Association between vascular endothelial dysfunction and stroke incidence in the general Japanese population: Results from the tohoku medical megabank community-based cohort study.

Background: Flow-mediated dilation (FMD) measures vascular endothelial function by evaluating the vasodilatory response of blood vessels to increased blood flow. Nevertheless, the association between FMD and stroke incidence in a general population remains unclear. This study investigated the association between vascular endothelial function and stroke incidence in the general Japanese population. Methods: Based on cohort data from the Tohoku Medical Megabank Community-based Cohort Study, participants aged ≥18 years were recruited from Iwate Prefecture, with the final sample comprising 2952 subjects. Results: The FMD level was 0.5%-27.1%, with a median of 5.0% (interquartile, 4.2%-11.3%). The mean follow-up period was 5.5 ± 1.8 years (range, 0.6-6.9 years). After dividing the participants into two subgroups according to the median FMD value, a multivariate Cox regression analysis adjusting for gender, age, smoking, alcohol consumption, systolic blood pressure, low-density lipoprotein cholesterol, estimated glomerular filtration rate, N-terminal pro-brain natriuretic peptide, high-sensitivity cardiac troponin T and hemoglobin A1c revealed that a lower FMD value was strongly associated with incidences of total stroke (hazard ratio[HR] = 2.13, 95% confidence interval[CI] = 1.48-3.07, p < 0.001), ischemic stroke (HR = 3.33, 95%CI = 2.00-5.52, p < 0.001), nonlacunar stroke (HR = 2.77, 95%CI = 1.49-5.16, p = 0.001), and lacunar stroke (HR = 5.12, 95%CI = 1.74-16.05, p = 0.003). Conclusions: This study showed that a low FMD value might reflect vascular endothelial dysfunction and then was associated with ischemic stroke incidence in the general Japanese population, suggesting that FMD can be used as a tool to identify future stroke risk.

Association between Plasma Xanthine Oxidoreductase Activity and the Renal Function in a General Japanese Population: The Tohoku Medical Megabank Community-Based Cohort Study.

INTRODUCTION: Xanthine oxidoreductase (XOR) has been identified as a critical source of reactive oxygen species in various pathophysiological conditions, including hypertension, endothelial dysfunction, and atherosclerosis. This study investigated the association between XOR and renal function in a general Japanese population. METHODS: The Iwate Tohoku Medical Megabank Organization pooled individual participant data from a community-based cohort study in Iwate prefecture. Chronic kidney disease (CKD) was estimated using the estimated glomerular filtration rate of cystatin C (eGFRcys). Individuals with a history of hyperuricemia or severe renal dysfunction (eGFRcys <15 mL/min/1.73 m2 or undergoing dialysis) were excluded from the study. We performed a multinominal multivariate logistic analysis adjusted for age, blood pressure, uric acid, glycated hemoglobin A1c, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol to associate XOR activity and renal function. RESULTS: The present study included 4,248 participants (male/female: 1,373/2,875, age: 62.9 ± 11.7 years). When participants were divided according to XOR quartiles, blood pressure, body mass index, uric acid, low-density lipoprotein cholesterol, and glycated hemoglobin A1c were highest in the highest XOR quartile (all p < 0.001). The XOR activity was significantly higher in the subgroup with CKD stage G3 and G4 (G1 vs. G2 vs. G3-G4: 44.8 ± 40.5 vs. 52.0 ± 42.9 vs. 54.1 ± 43.9 pmol/h/mL, p = 0.02). The higher XOR activity was significantly associated with an increase of CKD stage: the odd ratios (95% confidence intervals) per 1 pmol/h/mL increase in XOR activity with CKD stage G1 as a reference were 1.37 (1.13-1.73) in G2 and 1.51 (1.30-1.84) in G3-G4. CONCLUSION: The present study concluded that high XOR activity was associated with the severity of CKD in a general Japanese population, suggesting that upregulated XOR activity may be involved in advanced renal dysfunction.

Association between total type I collagen N-terminal propeptide and coronary artery disease risk score in the general Japanese population.

