Calcium/calmodulin-dependent protein kinase II binds to Raf-1 and modulates integrin-stimulated ERK activation

Theaflavin 3'-gallate activates G protein-coupled receptor 55 (GPR55) and enhances GLP-1 secretion via Ca2+/CaMKII/ERK signaling in enteroendocrine STC-1 cells, mitigating postprandial hyperglycemia in mice

The antihyperglycemic effect of black tea is well-known, and theaflavins (TFs) are considered active compounds. It is, however, unclear whether glucagon-like peptide-1 (GLP-1) is involved in the antihyperglycemic effects of TFs. We demonstrate that TFs suppress postprandial hyperglycemia by stimulating GLP-1 secretion in mice. In STC-1 cells, theaflavin 3'-gallate (TF2B), possessing a galloyl group at the 3'-position, showed the strongest effect on GLP-1 secretion among the four TFs. TF2B activated G protein-coupled receptor 55 (GPR55) and was confirmed to bind to the receptor, notably exhibiting the highest binding affinity. Moreover, GPR55 antagonist canceled TF2B-induced GLP-1 secretion. Downstream, TF2B increased intracellular Ca2+ levels and activated the Ca2+/calmodulin-dependent protein kinase II (CaMKII) and extracellular signal-regulated kinases 1/2 (ERK1/2) pathways. Inhibitors of Ca2+ signaling, CaMKII, and ERK pathways abolished TF2B-stimulated GLP-1 secretion. These findings suggest that TF2B from black tea prevents hyperglycemia through GPR55-dependent stimulation of GLP-1 secretion via Ca2+-Ca2+/CaMKII and ERK1/2 pathways.

The effects of Cheonwangbosim-dan, a traditional herbal medicine prescription, on scopolamine-induced cognitive dysfunction in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Cheonwangbosim-dan (CWBSD) as a traditional herbal medicine prescription has been used for cognitive dysfunction in terms of heart blood deficiency, however, there were few researches for cognitive dysfunction and its mode of action.

AIM OF THE STUDY

This study was aimed to examine the effects of CWBSD on hypocholinergic-induced memory impaired mice and unveil its mechanism of action on cognitive function.

MATERIALS AND METHODS

The standardized CWBSD was used in the present study. Several behavioral tests, including Y-maze task, the Morris water maze task (MWM), novel object recognition test (NORT) and passive avoidance test (PAT), were employed with administration of CWBSD (150, 500 or 1500 mg/kg) in scopolamine-treated mice. After behavioral tests, the mice were sacrificed and the Western blot analysis and electrophysiological analysis were conducted to investigate the mechanism of CWBSD on ameliorating cognitive function.

RESULTS

The administration of CWBSD improved cognitive functions measured by the Y-maze task, MWM, NORT and PAT in scopolamine-induced cognitive impaired mice. This memory improvement effect was associated with the activation of protein kinase C zeta (PKCζ)/calcium-calmodulin-dependent protein kinase Ⅱ (CaMKⅡ)-extracellular signal-regulated kinase (ERK)-cAMP response element-binding protein (CREB)-brain-derived neurotropic factor (BDNF) pathway via N-methyl-D-aspartate receptor subtype 2B (NR2B), and the activation of this pathway increased long-term potentiation in the brain of mice.

CONCLUSION

The administration of CWBSD could ameliorate spatial memory, recognition memory and long-term memory, and such ameliorating activities would be derived from the activation of NMDA receptor-associated pathway with increase of LTP in the brain. These results suggests that CWBSD would be a candidate for a new dementia treatment.

Lurcher Mouse as a Model of Cerebellar Syndromes

Cerebellar extinction lesions can manifest themselves with cerebellar motor and cerebellar cognitive affective syndromes. For investigation of the functions of the cerebellum and the pathogenesis of cerebellar diseases, particularly hereditary neurodegenerative cerebellar ataxias, various cerebellar mutant mice are used. The Lurcher mouse is a model of selective olivocerebellar degeneration with early onset and rapid progress. These mice show both motor deficits as well as cognitive and behavioral changes i.e., pathological phenotype in the functional domains affected in cerebellar patients. Therefore, Lurcher mice might be considered as a tool to investigate the mechanisms of functional impairments caused by cerebellar degenerative diseases. There are, however, limitations due to the particular features of the neurodegenerative process and a lack of possibilities to examine some processes in mice. The main advantage of Lurcher mice would be the expected absence of significant neuropathologies outside the olivocerebellar system that modify the complex behavioral phenotype in less selective models. However, detailed examinations and further thorough validation of the model are needed to verify this assumption.

Synapse-to-Nucleus ERK→CREB Transcriptional Signaling Requires Dendrite-to-Soma Ca2+ Propagation Mediated by L-Type Voltage-Gated Ca2+ Channels

The cAMP-response element-binding protein (CREB) transcription factor controls the expression of the neuronal immediate early genes c-fos, Arc, and Bdnf and is essential for long-lasting synaptic plasticity underlying learning and memory. Despite this critical role, there is still ongoing debate regarding the synaptic excitation-transcription (E-T) coupling mechanisms mediating CREB activation in the nucleus. Here we employed optical uncaging of glutamate to mimic synaptic excitation of distal dendrites in conjunction with simultaneous imaging of intracellular Ca2+ dynamics and transcriptional reporter gene expression to elucidate CREB E-T coupling mechanisms in hippocampal neurons cultured from both male and female rats. Using this approach, we found that CREB-dependent transcription was engaged following dendritic stimulation of N-methyl-d-aspartate receptors (NMDARs) only when Ca2+ signals propagated to the soma via subsequent activation of L-type voltage-gated Ca2+ channels resulting in activation of extracellular signal-regulated kinase MAP kinase signaling to sustain CREB phosphorylation in the nucleus. In contrast, dendrite-restricted Ca2+ signals generated by NMDARs failed to stimulate CREB-dependent transcription. Furthermore, Ca2+-CaM-dependent kinase-mediated signaling pathways that may transiently contribute to CREB phosphorylation following stimulation were ultimately dispensable for downstream CREB-dependent transcription and c-Fos induction. These findings emphasize the essential role that L-type Ca2+ channels play in rapidly relaying signals over long distances from synapses located on distal dendrites to the nucleus to control gene expression.

Activity-Dependent Internalization of Glun2B-Containing NMDARs Is Required for Synaptic Incorporation of Glun2A and Synaptic Plasticity

NMDA-type glutamate receptors are heterotetrameric complexes composed of two GluN1 and two GluN2 subunits. The precise composition of the GluN2 subunits determines the channel's biophysical properties and influences its interaction with postsynaptic scaffolding proteins and signaling molecules involved in synaptic physiology and plasticity. The precise regulation of NMDAR subunit composition at synapses is crucial for proper synaptogenesis, neuronal circuit development, and synaptic plasticity, a cellular model of memory formation. In the forebrain during early development, NMDARs contain solely the GluN2B subunit, which is necessary for proper synaptogenesis and synaptic plasticity. In rodents, GluN2A subunit expression begins in the second postnatal week, replacing GluN2B-containing NMDARs at synapses in an activity- or sensory experience-dependent process. This switch in NMDAR subunit composition at synapses alters channel properties and reduces synaptic plasticity. The molecular mechanism regulating the switch remains unclear. We have investigated the role of activity-dependent internalization of GluN2B-containing receptors in shaping synaptic NMDAR subunit composition. Using molecular, pharmacological, and electrophysiological approaches in cultured organotypic hippocampal slices from rats of both sexes, we show that the process of incorporating GluN2A-containing NMDAR receptors requires activity-dependent internalization of GluN2B-containing NMDARs. Interestingly, blockade of GluN2A synaptic incorporation was associated with impaired potentiation of AMPA-mediated synaptic transmission, suggesting a potential coupling between the trafficking of AMPARs into synapses and that of GluN2A-containing NMDARs. These insights contribute to our understanding of the molecular mechanisms underlying synaptic trafficking of glutamate receptors and synaptic plasticity. They may also have implications for therapeutic strategies targeting NMDAR function in neurological disorders.

Purinergic Ca2+ signaling as a novel mechanism of drug tolerance in BRAF mutant melanoma

Drug tolerance is a major cause of relapse after cancer treatment. In spite of intensive efforts1-9, its molecular basis remains poorly understood, hampering actionable intervention. We report a previously unrecognized signaling mechanism supporting drug tolerance in BRAF-mutant melanoma treated with BRAF inhibitors that could be of general relevance to other cancers. Its key features are cell-intrinsic intracellular Ca2+ signaling initiated by P2X7 receptors (purinergic ligand-gated cation channels), and an enhanced ability for these Ca2+ signals to reactivate ERK1/2 in the drug-tolerant state. Extracellular ATP, virtually ubiquitous in living systems, is the ligand that can initiate Ca2+ spikes via P2X7 channels. ATP is abundant in the tumor microenvironment and is released by dying cells, ironically implicating treatment-initiated cancer cell death as a source of trophic stimuli that leads to ERK reactivation and drug tolerance. Such a mechanism immediately offers an explanation of the inevitable relapse after BRAFi treatment in BRAF-mutant melanoma, and points to actionable strategies to overcome it.

