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Previous studies in mouse pulmonary arterial smooth muscle cells (PASMCs) showed that cannonical transient receptor potential channel TRPCI and stromal interaction molecule 1 (STIM1) mediate the sustained component of capacitative [Ca.sup.2+] entry (CCE), but the molecular candidate(s) that mediate the transient component of CCE remain unknown. The aim of the present study was to examine whether Orai1 mediates the transient component of CCE through activation of STIM1 in mouse PASMCs. In primary cultured mouse PASMCs loaded with fura-2, cyclopiazonic acid (CPA) caused a transient followed by a sustained rise in intracellular [Ca.sup.2+] concentration ([[Ca.sup.2+]].sub.i]). The transient but not the sustained rise in [[Ca.sup.2+].sub.i] was partially inhibited by nifedipine. The nifedipine-insensitive transient rise in [[Ca.sup.2+].sub.i] and the increase in [Mn.sup.2+] quench of fura-2 fluorescence caused by CPA were both reduced in cells treated with Orai1 siRNA. These responses to CPA were further reduced in cells treated with Orai1 and STIM1 small interfering (si)RNA. Moreover, overexpression of STIM1 enhanced the rise in [[Ca.sup.2+].sub.i] and the increase in [Mn.sup.2+] quench of fura-2 fluorescence caused by CPA, and these responses were reduced in cells treated with Orai1 siRNA. RT-PCR revealed Orai1 and STIM1 mRNAs, and Western blot analysis identified Orai1 and STIM1 proteins in mouse PASMCs. Furthermore, Orai1 was found to coimmunoprecipitate with STIM1, and the precipitation level of Orai1 was increased in cells subjected to store-depletion. Immunostaining revealed colocalization of Orai1 and STIM1 proteins, and the colocalization of these proteins was more apparent after store-depletion. These data provide direct evidence that the transient component of CCE is mediated by Orai1 channel as a result of STIM1 activation in mouse PASMCs. stromal interaction molecule 1; store-depletion; intracellular [Ca.sup.2+] concentration doi: 10.1152/ajpcell.00548.2009.

Recently, overexpression of the genes TMEM16A and TMEM16B has been shown to produce currents qualitatively similar to native [Ca.sup.2+]activated [Cl.sup.-] currents ([I.sub.CICa]) in vascular smooth muscle. However, there is no information about this new gene family in vascular smooth muscle, where C1 channels are a major depolarizing mechanism. Qualitatively similar C1 currents were evoked by a pipette solution containing 500 nM [Ca.sup.2+] in smooth muscle cells isolated from BALB/c mouse portal vein, thoracic aorta, and carotid artery. Quantitative PCR using SYBR Green chemistry and primers specific for transmembrane protein (TMEM) 16A or the closely related TMEM16B showed TMEM16A expression as follows: portal vein > thoracic aorta > carotid artery > brain. In addition, several alternatively spliced variant transcripts of TMEM16A were detected. In contrast, TMEM16B expression was very low in smooth muscle. Western blot analysis with different antibodies directed against TMEM16A revealed a number of products with a consistent band at 120 kDa, except portal vein, where an 80-kDa band predominated. TMEM16A protein was identified in the smooth muscle layers of 4-[micro]m-thick slices of portal vein, thoracic aorta, and carotid artery. In isolated myocytes, fluorescence specific to a TMEM 16A antibody was detected diffusely throughout the cytoplasm, as well as near the membrane. The same antibody used in Western blot analysis of lysates from vascular tissues also recognized an ~147-kDa mouse TMEM16A-green fluorescent protein (GFP) fusion protein expressed in HEK 293 cells, which correlated to a similar band detected by a GFP antibody. Patch-clamp experiments revealed that [I.sub.CICa] generated by transfection of TMEM16A-GFP in HEK 293 cells displayed remarkable similarities to [I.sub.CICa] recorded in vascular myocytes, including slow kinetics, steep outward rectification, and a response similar to the pharmacological agent niflumic acid. This study shows that TMEM16A expression is robust in murine vascular smooth muscle cells, consolidating the view that this gene is a viable candidate for the native [Ca.sup.2+]activated [Cl.sup.-] channel in this cell type. calcium-activated chloride channels; anoctamin 1; gene expression; smooth muscle contraction doi: 10.1152/ajpcell.00018.2010.