Background: Bone metabolic dysregulation plays an important role in the pathogenesis of atherosclerosis; however, whether its markers contribute to coronary artery disease (CAD) risk in the general population remains unclear. Therefore, this study aimed to analyze the association between bone metabolic markers and CAD risk score in the general Japanese population. Methods: The Iwate Medical Megabank Organization collected individual participant data during a community-based cohort study in the Iwate prefecture (n = 5,095, age = 58.9 ± 12.4 years). Participants with osteoporosis, chronic kidney disease, malignant disease, or primary wasting disease were excluded from the study. The present study measured the levels of circulating bone metabolic markers, including total type I collagen N-terminal propeptide (TP1NP), bone-type alkaline phosphatase, cross-linked N-telopeptide of type 1 collagen (NTX), and intact parathyroid hormone. CAD risk and atherosclerosis were evaluated using the Suita score and brachial-ankle pulse wave velocity (baPWV) measurement, respectively. Results: Among the bone metabolic markers, TP1NP was strongly associated with a high Suita score (≥56 points) (OR = 0.77, 95% CI = 0.69-0.82, P < 0.001). When participants were divided into quartiles of TP1NP levels, the subgroup with the lowest TP1NP level was associated with a high Suita score (≥56 points) and high baPWV (>1,400 cm/s). Conclusions: This study demonstrated that TP1NP levels decreased in participants with high Suita scores and high baPWV, suggesting that TP1NP downregulation may indicate future CAD risk and atherosclerosis progression in the general Japanese population.

Association between high-sensitivity cardiac troponin T levels and incident stroke in the elderly Japanese population: Results from the Tohoku Medical Megabank Community-based Cohort Study.

Elevated levels of circulating high-sensitivity cardiac troponin T (hs-cTnT) are associated with cardiovascular disease. This study aimed to examine whether hs-cTnT levels are associated with incident stroke in the elderly population. The Iwate Tohoku Medical Megabank Organization pooled participant data for a community-based cohort study (n = 15,063, 69.6 ± 3.4 years), with a mean follow-up period of 5.23 years for all-cause death and incident stroke. The follow-up revealed 316 incident strokes, including atherothrombotic (n = 98), cardioembolic (n = 54), lacunar (n = 63), hemorrhagic (n = 101), and 178 all-cause deaths. Participants were classified into quartiles according to hs-cTnT levels (Q1 ≦ 4 ng/L, Q2: 5-6 ng/L, Q3: 7-9 ng/L, and Q4 > 9 ng/L). After adjusting for sex, age, smoking, drinking, systolic blood pressure, estimated glomerular filtration rate, N-terminal pro-brain natriuretic peptide, hemoglobin A1c, and lipid profile, a Cox proportional hazard model showed that higher hs-cTnT levels were associated with ischemic stroke (Q1 vs. Q4, hazard ratio [HR] = 2.24, 95 % confidence interval [CI] = 1.12-4.51, p = 0.023). The incident of total stroke was not associated with hs-cTnT levels (Q1 vs. Q4, HR 1.39, 95 % CI = 0.89-1.74, p = 0.145). Numerical differences were highest regarding incident lacunar stroke subtypes; however, this association was not statistically significant. Higher hs-cTnT concentrations were associated with ischemic stroke in the elderly Japanese population.

A genome-wide association study for highly sensitive cardiac troponin T levels identified a novel genetic variation near a RBAK-ZNF890P locus in the Japanese general population.

BACKGROUND: Cardiovascular disease (CVD) is a major cause of mortality worldwide. High-sensitivity cardiac troponin T (hs-cTnT) is released into the bloodstream due to cardiomyocyte damage and is associated with a high CVD risk. This study aimed to investigate hs-cTnT-related genetic variation and to examine whether this is an associated risk factor for CVD in the Japanese general population. METHODS: This was a genome-wide association study (GWAS) based on a cohort from the 2013 Tohoku Medical Megabank Project community study. The GWAS was performed using a HumanOmniExpressExome BeadChip array with 914,035 autosomal single-nucleotide polymorphisms. The Framingham Risk Score and the Suita score were used to evaluate the future risk of CVD. RESULTS: The GWAS identified 10 loci reaching suggestive significance in the discovery cohort. A replication analysis confirmed that one of the 10 loci, rs7798496, is associated with elevated hs-cTnT levels. The combined P value in the discovery and replication cohorts for the association between the rs7798496 and hs-cTnT levels was 3.4 × 10-8, which indicates that the novel variant reached genome-wide significance. The rs7798496 loci was located at an intergenic region between the retinoblastoma gene product (RB)-associated Krüppell-associated box (KRAB) zinc finger, zinc finger protein 890, and pseudogene (ZNF890P). Logistic regression analysis revealed that the presence of the rs7798496 T allele was strongly associated with a high risk for CVD. CONCLUSIONS: This study provides insights into a link between a novel genetic variant, T allele of rs7798269, and elevated hs-cTnT levels as a future risk for CVD in the general Japanese population.