Human dental pulp stem cells derived extracellular matrix promotes mineralization via Hippo and Wnt pathways

Extracellular matrix (ECM) is an intricate structure providing the microenvironment niche that influences stem cell differentiation. This study aimed to investigate the efficacy of decellularized ECM derived from human dental pulp stem cells (dECM_DPSCs) and gingival-derived mesenchymal stem cells (dECM_GSCs) as an inductive scaffold for osteogenic differentiation of GSCs. The proteomic analysis demonstrated that common and signature matrisome proteins from dECM_DPSCs and dECM_GSCs were related to osteogenesis/osteogenic differentiation. RNA sequencing data from GSCs reseeded on dECM_DPSCs revealed that dECM_DPSCs upregulated genes related to the Hippo and Wnt signaling pathways in GSCs. In the inhibitor experiments, results revealed that dECM_DPSCs superiorly promoted GSCs osteogenic differentiation, mainly mediated through Hippo and Wnt signaling. The present study emphasizes the promising translational application of dECM_DPSCs as a bio-scaffold rich in favorable regenerative microenvironment for tissue engineering.

Sfrp2 promotes renal dysfunction of diabetic kidney disease via modulating Fzd5-induced cytosolic calcium ion concentration and CaMKII/Mek/Erk pathway in mesangial cells

OBJECTIVE

Mesangial cells (MCs) in the kidney play central role in maintaining glomerular integrity, and their abnormal proliferation leads to major glomerular diseases including diabetic kidney disease (DKD). Although high blood glucose elicits MCs impairment, the underlying molecular mechanism is poorly understood. The present study aimed to investigate the effect of secreted frizzled-related protein 2 (Sfrp2) from single-nucleus RNA profiling on MC proliferation of DKD in vitro and in vivo and explored the specific mechanisms.

RESULTS

By snRNA-seq analysis of isolated renal cells from leptin receptor-deficient db/db mice and control db/m mice, we found that Sfrp2 was increased in the MCs of DKD in comparison to other intrinsic renal cells, which was further verified in vitro and in vivo. We also found that the expression of Sfrp2 was significantly upregulated in DKD patients and correlated with renal function, demonstrating that Sfrp2 might serve as an independent biomarker for DKD patients. Functionally, we showed the loss and acquisition of Sfrp2 affected cytosolic Ca2+ concentration, cell proliferation and fibrosis of MC, albuminuria and kidney injury in vitro and in vivo. Mechanistically, we identify c-Jun as a transcription factor of Sfrp2 promoting its transcription, and the Ca2+ signaling related protein frizzled receptor 5 (Fzd5) as the binding protein of Sfrp2. And we further found Sfrp2 promoted Fzd5-induced cytosolic Ca2+ concentration and the downstream CaMKII/Mek/Erk pathway activation, leading to MC proliferation and fibrosis in DKD.

CONCLUSION

Our study revealed a novel involvement for Sfrp2 in the regulation of MC function and the effect of Sfrp2 on cell proliferation and fibrosis of MC via the Fzd5/Ca2+/CaMKII/Mek/Erk pathway, implying that Sfrp2 may be a possible biomarker and therapeutic target for DKD.

C-terminus of PIEZO1 governs Ca2+ influx and intracellular ERK1/2 signaling pathway in mechanotransduction

Cells sense and respond to extracellular mechanical stress through mechanotransduction receptors and ion channels, which regulate cellular behaviors such as cell proliferation and differentiation. Among them, PIEZO1, piezo-type mechanosensitive ion channel component 1, has recently been highlighted as a mechanosensitive ion channel in various cell types including mesenchymal stem cells. We previously reported that PIEZO1 is essential for ERK1/2 phosphorylation and osteoblast differentiation in bone marrow-derived mesenchymal stem cells (BMSCs), induced by hydrostatic pressure loading and treatment with the PIEZO1-specific activator Yoda1. However, the molecular mechanism underlying how PIEZO1 induces mechanotransduction remains unclear. In this study, we investigated that the role of the C-terminus in regulating extracellular Ca2+ influx and activating the ERK1/2 signaling pathway. We observed the activation of Fluo-4 AM in the Yoda1-stimulated human BMSC line UE7T-13, but not in a calcium-depleted cell culture medium. Similarly, Western blotting analysis revealed that Yoda1 treatment induced ERK1/2 phosphorylation, but this induction was not observed in calcium-depleted cell culture medium. To investigate the functional role of the C-terminus of PIEZO1, we generated HEK293 cells stably expressing the full-length mouse PIEZO1 (PIEZO1-FL) and a deletion-type PIEZO1 lacking the C-terminal intracellular region containing the R-Ras-binding domain (PIEZO1-ΔR-Ras). We found that Yoda1 treatment predominantly activated Flou-4 AM and ERK1/2 in PIEZO1-FL-trasfected cells but neither in PIEZO1-ΔR-Ras-transfected cells nor control cells. Our results indicate that the C-terminus of PIEZO1, which contains the R-Ras binding domain, plays an essential role in Ca2+ influx and activation of the ERK1/2 signaling pathway, suggesting that this domain is crucial for the mechanotransduction of osteoblastic differentiation in BMSCs.

Uterine WNTS modulates fibronectin binding activity required for blastocyst attachment through the WNT/CA2+ signaling pathway in mice

Adhesion of the implanting blastocyst involves the interaction between integrin proteins expressed by trophoblast cells and components present in the basement membrane of the endometrial luminal epithelium. Although several factors regulating integrins and their adhesion to fibronectin are already known, we showed that Wnt signaling is involved in the regulation of blastocyst adhesion through the trafficking of integrins expressed by trophoblast cells. Localization of Itgα5β1 by immunofluorescence and FN-binding assays were conducted on peri-implantation blastocysts treated with either Wnt5a or Wnt7a proteins. Both Wnt5a and Wnt7a induced a translocation of Itgα5β1 at the surface of the blastocyst and an increase in FN-binding activity. We further demonstrated that uterine fluid is capable of inducing integrin translocation and this activity can be specifically inhibited by the Wnt inhibitor sFRP2. To identify the Wnt signaling pathway involved in this activity, blastocysts were incubated with inhibitors of either p38MAPK, PI3K pathway or CamKII prior to the addition of Wnts. Whereas inhibition of p38MAPK and PI3K had not effect, inhibition of CamKII reduced FN-binding activity induced by Wnts. Finally, we demonstrated that inhibition of Wnts by sFRP2 reduced the binding efficiency of the blastocyst to uterine epithelial cells. Our findings provide new insight into the mechanism that regulates integrin trafficking and FN-binding activity and identifies Wnts as a key player in blastocyst attachment to the uterine epithelium.

ERK1/2-Dependent Phosphorylation of GABAB1(S867/T872), Controlled by CaMKIIβ, Is Required for GABAB Receptor Degradation under Physiological and Pathological Conditions

GABAB receptor-mediated inhibition is indispensable for maintaining a healthy neuronal excitation/inhibition balance. Many neurological diseases are associated with a disturbed excitation/inhibition balance and downregulation of GABAB receptors due to enhanced sorting of the receptors to lysosomal degradation. A key event triggering the downregulation of the receptors is the phosphorylation of S867 in the GABAB1 subunit mediated by CaMKIIβ. Interestingly, close to S867 in GABAB1 exists another phosphorylation site, T872. Therefore, the question arose as to whether phosphorylation of T872 is involved in downregulating the receptors and whether phosphorylation of this site is also mediated by CaMKIIβ or by another protein kinase. Here, we show that mutational inactivation of T872 in GABAB1 prevented the degradation of the receptors in cultured neurons. We found that, in addition to CaMKIIβ, also ERK1/2 is involved in the degradation pathway of GABAB receptors under physiological and ischemic conditions. In contrast to our previous view, CaMKIIβ does not appear to directly phosphorylate S867. Instead, the data support a mechanism in which CaMKIIβ activates ERK1/2, which then phosphorylates S867 and T872 in GABAB1. Blocking ERK activity after subjecting neurons to ischemic stress completely restored downregulated GABAB receptor expression to normal levels. Thus, preventing ERK1/2-mediated phosphorylation of S867/T872 in GABAB1 is an opportunity to inhibit the pathological downregulation of the receptors after ischemic stress and is expected to restore a healthy neuronal excitation/inhibition balance.