The purpose of this study was to determine whether extracellular matrix (ECM) composition through integrin receptors modulated the volume-sensitive osmolyte anion channels (VSOACs) in skeletal muscle-derived C2C12 cells. [Cl.sup.-] currents were recorded in whole cell voltage-clamped cells grown on laminin (LM), fibronectin (FN), or in the absence of a defined ECM (NM). Basal membrane currents recorded in isotonic media (300 mosmol/kg) were larger in cells grown on FN (3.8-fold at +100 mV) or LM (8.8-fold at +100 mV) when compared with NM. VSOAC currents activated by cell exposure to hypotonic solution were larger in cells grown on LM (1.72-fold at +100 mV) or FN (1.75-fold at +100 mV) compared with NM. Additionally, the kinetics of VSOAC activation was [approximately equal to]27% quicker on FN and LM. These currents were tamoxifen sensitive, displayed outward rectification, reversed at the equilibrium potential of [Cl.sup.-] and inactivated at potentials >+60 mV. Specific knockdown of [[beta].sub.1]-integrin by short hairpin RNA interference strongly inhibited the VSOAC [Cl.sup.-] currents in cells plated on FN. In conclusion, ECM composition and integrins profoundly influence the biophysical properties and mechanisms of onset of VSOACs. [Cl.sup.-] currents; C2C12 mouse myoblasts; short hairpin RNA interference knockdown doi: 10.1152/ajpcell.00359.2009.

Atrial (ANP) and brain (BNP) natriuretic peptides are hormones of myocardial cell origin. These hormones bind to the natriuretic peptide A receptor (NPRA) throughout the body, stimulating cGMP production and playing a key role in blood pressure control. Because NPRA receptors are present on cardiomyocytes, we hypothesized that natriuretic peptides may have direct autocrine or paracrine effects on cardiomyocytes or adjacent cardiac cells. Because both natriuretic peptides and NPRA gene expression are upregulated in states of pressure overload, we speculated that the effects of the natriuretic peptides on cardiac structure and function would be most apparent after pressure overload. To attenuate cardiomyocyte NPRA activity, transgenic mice with cardiac specific expression of a dominant-negative (DN-NPRA) mutation (HCAT D 893A) in the NPRA receptor were created. Cardiac structure and function were assessed (avertin anesthesia) in the absence and presence of pressure overload produced by suprarenal aortic banding. In the absence of pressure overload, basal and BNP-stimulated guanylyl cyclase activity assessed in cardiac membrane fractions was reduced. However, systolic blood pressure, myocardial cGMP, log plasma ANP levels, and ventricular structure and function were similar in wild-type (WT-NPRA) and DN-NPRA mice. In the presence of pressure overload, myocardial cGMP levels were reduced, and ventricular hypertrophy, fibrosis, filling pressures, and mortality were increased in DN-NPRA compared with WT-NPRA mice. In addition to their hormonal effects, endogenous natriuretic peptides exert physiologically relevant autocrine and paracrine effects via cardiomyocyte NPRA receptors to modulate cardiac hypertrophy and fibrosis in response to pressure overload. natriuretic peptides; diastole; hypertrophy; fibrosis

