterol (TC), LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C) and triglyceride (TG) levels were evaluated with commercial kits. Apoptotic cardiomyocytes were detected by the terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) method. The expression levels of GRP78, ATF6, PERK/pPERK and CHOP were assessed by quantitative PCR and Western blot.

RESULTS

Treatment with HXQY decoction resulted in significantly reduced SBP, BW, LVMI, Ang II, TC and LDL-C levels, as well as the homeostasis model assessment of insulin resistance (HOMA-IR) score in obese SHRs. Apoptosis in heart tissues of obese SHRs was significantly attenuated after HXQY decoction administration, paralleling reduced expression of GRP78, ATF6, PERK/pPERK and CHOP at both mRNA and protein levels.

CONCLUSION

Cardiac remodeling in obese SHRs is ameliorated by intervention with HXQY decoction in association with inhibited ATF6-CHOP ER stress signaling pathway.

Rock protein as cardiac hypertrophy modulator in obesity and physical exercise

Obesity and cardiovascular diseases are worldwide public health issues. In this review, we discussed the participation of ROCK protein in cardiac hypertrophy, mainly through the modulation of leptin and insulin signaling pathways. Leptin plays a role in cardiovascular disease development and, through the Rho-associated protein kinase (ROCK), promotes cardiac hypertrophy. ROCK protein, is regulated by small Rho-GTPases and has two isoforms with high homology. ROCK is able to activate the MAP kinase (MAPK) pathway and modulate insulin signaling in the heart, participating in cardiac hypertrophy development of concentric and eccentric left ventricle growth. Although different types of stimulus can lead to morphologically antagonistic heart growth, physical exercise promotes improvements in hemodynamic function, emerging as a promising non-pharmacological tool to improve overall health. Leptin can activate ROCK in a pathological way, increasing MAPK activity and decreasing insulin signaling via insulin receptor substrate 1 (IRS1) serine 307 residue phosphorylation, phosphatase and tensin homolog, and protein kinase Cβ2. In turn, physical exercise decreases leptin levels and positively modulates insulin signaling as well as increases ROCK-dependent IRS1 (Ser632/635) phosphorylation, improving phosphatidylinositol 3-kinase/protein kinase B axis and promoting physiologic heart growth. Currently, there is a lack of studies about differences in ROCK isoforms, especially during exercise and/or obesity. However, the understanding of its biological function and the complex mechanism underlying the distinct types of cardiac hypertrophy development can be a useful tool in the improvement and treatment of cardiovascular outcomes.

Vascular smooth muscle contraction in hypertension

Hypertension is a major risk factor for many common chronic diseases, such as heart failure, myocardial infarction, stroke, vascular dementia, and chronic kidney disease. Pathophysiological mechanisms contributing to the development of hypertension include increased vascular resistance, determined in large part by reduced vascular diameter due to increased vascular contraction and arterial remodelling. These processes are regulated by complex-interacting systems such as the renin-angiotensin-aldosterone system, sympathetic nervous system, immune activation, and oxidative stress, which influence vascular smooth muscle function. Vascular smooth muscle cells are highly plastic and in pathological conditions undergo phenotypic changes from a contractile to a proliferative state. Vascular smooth muscle contraction is triggered by an increase in intracellular free calcium concentration ([Ca²⁺]_i), promoting actin–myosin cross-bridge formation. Growing evidence indicates that contraction is also regulated by calcium-independent mechanisms involving RhoA-Rho kinase, protein Kinase C and mitogen-activated protein kinase signalling, reactive oxygen species, and reorganization of the actin cytoskeleton. Activation of immune/inflammatory pathways and non-coding RNAs are also emerging as important regulators of vascular function. Vascular smooth muscle cell [Ca²⁺]_i not only determines the contractile state but also influences activity of many calcium-dependent transcription factors and proteins thereby impacting the cellular phenotype and function. Perturbations in vascular smooth muscle cell signalling and altered function influence vascular reactivity and tone, important determinants of vascular resistance and blood pressure. Here, we discuss mechanisms regulating vascular reactivity and contraction in physiological and pathophysiological conditions and highlight some new advances in the field, focusing specifically on hypertension.