Remodeling of the focal adhesion complex by hydrogen-peroxide-induced senescence

Cellular senescence is a phenotype characterized by cessation of cell division, which can be caused by exhaustive replication or environmental stress. It is involved in age-related pathophysiological conditions and affects both the cellular cytoskeleton and the prime cellular mechanosensors, focal adhesion complexes. While the size of focal adhesions increases during senescence, it is unknown if and how this is accompanied by a remodeling of the internal focal adhesion structure. Our study uses metal-induced energy transfer to study the axial dimension of focal adhesion proteins from oxidative-stress-induced senescent cells with nanometer precision, and compares these to unstressed cells. We influenced cytoskeletal tension and the functioning of mechanosensitive ion channels using drugs and studied the combined effect of senescence and drug intervention on the focal adhesion structure. We found that H2O2-induced restructuring of the focal adhesion complex indicates a loss of tension and altered talin complexation. Mass spectroscopy-based proteomics confirmed the differential regulation of several cytoskeletal proteins induced by H2O2 treatment.

Chromosome-Level Assembly of Male Opsariichthys bidens Genome Provides Insights into the Regulation of the GnRH Signaling Pathway and Genome Evolution

The hook snout carp Opsariichthys bidens is an important farmed fish in East Asia that shows sexual dimorphism in growth, with males growing faster and larger than females. To understand these complex traits and improve molecular breeding, chromosome-level genome assembly of male O. bidens was performed using Illumina, Nanopore, and Hi-C sequencing. The 992.9 Mb genome sequences with a contig N50 of 5.2 Mb were anchored to 38 chromosomes corresponding to male karyotypes. Of 30,922 functionally annotated genes, 97.5% of BUSCO genes were completely detected. Genome evolution analysis showed that the expanded and contracted gene families in the male O. bidens genome were enriched in 76 KEGG pathways, and 78 expanded genes were involved in the GnRH signaling pathway that regulates the synthesis and secretion of luteinizing hormone and glycoprotein hormones, further acting on male growth by inducing growth hormone. Compared to the released female O. bidens genome, the number of annotated genes in males was much higher (23,992). The male chromosome LG06 exhibited over 97% identity with the female GH14/GH38. Male-specific genes were identified for LG06, where structural variation, including deletions and insertions, occurred at a lower rate, suggesting a centric fusion of acrocentric chromosomes GH14 and GH38. The genome-synteny analysis uncovered significant inter-chromosome conservation between male O. bidens and grass carp, the former originating from ancestral chromosome breakage to increase the chromosome number. Our results provide a valuable genetic resource for studying the regulation of sexual dimorphism, sex-determining mechanisms, and molecular-guided breeding of O. bidens.

Study of the Mechanism of Antiemetic Effect of Lavandula angustifolia Mill. Essential Oil Based on Ca2+/CaMKII/ERK1/2 Pathway

Purpose

To investigate the effective components and possible mechanism of action of Lavandula angustifolia Mill. essential oil (LEO) in preventing vomiting through the olfactory pathway.

Materials and Methods

A new network pharmacology-based method was established to analyze main components and pathways of LEO involved in antiemetic effects by introducing component content; biological activities of key proteins of the olfactory pathway and their corresponding compounds were verified by molecular docking technique; and finally pica in a rat model was established to verify the molecular mechanism of antiemetic effects of LEO by enzyme-linked immunosorbent assay (ELISA) to determine the serum 5-HT, substance P, and DA levels in each group and by immunohistochemistry to determine the contents of 5-HT3R, CaMKII and ERK1/2 proteins in the medulla oblongata tissue.

Results

Network pharmacology combined with molecular docking analysis showed that the mechanism of the antiemetic effect of LEO may be related to (2Z)-3,7-dimethyl-2,6-octadienyl acetate, linalyl acetate, butanoic acid, hexyl ester, 4-hexen-1-ol, 5-methyl-2-(1-methylethenyl)-, acetate, .tau.-cadinol and other active ingredients, which regulate the cyclic adenosine monophosphate (cAMP) signaling pathway and the expression of BRAF, PDE and other targets on the pathway. An ELISA revealed that LEO reduced the levels of 5-hydroxytryptamine (5-HT), substance P, and dopamine in serum compared with the model group (P <0.05). Immunohistochemical analysis showed that LEO decreased the expression of 5-HT3R, CaMKII, and ERK1/2 proteins in the medulla oblongata of rats compared with the model group (P <0.01).

Conclusion

LEO may achieve the antiemetic effect by reducing the content of 5-HT and inhibiting its related receptors, thereby regulating downstream Ca2+/CaMKII/ERK1/2 pathway of the cAMP signaling pathway.

Tumor suppressor p53 restrains cancer cell dissemination by modulating mitochondrial dynamics

Tumor suppressor p53 plays a central role in preventing tumorigenesis. Here, we unravel how p53 modulates mitochondrial dynamics to restrain the metastatic properties of cancer cells. p53 inhibits the mammalian target of rapamycin complex 1 (mTORC1) signaling to attenuate the protein level of mitochondrial fission process 1 (MTFP1), which fosters the pro-fission dynamin-related protein 1 (Drp1) phosphorylation. This regulatory mechanism allows p53 to restrict cell migration and invasion governed by Drp1-mediated mitochondrial fission. Downregulating p53 expression or elevating the molecular signature of mitochondrial fission correlates with aggressive tumor phenotypes and poor prognosis in cancer patients. Upon p53 loss, exaggerated mitochondrial fragmentation stimulates the activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling resulting in epithelial-to-mesenchymal transition (EMT)-like changes in cell morphology, accompanied by accelerated matrix metalloproteinase 9 (MMP9) expression and invasive cell migration. Notably, blocking the activation of mTORC1/MTFP1/Drp1/ERK1/2 axis completely abolishes the p53 deficiency-driven cellular morphological switch, MMP9 expression, and cancer cell dissemination. Our findings unveil a hitherto unrecognized mitochondria-dependent molecular mechanism underlying the metastatic phenotypes of p53-compromised cancers.

Calcium channel blockers potentiate gemcitabine chemotherapy in pancreatic cancer

There is currently no effective treatment for pancreatic ductal adenocarcinoma (PDAC). While palliative chemotherapy offers a survival benefit to most patients, nearly all will eventually progress on treatment and long-term survivability remains poor. Given the lack of subsequent line treatment options, in this study, we sought to identify novel strategies to prevent, delay, or overcome resistance to gemcitabine, one of the most widely used medications in PDAC. Using a combination of single-cell RNA sequencing and high-throughput proteomic analysis, we identified a subset of gemcitabine-resistant tumor cells enriched for calcium/calmodulin signaling. Pharmacologic inhibition of calcium-dependent calmodulin activation led to the rapid loss of drug-resistant phenotypes in vitro, which additional single-cell RNA sequencing identified was due to impaired activation of the RAS/ERK signaling pathway. Consistent with these observations, calcium chelation or depletion of calcium in the culture media also impaired ERK activation in gemcitabine-resistant cells, and restored therapeutic responses to gemcitabine in vitro. We observed similar results using calcium channel blockers (CCBs) such as amlodipine, which inhibited prosurvival ERK signaling in vitro and markedly enhanced therapeutic responses to gemcitabine in both orthotopic xenografts and transgenic models of PDAC. Combined, these results offer insight into a potential means of gemcitabine resistance and suggest that select CCBs may provide a clinical benefit to PDAC patients receiving gemcitabine-based chemotherapy.

Trans-cinnamaldehyde protects against phenylephrine-induced cardiomyocyte hypertrophy through the CaMKII/ERK pathway

BACKGROUND

Trans-cinnamaldehyde (TCA) is one of the main pharmaceutical ingredients of Cinnamomum cassia Presl, which has been shown to have therapeutic effects on a variety of cardiovascular diseases. This study was carried out to characterize and reveal the underlying mechanisms of the protective effects of TCA against cardiac hypertrophy.

METHODS

We used phenylephrine (PE) to induce cardiac hypertrophy and treated with TCA in vivo and in vitro. In neonatal rat cardiomyocytes (NRCMs), RNA sequencing and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were carried out to identify potential pathways of TCA. Then, the phosphorylation and nuclear localization of calcium/calmodulin-dependent protein kinase II (CaMKII) and extracellular signal-related kinase (ERK) were detected. In adult mouse cardiomyocytes (AMCMs), calcium transients, calcium sparks, sarcomere shortening and the phosphorylation of several key proteins for calcium handling were evaluated. For mouse in vivo experiments, cardiac hypertrophy was evaluated by assessing morphological changes, echocardiographic parameters, and the expression of hypertrophic genes and proteins.

RESULTS

TCA suppressed PE-induced cardiac hypertrophy and the phosphorylation and nuclear localization of CaMKII and ERK in NRCMs. Our data also demonstrate that TCA blocked the hyperphosphorylation of ryanodine receptor type 2 (RyR2) and phospholamban (PLN) and restored Ca2+ handling and sarcomere shortening in AMCMs. Moreover, our data revealed that TCA alleviated PE-induced cardiac hypertrophy in adult mice and downregulated the phosphorylation of CaMKII and ERK.

CONCLUSION

TCA has a protective effect against PE-induced cardiac hypertrophy that may be associated with the inhibition of the CaMKII/ERK pathway.