Doxycycline-inducible expression of SERCA2a improves calcium handling and reverts cardiac dysfunction in pressure overload-induced cardiac hypertrophy. Ant J Physiol Heart Circ Physiol 287: H2164-H2172, 2004. First published July 15, 2004; doi:10.1152/ajpheart.00428. 2004.--Delayed cardiac relaxation in failing hearts has been attributed to reduced activity and/or expression of sarco(endo)plasmic reticulum [Ca.sup.2+]-ATPase 2a (SERCA2a). Although constitutive overexpression of SERCA2a has proven effective in preventing cardiac dysfunction, it is unclear whether increasing SERCA2a expression in hearts with preexisting hypertrophy will be therapeutic. To test this hypothesis, we generated a binary transgenic (BTG) system that allows tetracycline-inducible, cardiac-specific SERCA2a expression. In this system (tet-on SERCA2a), a FLAG-tagged SERCA2a transgene is expressed in the presence of doxycycline (Dox) but not in the absence of Dox (2.3-fold more mRNA, 45% more SERCA2a protein). Calcium transients measured in isolated cardiac myocytes from nonbanded Dox-treated BTG mice showed an accelerated calcium decline and an increased systolic [Ca.sup.2+] peak. Sarcoplasmic reticulum (SR) calcium loading was increased by 45% in BTG mice. In the presence of pressure overload (aortic banding), echocardiographic analysis revealed that expression of SERCA2a-FLAG caused an improvement in fractional shortening. SERCA2a-FLAG expression alleviated the resultant cardiac dysfunction. This was illustrated by an increase in the rate of decline of the calcium transient. Cell shortening and SR calcium loading were also improved in cardiac myocytes isolated from banded BTG mice after SERCA2a overexpression. In conclusion, we generated a novel transgenic mouse that conditionally overexpresses SERCA2a. This model is suitable for both long- and short-term studies of the effects of controlled SERCA2a expression on cardiac function. In addition, inducible overexpression of SERCA2a improved cardiac function and calcium handling in mice with established contractile dysfunction. heart failure; cardiac myocytes; transgenic mice; sarco(endo)plasmic reticulum [Ca.sup.2+]-ATPase

Cardiac expression of a gain-of-function [[Alpha].sub.5]-integrin results in perinatal lethality. Am J Physiol Heart Circ Physiol 280: H361-H367, 2001.--Communication between the extracellular matrix and the intracellular signal transduction and cytoskeletal system is mediated by integrin receptors. [[Alpha].sub.5][Beta].sub.1]-Integrin and its cognate ligand fibronectin are essential in development of mesodermal structures, myocyte differentiation, and normal cardiac development. To begin to explore the potential roles of [[Alpha].sub.5][[Beta].sub.1]-integrin specifically in cardiomyocytes, we used a transgenic expression strategy. We overexpressed two forms of the human [[Alpha].sub.5]-integrin in cardiomyocytes: the full-length wild-type [[Alpha].sub.5]-integrin and a putative gain-of-function mutation created by truncating the cytoplasmic domain, designated [[Alpha].sub.5-1]-integrin. Overexpression of the wild-type [[Alpha].sub.5]-integrin has no detectable adverse effects in the mouse, whereas expression of [[Alpha].sub.5-1]-integrin caused electrocardiographic abnormalities, fibrotic changes in the ventricle, and perinatal lethality. Thus physiological regulation of integrin function appears essential for maintenance of normal cardiomyocyte structure and function. This strengthens the role of inside-out signaling in regulation of integrins in vivo and suggests that integrins and associated signaling molecules are important in cardiomyocyte function. inside-out signaling; electrocardiogram abnormalities; cardiomyopathy; fibrosis

Previous studies in mouse pulmonary arterial smooth muscle cells (PASMCs) showed that cannonical transient receptor potential channel TRPC1 and stromal interaction molecule 1 (STIM1) mediate the sustained component of capacitative Ca2+ entry (CCE), but the molecular candidate(s) that mediate the transient component of CCE remain unknown. The aim of the present study was to examine whether Orai1 mediates the transient component of CCE through activation of STIM1 in mouse PASMCs. In primary cultured mouse PASMCs loaded with fura-2, cyclopiazonic acid (CPA) caused a transient followed by a sustained rise in intracellular Ca2+ concentration ([Ca2+]i). The transient but not the sustained rise in [Ca2+]i was partially inhibited by nifedipine. The nifedipine-insensitive transient rise in [Ca2+]i and the increase in Mn2+ quench of fura-2 fluorescence caused by CPA were both reduced in cells treated with Orai1 siRNA. These responses to CPA were further reduced in cells treated with Orai1 and STIM1 small interfering (si)RNA. Moreover, overexpression of STIM1 enhanced the rise in [Ca2+]i and the increase in Mn2+ quench of fura-2 fluorescence caused by CPA, and these responses were reduced in cells treated with Orai1 siRNA. RT-PCR revealed Orai1 and STIM1 mRNAs, and Western blot analysis identified Orai1 and STIM1 proteins in mouse PASMCs. Furthermore, Orai1 was found to coimmunoprecipitate with STIM1, and the precipitation level of Orai1 was increased in cells subjected to store-depletion. Immunostaining revealed colocalization of Orai1 and STIM1 proteins, and the colocalization of these proteins was more apparent after storedepletion. These data provide direct evidence that the transient component of CCE is mediated by Orai1 channel as a result of STIM1 activation in mouse PASMCs. [ABSTRACT FROM AUTHOR]

