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Signal transduction via guanine nucleotide binding proteins (G proteins) is involved in cardiovascular, neural, endocrine, and immune cell function. Regulators of G protein signaling (RGS proteins) speed the turn-off of G protein signals and inhibit signal transduction, but the in vivo roles of RGS proteins remain poorly defined. To overcome the redundancy of RGS functions and reveal the total contribution of RGS regulation at the G␣ i2 subunit, we prepared a genomic knock-in of the RGS-insensitive G184S Gnai2 allele. The G␣ i2 G184S knock-in mice show a dramatic and complex phenotype affecting multiple organ systems (heart, myeloid, skeletal, and central nervous system). Both homozygotes and heterozygotes demonstrate reduced viability and decreased body weight. Other phenotypes include shortened long bones, a markedly enlarged spleen, elevated neutrophil counts, an enlarged heart, and behavioral hyperactivity. Heterozygous G␣ i2 ؉/G184S mice show some but not all of these abnormalities. Thus, loss of RGS actions at G␣ i2 produces a dramatic and pleiotropic phenotype which is more evident than the phenotype seen for individual RGS protein knockouts.Cell-cell communication is fundamental to the maintenance of homeostasis. The G protein-coupled receptor superfamily is arguably the most abundant and diverse protein family in cellular signaling and is tightly regulated. A novel family of Ͼ20 proteins termed regulators of G protein signaling, or RGS proteins, both tonically inhibit G protein function and also serve as signal control points (2,22,34,39,69). RGS-mediated inhibition of G protein signaling occurs through direct binding of the RGS protein to the G␣ subunit, with subsequent GTPase-accelerating protein (GAP) actions to rapidly deactivate G␣ (2). Deactivation may be accelerated up to 1,000-fold and shuts down both G␣ and G␤␥ signals (42, 48). RGS proteins may also competitively inhibit G␣ binding to effectors such as phospholipase C (32). Most of the currently known RGS proteins interact with either Gi or Gq family G proteins and influence cyclic AMP (cAMP), Ca 2ϩ , mitogen-activated protein kinase, and ion channel signaling. There is strong evidence implicating them in the subsecond kinetics of G i -and G o -mediated ion channel activation and deactivation in the heart (10, 21, 36) and neurons (36). In addition, the conserved RGS domain has been found to serve as a multifunctional protein adapter which can recruit many effectors or regulators to the vicinity of activated G proteins (31,53,62). Notable examples include p115rhoGEF (30, 40) and GRK2 (44). There is also emerging interest in RGS proteins as drug targets (9,20,53,72).However, the physiological functions of RGS proteins remain poorly defined. A number of RGS knockouts have been reported (for example, RGS1, -2, -4, and -9). The RGS9-1 knockout shows prolonged visual potentials (7), and RGS9-2 disruption results in markedly enhanced responses to drugs of abuse, such as cocaine, amphetamines, and opiates (56, 71). A human disorder, bradyopsia, with r...

Abstract-Cardiac automaticity is controlled by G protein-coupled receptors, such as adrenergic, muscarinic, and adenosine receptors. The strength and duration of G protein signaling is attenuated by regulator of G protein signaling (RGS) proteins acting as GTPase-activating proteins for G␣ subunits; however, little is known about the role of endogenous RGS proteins in cardiac function. We created point mutations in G␣ subunits that disrupt G␣-RGS binding and introduced them into embryonic stem (ES) cells by homologous recombination. Spontaneously contacting cardiocytes derived from the ES cells were used to evaluate the role of endogenous RGS proteins in chronotropic regulation. The RGS-insensitive G␣ o G184S homozygous knock-in (G␣ o GS/GS) cells demonstrated enhanced adenosine A 1 and muscarinic M 2 receptor-mediated bradycardic responses. In contrast, G␣ i2 GS/GS cells showed enhanced responses to M 2 but not A 1 receptors. Similarly M 2 but not A 1 bradycardic responses were dramatically enhanced in G␣ i2 GS/GS mice. Blocking G protein-coupled inward rectifying K ϩ (GIRK) channels largely abolished the mutation-induced enhancement of the M 2 receptor-mediated response but had a minimal effect on A 1 responses. The G␣ s -dependent stimulation of beating rate by the ␤ 2 adrenergic receptor agonist procaterol was significantly attenuated in G␣ o GS/GS and nearly abolished in G␣ i2 GS/GS cells because of enhanced signaling via a pertussis toxin sensitive mechanism. Thus, endogenous RGS proteins potently reduce the actions of G␣ i/o -linked receptors on cardiac automaticity. Key Words: RGS Ⅲ automaticity Ⅲ adenosine receptor Ⅲ ␤ 2 adrenergic receptor Ⅲ muscarinic receptor G protein-coupled receptors (GPCRs) control many cardiovascular functions, such as automaticity and contractility and cell growth and survival. 1 Cardiac ion channels are key effectors, including activation of the G protein-coupled inward rectifying potassium (GIRK) channels by ␤␥ subunits released from G␣ i and inhibition of I f and I Ca,L by G␣ o , whereas I Ca,L is also regulated by G␣ i and nitric oxide. [2][3][4][5] GIRK channels contribute approximately 50% of the in vivo bradycardic response to vagal stimulation, 6 but the relative contribution of different G␣ subunits to in vivo cardiac automaticity is less clear.The recently identified regulators of G protein signaling (RGS) proteins reduce the strength and duration of G protein signaling by acting as GTPase accelerating proteins (GAPs) through their conserved RGS domain. 7 Mammalian myocardium expresses more than 10 different RGS proteins (2, 3, 4, 5, 6, 7, 12, 14, 16, and 19), which have GAP activity toward G␣ i/o and G␣ q/11 family G proteins. 8 Indeed, the first reported mammalian RGS effect was the rapid deactivation of GIRK currents in atrium 9 and RGS proteins also contribute to agonist-, calcium-, and voltage-dependent relaxation of GIRK currents. 10 -12 These results suggest an important role for RGS proteins in sinoatrial (SA) node function and potentially in atrial arrhyth...