Circadian Regulation of Retinal Pigment Epithelium Function

The retinal pigment epithelium (RPE) is a single layer of cells located between the choriocapillaris vessels and the light-sensitive photoreceptors in the outer retina. The RPE performs physiological processes necessary for the maintenance and support of photoreceptors and visual function. Among the many functions performed by the RPE, the timing of the peak in phagocytic activity by the RPE of the photoreceptor outer segments that occurs 1-2 h. after the onset of light has captured the interest of many investigators and has thus been intensively studied. Several studies have shown that this burst in phagocytic activity by the RPE is under circadian control and is present in nocturnal and diurnal species and rod and cone photoreceptors. Previous investigations have demonstrated that a functional circadian clock exists within multiple retinal cell types and RPE cells. However, the anatomical location of the circadian controlling this activity is not clear. Experimental evidence indicates that the circadian clock, melatonin, dopamine, and integrin signaling play a key role in controlling this rhythm. A series of very recent studies report that the circadian clock in the RPE controls the daily peak in phagocytic activity. However, the loss of the burst in phagocytic activity after light onset does not result in photoreceptor or RPE deterioration during aging. In the current review, we summarized the current knowledge on the mechanism controlling this phenomenon and the physiological role of this peak.

Calcium/calmodulin-dependent kinases can regulate the TSH expression in the rat pituitary

PURPOSE

The endocrine secretion of TSH is a finely orchestrated process controlled by the thyrotropin-releasing hormone (TRH). Its homeostasis and signaling rely on many calcium-binding proteins belonging to the "EF-hand" protein family. The Ca²⁺/calmodulin (CaM) complex is associated with Ca²⁺/CaM-dependent kinases (Ca²⁺/CaMK). We have investigated Ca²⁺/CaMK expression and regulation in the rat pituitary.

METHODS

The expression of CaMKII and CaMKIV in rat anterior pituitary cells was shown by immunohistochemistry. Cultured anterior pituitary cells were stimulated by TRH in the presence and absence of KN93, the pharmacological inhibitor of CaMKII and CaMKIV. Western blotting was then used to measure the expression of these kinases and of the cAMP response element-binding protein (CREB). TSH production was measured by RIA after time-dependent stimulation with TRH. Cells were infected with a lentiviral construct coding for CaMKIV followed by measurement of CREB phosphorylation and TSH.

RESULTS

Our study shows that two CaM kinases, CaMKII and CaMKII, are expressed in rat pituitary cells and their phosphorylation in response to TRH occurs at different time points, with CaMKIV being activated earlier than CaMKII. TRH induces CREB phosphorylation through the activity of both CaMKII and CaMKIV. The activation of CREB increases TSH gene expression. CaMKIV induces CREB phosphorylation while its dominant negative and KN93 exert the opposite effects.

CONCLUSION

Our data indicate that the expression of Ca²⁺/CaMK in rat anterior pituitary are correlated to the role of CREB in the genetic regulation of TSH, and that TRH stimulation activates CaMKIV, which in turn phosphorylates CREB. This phosphorylation is linked to the production of thyrotropin.

Signaling Pathways in Proton and Non-proton ASIC1a Activation

Acid-sensing ion channels (ASICs) regulate synaptic activities and play important roles in neurodegenerative diseases as well as pain conditions. Classically, ASICs are described as transiently activated by a reduced pH, followed by desensitization; the activation allows sodium influx, and in the case of ASIC1a-composed channels, also calcium to some degree. Several factors are emerging and extensively analyzed as modulators, activating, inhibiting, and potentiating specific channel subunits. However, the signaling pathways triggered by channel activation are only starting to be revealed.The channel has been recently shown to be activated through a mechanism other than proton-mediated. Indeed, the large extracellular loop of these channels opens the possibility that other non-proton ligands might exist. One such molecule discovered was a toxin present in the Texas coral snake venom. The finding was associated with the activation of the channel at neutral pH via the toxin and causing intense and unremitting pain.By using different pharmacological tools, we analyzed the downstream signaling pathway triggered either by the proton and non-proton activation for human, mouse, and rat ASIC1a-composed channels in in vitro models. We show that for all species analyzed, the non-protonic mode of activation determines the activation of the ERK signaling cascade at a higher level and duration compared to the proton mode.This study adds to the growing evidence of the important role ASIC1a channels play in different physiological and pathological conditions and also hints at a possible pathological mechanism for a sustained effect.

Interleukin 1 beta-induced calcium signaling via TRPA1 channels promotes mitogen-activated protein kinase-dependent mesangial cell proliferation

Glomerular mesangial cell (GMC)-derived pleiotropic cytokine, interleukin-1 (IL-1), contributes to hypercellularity in human and experimental proliferative glomerulonephritis. IL-1 promotes mesangial proliferation and may stimulate extracellular matrix accumulation, mechanisms of which are unclear. The present study shows that the beta isoform of IL-1 (IL-1β) is a potent inducer of IL-1 type I receptor-dependent Ca²⁺ entry in mouse GMCs. We also demonstrate that the transient receptor potential ankyrin 1 (TRPA1) is an intracellular store-independent diacylglycerol-sensitive Ca²⁺ channel in the cells. IL-1β-induced Ca²⁺ and Ba²⁺ influxes in the cells were negated by pharmacological inhibition and siRNA-mediated knockdown of TRPA1 channels. IL-1β did not stimulate fibronectin production in cultured mouse GMCs and glomerular explants but promoted Ca²⁺ -dependent cell proliferation. IL-1β also stimulated TRPA1-dependent ERK mitogen-activated protein kinase (MAPK) phosphorylation in the cells. Concomitantly, IL-1β-induced GMC proliferation was attenuated by TRPA1 and RAF1/ MEK/ERK inhibitors. These findings suggest that IL-1β-induced Ca²⁺ entry via TRPA1 channels engenders MAPK-dependent mesangial cell proliferation. Hence, TRPA1-mediated Ca²⁺ signaling could be of pathological significance in proliferative glomerulonephritis.

In vivo proteomic mapping through GFP-directed proximity-dependent biotin labelling in zebrafish

Protein interaction networks are crucial for complex cellular processes. However, the elucidation of protein interactions occurring within highly specialised cells and tissues is challenging. Here, we describe the development, and application, of a new method for proximity-dependent biotin labelling in whole zebrafish. Using a conditionally stabilised GFP-binding nanobody to target a biotin ligase to GFP-labelled proteins of interest, we show tissue-specific proteomic profiling using existing GFP-tagged transgenic zebrafish lines. We demonstrate the applicability of this approach, termed BLITZ (Biotin Labelling In Tagged Zebrafish), in diverse cell types such as neurons and vascular endothelial cells. We applied this methodology to identify interactors of caveolar coat protein, cavins, in skeletal muscle. Using this system, we defined specific interaction networks within in vivo muscle cells for the closely related but functionally distinct Cavin4 and Cavin1 proteins.

Context-specific network modeling identifies new crosstalk in β-adrenergic cardiac hypertrophy

Cardiac hypertrophy is a context-dependent phenomenon wherein a myriad of biochemical and biomechanical factors regulate myocardial growth through a complex large-scale signaling network. Although numerous studies have investigated hypertrophic signaling pathways, less is known about hypertrophy signaling as a whole network and how this network acts in a context-dependent manner. Here, we developed a systematic approach, CLASSED (Context-specific Logic-bASed Signaling nEtwork Development), to revise a large-scale signaling model based on context-specific data and identify main reactions and new crosstalks regulating context-specific response. CLASSED involves four sequential stages with an automated validation module as a core which builds a logic-based ODE model from the interaction graph and outputs the model validation percent. The context-specific model is developed by estimation of default parameters, classified qualitative validation, hybrid Morris-Sobol global sensitivity analysis, and discovery of missing context-dependent crosstalks. Applying this pipeline to our prior-knowledge hypertrophy network with context-specific data revealed key signaling reactions which distinctly regulate cell response to isoproterenol, phenylephrine, angiotensin II and stretch. Furthermore, with CLASSED we developed a context-specific model of β-adrenergic cardiac hypertrophy. The model predicted new crosstalks between calcium/calmodulin-dependent pathways and upstream signaling of Ras in the ISO-specific context. Experiments in cardiomyocytes validated the model’s predictions on the role of CaMKII-Gβγ and CaN-Gβγ interactions in mediating hypertrophic signals in ISO-specific context and revealed a difference in the phosphorylation magnitude and translocation of ERK1/2 between cardiac myocytes and fibroblasts. CLASSED is a systematic approach for developing context-specific large-scale signaling networks, yielding insights into new-found crosstalks in β-adrenergic cardiac hypertrophy.

