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Hsien-Yu Wang

Publications and source records attributed to Hsien-Yu Wang.

13 recordsLinked to original sources
PubMed2007

Src docks to A-kinase anchoring protein gravin, regulating beta2-adrenergic receptor resensitization and recycling.

Gravin (AKAP12) is a membrane-associated scaffold that provides docking for protein kinases, phosphatases, and adaptor molecules obligate for resensitization and recycling of beta(2)-adrenergic receptors. Gravin binds to the cell membrane in a Ca(2+)-sensitive manner and to receptors through well characterized protein-protein interactions. Although the interaction of serine/threonine, cyclic AMP-dependent protein kinase with protein kinase A-anchoring proteins is well described and involves a kinase regulatory subunit binding domain in the C terminus of these proteins, far less is known about tyrosine kinase docking to members of this family of scaffolds. The non-receptor tyrosine kinase Src regulates resensitization of beta(2)-adrenergic receptors and docks to gravin. Gravin displays nine proline-rich domains distributed throughout the molecule. One class I ligand for Src homology domain 3 docking, found in the N terminus ((10)RXPXXP(15)) of gravin, is shown to bind Src. Binding of Src to gravin activates the intrinsic tyrosine kinase of Src. Mutagenesis/deletion of the class I ligand (P15A,P16A) on the N terminus of gravin abolishes both the docking of Src to gravin as well as the receptor resensitization and recycling catalyzed by gravin. The Src-binding peptide-(1-51) of gravin behaves as a dominant-negative for AKAP gravin regulation of receptor resensitization/recycling. The tyrosine kinase Src plays an essential role in the AKAP gravin-mediated receptor resensitization and recycling, an essential aspect of receptor biology.

A Kinase Anchor Proteins↗
PubMed2006

Yeast Ste2 receptors as tools for study of mammalian protein kinases and adaptors involved in receptor trafficking.

BACKGROUND: Mammalian receptors that couple to effectors via heterotrimeric G proteins (e.g., beta 2-adrenergic receptors) and receptors with intrinsic tyrosine kinase activity (e.g., insulin and IGF-I receptors) constitute the proximal points of two dominant cell signaling pathways. Receptors coupled to G proteins can be substrates for tyrosine kinases, integrating signals from both pathways. Yeast cells, in contrast, display G protein-coupled receptors (e.g., alpha-factor pheromone receptor Ste2) that have evolved in the absence of receptor tyrosine kinases, such as those found in higher organisms. We sought to understand the motifs in G protein-coupled receptors that act as substrates for receptor tyrosine kinases and the functional consequence of such phosphorylation on receptor biology. We expressed in human HEK 293 cells yeast wild-type Ste2 as well as a Ste2 chimera engineered with cytoplasmic domains of the beta2-adrenergic receptor and tested receptor sequestration in response to activation of the insulin receptor tyrosine kinase. RESULTS: The yeast Ste2 was successfully expressed in HEK 293 cells. In response to alpha-factor, Ste2 signals to the mitogen-activated protein kinase pathway and internalizes. Wash out of agonist and addition of antagonist does not lead to Ste2 recycling to the cell membrane. Internalized Ste2 is not significantly degraded. Beta2-adrenergic receptors display internalization in response to agonist (isoproterenol), but rapidly recycle to the cell membrane following wash out of agonist and addition of antagonist. Beta2-adrenergic receptors display internalization in response to activation of insulin receptors (i.e., cross-regulation), whereas Ste2 does not. Substitution of the cytoplasmic domains of the beta2-adrenergic receptor for those of Ste2 creates a Ste2/beta2-adrenergic receptor chimera displaying insulin-stimulated internalization. CONCLUSION: Chimera composed of yeast Ste2 into which domains of mammalian G protein-coupled receptors have been substituted, when expressed in animal cells, provide a unique tool for study of the regulation of G protein-coupled receptor trafficking by mammalian receptor tyrosine kinases and adaptor proteins.

Journal Article↗
PubMed2006

G-Protein-coupled receptor-associated A-kinase anchoring proteins: AKAP79 and AKAP250 (gravin).