Fhod1, an actin-organizing formin family protein, is dispensable for cardiac development and function in mice

The formin family proteins have the ability to regulate actin filament assembly, thereby functioning in diverse cytoskeletal processes. Fhod3, a cardiac member of the family, plays a crucial role in development and functional maintenance of the heart. Although Fhod1, a protein closely-related to Fhod3, has been reported to be expressed in cardiomyocytes, the role of Fhod1 in the heart has still remained elusive. To know the physiological role of Fhod1 in the heart, we disrupted the Fhod1 gene in mice by replacement of exon 1 with a lacZ reporter gene. Histological lacZ staining unexpectedly revealed no detectable expression of Fhod1 in the heart, in contrast to intensive staining in the lung, a Fhod1-containing organ. Consistent with this, expression level of the Fhod1 protein in the heart was below the lower limit of detection of the present immunoblot analysis with three independent anti-Fhod1 antibodies. Homozygous Fhod1-null mice did not show any defects in gross and histological appearance of the heart or upregulate fetal cardiac genes that are induced under stress conditions. Furthermore, Fhod1 ablation did not elicit compensatory increase in expression of other formins. Thus, Fhod1 appears to be dispensable for normal development and function of the mouse heart, even if a marginal amount of Fhod1 is expressed in the heart.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

The renin-angiotensin-aldosterone system plays crucial roles in cardiovascular physiology and pathophysiology. However, many of the signaling mechanisms have been unclear. The angiotensin II (ANG II) type 1 receptor (AT₁R) is believed to mediate most functions of ANG II in the system. AT₁R utilizes various signal transduction cascades causing hypertension, cardiovascular remodeling, and end organ damage. Moreover, functional cross-talk between AT₁R signaling pathways and other signaling pathways have been recognized. Accumulating evidence reveals the complexity of ANG II signal transduction in pathophysiology of the vasculature, heart, kidney, and brain, as well as several pathophysiological features, including inflammation, metabolic dysfunction, and aging. In this review, we provide a comprehensive update of the ANG II receptor signaling events and their functional significances for potential translation into therapeutic strategies. AT₁R remains central to the system in mediating physiological and pathophysiological functions of ANG II, and participation of specific signaling pathways becomes much clearer. There are still certain limitations and many controversies, and several noteworthy new concepts require further support. However, it is expected that rigorous translational research of the ANG II signaling pathways including those in large animals and humans will contribute to establishing effective new therapies against various diseases.

Inhibition of BRD4 attenuates transverse aortic constriction- and TGF-β-induced endothelial-mesenchymal transition and cardiac fibrosis

Cardiac fibrosis (CF), a process characterized by potentiated proliferation of cardiac fibroblasts and excessive secretion and deposition of extracellular matrix (ECM) from the cells, contributes strongly to the pathogenesis of a series of cardiovascular (CV) diseases, including AMI, heart failure and atrial fibrillation. Endothelial-mesenchymal transition (EndMT), one of the sources of transformed cardiac fibroblasts, has been reported as a key factor involved in CF. However, the molecular basis of EndMT has not been thoroughly elucidated to date. At the posttranscriptional level, of the three epigenetic regulators, writer and eraser are reported to be involved in EndMT, but the role of reader in the process is still unknown. In this study, we aimed to explore the role of Bromodomain-containing protein 4 (BRD4), an acetyl-lysine reader protein, in EndMT-induced CF and related mechanisms. We found that BRD4 was upregulated in endothelial cells (ECs) in the pressure-overload mouse heart and that its functional inhibitor JQ1 potently attenuated the TAC-induced CF and preserved cardiac function. In umbilical vein endothelial cells (HUVECs) and mouse aortic endothelial cells (MAECs), bothJQ1 and shRNA-mediated silencing of BRD4 blocked TGF-β-induced EC migration, EndMT and ECM synthesis and preserved the EC sprouting behavior, possibly through the downregulation of a group of transcription factors specific for EndMT (Snail, Twist and Slug), the Smads pathway and TGF-β receptor I. In the absence of TGF-β stimulation, ectopic expression of BRD4 alone could facilitate EndMT, accelerate migration and increase the synthesis of ECM. In vivo, JQ1 also attenuated TAC-induced EndMT and CF, which was consistent with JQ1's intracellular mechanisms of action. Our results showed that BRD4 plays a critical role in EndMT-induced CF and that targeting BRD4 might be a novel therapeutic option for CF.

