Golgi localized β1-adrenergic receptors stimulate Golgi PI4P hydrolysis by PLCε to regulate cardiac hypertrophy.

Increased adrenergic tone resulting from cardiovascular stress leads to development of heart failure, in part, through chronic stimulation of β1 adrenergic receptors (βARs) on cardiac myocytes. Blocking these receptors is part of the basis for β-blocker therapy for heart failure. Recent data demonstrate that G protein-coupled receptors (GPCRs), including βARs, are activated intracellularly, although the biological significance is unclear. Here we investigated the functional role of Golgi βARs in rat cardiac myocytes and found they activate Golgi localized, prohypertrophic, phosphoinositide hydrolysis, that is not accessed by cell surface βAR stimulation. This pathway is accessed by the physiological neurotransmitter norepinephrine (NE) via an Oct3 organic cation transporter. Blockade of Oct3 or specific blockade of Golgi resident β1ARs prevents NE dependent cardiac myocyte hypertrophy. This clearly defines a pathway activated by internal GPCRs in a biologically relevant cell type and has implications for development of more efficacious β-blocker therapies

A Novel Gβγ-Subunit Inhibitor Selectively Modulates μ-Opioid- Dependent Antinociception and Attenuates Acute Morphine-Induced Antinociceptive Tolerance and Dependence

The Gβγ subunit has been implicated in many downstream signaling events associated with opioids. We previously demonstrated that a small molecule inhibitor of Gβγ-subunit-dependent phospholipase (PLC) activation potentiated morphine-induced analgesia (Bonacci et al., 2006). Here, we demonstrate that this inhibitor, M119 (cyclohexanecarboxylic acid [2-(4,5,6-trihydroxy-3-oxo-3H-xanthen-9-yl)-(9Cl)]), is selective for μ-opioid receptor-dependent analgesia and has additional efficacy in mouse models of acute tolerance and dependence. When administered by an intracerebroventricular injection in mice, M119 caused 10-fold and sevenfold increases in the potencies of morphine and the μ-selective peptide, DAMGO, respectively. M119 had little or no effect on analgesia induced by the κ agonist U50,488 or δ agonists DPDPE or Deltorphin II. Similar results were obtained in vitro, as only activation of the μ-opioid receptor stimulated PLC activation, whereas no effect was seen with the κ- and δ-opioid receptors. M119 inhibited μ-receptor-dependent PLC activation. In studies to further explore the in vivo efficacy of M119, systemic administration M119 also resulted in a fourfold shift increase in potency of systemically administered morphine. Of particular interest, M119 was also able to attenuate acute, antinociceptive tolerance and dependence in mice treated concomitantly with both M119 and morphine. These studies suggest that small organic molecules, such as M119, that specifically regulate Gβγ subunit signaling may have important therapeutic applications in enhancing opioid analgesia, while attenuating the development of tolerance and dependence

From laterally modulated two-dimensional electron gas towards artificial graphene

Cyclotron resonance has been measured in far-infrared transmission of GaAs/Al$_x$Ga$_{1-x}$As heterostructures with an etched hexagonal lateral superlattice. Non-linear dependence of the resonance position on magnetic field was observed as well as its splitting into several modes. Our explanation, based on a perturbative calculation, describes the observed phenomena as a weak effect of the lateral potential on the two-dimensional electron gas. Using this approach, we found a correlation between parameters of the lateral patterning and the created effective potential and obtain thus insights on how the electronic miniband structure has been tuned. The miniband dispersion was calculated using a simplified model and allowed us to formulate four basic criteria that have to be satisfied to reach graphene-like physics in such systems

Magnetotransport in graphene on silicon side of SiC

We have studied the transport properties of graphene grown on silicon side of SiC. Samples under study have been prepared by two different growth methods in two different laboratories. Magnetoresistance and Hall resistance have been measured at temperatures between 4 and 100 K in resistive magnet in magnetic fields up to 22 T. In spite of differences in sample preparation, the field dependence of resistances measured on both sets of samples exhibits two periods of magneto-oscillations indicating two different parallel conducting channels with different concentrations of carriers. The semi-quantitative agreement with the model calculation allows for conclusion that channels are formed by high-density and low-density Dirac carriers. The coexistence of two different groups of carriers on the silicon side of SiC was not reported before.Comment: 5 pages, 6 figures, accepted for publication in the "IOP Journal of Physics: Conference series" as a contribution to the proceedings of the 20th International Conference on "High Magnetic Fields in Semiconductor Physics", HMF 2