A-kinase anchoring proteins (AKAPs) define an expanding group of scaffold proteins that display a signature binding site for the RI/RII subunit of protein kinase A. AKAPs are multivalent and a subset of these scaffold proteins also display the ability to associate with the prototypic member of G-protein-coupled receptors, the beta(2)-adrenergic receptor. Both AKAP79 (also known as AKAP5) and AKAP250 (also known as gravin or AKAP12) have been shown to associate with the beta(2)-adrenergic receptor, but each directs downstream signaling events in decidedly different manners. The primary structures, common and unique protein motifs are of interest. Both proteins display largely natively unfolded primary sequences that provide a necklace on which short, structured regions of sequence are found. Membrane association appears to involve both interactions with the lipid bilayer via docking to a G-protein-coupled receptor as well as interactions of short positively charged domains with the inner leaflet of the cell membrane. Gravin, unlike AKAP79, displays a canonical site at its N-terminus that is subject to N-myristoylation. AKAP79 appears to function in switching signaling pathways of the receptor from adenylylcyclase to activation of the mitogen-activated protein kinase cascade. Gravin, in contrast, is essential for the resensitization and recycling of the receptors following agonist-induced activation, desensitization, and internalization. Each AKAP provides a template that enables space-time continuum features to G-protein-coupled signaling pathways as well as a paradigm for explaining apparent compartmentalization of cell signaling.

A Kinase Anchor Proteins↗
PubMed2006

Dishevelled: a mobile scaffold catalyzing development.

Wnt proteins are secreted glycoprotein ligands that regulate critical aspects of development, including cell proliferation, apoptosis, and cell fate. For those pathways downstream from the "canonical" Wnt/beta-catenin signaling, from the "non-canonical" or planar cell polarity (PCP), and from the Wnt-Ca(2+)/cyclic guanosine monophosphate (cGMP) pathway, Wnt activation of its cellular receptor, a member of the superfamily of G-protein-coupled receptor Frizzled family, requires both heterotrimeric G proteins and the phosphoprotein Dishevelled. Our understanding of the roles of Dishevelled proteins in development is evolving and most recent observations suggest that Dishevelled proteins act as scaffolds essential for Wnt signaling, providing docking sites for a diverse and interesting set of protein kinases, phosphatases, adaptor proteins, G proteins, and other scaffolds such as Axin. The protein-protein interactions of Dishevelled are dynamic, as is the spatial localization of this "toolbox" of signaling molecules involved in development. Much excitement awaits the elucidation of the complete set of tools in the toolbox and of the dynamic regulation of Dishevelled proteins and their interacting proteins.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Successful expression of a functional yeast G-protein-coupled receptor (Ste2) in mammalian cells.

G-protein-coupled receptors (GPCRs) are membrane-embedded cell signaling devices transducing ligand binding to activation of heterotrimeric G-proteins, providing a paradigm for signaling for yeast and mammals alike. Probing the extent to which yeast GPCRs may couple to mammalian G-proteins has been problematic. In the current work, we explored conditions that enable the cell-surface expression of a yeast alpha-factor pheromone receptor (Ste2). When expressed in human HEK293 cells, Ste2 is shown to bind its ligand alpha-factor, to be functional and catalyze activation of the mitogen-activated protein kinase cascade, and to demonstrate agonist-induced internalization. In response to agonist Ste2 as maintained intracellularly for several hours and avoids the degradation process observed for Ste2 in yeast cells. This is the first successful demonstration of the ability to express a functional yeast GPCR in mammalian cells.

Animals↗
PubMed2004

Ku80 is required but not sufficient for Galpha13-mediated endodermal differentiation in P19 embryonic carcinoma cells.

We have shown that a constitutively active Galpha13 (Galpha13Q226L) induces differentiation in P19 embryonic carcinoma cells to an endodermal phenotype. In this report, we demonstrate that Ku, a heterodimer of p80 (Ku80) and p70 (Ku70), is upregulated in P19 cells overexpressing Galpha13Q226L. Ku is the regulatory subunit of the DNA-dependent protein kinase and is primarily involved in DNA repair and recombination. Ku80 also is a somatostatin receptor. We show that while overexpression of Ku80 drastically reduced P19 cell proliferation, it was not sufficient to induce endodermal differentiation. However, coexpression of Galpha13Q226L and an antisense Ku80 abrogated the retarded growth rate and endodermal differentiation observed in cells expressing only Galpha13Q226L. Overexpression of Galpha13Q226L or Ku80 downregulated RNA polymerase I-mediated transcriptional activity and overexpression of antisense Ku80 restored the activity to control level. These results suggest that Ku80 is required for Galpha13-mediated endodermal differentiation in P19 cells.