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The pyrolysis kinetics of charring materials plays an important role in understanding material combustions especially for constructions materials with complex degradation chemistry. Thermogravimetric analysis (TGA) is frequently used to study the heterogeneous kinetics of solid fuels, however, there is no agreed method to determine the pyrolysis scheme and kinetic parameters for charring polymers with multiple components and competing reaction pathways. This study develops a new technique to estimate the possible numbers of species and sub-reactions in pyrolysis by analysing the second derivatives of TG (DDTG) curves.The pyrolysis of a medium density fibreboard (MDF) in nitrogen is studied in detail, and the DDTG curves are used to locate the temperature of peak mass-loss rate for each sub-reactions. Then, based on the TG data under multiple heating rates, the Kissinger's method is used to quickly find the possible range of values of the kinetic parameters (A and E). These ranges are used to accelerate the optimization of the inverse problem using genetic algorithm (GA) for the kinetic and stoichiometric parameters. The proposed method and the kinetic scheme found are shown to match the experimental data and are able to predict accurately results at different heating rate better than the Kissinger's method. Moreover, the search method (K-K method) is highly efficient, faster than the regular GA search alone. Modelling results show that as the TG data available increases, the interdependence among kinetic parameters becomes weak and the accuracy of first-order model declines. Furthermore, conducting TG experiment under multiple heating rates is found to be crucial in obtaining good kinetic parameters.

Elevating serotonin (5-HT) levels with selective serotonin reuptake inhibitors (SSRIs) is the most widely used treatment for depression. However, current therapies are ineffective, have delayed benefit, or cause side effects in many patients. Here, we define a mechanism downstream of 5-HT1A receptors that mediates antidepressant-like behavior and is profoundly and selectively enhanced by genetic disruption of regulators of G protein signaling (RGS) activity at Gαi2. Animals rendered insensitive to RGS protein regulation through a mutation in Gαi2 (G184S) exhibited spontaneous antidepressant-and anxiolytic-like behaviors. Mice expressing RGS-insensitive Gαi2 also exhibited increased cortical and hippocampal phosphorylation of glycogen synthase kinase-3β, a constitutively active proapoptotic kinase that is inhibited through phosphorylation in response to serotonin, SSRIs, and 5-HT1 receptor agonists. Both behavioral and biochemical phenotypes were blocked by treatment with WAY 100635, a 5-HT1A-selective antagonist. RGS-insensitive mice were also 5-10 times more responsive to the antidepressant-like effects of the SSRI fluvoxamine and 5-HT1A-selective agonist 8-hydroxy-2-dipropylaminotetralin. In contrast, the antidepressant potency of agents acting through nonserotonergic mechanisms was unchanged as was 5-HT1A action on body temperature. The findings point to a critical role for endogenous RGS proteins to suppress the antidepressant-like effects of 5-HT1A receptor activation. By selectively enhancing the beneficial effects of serotonin, inhibition of RGS proteins represents a therapeutic approach for the treatment of mood disorders.5-HT1A receptors | depression | G protein | regulator of G protein signaling proteins | transgenic mouse S elective serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed antidepressants (1). Their use is based on a strategy of augmenting the effects of endogenous serotonin by increasing synaptic concentrations. However, the therapeutic benefit of SSRI administration is delayed by weeks or even months. In addition, these drugs are ineffective in many patients and often cause unpleasant and harmful side effects (2). SSRI therapy causes general increases in synaptic serotonin that activate many types of serotonin (5-HT) receptors with a diverse distribution that couple to a wide array of signaling pathways. Manipulation of 5-HT1 receptor activity is generally thought to underlie the beneficial as well as the unfavorable effects of SSRIs. The 5-HT1 receptors are members of the superfamily of G protein-coupled receptors that activate the adenylyl cyclasecoupled inhibitory class of heterotrimeric G proteins. Although multiple lines of evidence suggest that 5-HT1 receptors preferentially couple to Gαi2 in vitro (3), the relative contribution of different Gαi/o-family proteins to these beneficial and unfavorable effects of 5-HT1A receptor activation is not known.Regulator of G protein signaling (RGS) proteins are a family of more than 30 members defined by a characteristic 120-...

The thermochemical conversion of biomass in smouldering combustion is investigated here by combining experiments and modeling at two scales: matter (1mg) and bench (100g) scales. Emphasis is put on the effect of oxygen (0-33vol.%) and oxidation reactions because these are poorly studied in the literature in comparison to pyrolysis. The results are obtained for peat as a representative biomass for which there is high-quality experimental data published previously. Three kinetic schemes are explored, including various steps of drying, pyrolysis and oxidation. The kinetic parameters are found using the Kissinger-Genetic Algorithm method, and then implemented in a one-dimensional model of heat and mass transfer. The predictions are validated with thermogravimetric and bench-scale experiments and then analyzed to unravel the role of heterogeneous reaction. This is the first time that the influence of oxygen on biomass smouldering is explained in terms of both chemistry and transport phenomena across scales.