PLCε1 suppresses tumor growth by regulating murine T cell mobilization

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154282/1/cei13409.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154282/2/cei13409_am.pd

Structural and molecular characterization of a preferred protein interaction surface on G protein beta gamma subunits

G protein betagamma subunits associate with many binding partners in cellular signaling cascades. In previous work, we used random-peptide phage display screening to identify a diverse family of peptides that bound to a common surface on Gbetagamma subunits and blocked a subset of Gbetagamma effectors. Later studies showed that one of the peptides caused G protein activation through a novel Gbetagamma-dependent, nucleotide exchange-independent mechanism. Here we report the X-ray crystal structure of Gbeta(1)gamma(2) bound to this peptide, SIGK (SIGKAFKILGYPDYD), at 2.7 A resolution. SIGK forms a helical structure that binds the same face of Gbeta(1) as the switch II region of Galpha. The interaction interface can be subdivided into polar and nonpolar interfaces that together contain a mixture of binding determinants that may be responsible for the ability of this surface to recognize multiple protein partners. Systematic mutagenic analysis of the peptide-Gbeta(1) interface indicates that distinct sets of amino acids within this interface are required for binding of different peptides. Among these unique amino acid interactions, specific electrostatic binding contacts within the polar interface are required for peptide-mediated subunit dissociation. The data provide a mechanistic basis for multiple target recognition by Gbetagamma subunits with diverse functional interactions within a common interface and suggest that pharmacological targeting of distinct regions within this interface could allow for selective manipulation of Gbetagamma-dependent signaling pathways

G protein βγ subunits regulate cardiomyocyte hypertrophy through a perinuclear Golgi phosphatidylinositol 4-phosphate hydrolysis pathway.

We recently identified a novel GPCR-dependent pathway for regulation of cardiac hypertrophy that depends on Golgi phosphatidylinositol 4-phosphate (PI4P) hydrolysis by a specific isoform of phospholipase C (PLC), PLCε, at the nuclear envelope. How stimuli are transmitted from cell surface GPCRs to activation of perinuclear PLCε is not clear. Here we tested the role of G protein βγ subunits. Gβγ inhibition blocked ET-1-stimulated Golgi PI4P depletion in neonatal and adult ventricular myocytes. Blocking Gβγ at the Golgi inhibited ET-1-dependent PI4P depletion and nuclear PKD activation. Translocation of Gβγ to the Golgi stimulated perinuclear Golgi PI4P depletion and nuclear PKD activation. Finally, blocking Gβγ at the Golgi or PM blocked ET-1-dependent cardiomyocyte hypertrophy. These data indicate that Gβγ regulation of the perinuclear Golgi PI4P pathway and a separate pathway at the PM is required for ET-1-stimulated hypertrophy, and the efficacy of Gβγ inhibition in preventing heart failure maybe due in part to its blocking both these pathways

Density of states and electron concentration of double heterojunctions subjected to an in-plane magnetic field

We calculate the electronic states of Al$_x$Ga$_{1-x}$As/GaAs/Al$_x$Ga$_{1-x}$As double heterojunctions subjected to a magnetic field parallel to the quasi two-dimensional electron gas. We study the energy dispersion curves, the density of states, the electron concentration and the distribution of the electrons in the subbands. The parallel magnetic field induces severe changes in the density of states, which are of crucial importance for the explanation of the magnetoconductivity in these structures. However, to our knowledge, there is no systematic study of the density of states under these circumstances. We attempt a contribution in this direction. For symmetric heterostructures, the depopulation of the higher subbands, the transition from a single to a bilayer electron system and the domination of the bulk Landau levels in the centre the wide quantum well, as the magnetic field is continuously increased, are presented in the ``energy dispersion picture'' as well as in the ``electron concentration picture'' and in the ``density of states picture''.Comment: J. Phys.: Condens. Matter 11 No 26 (5 July 1999) 5131-5141 Figures (three) embedde