While considerable evidence supports the causal relationship between increases in c-Myc (Myc) and cardiomyopathy as a part of a ''fetal re-expression'' pattern, the functional role of Myc in mechanisms of cardiomyopathy remains unclear. To address this, we developed a bitransgenic mouse that inducibly expresses Myc under the control of the cardiomyocyte-specific MHC promoter. In adult mice the induction of Myc expression in cardiomyocytes in the heart led to the development of severe hypertrophic cardiomyopathy followed by ventricular dysfunction and ultimately death from congestive heart failure. Mechanistically, following Myc activation, cell cycle markers and other indices of DNA replication were significantly increased suggesting that cell cycle-related events might be a primary mechanism of cardiac dysfunction. Furthermore, pathological alterations at the cellular level included alterations in mitochondrial function with dysregulation of mitochondrial biogenesis and defects in electron transport chain complexes I and III. These data are consistent with the known role of Myc in several different pathways including cell cycle activation, mitochondrial proliferation, and apoptosis, and indicate that Myc activation in cardiomyocytes is an important regulator of downstream pathological sequelae. Moreover, our findings indicate that the induction of Myc in cardiomyocytes is sufficient to cause cardiomyopathy and heart failure, and that sustained induction of Myc, leading to cell cycle re-entry in adult cardiomyocytes, represents a maladaptive response for the mature heart. [ABSTRACT FROM AUTHOR]

Presents information on a study which explored the potential roles of alpha[sub 5]beta[sub 1]-integrin in myocytes using a transgenic expression strategy. Details on integrins; Forms of the human alpha[sub 5]-integrin subunit in mice; Methodology; Results; Discussion.

The present study was undertaken to determine whether the two ubiquitously expressed Ca2+-independent phosphatases PP1 and PP2A regulate Ca2+-activated Cl- currents (ICl(Ca)) elicited by 500 nM [Ca2+]i in rabbit pulmonary artery (PA) myocytes dialyzed with or without 3mM ATP. Reverse transcriptionPCR experiments revealed the expression of PP1α, PP1β/δ, PP1γ, PP2Aα, PP2Aβ, PP2Bα (calcineurin (CaN) Aα), and PP2Bβ (CaN Aβ) but not PP2Bγ (CaN Aγ) in rabbit PA. Western blot and immunofluorescence experiments confirmed the presence of all three PP1 isoforms and PP2A. Intracellular dialysis with a peptide inhibitor of calcineurin (CaN-AlP); the nonselective PP1/PP2A inhibitors okadaic acid (0.5, 10, or 30 nM), calyculin A (10 nM), or cantharidin (100 nM); and the selective PP1 inhibitor NIPP-1 (100 pM) potently antagonized the recovery of ICl(Ca) in cells dialyzed with no ATP, whereas the PP2A-selective antagonist fostriecin (30 or 150 nM) was ineffective. The combined application of okadaic acid (10 nM) and CaNautoinhibitory peptide (50 μM) did not potentiate the response of ICl(Ca) in 0 ATP produced by maximally inhibiting CaN or PP1/PP2A alone. Consistent with the non-additive effects of either classes of phosphatases, the PP1 inhibitor NIPP-1 (100 pM) antagonized the recovery of ICl(Ca) induced by exogenous CaN Aα (0.5 μM). These results demonstrate that ICl(Ca) in PA myocytes is regulated by CaN and PP1 and/or PP2A. Our data also suggest the existence of a functional link between these two classes of phosphatases. [ABSTRACT FROM AUTHOR]