Pathological cardiac hypertrophy is a disease in which the heart grows abnormally in response to different motivators such as high blood pressure or variations in hormones and growth factors. The shape of the heart after its growth depends on the context in which it grows. Since cell signaling in the cardiac cells plays a key role in the determination of heart shape, a thorough understanding of cardiac cells signaling in each context enlightens the mechanisms which control response of cardiac cells. However, cell signaling in cardiac hypertrophy comprises a complex web of pathways with numerous interactions, and predicting how these interactions control the hypertrophic signal in each context is not achievable by only experiments or general computational models. To address this need, we developed an approach to bring together the experimental data of each context with a signaling network curated from literature to identify the main players of cardiac cells response in each context and attain the context-specific models of cardiac hypertrophy. By utilizing our approach, we identified the main regulators of cardiac hypertrophy in four important contexts. We developed a network model of β-adrenergic cardiac hypertrophy, and predicted and validated new interactions that regulate cardiac cells response in this context.

NADPH oxidase in the vasculature: Expression, regulation and signalling pathways; role in normal cardiovascular physiology and its dysregulation in hypertension

The last 20-25 years have seen an explosion of interest in the role of NADPH oxidase (NOX) in cardiovascular function and disease. In vascular smooth muscle and endothelium, NOX generates reactive oxygen species (ROS) that act as second messengers, contributing to the control of normal vascular function. NOX activity is altered in response to a variety of stimuli, including G-protein coupled receptor agonists, growth-factors, perfusion pressure, flow and hypoxia. NOX-derived ROS are involved in smooth muscle constriction, endothelium-dependent relaxation and smooth muscle growth, proliferation and migration, thus contributing to the fine-tuning of blood flow, arterial wall thickness and vascular resistance. Through reversible oxidative modification of target proteins, ROS regulate the activity of protein tyrosine phosphatases, kinases, G proteins, ion channels, cytoskeletal proteins and transcription factors. There is now considerable, but somewhat contradictory evidence that NOX contributes to the pathogenesis of hypertension through oxidative stress. Specific NOX isoforms have been implicated in endothelial dysfunction, hyper-contractility and vascular remodelling in various animal models of hypertension, pulmonary hypertension and pulmonary arterial hypertension, but also have potential protective effects, particularly NOX4. This review explores the multiplicity of NOX function in the healthy vasculature and the evidence for and against targeting NOX for antihypertensive therapy.

Trace amine-associated receptor 1 (TAAR1) promotes anti-diabetic signaling in insulin-secreting cells

Pancreatic β-cell failure in type 2 diabetes mellitus is a serious challenge that results in an inability of the pancreas to produce sufficient insulin to properly regulate blood glucose levels. Trace amine-associated receptor 1 (TAAR1) is a G protein-coupled receptor expressed by β-cells that has recently been proposed as a potential target for improving glycemic control and suppressing binge eating behaviors. We discovered that TAAR1 is coupled to Gα_s-signaling pathways in insulin-secreting β-cells to cause protein kinase A (PKA)/exchange protein activated by cAMP (Epac)-dependent release of insulin, activation of RAF proto-oncogene, Ser/Thr kinase (Raf)-mitogen-activated protein kinase (MAPK) signaling, induction of cAMP response element-binding protein (CREB)-insulin receptor substrate 2 (Irs-2), and increased β-cell proliferation. Interestingly, TAAR1 triggered cAMP-mediated calcium influx and release from internal stores, both of which were required for activation of a MAPK cascade utilizing calmodulin-dependent protein kinase II (CaMKII), Raf, and MAPK/ERK kinase 1/2 (MEK1/2). Together, these data identify TAAR1/Gα_s-mediated signaling pathways that promote insulin secretion, improved β-cell function and proliferation, and highlight TAAR1 as a promising new target for improving β-cell health in type 2 diabetes mellitus.

Intracellular emetic signaling cascades by which the selective neurokinin type 1 receptor (NK1R) agonist GR73632 evokes vomiting in the least shrew (Cryptotis parva)

To characterize mechanisms involved in neurokinin type 1 receptor (NK₁R)-mediated emesis, we investigated the brainstem emetic signaling pathways following treating least shrews with the selective NK₁R agonist GR73632. In addition to episodes of vomiting over a 30-min observation period, a significant increase in substance P-immunoreactivity in the emetic brainstem dorsal motor nucleus of the vagus (DMNX) occurred at 15 min post an intraperitoneal (i.p.) injection GR73632 (5 mg/kg). In addition, time-dependent upregulation of phosphorylation of several emesis -associated protein kinases occurred in the brainstem. In fact, Western blots demonstrated significant phosphorylations of Ca²⁺/calmodulin kinase IIα (CaMKIIα), extracellular signal-regulated protein kinase1/2 (ERK1/2), protein kinase B (Akt) as well as α and βII isoforms of protein kinase C (PKCα/βII). Moreover, enhanced phospho-ERK1/2 immunoreactivity was also observed in both brainstem slices containing the dorsal vagal complex emetic nuclei as well as in jejunal sections from the shrew small intestine. Furthermore, our behavioral findings demonstrated that the following agents suppressed vomiting evoked by GR73632 in a dose-dependent manner: i) the NK₁R antagonist netupitant (i.p.); ii) the L-type Ca²⁺ channel (LTCC) antagonist nifedipine (subcutaneous, s.c.); iii) the inositol trisphosphate receptor (IP₃R) antagonist 2-APB (i.p.); iv) store-operated Ca²⁺ entry inhibitors YM-58483 and MRS-1845, (i.p.); v) the ERK1/2 pathway inhibitor U0126 (i.p.); vi) the PKC inhibitor GF109203X (i.p.); and vii) the inhibitor of phosphatidylinositol 3-kinase (PI3K)-Akt pathway LY294002 (i.p.). Moreover, NK₁R, LTCC, and IP₃R are required for GR73632-evoked CaMKIIα, ERK1/2, Akt and PKCα/βII phosphorylation. In addition, evoked ERK1/2 phosphorylation was sensitive to inhibitors of PKC and PI3K. These findings indicate that the LTCC/IP₃R-dependent PI3K/PKCα/βII-ERK1/2 signaling pathways are involved in NK₁R-mediated vomiting.

Memantine attenuated alcohol withdrawal-induced anxiety-like behaviors through down-regulating NR1-CaMKII-ERK signaling pathway

Alcohol abuse and anxiety disorders often occur concurrently, but their underlying cellular mechanisms remain unclear. N-methyl-D-aspartic acid receptors (NMDARs) have recently received attention from those interested in the neurobiology of anxiety. A chronic alcohol exposure rat model (28 consecutive days of 20% alcohol intake and 6 h of withdrawal) was established. Here, we investigated the NMDAR1 (NR1), Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) and extracellular signal-regulated kinases (ERK) pathway in the modulation of anxiety-like behaviors in rats exposed to an open field and elevated plus maze (EPM) through systematic injections of memantine (a NMDAR inhibitor). We found that the NR1-CaMKII-ERK signaling pathway was activated after alcohol withdrawal in medial prefrontal cortex (mPFC) and nucleus accumbens shell (NAcSh) but not core (NAcC). Memantine treatment greatly ameliorated anxiety-like behavior in the rats experiencing alcohol withdrawal. Moreover, memantine uniformly suppressed the phosphorylation of NR1-CaMKII-ERK pathway induced by alcohol withdrawal. Our results suggest that activation of the NR1-CaMKII-ERK pathway in the mPFC and NAcSh is an important contributor to the molecular mechanisms underlying alcohol withdrawal-induced anxiety behaviors. NMDAR signaling pathway inhibitors are thus potential therapeutics for treating alcohol abuse.

A Putative Mechanism of Age-Related Synaptic Dysfunction Based on the Impact of IGF-1 Receptor Signaling on Synaptic CaMKIIα Phosphorylation

Insulin-like growth factor 1 receptor (IGF-1R) signaling regulates the activity and phosphorylation of downstream kinases linked to inflammation, neurodevelopment, aging and synaptic function. In addition to the control of Ca2+ currents, IGF-1R signaling modulates the activity of calcium-calmodulin-dependent kinase 2 alpha (CaMKIIα) and mitogen activated protein kinase (MAPK/ErK) through multiple signaling pathways. These proteins (CaMKIIα and MAPK) regulate Ca2+ movement and long-term potentiation (LTP). Since IGF-1R controls the synaptic activity of Ca2+, CaMKIIα and MAPK signaling, the possible mechanism through which an age-dependent change in IGF-1R can alter the synaptic expression and phosphorylation of these proteins in aging needs to be investigated. In this study, we evaluated the relationship between an age-dependent change in brain IGF-1R and phosphorylation of CaMKIIα/MAPK. Furthermore, we elucidated possible mechanisms through which dysregulated CaMKIIα/MAPK interaction may be linked to a change in neurotransmitter processing and synaptic function. Male C57BL/6 VGAT-Venus mice at postnatal days 80 (P80), 365 and 730 were used to study age-related neural changes in two brain regions associated with cognitive function: hippocampus and prefrontal cortex (PFC). By means of high throughput confocal imaging and quantitative immunoblotting, we evaluated the distribution and expression of IGF-1, IGF-1R, CaMKIIα, p-CaMKIIα, MAPK and p-MAPK in whole brain lysate, hippocampus and cortex. Furthermore, we compared protein expression patterns and regional changes at P80, P365 and P730. Ultimately, we determined the relative phosphorylation pattern of CaMKIIα and MAPK through quantification of neural p-CaMKIIα and p-MAPK/ErK, and IGF-1R expression for P80, P365 and P730 brain samples. In addition to a change in synaptic function, our results show a decrease in neural IGF-1/IGF-1R expression in whole brain, hippocampus and cortex of aged mice. This was associated with a significant upregulation of phosphorylated neural MAPK (p-MAPK) and decrease in total brain CaMKIIα (i.e., CaMKIIα and p-CaMKIIα) in the aged brain. Taken together, we showed that brain aging is associated with a change in neural IGF-1/IGF-1R expression and may be linked to a change in phosphorylation of synaptic kinases (CaMKIIα and MAPK) that are involved in the modulation of LTP.