The Value of a Cystatin C-based Estimated Glomerular Filtration Rate for Cardiovascular Assessment in a General Japanese Population: Results From the Iwate Tohoku Medical Megabank Project.

BACKGROUND: Epidemiological studies have shown that high circulating cystatin C is associated with a risk of cardiovascular disease (CVD) independent of creatinine-based renal function measurements. The present study investigated the comparison between the cystatin C-based estimated glomerular filtration rate (GFRcys) and creatinine-based GFR (GFRcr) to determine whether these measurements are associated with CV biomarkers and elevated CVD risk in a general Japanese population. METHODS: The Iwate Tohoku Medical Megabank Organization pooled individual participant data from a general population-based cohort study in Iwate prefecture (n = 29,375). Chronic kidney disease (CKD) was estimated using the GFRcys, GFRcr and the urine albumin-to-creatinine ratio (UACR). RESULTS: The prevalence of CKD in the participants was found to be higher based on the GFRcr than the GFRcys. Multiple variable analyses after adjusting for baseline characteristics showed that high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP) were associated with the GFRcys. The area under the receiver operating characteristic (AUROC) curve for identifying individuals with a high Suita score was higher for the GFRcys (AUROC = 0.68) than it was for the GFRcr (AUROC = 0.64, P < 0.001). The GFRcys provided reclassification improvement for the CVD risk prediction model by the GFRcr (net reclassification improvement = 0.341; integrated discrimination improvement = 0.018, respectively, P < 0.001). CONCLUSIONS: The GFRcys is more closely associated with CV biomarkers, including hs-cTnT and NT-proBNP levels, and a high Suita score than the GFRcr, and it provides additional value in the assessment of CVD risk using GFRcr.

Myocardin-related transcription factor A (MRTF-A) activity-dependent cell adhesion is correlated to focal adhesion kinase (FAK) activity.

The regulation of cell-substrate adhesion is tightly linked to the malignant phenotype of tumor cells and plays a role in their migration, invasion, and metastasis. Focal adhesions (FAs) are dynamic adhesion structures that anchor the cell to the extracellular matrix. Myocardin-related transcription factors (MRTFs), co-regulators of the serum response factor (SRF), regulate expression of a set of genes encoding actin cytoskeletal/FA-related proteins. Here we demonstrated that the forced expression of a constitutively active MRTF-A (CA-MRTF-A) in B16F10 melanoma cells induced the up-regulation of actin cytoskeletal and FA proteins, resulting in FA reorganization and the suppression of cell migration. Expression of CA-MRTF-A markedly increased phosphorylation of focal adhesion kinase (FAK) and paxillin, which are important components for FA dynamics. Notably, FAK activation was triggered by the clustering of up-regulated integrins. Our results revealed that the MRTF-SRF-dependent regulation of cell migration requires both the up-regulation of actin cytoskeletal/FA proteins and the integrin-mediated regulation of FA components via the FAK/Src pathway. We also demonstrated that activation of the MRTF-dependent transcription correlates FAK activation in various tumor cells. The elucidation of the correlation between MRTF and FAK activities would be an effective therapeutic target in focus of tumor cell migration.