This study explored the mechanism by which Ca 2+ -activated Cl - channels (CaCCs) encoded by the Tmem16a gene are regulated by calmodulin-dependent protein kinase II (CaMKII) and protein phosphatases 1 (PP1) and 2A (PP2A). Ca 2+ -activated Cl - currents ( I ClCa ) were recorded from HEK-293 cells expressing mouse TMEM16A. I ClCa were evoked using a pipette solution in which free Ca 2+ concentration was clamped to 500 nM, in the presence (5 mM) or absence of ATP. With 5 mM ATP, I ClCa decayed to <50% of the initial current magnitude within 10 min after seal rupture. I ClCa rundown seen with ATP-containing pipette solution was greatly diminished by omitting ATP. I ClCa recorded after 20 min of cell dialysis with 0 ATP were more than twofold larger than those recorded with 5 mM ATP. Intracellular application of autocamtide-2-related inhibitory peptide (5 µM) or KN-93 (10 µM), two specific CaMKII inhibitors, produced a similar attenuation of TMEM16A rundown. In contrast, internal application of okadaic acid (30 nM) or cantharidin (100 nM), two nonselective PP1 and PP2A blockers, promoted the rundown of TMEM16A in cells dialyzed with 0 ATP. Mutating serine 528 of TMEM16A to an alanine led to a similar inhibition of TMEM16A rundown to that exerted by either one of the two CaMKII inhibitors tested, which was not observed for three putative CaMKII consensus sites for phosphorylation (T273, T622, and S730). Our results suggest that TMEM16A-mediated CaCCs are regulated by CaMKII and PP1/PP2A. Our data also suggest that serine 528 of TMEM16A is an important contributor to the regulation of I ClCa by CaMKII.

The formation of small Aβ 42 oligomers has been implicated as a toxic species in Alzheimer disease (AD). In strong support of this hypothesis we found that overexpression of Yap1802, the yeast ortholog of the human AD risk factor, phosphatidylinositol binding clathrin assembly protein (PICALM), reduced oligomerization of Aβ 42 fused to a reporter in yeast. Thus we used the Aβ 42 -reporter system to identify drugs that could be developed into therapies that prevent or arrest AD. From a screen of 1,200 FDA approved drugs and drug-like small compounds we identified 7 drugs that reduce Aβ 42 oligomerization in yeast: 3 antipsychotics (bromperidol, haloperidol and azaperone), 2 anesthetics (pramoxine HCl and dyclonine HCl), tamoxifen citrate, and minocycline HCl. Also, all 7 drugs caused Aβ 42 to be less toxic to PC12 cells and to relieve toxicity of another yeast AD model in which Aβ 42 aggregates targeted to the secretory pathway are toxic. Our results identify drugs that inhibit Aβ 42 oligomers from forming in yeast. It remains to be determined if these drugs inhibit Aβ 42 oligomerization in mammals and could be developed as a therapeutic treatment for AD., Competing Interests: Conflict of interest: The authors declare there is no conflict of interest.

Pulmonary artery smooth muscle cells (PASMCs) are more depolarized and display higher Ca(2+) levels in pulmonary hypertension (PH). Whether the functional properties and expression of Ca(2+)-activated Cl- channels (Cl(Ca)), an important excitatory mechanism in PASMCs, are altered in PH is unknown. The potential role of Cl(Ca) channels in PH was investigated using the monocrotaline (MCT)-induced PH model in the rat. Three weeks postinjection with a single dose of MCT (50 mg/kg ip), the animals developed right ventricular hypertrophy (heart weight measurements) and changes in pulmonary arterial flow (pulse-waved Doppler imaging) that were consistent with increased pulmonary arterial pressure and PH. Whole cell patch experiments revealed an increase in niflumic acid (NFA)-sensitive Ca(2+)-activated Cl(-) current [I(Cl(Ca))] density in PASMCs from large conduit and small intralobar pulmonary arteries of MCT-treated rats vs. aged-matched saline-injected controls. Quantitative RT-PCR and Western blot analysis revealed that the alterations in I(Cl(Ca)) were accompanied by parallel changes in the expression of TMEM16A, a gene recently shown to encode for Cl(Ca) channels. The contraction to serotonin of conduit and intralobar pulmonary arteries from MCT-treated rats exhibited greater sensitivity to nifedipine (1 μM), an l-type Ca(2+) channel blocker, and NFA (30 or 100 μM, with or without 10 μM indomethacin to inhibit cyclooxygenases) or T16A(Inh)-A01 (10 μM), TMEM16A/Cl(Ca) channel inhibitors, than that of control animals. In conclusion, augmented Cl(Ca)/TMEM16A channel activity is a major contributor to the changes in electromechanical coupling of PA in this model of PH. TMEM16A-encoded channels may therefore represent a novel therapeutic target in this disease.