Animals↗
PubMed2004

The 15-amino acid motif of the C terminus of the beta2-adrenergic receptor is sufficient to confer insulin-stimulated counterregulation to the beta1-adrenergic receptor.

Insulin counterregulates catecholamine action in part by inducing the sequestration of beta2-adrenergic receptors. Although similar to agonist-induced sequestration, insulin-induced internalization of beta2-adrenergic receptors operates through a distinct and better-understood cellular pathway. The effects of insulin treatment on the function and trafficking of both beta1- and beta2-adrenergic receptors were tested. The beta2-adrenergic receptors were counterregulated and internalized in response to insulin. The beta1-adrenergic receptors, in sharp contrast, are shown to be resistant to the ability of insulin to counterregulate function and induce receptor internalization. Using chimeric receptors composed of beta1-/beta2-adrenergic receptors in tandem with mutagenesis, we explored the role of the C-terminal cytoplasmic tail of the beta2-adrenergic receptors for insulin-induced counterregulation. Substitution of the C-terminal cytoplasmic tail of the beta2-adrenergic receptor on the beta1-adrenergic receptor enabled the chimeric G protein-coupled receptor to be functionally and spatially regulated by insulin. Truncation of the beta2-adrenergic receptor C-terminal cytoplasmic tail to a 15-amino acid motif harboring a potential Src homology 2-binding domain at Y350 and an Akt phosphorylation site at S345,346 was sufficient to enable receptor regulation by insulin.

Adrenergic beta-Agonists↗
PubMed2004

Gene profiling of Frizzled-1 and Frizzled-2 signaling: expression of G-protein-coupled receptor chimeras in mouse F9 teratocarcinoma embryonal cells.

Wnt-Frizzled signaling via heterotrimeric G-proteins controls various aspects of early development. Because Wnts may activate more than one Frizzled, understanding the downstream signaling mechanisms and target genes for Frizzled activation has been a challenge. We constructed functional, chimeric receptors with the ligand-binding and transmembrane segments from the beta2-adrenergic receptor and the cytoplasmic domains from either rat Frizzled-1 (Rfz1) or Frizzled-2 (Rfz2). Activation with beta-agonist enables stimulation of only a single Frizzled pathway and profiling of genes targeted by this Frizzled-specific approach. Genes activated in mouse totipotent F9 teratocarcinoma cells solely by activation of the Rfz1 chimera include Lefty1, STAM, JAB, Erk1, MyD118, Fcer Ig, and follistatin, genes implicated in development. Stimulation of Rfz2 chimera, but not Rfz1, leads to activation of a smaller set of genes, including those for REST/NRSF, Groucho, nucleophosmin, and Ubc4/5E2. Activation of either Rfz1- or Rfz2-specific chimera leads, in these totipotent stem cells, to some differential activation of a common set of genes, including those for Msx-1, Msx-2, CBP/P300-associated factor, ephrin A3, and Nip-3. We demonstrate the utility of beta2-adrenergic receptor-Frizzled chimeras to provide the tools with which to activate and to probe Frizzled-specific downstream signaling to gene activation.

Animals↗
PubMed2003

Protein kinase A regulates AKAP250 (gravin) scaffold binding to the beta2-adrenergic receptor.

A-kinase-anchoring protein 250 (AKAP250; gravin) acts as a scaffold that binds protein kinase A (PKA), protein kinase C and protein phosphatases, associating reversibly with the beta(2)-adrenergic receptor. The receptor-binding domain of the scaffold and the regulation of the receptor-scaffold association was revealed through mutagenesis and biochemical analyses. The AKAP domain found in other members of this superfamily is essential for the scaffold-receptor interactions. Gravin constructs lacking the AKAP domain displayed no binding to the receptor. Metabolic labeling studies in vivo demonstrate agonist-stimulated phosphorylation of gravin and enhanced gravin-receptor association. Analysis of the AKAP domain revealed two canonical PKA sites phosphorylated in response to elevated cAMP, blocked by PKA inhibitor, and essential for scaffold-receptor association and for resensitization of the receptor. The AKAP appears to provide the catalytic PKA activity responsible for phosphorylation of the scaffold in response to agonist activation of the receptor as well as for the association of the scaffold with the receptor, a step critical to receptor resensitization.