Docosahexaenoic Acid Promotes Axon Outgrowth by Translational Regulation of Tau and Collapsin Response Mediator Protein 2 Expression.

n-3 PUFAs are essential for neuronal development and brain function. However, the molecular mechanisms underlying their biological effects remain unclear. Here we examined the mechanistic action of docosahexaenoic acid (DHA), the most abundant n-3 polyunsaturated fatty acids in the brain. We found that DHA treatment of cortical neurons resulted in enhanced axon outgrowth that was due to increased axon elongation rates. DHA-mediated axon outgrowth was accompanied by the translational up-regulation of Tau and collapsin response mediator protein 2 (CRMP2), two important axon-related proteins, and the activation of Akt and p70 S6 kinase. Consistent with these findings, rapamycin, a potent inhibitor of mammalian target of rapamycin (mTOR), prevented DHA-mediated axon outgrowth and up-regulation of Tau and CRMP2. In addition, DHA-dependent activation of the Akt-mTOR-S6K pathway enhanced 5'-terminal oligopyrimidine tract-dependent translation of Tau and CRMP2. Therefore, our results revealed an important role for the Akt-mTOR-S6K pathway in DHA-mediated neuronal development.

PSD-Zip70 Deficiency Causes Prefrontal Hypofunction Associated with Glutamatergic Synapse Maturation Defects by Dysregulation of Rap2 Activity.

Dysregulation of synapse formation and plasticity is closely related to the pathophysiology of psychiatric and neurodevelopmental disorders. The prefrontal cortex (PFC) is particularly important for executive functions such as working memory, cognition, and emotional control, which are impaired in the disorders. PSD-Zip70 (Lzts1/FEZ1) is a postsynaptic density (PSD) protein predominantly expressed in the frontal cortex, olfactory bulb, striatum, and hippocampus. Here we found that PSD-Zip70 knock-out (PSD-Zip70KO) mice exhibit working memory and cognitive defects, and enhanced anxiety-like behaviors. These abnormal behaviors are caused by impaired glutamatergic synapse transmission accompanied by tiny-headed immature dendritic spines in the PFC, due to aberrant Rap2 activation, which has roles in synapse formation and plasticity. PSD-Zip70 modulates the Rap2 activity by interacting with SPAR (spine-associated RapGAP) and PDZ-GEF1 (RapGEF) in the postsynapse. Furthermore, suppression of the aberrant Rap2 activation in the PFC rescued the behavioral defects in PSD-Zip70KO mice. Our data demonstrate a critical role for PSD-Zip70 in Rap2-dependent spine synapse development in the PFC and underscore the importance of this regulation in PFC-dependent behaviors. SIGNIFICANCE STATEMENT: PSD-Zip70 deficiency causes behavioral defects in working memory and cognition, and enhanced anxiety due to prefrontal hypofunction. This study revealed that PSD-Zip70 plays essential roles in glutamatergic synapse maturation via modulation of the Rap2 activity in the PFC. PSD-Zip70 interacts with both SPAR (spine-associated RapGAP) and PDZ-GEF1 (RapGEF) and modulates the Rap2 activity in postsynaptic sites. Our results provide a novel Rap2-specific regulatory mechanism in synaptic maturation involving PSD-Zip70.

Diversification of caldesmon-linked actin cytoskeleton in cell motility.

The actin cytoskeleton plays a key role in regulating cell motility. Caldesmon (CaD) is an actin-linked regulatory protein found in smooth muscle and non-muscle cells that is conserved among a variety of vertebrates. It binds and stabilizes actin filaments, as well as regulating actin-myosin interaction in a calcium (Ca2+)/calmodulin (CaM)- and/or phosphorylation-dependent manner. CaD function is regulated qualitatively by Ca2+/CaM and by its phosphorylation state and quantitatively at the mRNA level, by three different transcriptional regulation of the CALD1 gene. CaD has numerous functions in cell motility, such as migration, invasion, and proliferation, exerted via the reorganization of the actin cytoskeleton. Here we will outline recent findings regarding CaD's structural features and functions.

Caldesmon, an actin-linked regulatory protein, comes across glucocorticoids.

The glucocorticoids (GCs), the most downstream effectors of the hypothalamic-pituitary-adrenal (HPA) axis, are the main mediators of stress response. Stress-triggered GCs as well as acute and chronic GC treatment can impair the structural plasticity and function of the brain. The exposure of perinatal animals and humans to excess stress or GCs can affect the brain development, resulting in altered behaviors in the adult offspring of animals and an increased risk of psychiatric disorders in humans. Despite the numerous studies documenting these effects, the underlying mechanism remains unclear. In this commentary we will focus on the effect of excess GCs on cortical development. We have recently showed that excess-GC-dependent retardation of the radial migration of neural progenitor cells (NPCs) is caused by the dysregulation of actin-myosin interaction via upregulation of caldesmon (CaD), an actin-linked regulatory protein. The elucidation of the molecular mechanisms that underlie the detrimental action of GCs on cortical development will expand our understanding of how stress/GCs alter the formation of neural networks and affect behaviors later in life.