Previous studies in mouse pulmonary arterial smooth muscle cells (PASMCs) showed that cannonical transient receptor potential channel TRPC1 and stromal interaction molecule 1 (STIM1) mediate the sustained component of capacitative Ca(2+) entry (CCE), but the molecular candidate(s) that mediate the transient component of CCE remain unknown. The aim of the present study was to examine whether Orai1 mediates the transient component of CCE through activation of STIM1 in mouse PASMCs. In primary cultured mouse PASMCs loaded with fura-2, cyclopiazonic acid (CPA) caused a transient followed by a sustained rise in intracellular Ca(2+) concentration ([Ca(2+)](i)). The transient but not the sustained rise in [Ca(2+)](i) was partially inhibited by nifedipine. The nifedipine-insensitive transient rise in [Ca(2+)](i) and the increase in Mn(2+) quench of fura-2 fluorescence caused by CPA were both reduced in cells treated with Orai1 siRNA. These responses to CPA were further reduced in cells treated with Orai1 and STIM1 small interfering (si)RNA. Moreover, overexpression of STIM1 enhanced the rise in [Ca(2+)](i) and the increase in Mn(2+) quench of fura-2 fluorescence caused by CPA, and these responses were reduced in cells treated with Orai1 siRNA. RT-PCR revealed Orai1 and STIM1 mRNAs, and Western blot analysis identified Orai1 and STIM1 proteins in mouse PASMCs. Furthermore, Orai1 was found to coimmunoprecipitate with STIM1, and the precipitation level of Orai1 was increased in cells subjected to store-depletion. Immunostaining revealed colocalization of Orai1 and STIM1 proteins, and the colocalization of these proteins was more apparent after store-depletion. These data provide direct evidence that the transient component of CCE is mediated by Orai1 channel as a result of STIM1 activation in mouse PASMCs.

Yeast two-hybrid analysis (Fields and Song, 1989, Nature, 340:245-246) was used to screen a human heart library to isolate proteins interacting with the adult muscle-specific beta1D integrin but not with beta1A integrin. In addition to previously identified interactions (RACK 1(Liliental and Chang, 1998, Journal of Biological Chemistry, 273:2379-2383) and alpha-actinin (Otey et al., 1990, Journal of Cell Biology, 111:721-729), the authors isolated several novel candidates. These include subunit 3 (CSN3/Sgn3) of the COP9 signalosome complex, cyclins D1, D2, and D3, RanBPM, and a recently identified protein COG8/DOR1. These protein interactions were specific for beta1D integrin, as no binding to beta1A integrin cytoplasmic domain was measurable by two-hybrid analysis. This paper presents the initial characterization of the interaction of CSN3 with beta1D integrin, the localization of CSN3 and the other COP9 signalosome subunits in embryonic and adult cardiac myocytes and their response to muscle cell differentiation.

Recent evidence has identified the peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) as a regulator of cardiac energy metabolism and mitochondrial biogenesis. We describe the development of a transgenic system that permits inducible, cardiac-specific overexpression of PGC-1alpha. Expression of the PGC-1alpha transgene in this system (tet-on PGC-1alpha) is cardiac-specific in the presence of doxycycline (dox) and is not leaky in the absence of dox. Overexpression of PGC-1alpha in tet-on PGC-1alpha mice during the neonatal stages leads to a dramatic increase in cardiac mitochondrial number and size coincident with upregulation of gene markers associated with mitochondrial biogenesis. In contrast, overexpression of PGC-1alpha in the hearts of adult mice leads to a modest increase in mitochondrial number, derangements of mitochondrial ultrastructure, and development of cardiomyopathy. The cardiomyopathy in adult tet-on PGC-1alpha mice is characterized by an increase in ventricular mass and chamber dilatation. Surprisingly, removal of dox and cessation of PGC-1alpha overexpression in adult mice results in complete reversal of cardiac dysfunction within 4 weeks. These results indicate that PGC-1alpha drives mitochondrial biogenesis in a developmental stage-dependent manner permissive during the neonatal period. This unique murine model should prove useful for the study of the molecular regulatory programs governing mitochondrial biogenesis and characterization of the relationship between mitochondrial dysfunction and cardiomyopathy and as a general model of inducible, reversible cardiomyopathy.