The extracellular matrix protein EMILIN1 silences the RAS-ERK pathway via α4β1 integrin and decreases tumor cell growth

The extracellular matrix plays a fundamental role in physiological and pathological proliferation. It exerts its function through a signal cascade starting from the integrins that take direct contact with matrix constituents most of which behave as pro-proliferative clues. On the contrary, EMILIN1, a glycoprotein interacting with the α4β1 integrin through its gC1q domain, plays a paradigmatic anti-proliferative role. Here, we demonstrate that the EMILIN1-α4 interaction de-activates the MAPK pathway through HRas. Epithelial cells expressing endogenous α4 integrin and persistently plated on gC1q inhibited pERK1/2 increasing HRasGTP and especially the HRasGTP ubiquitinated form (HRasGTP-Ub). The drug salirasib reversed this effect. In addition, only the gC1q-ligated α4 integrin chain co-immunoprecipitated the ubiquitinated HRas. Only epithelial cells transfected with the wild type form of the α4 integrin chain showed the EMILIN1/α4β1/HRas/pERK1/2 link, whereas cells transfected with a α4 integrin chain carrying a truncated cytoplasmic tail had no effect. In this study we unveiled the pathway activated by the gC1q domain of EMILIN1 through α4β1 integrin engagement and leading to the decrease of proliferation in an epithelial system.

Calreticulin promotes EGF-induced EMT in pancreatic cancer cells via Integrin/EGFR-ERK/MAPK signaling pathway

Our previous study showed that Calreticulin (CRT) promoted the development of pancreatic cancer (PC) through ERK/MAPK pathway. We next investigate whether CRT promotes EGF-induced epithelial-mesenchymal transition (EMT) in PC via Integrin/EGFR-ERK/MAPK signaling, which has not been reported yet to our knowledge. EGF simultaneously induced EMT and activated Integrin/EGFR-ERK/MAPK signaling pathway in 3 PC cells. However, CRT silencing significantly inhibited EGF function, including inhibiting EGF-induced EMT-like cell morphology, EGF-enhanced cell invasion and migration, and EGF induced the decrease of E-cadherin, ZO-1, and β-catenin and the increase of the key proteins in Integrin/EGFR-ERK/MAPK signaling (pEGFR-tyr1173, Fibronectin, Integrinβ1, c-Myc and pERK). Conversely, CRT overexpression rescued the change of EMT-related proteins induced by EGF in CRT silencing PC cells. Additionally, CRT was co-stained with pEGFR1173 (with EGF), Fibronectin and Integrinβ1 by IF under confocal microscopy and was co-immunoprecipitated with Fibronectin, Integrinβ1 and c-Myc in both PC cells, all of which indicating a close interaction of CRT with Integrin/EGFR-ERK/MAPK signaling pathway in PC. In vivo, CRT silencing inhibited subcutaneous tumor growth and liver metastasis of pancreatic tumor. A positive relationship of CRT with Fibronectin, Integrinβ1, c-Myc and pERK and a negative association of CRT with E-cad was also observed in vivo and clinical samples. Meanwhile, overexpression of the above proteins was closely associated with multiple aggressive clinicopathological characteristics and the poor prognosis of PC patients. CRT promotes EGF-induced EMT in PC cells via Integrin/EGFR-ERK/MAPK signaling pathway, which would be a promising therapy target for PC.

Ranolazine promotes muscle differentiation and reduces oxidative stress in C2C12 skeletal muscle cells

PURPOSE

The purpose of this study is to investigate Ranolazine action on skeletal muscle differentiation and mitochondrial oxidative phenomena. Ranolazine, an antianginal drug, which acts blocking the late INaL current, was shown to lower hemoglobin A1c in patients with diabetes. In the present study, we hypothesized an action of Ranolazine on skeletal muscle cells regeneration and oxidative process, leading to a reduction of insulin resistance.

METHODS

10 μM Ranolazine was added to C2C12 murine myoblastic cells during proliferation, differentiation and newly formed myotubes.

RESULTS

Ranolazine promoted the development of a specific myogenic phenotype: increasing the expression of myogenic regulator factors and inhibiting cell cycle progression factor (p21). Ranolazine stimulated calcium signaling (calmodulin-dependent kinases) and reduced reactive oxygen species levels. Furthermore, Ranolazine maintained mitochondrial homeostasis. During the differentiation phase, Ranolazine promoted myotubes formation. Ranolazine did not modify kinases involved in skeletal muscle differentiation and glucose uptake (extracellular signal-regulated kinases 1/2 and AKT pathways), but activated calcium signaling pathways. During proliferation, Ranolazine did not modify the number of mitochondria while decreasing osteopontin protein levels. Lastly, neo-formed myotubes treated with Ranolazine showed typical hypertrophic phenotype.

CONCLUSION

In conclusion, our results indicate that Ranolazine stimulates myogenesis and reduces a pro-oxidant inflammation/oxidative condition, activating a calcium signaling pathway. These newly described mechanisms may partially explain the glucose lowering effect of the drug.

Overexpression of stathmin plays a pivotal role in the metastasis of esophageal squamous cell carcinoma

Purpose

Esophageal squamous cell carcinoma (ESCC) is a serious malignant tumor that affects human health. We analyzed the correlation between serum stathmin level and ESCC and elucidated the molecular mechanisms of stathmin's promotion of ESCC cell invasion and metastasis.

Methods

Stathmin level in ESCC and healthy control serum were detected by enzyme-linked immunosorbent assay (ELISA), and the clinical parameters were analyzed. We established ESCC cells with stathmin overexpression or knockdown and then evaluated the effects of stathmin on invasion and metastasis in ESCC. Differentially expressed genes were analyzed by Human Transcriptome Array and confirmed by RT-PCR. The expression levels of the integrin family, focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK) were detected by immunoblotting.

Results

Serum levels of stathmin were significantly higher in ESCC than in control serum and associated with lymph node metastasis, tumor stage and size. Furthermore, we found that stathmin promoted migration and invasion of ESCC cells in vitro and in vivo. In addition, we confirmed that the activation of the integrinα5β1/FAK/ERK pathway is increased in stathmin-overexpression cells and accelerates cell motility by enhancing cell adhesion ability.

Conclusion

Stathmin may predict a potential metastasis biomarker for ESCC.

Retinoschisin is linked to retinal Na/K-ATPase signaling and localization

Retinoschisin binds to the extracellular domain of Na/K-ATPase subunit β2. Retinoschisin inhibits Na/K-ATPase–associated signaling cascades and affects Na/K-ATPase localization. The retinoschisin-Na/K-ATPase complex overlaps with signaling mediators. Defective Na/K-ATPase signaling by retinoschisin deficiency may promote retinal dystrophy.

Mutations in the RS1 gene cause X-linked juvenile retinoschisis (XLRS), a hereditary retinal dystrophy. We recently showed that retinoschisin, the protein encoded by RS1, regulates ERK signaling and apoptosis in retinal cells. In this study, we explored an influence of retinoschisin on the functionality of the Na/K-ATPase, its interaction partner at retinal plasma membranes. We show that retinoschisin binding requires the β2-subunit of the Na/K-ATPase, whereas the α-subunit is exchangeable. Our investigations revealed no effect of retinoschisin on Na/K-ATPase–mediated ATP hydrolysis and ion transport. However, we identified an influence of retinoschisin on Na/K-ATPase–regulated signaling cascades and Na/K-ATPase localization. In addition to the known ERK deactivation, retinoschisin treatment of retinoschisin-deficient (Rs1h^-/Y) murine retinal explants decreased activation of Src, an initial transmitter in Na/K-ATPase signal transduction, and of Ca²⁺ signaling marker Camk2. Immunohistochemistry on murine retinae revealed an overlap of the retinoschisin–Na/K-ATPase complex with proteins involved in Na/K-ATPase signaling, such as caveolin, phospholipase C, Src, and the IP3 receptor. Finally, retinoschisin treatment altered Na/K-ATPase localization in photoreceptors of Rs1h^-/Y retinae. Taken together, our results suggest a regulatory effect of retinoschisin on Na/K-ATPase signaling and localization, whereas Na/K-ATPase-dysregulation caused by retinoschisin deficiency could represent an initial step in XLRS pathogenesis.