MRTF-A/B suppress the oncogenic properties of v-ras- and v-src-mediated transformants.

Two members of the myocardin protein family, myocardin-related transcription factor (MRTF)-A and MRTF-B are co-activators of serum response factor (SRF). We recently reported that MRTF-A/B activates the transcription of several actin cytoskeletal/focal adhesion genes SRF dependently, thereby enhancing the formation of stress fibers and focal adhesions. Here, we showed that the levels of caldesmon and tropomyosin, both SRF/MRTF-regulated actin cytoskeletal proteins, were reduced in rat intestinal epithelial (RIE) cell lines that had been transformed with oncogenic ras (RIE-ras) or src (RIE-src) compared with their parental cell line. These cells exhibited morphological abnormalities associated with a disorganized actin cytoskeleton. The serum-stimulated nuclear translocation of MRTF-A/B was suppressed in the RIE-ras and RIE-src cells. However, the transient expression of constitutively active (CA) MRTF-A or MRTF-B reversed the reduced expression levels of caldesmon and tropomyosin and the associated morphological phenotypes. We isolated stable CA-MRTF-A-expressing cell lines from transfected RIE-ras and RIE-src cells and found that their levels of caldesmon and tropomyosin were close to those of untransformed RIE cells. Their morphologies were also normal, with a flattened cell shape and well-developed stress fibers. The CA-MRTF-A-expressing RIE-ras and RIE-src lines also showed lower invasiveness and anchorage-independent growth than their transformed parental cells, in vitro. In vivo, CA-MRTF-A expression suppressed tumor formation and reduced liver metastases. Therefore, we concluded that MRTF-A/B are potent repressors of cancer progression and metastasis and may be good targets for cancer therapy.

Myocardin functions as an effective inducer of growth arrest and differentiation in human uterine leiomyosarcoma cells.

Myocardin is an important transcriptional regulator in smooth and cardiac muscle development. We noticed that the expression of myocardin was markedly downregulated in human uterine leiomyosarcoma cells. Restoration of myocardin expression induced the reexpression of smooth muscle marker proteins and the formation of well-developed actin fibers. A concomitant increase in the expression of a cyclin-dependent kinase inhibitor, p21, led to significantly reduced cell proliferation, via p21's inhibition of the G(1)-S transition. A p21 promoter-reporter assay showed that myocardin markedly increased p21's promoter activity. Furthermore, a serum response factor (SRF)-binding cis-element CArG box in the p21 promoter region was required for this myocardin effect. Chromatin immunoprecipitation and DNA-protein binding assays showed that myocardin indirectly bound to the CArG box in the p21 promoter through the interaction with SRF. Furthermore, immunohistochemistry revealed that the levels of myocardin and p21 were both lower in leiomyosarcoma samples than in normal smooth muscle tissue. Taken together, our results indicate that the downregulation of myocardin expression facilitates cell cycle progression via the reduction of p21 expression in human leimyosarcomas and suggest that myocardin could be a useful therapeutic target for this disease.

Expression profiles of nestin in vascular smooth muscle cells in vivo and in vitro.

Nestin is an intermediate filament protein expressed in neural and mesenchymal stem cells. Here, we investigated the expression of nestin in vascular smooth muscle cells (VSMCs) in vivo and in vitro. In the developing arteries, medial VSMCs were found to express nestin; its expression was prominent in embryos but was down-regulated after birth (3-6 weeks) in a region-dependent manner; its expression was abolished in the adult. Thus, the expression of nestin is specific to developing VSMCs. In primary VMSC cultures, nestin expression was induced by serum, but was independent of cell-cycle progression. Signaling analyses revealed that the serum-induced nestin expression depended on the extracellular signal-regulated kinase (ERK) and protein kinase B (PKB)(Akt) pathways, via the platelet derived growth factor (PDGF) and epidermal growth factor (EGF) receptors. Nestin expression was closely related to the up-regulation and activation of Sp1 and Sp3. Among major serum growth factors and cytokines, PDGF-BB was the most potent inducer of nestin expression. Nestin was also up-regulated in arteries undergoing vascular remodeling following balloon injury. Its expression was particularly strong in the cells lining the lumen of the neointima, suggesting a possible correlation between nestin expression and the progression of vascular remodeling.