A Kinase Anchor Proteins↗
PubMed2003

Wnt signaling, Ca2+, and cyclic GMP: visualizing Frizzled functions.

Wnts control the specification of cell fate, cell adhesion, migration, polarity, and proliferation. Their roles in development have been probed in fruit flies, nematodes, zebrafish, frogs, and mice. Some Wnts inhibit the degradation of beta-catenin, which can regulate transcription of specific genes. Other Wnts exert their influences in other ways, such as increasing intracellular concentrations of Ca2+ and decreasing intracellular concentrations of cyclic guanosine monophosphate (cGMP). Heterotrimeric guanine nucleotide-binding proteins (G proteins) and RGS proteins have been implicated in Wnt signaling. Wnt regulation of intracellular Ca2+ and cGMP levels requires the G protein transducin and a cGMP-specific phosphodiesterase, which are major elements in signaling of the visual pathway.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2002

The Frizzled-1/(beta(2))-adrenergic receptor chimera: pharmacological properties of a unique G protein-linked receptor.

The frizzled gene family of Wnt receptors encodes proteins that have a seven-transmembrane-spanning motif characteristic of G-protein-coupled receptors. Using a chimeric receptor composed of the exofacial and the transmembrane, ligand-binding domain of the beta(2)-adrenergic receptor (beta2AR) fused with the corresponding cytoplasmic domains of the rat Frizzled-1 receptor (Rfz1), we created a unique chimera between distant members of the superfamily of G protein-coupled receptors. Herein, we describe the pharmacological properties of the chimera, which represents a receptor in which the exofacial and cytoplasmic domains are minimized in length. This unique chimera retains much of the pharmacological character of the native beta2AR, whereas the coupling can be ascribed to Rfz1 domains which operate via G alpha q and not G alpha s. The Rfz1 chimera demonstrates a robust agonist (isoproterenol)-induced sequestration. Since the Rfz1 cytoplasmic domains possess canonical sites for several protein kinases, we were able to investigate the effects of kinase inhibitors on Rfz1 chimera sequestration. Only the protein kinase A inhibitor KT5720, but not inhibitors of protein kinase C, calcium/calmodulin-sensitive kinase-2, casein kinase-2, and Src, inhibited agonist-induced sequestration. Expression of a dominant-negative form of beta-arrestin blocked sequestration of the beta2AR, but only reduced modestly that of the Rfz1 chimera. These data demonstrate that the Frizzled-1 chimera displays cardinal features of a G protein-coupled receptor, including agonist-induced sequestration, but appears to do so largely even in the presence of dominant-negative beta-arrestins.

Adrenergic beta-Agonists↗
PubMed2002

Targeted expression of activated Q227L G(alpha)(s) in vivo.

We report the creation of transgenic mice with an inducible, tissue-targeted expression of a constitutively active mutant form (Q227L) of G(alpha)(s). Mice expressing activated G(alpha)(s) in fat tissue, liver, and skeletal muscle displayed normal body mass and blunted glucose metabolism. cAMP accumulation in adipose tissue was increased in the basal state, but far less than would be expected. Marked adaptation to elevated cAMP levels occurred, leading to an increase in total cAMP-specific phosphodiesterase activity, a 50% decline in cAMP-dependent protein kinase (protein kinase A) activity, and an increased expression of G(alpha)(i2). The reduction in kinase activity coincided with >50% increase in the expression of RIalpha and RIIalpha regulatory subunits of protein kinase A, with no change in the amount of catalytic subunit. These data demonstrate the existence of adaptive responses of protein kinase A, phosphodiesterase, and G(alpha)(i2) in tissues expressing constitutively active G(alpha)(s) that may act to rectify the impact of increased cAMP accumulation.

Adaptation, Physiological↗