Absence of suppressor of cytokine signaling 2 turns cardiomyocytes unresponsive to LIF-dependent increases in Ca2+ levels

Little is known regarding the role of suppressor of cytokine signaling (SOCS) in the control of cytokine signaling in cardiomyocytes. We investigated the consequences of SOCS2 ablation for leukemia inhibitory factor (LIF)-induced enhancement of intracellular Ca²⁺ ([Ca²⁺]_i) transient by performing experiments with cardiomyocytes from SOCS2-knockout (ko) mice. Similar levels of SOCS3 transcripts were seen in cardiomyocytes from wild-type and SOCS2-ko mice, while SOCS1 mRNA was reduced in SOCS2-ko. Immunoprecipitation experiments showed increased SOCS3 association with gp130 receptor in SOCS2-ko myocytes. Measurements of Ca²⁺ in wild-type myocytes exposed to LIF showed a significant increase in the magnitude of the Ca²⁺ transient. This change was absent in LIF-treated SOCS2-ko cells. LIF activation of ERK and STAT3 was observed in both wild-type and SOCS2-ko cells, indicating that in SOCS2-ko, LIF receptors were functional, despite the lack of effect in the Ca²⁺ transient. In wild-type cells, LIF-induced increase in [Ca²⁺]_i and phospholamban Thr17 [PLN(Thr17)] phosphorylation was inhibited by KN-93, indicating a role for CaMKII in LIF-induced Ca²⁺ raise. LIF-induced phosphorylation of PLN(Thr17) was abrogated in SOCS2-ko myocytes. In wild-type cardiomyocytes, LIF treatment increased L-type Ca²⁺ current (I_Ca,L), a key activator of CaMKII in response to LIF. Conversely, SOCS2-ko myocytes failed to activate I_Ca,L in response to LIF, providing a rationale for the lack of LIF effect on Ca²⁺ transient. Our data show that absence of SOCS2 turns cardiomyocytes unresponsive to LIF-induced [Ca²⁺] raise, indicating that endogenous levels of SOCS2 are crucial for full activation of LIF signaling in the heart.

Cellular subtype expression and activation of CaMKII regulate the fate of atherosclerotic plaque

BACKGROUND AND AIMS

Atherosclerosis is a degenerative process of the arterial wall implicating activation of macrophages and proliferation of vascular smooth muscle cells. Calcium-calmodulin dependent kinase type II (CaMKII) in vascular smooth muscle cells (VSMCs) regulates proliferation, while in macrophages, this kinase governs diapedesis, infiltration and release of extracellular matrix enzymes. We aimed at understanding the possible role of CaMKII in atherosclerosis plaques to regulate plaque evolution towards stability or instability.

METHODS

Clinically defined stable and unstable plaques obtained from patients undergoing carotid end arteriectomy were processed for evaluation of CaMKs protein expression, activity and localization.

RESULTS

The larger content of CaMKII was found in CD14+myeloid cells that were more abundant in unstable rather than stable plaques. To test the biological effect of activated CD14+myeloid cells, VSMCs were exposed to the conditioned medium (CM) of macrophages extracted from carotid plaques. CM induced attenuation of CaMKs expression and activity in VSMCs, leading to the reduction of VSMCs proliferation. This appears to be due to the CaMKII dependent release of cytokines.

CONCLUSIONS

These results indicate a pivotal role of CaMKs in atherosclerosis by regulating activated myeloid cells on VSMCs activity. CaMKII could represent a possible target for therapeutic strategies based on macrophages specific inhibition for the stabilization of arteriosclerotic lesions.

Ca2+/Calmodulin-Dependent Protein Kinase II in Vascular Smooth Muscle

Ca²⁺-dependent signaling pathways are central regulators of differentiated vascular smooth muscle (VSM) contractile function. In addition, Ca²⁺ signals regulate VSM gene transcription, proliferation, and migration of dedifferentiated or "synthetic" phenotype VSM cells. Synthetic phenotype VSM growth and hyperplasia are hallmarks of pervasive vascular diseases including hypertension, atherosclerosis, postangioplasty/in-stent restenosis, and vein graft failure. The serine/threonine protein kinase Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) is a ubiquitous mediator of intracellular Ca²⁺ signals. Its multifunctional nature, structural complexity, diversity of isoforms, and splice variants all characterize this protein kinase and make study of its activity and function challenging. The kinase has unique autoregulatory mechanisms, and emerging studies suggest that it can function to integrate Ca²⁺ and reactive oxygen/nitrogen species signaling. Differentiated VSM expresses primarily CaMKIIγ and -δ isoforms. CaMKIIγ isoform expression correlates closely with the differentiated phenotype, and some studies link its function to regulation of contractile activity and Ca²⁺ homeostasis. Conversely, synthetic phenotype VSM cells primarily express CaMKIIδ and substantial evidence links it to regulation of gene transcription, proliferation, and migration of VSM in vitro, and vascular hypertrophic and hyperplastic remodeling in vivo. CaMKIIδ and -γ isoforms have opposing functions at the level of cell cycle regulation, proliferation, and VSM hyperplasia in vivo. Isoform switching following vascular injury is a key step in promoting vascular remodeling. Recent availability of genetically engineered mice with smooth muscle deletion of specific isoforms and transgenics expressing an endogenous inhibitor protein (CAMK2N) has enabled a better understanding of CaMKII function in VSM and should facilitate future studies.

Stochastic Induction of Long-Term Potentiation and Long-Term Depression

Long-term depression (LTD) and long-term potentiation (LTP) of granule-Purkinje cell synapses are persistent synaptic alterations induced by high and low rises of the intracellular calcium ion concentration ([Ca²⁺]), respectively. The occurrence of LTD involves the activation of a positive feedback loop formed by protein kinase C, phospholipase A₂, and the extracellular signal-regulated protein kinase pathway, and its expression comprises the reduction of the population of synaptic AMPA receptors. Recently, a stochastic computational model of these signalling processes demonstrated that, in single synapses, LTD is probabilistic and bistable. Here, we expanded this model to simulate LTP, which requires protein phosphatases and the increase in the population of synaptic AMPA receptors. Our results indicated that, in single synapses, while LTD is bistable, LTP is gradual. Ca²⁺ induced both processes stochastically. The magnitudes of the Ca²⁺ signals and the states of the signalling network regulated the likelihood of LTP and LTD and defined dynamic macroscopic Ca²⁺ thresholds for the synaptic modifications in populations of synapses according to an inverse Bienenstock, Cooper and Munro (BCM) rule or a sigmoidal function. In conclusion, our model presents a unifying mechanism that explains the macroscopic properties of LTP and LTD from their dynamics in single synapses.

MicroRNA and receptor mediated signaling pathways as potential therapeutic targets in heart failure

INTRODUCTION

Cardiac remodelling is a complex pathogenetic pathway involving genome expression, molecular, cellular, and interstitial changes that cause changes in size, shape and function of the heart after cardiac injury. Areas covered: We will review recent advances in understanding the role of several receptor-mediated signaling pathways and micro-RNAs, in addition to their potential as candidate target pathways in the pathogenesis of heart failure. The myocyte is the main target cell involved in the remodelling process via ischemia, cell necrosis and apoptosis (by means of various receptor pathways), and other mechanisms mediated by micro-RNAs. We will analyze the role of some receptor mediated signaling pathways such as natriuretic peptides, mediators of glycogen synthase kinase 3 and ERK1/2 pathways, beta-adrenergic receptor subtypes and relaxin receptor signaling mechanisms, TNF/TNF receptor family and TWEAK/Fn14 axis, and some micro-RNAs as candidate target pathways in pathogenesis of heart failure. These mediators of receptor-mediated pathways and micro-RNA are the most addressed targets of emerging therapies in modern heart failure treatment strategies. Expert opinion: Future treatment strategies should address mediators involved in multiple steps within heart failure pathogenetic pathways.

Glutamine up-regulates MAPK phosphatase-1 induction via activation of Ca2+→ ERK cascade pathway

The non-essential amino acid L-glutamine (Gln) displays potent anti-inflammatory activity by deactivating p38 mitogen activating protein kinase and cytosolic phospholipase A₂ via induction of MAPK phosphatase-1 (MKP-1) in an extracellular signal-regulated kinase (ERK)-dependent way. In this study, the mechanism of Gln-mediated ERK-dependency in MKP-1 induction was investigated. Gln increased ERK phosphorylation and activity, and phosphorylations of Ras, c-Raf, and MEK, located in the upstream pathway of ERK, in response to lipopolysaccharidein vitro and in vivo. Gln-induced dose-dependent transient increases in intracellular calcium ([Ca²⁺]_i) in MHS macrophage cells. Ionomycin increased [Ca²⁺]_i and activation of Ras → ERK pathway, and MKP-1 induction, in the presence, but not in the absence, of LPS. The Gln-induced pathways involving Ca²⁺→ MKP-1 induction were abrogated by a calcium blocker. Besides Gln, other amino acids including L-phenylalanine and l-cysteine (Cys) also induced Ca²⁺ response, activation of Ras → ERK, and MKP-1 induction, albeit to a lesser degree. Gln and Cys were comparable in suppression against 2, 4-dinitrofluorobenzene-induced contact dermatitis. Gln-mediated, but not Cys-mediated, suppression was abolished by MKP-1 small interfering RNA. These data indicate that Gln induces MKP-1 by activating Ca²⁺→ ERK pathway, which plays a key role in suppression of inflammatory reactions.