Glucocorticoid receptor-mediated expression of caldesmon regulates cell migration via the reorganization of the actin cytoskeleton.

Glucocorticoids (GCs) play important roles in numerous cellular processes, including growth, development, homeostasis, inhibition of inflammation, and immunosuppression. Here we found that GC-treated human lung carcinoma A549 cells exhibited the enhanced formation of the thick stress fibers and focal adhesions, resulting in suppression of cell migration. In a screen for GC-responsive genes encoding actin-interacting proteins, we identified caldesmon (CaD), which is specifically up-regulated in response to GCs. CaD is a regulatory protein involved in actomyosin-based contraction and the stability of actin filaments. We further demonstrated that the up-regulation of CaD expression was controlled by glucocorticoid receptor (GR). An activated form of GR directly bound to the two glucocorticoid-response element-like sequences in the human CALD1 promoter and transactivated the CALD1 gene, thereby up-regulating the CaD protein. Forced expression of CaD, without GC treatment, also enhanced the formation of thick stress fibers and focal adhesions and suppressed cell migration. Conversely, depletion of CaD abrogated the GC-induced phenotypes. The results of this study suggest that the GR-dependent up-regulation of CaD plays a pivotal role in regulating cell migration via the reorganization of the actin cytoskeleton.

Rho/Rho-associated kinase signal regulates myogenic differentiation via myocardin-related transcription factor-A/Smad-dependent transcription of the Id3 gene.

RhoA is known to be involved in myogenic differentiation, but whether it acts as a positive or negative regulator is controversial. To resolve this issue, we investigated the differentiation stage-specific roles of RhoA and its effector, Rho-associated kinase, using C2C12 myoblasts. We found that proliferating myoblasts show high levels of RhoA and serum-response factor activities and strong expression of the downstream target of RhoA, myocardin-related transcription factor-A (MRTF-A or MAL); these activities and expression are markedly lower in differentiating myocytes. We further demonstrated that, in proliferating myoblasts, an increase in MRTF-A, which forms a complex with Smad1/4, strikingly activates the expression level of the Id3 gene; the Id3 gene product is a potent inhibitor of myogenic differentiation. Finally, we found that during differentiation, one of the forkhead transcription factors translocates into the nucleus and suppresses Id3 expression by preventing the association of the MRTF-A-Smad complex with the Id3 promoter, which leads to the enhancement of myogenic differentiation. We conclude that RhoA/Rho-associated kinase signaling plays positive and negative roles in myogenic differentiation, mediated by MRTF-A/Smad-dependent transcription of the Id3 gene in a differentiation stage-specific manner.

Dual roles of myocardin-related transcription factors in epithelial mesenchymal transition via slug induction and actin remodeling.

Epithelial-mesenchymal transition (EMT) is a critical process occurring during embryonic development and in fibrosis and tumor progression. Dissociation of cell-cell contacts and remodeling of the actin cytoskeleton are major events of the EMT. Here, we show that myocardin-related transcription factors (MRTFs; also known as MAL and MKL) are critical mediators of transforming growth factor beta (TGF-beta) 1-induced EMT. In all epithelial cell lines examined here, TGF-beta1 triggers the nuclear translocation of MRTFs. Ectopic expression of constitutive-active MRTF-A induces EMT, whereas dominant-negative MRTF-A or knockdown of MRTF-A and -B prevents the TGF-beta1-induced EMT. MRTFs form complexes with Smad3. Via Smad3, the MRTF-Smad3 complexes bind to a newly identified cis-element GCCG-like motif in the promoter region of Canis familiaris and the human slug gene, which activates slug transcription and thereby dissociation of cell-cell contacts. MRTFs also increase the expression levels of actin cytoskeletal proteins via serum response factor, thereby triggering reorganization of the actin cytoskeleton. Thus, MRTFs are important mediators of TGF-beta1-induced EMT.

Changes in the balance between caldesmon regulated by p21-activated kinases and the Arp2/3 complex govern podosome formation.