Estrogen receptor beta maintains expression of KLF15 to prevent cardiac myocyte hypertrophy in female rodents

Maintaining a healthy, anti-hypertrophic state in the heart prevents progression to cardiac failure. In humans, angiotensin II (AngII) indirectly and directly stimulates hypertrophy and progression, while estrogens acting through estrogen receptor beta (ERβ) inhibit these AngII actions. The KLF15 transcription factor has been purported to provide anti-hypertrophic action. In cultured neonatal rat cardiomyocytes, we found AngII inhibited KLF1 expression and nuclear localization, substantially prevented by estradiol (E2) or β-LGND2 (β-LGND2), an ERβ agonist. AngII stimulation of transforming growth factor beta expression in the myocytes activated p38α kinase via TAK1 kinase, inhibiting KLF15 expression. All was comparably reduced by E2 or β-LGND2. Knockdown of KLF15 in the myocytes induced myocyte hypertrophy and limited the anti-hypertrophic actions of E2 and β-LGND2. Key aspects were confirmed in an in-vivo model of cardiac hypertrophy. Our findings define additional anti-hypertrophic effects of ERβ supporting testing specific receptor agonists in humans to prevent progression of cardiac disease.

Rho kinase signaling and cardiac physiology

Rho kinases (ROCKs) are the first discovered RhoA effectors that are now widely known for their effects on actin organization. Recent studies have shown that ROCKs play important roles in cardiac physiology. Abnormal activation of ROCKs participate in multiple cardiovascular pathological processes, including cardiac hypertrophy, apoptosis, fibrosis, systemic hypertension, and pulmonary hypertension. ROCK inhibitors, fasudil and statins, have shown beneficial cardiovascular effects in many animal studies, clinical trials, and applications. Here, we mainly discuss the current understanding of the physiological roles of Rho kinase signaling in the heart, and briefly summarize the roles of ROCKs in cardiac-related vascular dysfunctions. We will also discuss the clinical application of ROCK inhibitors.

The actin-organizing formin protein Fhod3 is required for postnatal development and functional maintenance of the adult heart in mice

Cardiac development and function require actin-myosin interactions in the sarcomere, a highly organized contractile structure. Sarcomere assembly mediated by formin homology 2 domain-containing 3 (Fhod3), a member of formins that directs formation of straight actin filaments, is essential for embryonic cardiogenesis. However, the role of Fhod3 in the neonatal and adult stages has remained unknown. Here, we generated floxed Fhod3 mice to bypass the embryonic lethality of an Fhod3 knockout (KO). Perinatal KO of Fhod3 in the heart caused juvenile lethality at around day 10 after birth with enlarged hearts composed of severely impaired myofibrils, indicating that Fhod3 is crucial for postnatal heart development. Tamoxifen-induced conditional KO of Fhod3 in the adult heart neither led to lethal effects nor did it affect sarcomere structure and localization of sarcomere components. However, adult Fhod3-deleted mice exhibited a slight cardiomegaly and mild impairment of cardiac function, conditions that were sustained over 1 year without compensation during aging. In addition to these age-related changes, systemic stimulation with the α1-adrenergic receptor agonist phenylephrine, which induces sustained hypertension and hypertrophy development, induced expression of fetal cardiac genes that was more pronounced in adult Fhod3-deleted mice than in the control mice, suggesting that Fhod3 modulates hypertrophic changes in the adult heart. We conclude that Fhod3 plays a crucial role in both postnatal cardiac development and functional maintenance of the adult heart.