Calcium and Superoxide-Mediated Pathways Converge to Induce Nitric Oxide-Dependent Apoptosis in Mycobacterium fortuitum-Infected Fish Macrophages

Mycobacterium fortuitum causes ‘mycobacteriosis’ in wide range of hosts although the mechanisms remain largely unknown. Here we demonstrate the role of calcium (Ca⁺²)-signalling cascade on M. fortuitum-induced apoptosis in headkidney macrophages (HKM) of Clarias sp. M. fortuitum could trigger intracellular-Ca⁺² influx leading to the activation of calmodulin (CaM), protein kinase C alpha (PKCα) and Calmodulin kinase II gamma (CaMKIIg). Gene silencing and inhibitor studies established the role of CaM in M. fortuitum pathogenesis. We noted that CaMKIIg activation is regulated by CaM as well as PKCα-dependent superoxide anions. This is altogether first report of oxidised CaMKIIg in mycobacterial infections. Our studies with targeted-siRNA and pharmacological inhibitors implicate CaMKIIg to be pro-apoptotic and critical for the activation of extra-cellular signal regulated kinase 1/2 (ERK1/2). Inhibiting the ERK1/2 pathway attenuated nitric oxide synthase 2 (NOS2)-induced nitric oxide (NO) production. Conversely, inhibiting the NOS2-NO axis by specific-siRNA and inhibitors down-regulated ERK1/2 activation suggesting the crosstalk between ERK1/2 and NO is essential for pathogenesis induced by the bacterium. Silencing the NOS2-NO axis enhanced intracellular bacterial survival and attenuated caspase-8 mediated activation of caspase-3 in the infected HKM. Our findings unveil hitherto unknown mechanism of M. fortuitum pathogenesis. We propose that M. fortuitum triggers intracellular Ca⁺² elevations resulting in CaM activation and PKCα-mediated superoxide generation. The cascade converges in common pathway mediated by CaMKIIg resulting in the activation of ERK1/2-NOS2 axis. The crosstalk between ERK1/2 and NO shifts the balance in favour of caspase dependent apoptosis of M. fortuitum-infected HKM.

Synergistic effect of ascorbic acid and collagen addition on the increase in type 2 collagen accumulation in cartilage-like MSC sheet

Aiming to increase the content of type 2 collagen in scaffold-free cartilage-like cell sheets prepared using human bone marrow mesenchymal stem cells, the effect of several kinds of additives in a chondrogenic medium was investigated. Addition of ascorbic acid 2 phosphate (VCP) at a high concentration (250 µg/ml) and type 1 atelocollagen (5 µg/ml) increased the accumulation of type 2 collagen by fourfold and twofold, respectively. On the other hand, an antioxidant, glutathione showed no such effect. The synergistic effect of VCP and type 1 atelocollagen resulted in an eightfold increase in the accumulation level of type 2 collagen. Furthermore, the gene expression level of type 2 collagen increased and that of matrix metalloproteinase-13 (MMP-13) decreased to approximately one-third of the control. The increase in type 2 collagen accumulation in the scaffold-free cartilage-like cell sheet might be due to not only the enhancement of the synthesis but also the suppression of the degradation of type 2 collagen by MMP-13.

Calmodulin and CaMKII modulate ENaC activity by regulating the association of MARCKS and the cytoskeleton with the apical membrane

Phosphatidylinositol bisphosphate (PIP2) regulates epithelial sodium channel (ENaC) open probability. In turn, myristoylated alanine-rich C kinase substrate (MARCKS) protein or MARCKS-like protein 1 (MLP-1) at the plasma membrane regulates the delivery of PIP2 to ENaC. MARCKS and MLP-1 are regulated by changes in cytosolic calcium; increasing calcium promotes dissociation of MARCKS from the membrane, but the calcium-regulatory mechanisms are unclear. However, it is known that increased intracellular calcium can activate calmodulin and we show that inhibition of calmodulin with calmidazolium increases ENaC activity presumably by regulating MARCKS and MLP-1. Activated calmodulin can regulate MARCKS and MLP-1 in two ways. Calmodulin can bind to the effector domain of MARCKS or MLP-1, inactivating both proteins by causing their dissociation from the membrane. Mutations in MARCKS that prevent calmodulin association prevent dissociation of MARCKS from the membrane. Calmodulin also activates CaM kinase II (CaMKII). An inhibitor of CaMKII (KN93) increases ENaC activity, MARCKS association with ENaC, and promotes MARCKS movement to a membrane fraction. CaMKII phosphorylates filamin. Filamin is an essential component of the cytoskeleton and promotes association of ENaC, MARCKS, and MLP-1. Disruption of the cytoskeleton with cytochalasin E reduces ENaC activity. CaMKII phosphorylation of filamin disrupts the cytoskeleton and the association of MARCKS, MLP-1, and ENaC, thereby reducing ENaC open probability. Taken together, these findings suggest calmodulin and CaMKII modulate ENaC activity by destabilizing the association between the actin cytoskeleton, ENaC, and MARCKS, or MLP-1 at the apical membrane.

Targeting the CaMKII/ERK Interaction in the Heart Prevents Cardiac Hypertrophy

Aims

Activation of Ca²⁺/Calmodulin protein kinase II (CaMKII) is an important step in signaling of cardiac hypertrophy. The molecular mechanisms by which CaMKII integrates with other pathways in the heart are incompletely understood. We hypothesize that CaMKII association with extracellular regulated kinase (ERK), promotes cardiac hypertrophy through ERK nuclear localization.

Methods and Results

In H9C2 cardiomyoblasts, the selective CaMKII peptide inhibitor AntCaNtide, its penetratin conjugated minimal inhibitory sequence analog tat-CN17β, and the MEK/ERK inhibitor UO126 all reduce phenylephrine (PE)-mediated ERK and CaMKII activation and their interaction. Moreover, AntCaNtide or tat-CN17β pretreatment prevented PE induced CaMKII and ERK nuclear accumulation in H9C2s and reduced the hypertrophy responses. To determine the role of CaMKII in cardiac hypertrophy in vivo, spontaneously hypertensive rats were subjected to intramyocardial injections of AntCaNtide or tat-CN17β. Left ventricular hypertrophy was evaluated weekly for 3 weeks by cardiac ultrasounds. We observed that the treatment with CaMKII inhibitors induced similar but significant reduction of cardiac size, left ventricular mass, and thickness of cardiac wall. The treatment with CaMKII inhibitors caused a significant reduction of CaMKII and ERK phosphorylation levels and their nuclear localization in the heart.

Conclusion

These results indicate that CaMKII and ERK interact to promote activation in hypertrophy; the inhibition of CaMKII-ERK interaction offers a novel therapeutic approach to limit cardiac hypertrophy.

A novel crosstalk between calcium/calmodulin kinases II and IV regulates cell proliferation in myeloid leukemia cells

CaMKs link transient increases in intracellular Ca(2+) with biological processes. In myeloid leukemia cells, CaMKII, activated by the bcr-abl oncogene, promotes cell proliferation. Inhibition of CaMKII activity restricts cell proliferation, and correlates with growth arrest and differentiation. The mechanism by which the inhibition of CaMKII results in growth arrest and differentiation in myeloid leukemia cells is still unknown. We report that inhibition of CaMKII activity results in an upregulation of CaMKIV mRNA and protein in leukemia cell lines. Conversely, expression of CaMKIV inhibits autophosphorylation and activation of CaMKII, and elicits G0/G1cell cycle arrest,impairing cell proliferation. Furthermore, U937 cells expressing CaMKIV show elevated levels of Cdk inhibitors p27(kip1) and p16(ink4a) and reduced levels of cyclins A, B1 and D1. These findings were also confirmed in the K562 leukemic cell line. The relationship between CaMKII and CaMKIV is also observed in primary acute myeloid leukemia (AML) cells, and it correlates with their immunophenotypic profile. Indeed, immature MO/M1 AML showed increased CaMKIV expression and decreased pCaMKII, whereas highly differentiated M4/M5 AML showed decreased CaMKIV expression and increased pCaMKII levels. Our data reveal a novel cross-talk between CaMKII and CaMKIV and suggest that CaMKII suppresses the expression of CaMKIV to promote leukemia cell proliferation.