Podosomes are dynamic cell adhesion structures that degrade the extracellular matrix, permitting extracellular matrix remodeling. Accumulating evidence suggests that actin and its associated proteins play a crucial role in podosome dynamics. Caldesmon is localized to the podosomes, and its expression is down-regulated in transformed and cancer cells. Here we studied the regulatory mode of caldesmon in podosome formation in Rous sarcoma virus-transformed fibroblasts. Exogenous expression analyses revealed that caldesmon represses podosome formation triggered by the N-WASP-Arp2/3 pathway. Conversely, depletion of caldesmon by RNA interference induces numerous small-sized podosomes with high dynamics. Caldesmon competes with the Arp2/3 complex for actin binding and thereby inhibits podosome formation. p21-activated kinases (PAK)1 and 2 are also repressors of podosome formation via phosphorylation of caldesmon. Consequently, phosphorylation of caldesmon by PAK1/2 enhances this regulatory mode of caldesmon. Taken together, we conclude that in Rous sarcoma virus-transformed cells, changes in the balance between PAK1/2-regulated caldesmon and the Arp2/3 complex govern the formation of podosomes.

Differential modulation of NR1-NR2A and NR1-NR2B subtypes of NMDA receptor by PDZ domain-containing proteins.

The PSD-95/Dlg/ZO-1 (PDZ) domain-containing proteins MALS and PSD-95 localize to post-synaptic densities and bind the COOH-termini of NR2 subunits of the NMDA receptor. The effects of MALS-2 and PSD-95 on the channel activity of NMDA receptors were compared using the Xenopus oocyte expression system. Both MALS-2 and PSD-95 increased the current response of the NR1-NR2B receptor to l-glutamate. In contrast, the current response of the NR1-NR2A receptor was increased by PSD-95 but not by MALS-2. MALS-2 had no effect either on the potentiation of NR1-NR2A or NR1-NR2B channel activity by protein kinase C, or on Src-mediated potentiation of NR1-NR2A activity, whereas PSD-95 almost completely inhibited the effects of these protein kinases. Construction of chimeras of MALS-2 and PSD-95 revealed that the first two PDZ domains and two NH(2)-terminal cysteine residues are essential for the inhibitory effects of PSD-95 on protein kinase C-mediated potentiation of NR1-NR2A and NR1-NR2B channel activity, respectively. The second of the three PDZ domains of PSD-95 was required for its inhibition of Src-mediated potentiation of NR1-NR2A activity. These results indicate that the NR1-NR2A and NR1-NR2B receptors are modulated differentially by MALS-2 and PSD-95, and that similar regulatory effects of PSD-95 on these receptors are achieved by distinct mechanisms.

Epiregulin as a major autocrine/paracrine factor released from ERK- and p38MAPK-activated vascular smooth muscle cells.

BACKGROUND: The coordinated activation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38MAPK) is critical for the induction of vascular and visceral smooth muscle cell (SMC) dedifferentiation. We previously reported that on the forced activation of both MAPKs, visceral SMCs secrete a non-heparin-binding protein factor(s) that is involved in the dedifferentiation of neighboring SMCs. In this study, we sought to identify the dedifferentiation factor(s) derived from vascular SMCs (VSMCs). METHODS AND RESULTS: We fractionated the VSMC dedifferentiation factor(s) in the conditioned medium obtained from differentiated VSMCs in which both ERK and p38MAPK were forcedly activated and identified epiregulin as a major autocrine/paracrine factor for VSMC dedifferentiation. The epiregulin-induced VSMC dedifferentiation was mediated through the coordinated activation of ERK and p38MAPK. Unsaturated lysophosphatidic acid and platelet-derived growth factor-BB, which are potent VSMC dedifferentiation factors, rapidly upregulated epiregulin mRNA expression in an ERK- and p38MAPK-dependent manner. Reverse transcriptase-polymerase chain reaction and/or immunohistological analyses revealed the restricted expression of epiregulin in human atherosclerotic and balloon-injured rat arteries, in which the phenotypic modulation of medial VSMCs occurred in vivo. CONCLUSIONS: Epiregulin is released from VSMCs primed by atherogenic factors and acts as a major autocrine/paracrine factor for VSMC dedifferentiation. It may be involved in the progression of vascular remodeling such as atherosclerosis.