Pleckstrin Homology (pleckstrin + homology)

Distribution by Scientific Domains

Terms modified by Pleckstrin Homology

  • pleckstrin homology domain

  • Selected Abstracts


    RGS9-2 mediates specific inhibition of agonist-induced internalization of D2 -dopamine receptors

    JOURNAL OF NEUROCHEMISTRY, Issue 3 2010
    Jeremy Celver
    J. Neurochem. (2010) 114, 739,749. Abstract Regulator of G protein signaling 9-2 (RGS9-2), a member of the RGS family of GTPase accelerating proteins, is expressed specifically in the striatum, a brain region involved in controlling movement, motivation, mood and addiction. RGS9-2 can be found co-localized with D2 -class dopamine receptors in medium spiny striatal neurons and altered functioning of both RGS9-2 and D2 -like dopamine receptors have been implicated in schizophrenia, movement disorders and reward responses. Previously we showed that RGS9-2 can specifically co-localize with D2 -dopamine receptors (D2R). Here we provide further evidence of the specificity of RGS9-2 for regulating D2R cellular functions: the expression of RGS9-2 inhibits dopamine-mediated cellular internalization of D2R, while the expression of another RGS protein, RGS4, had no effect. In addition, the agonist-mediated internalization of the G protein coupled delta opioid receptor was unaffected by RGS9-2 expression. We utilized mutant constructs of RGS9-2 to show that the RGS9-2 DEP (for Disheveled, EGL-10, Pleckstrin homology) domain and the GTPase accelerating activity of RGS9-2 were necessary for mediating specific inhibition of D2R internalization. [source]


    PDK1 and PKB/Akt: Ideal Targets for Development of New Strategies to Structure-Based Drug Design

    IUBMB LIFE, Issue 3 2003
    Thomas Harris
    Abstract Growth factor binding events to receptor tyrosine kinases result in activation of phosphatidylinositol 3-kinase (PI3K), and activated PI3K generates the membrane-bound second messengers phosphatidylinositol 3,4-diphosphate [PI(3,4)P2] and PI(3,4,5)P3, which mediate membrane translocation of the phosphoinositide-dependent kinase-1 (PDK1) and protein kinase B (PKB, also known as Akt). In addition to the kinase domain, PDK1 and PKB contain a pleckstrin homology (PH) domain that binds to the second messenger, resulting in the phosphorylation and activation of PKB by PDK1. Recent evidence indicates that constitutive activation of PKB contributes to cancer progression by promoting proliferation and increased cell survival. The indicating of PDK1 and PKB as primary targets for discovery of anticancer drugs, together with the observations that both PDK1 and PKB contain small-molecule regulatory binding sites that may be in proximity to the kinase active site, make PDK1 and PKB ideal targets for the development of new strategies to structure-based drug design. While X-ray structures have been reported for the kinase domains of PDK1 and PKB, no suitable crystals have been obtained for either PDK1 or PKB with their PH domains intact. In this regard, a novel structure-based strategy is proposed, which utilizes segmental isotopic labeling of the PH domain in combination with site-directed spin labeling of the kinase active site. Then, long-range distance restraints between the 15N-labeled backbone amide groups of the PH domain and the unpaired electron of the active site spin label can be determined from magnetic resonance studies of the enhancement effect that the paramagnetic spin label has on the nuclear relaxation rates of the amide protons. The determination of the structure and position of the PH domain with respect to the known X-ray structure of the kinase active site could be useful in the rational design of potent and selective inhibitors of PDK1 and PKB by 'linking' the free energies of binding of substrate (ATP) analogs with analogs of the inositol polar head group of the phospholipid second messenger. The combined use of X-ray crystallography, segmental isotopic and spin labeling, and magnetic resonance studies can be further extended to the study of other dynamic multidomain proteins and targets for structure-based drug design. IUBMB Life, 55: 117-126, 2003 [source]


    Essential role of PSM/SH2-B variants in insulin receptor catalytic activation and the resulting cellular responses

    JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2008
    Manchao Zhang
    Abstract The positive regulatory role of PSM/SH2-B downstream of various mitogenic receptor tyrosine kinases or gene disruption experiments in mice support a role of PSM in the regulation of insulin action. Here, four alternative PSM splice variants and individual functional domains were compared for their role in the regulation of specific metabolic insulin responses. We found that individual PSM variants in 3T3-L1 adipocytes potentiated insulin-mediated glucose and amino acid transport, glycogenesis, lipogenesis, and key components in the metabolic insulin response including p70 S6 kinase, glycogen synthase, glycogen synthase kinase 3 (GSK3), Akt, Cbl, and IRS-1. Highest activity was consistently observed for PSM alpha, followed by beta, delta, and gamma with decreasing activity. In contrast, dominant-negative peptide mimetics of the PSM Pro-rich, pleckstrin homology (PH), or src homology 2 (SH2) domains inhibited any tested insulin response. Potentiation of the insulin response originated at the insulin receptor (IR) kinase level by PSM variant-specific regulation of the Km (ATP) whereas the Vmax remained unaffected. IR catalytic activation was inhibited by peptide mimetics of the PSM SH2 or dimerization domain (DD). Either peptide should disrupt the complex of a PSM dimer linked to IR via SH2 domains as proposed for PSM activation of tyrosine kinase JAK2. Either peptide abolished downstream insulin responses indistinguishable from PSM siRNA knockdown. Our results implicate an essential role of the PSM variants in the activation of the IR kinase and the resulting metabolic insulin response. PSM variants act as internal IR ligands that in addition to potentiating the insulin response stimulate IR catalytic activation even in the absence of insulin. J. Cell. Biochem. 103: 162,181, 2008. © 2007 Wiley-Liss, Inc. [source]


    Serum and glucocorticoid-regulated protein kinases: Variations on a theme

    JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2006
    Maude Tessier
    Abstract The phosphatidylinositol 3, kinase (PI3K)-signaling pathway plays a critical role in a variety of cellular responses such as modulation of cell survival, glucose homeostasis, cell division, and cell growth. PI3K generates important lipid second messengers,phosphatidylinositides that are phosphorylated at the 3, position of their inositol ring head-group. These membrane restricted lipids act by binding with high affinity to specific protein domains such as the pleckstrin homology (PH) domain. Effectors of PI3K include molecules that harbor such domains such as phosphoinositide-dependent kinase (PDK1) and protein kinase B (PKB), also termed Akt. The mammalian genome encodes three different PKB genes (,, ,, and ,; Akt1, 2, and 3, respectively) and each is an attractive target for therapeutic intervention in diseases such as glioblastoma and breast cancer. A second family of three protein kinases, termed serum and glucocorticoid-regulated protein kinases (SGKs), is structurally related to the PKB family including regulation by PI3K but lack a PH domain. However, in addition to PH domains, a second class of 3, phosphorylated inositol phospholipid-binding domains exists that is termed Phox homology (PX) domain: this domain is found in one of the SGKs (SGK3). Here, we summarize knowledge of the three SGK isoforms and compare and contrast them to PKB with respect to their possible importance in cellular regulation and potential as therapeutic targets. J. Cell. Biochem. © 2006 Wiley-Liss, Inc. [source]


    Purification, crystallization and preliminary X-ray diffraction of a proteolytic fragment of PDK1 containing the pleckstrin homology domain

    ACTA CRYSTALLOGRAPHICA SECTION D, Issue 2 2004
    David Komander
    3-Phosphoinositide-dependent protein kinase-1 (PDK1) is a Ser/Thr kinase with an essential role in insulin and growth-factor signalling. PDK1 activity towards protein kinase B (PKB) is partially regulated by its pleckstrin homology (PH) domain, which preferentially binds to 3-phosphoinositides. However, the precise molecular mechanism of this regulation is not well understood. Here, the cloning, purification and crystallization of a 150-amino-acid C-terminal region of PDK1 containing the PH domain is reported. A crystal of the PDK1 PH domain grown in the presence of inositol 1,3,4,5-tetrakisphosphate and derivatized with AuCN diffracted to 1.5,Å at a synchrotron source. Diffraction data collected near the Au edge resulted in an anomalous Patterson map with a 30, peak. [source]


    The role of Gab family scaffolding adapter proteins in the signal transduction of cytokine and growth factor receptors

    CANCER SCIENCE, Issue 12 2003
    Keigo Nishida
    The Grb2-associated binder (Gab) family adapter proteins are scaffolding adapter molecules that display sequence similarity with Drosophila DOS (daughter of sevenless), which is a substrate for the protein tyrosine phosphatase Corkscrew. Gab proteins contain a pleckstrin homology (PH) domain and binding sites for SH2 and SH3 domains. A number of studies in multiple systems have implicated Gab in signaling via many different types of receptors, such as growth factor, cytokine, and antigen receptors, and via oncoproteins. Recent studies of Gab1 and Gab2 knockout mice have clearly indicated an important role for Gabs in vivo. Gab1-deficient mice die as embryos with multiple defects in placental, heart, skin, and muscle development. Gab2-deficient mice are viable, but have a defect in the mast cell lineages and in allergic reactions. Given the apparently central role played by Gab signaling via many receptors, delineating the precise mechanism(s) of Gab-mediated signaling is critical to understanding how cytokines, growth factors, and oncoproteins mediate a variety of biological activities: cell growth, differentiation, survival and malignant transformation. [source]