Article

Novel inositol phospholipid headgroup surrogate crystallized in the pleckstrin homology domain of protein kinase Balpha.

ACS Chemical Biology (Impact Factor: 5.44). 05/2007; 2(4):242-6. DOI: 10.1021/cb700019r
Source: PubMed

ABSTRACT Protein kinase B (PKB/Akt) plays a key role in cell signaling. The PH domain of PKB binds phosphatidylinositol 3,4,5-trisphosphate translocating PKB to the plasma membrane for activation by 3-phosphoinositide-dependent protein kinase 1. The crystal structure of the headgroup inositol 1,3,4,5-tetrakisphosphate Ins(1,3,4,5)P4-PKB complex facilitates in silico ligand design. The novel achiral analogue benzene 1,2,3,4-tetrakisphosphate (Bz(1,2,3,4)P4) possesses phosphate regiochemistry different from that of Ins(1,3,4,5)P4 and surprisingly binds with similar affinity as the natural headgroup. Bz(1,2,3,4)P4 co-crystallizes with the PKBalpha PH domain in a fashion also predictable in silico. The 2-phosphate of Bz(1,2,3,4)P4 does not interact with any residue, and the D5-phosphate of Ins(1,3,4,5)P4 is not mimicked by Bz(1,2,3,4)P4. Bz(1,2,3,4)P4 is an example of a simple inositol phosphate surrogate crystallized in a protein, and this approach could be applied to design modulators of inositol polyphosphate binding proteins.

0 Bookmarks
 · 
68 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Phosphoinositides regulate many cellular processes, and cellular levels are controlled by kinases and phosphatases. SHIP2 (SH2 (Src homology 2)-domain-containing inositol-phosphatase-2) plays a critical role in phosphoinositide signaling, cleaving the 5-phosphate from phosphatidylinositol 3,4,5-trisphosphate. SHIP2 is thought to be involved in type-2 diabetes and obesity, conditions that could therefore be open to pharmacological modulation of the enzyme. However, rational design of SHIP2 inhibitors has been limited by the absence of a high-resolution structure. Here, we present a 2.1 Å resolution crystal structure of the phosphatase domain of SHIP2 bound to the synthetic ligand biphenyl 2,3',4,5',6-pentakisphosphate (BiPh(2,3',4,5',6)P(5)). BiPh(2,3',4,5',6)P(5) is not a SHIP2 substrate but inhibits Ins(1,3,4,5)P(4) hydrolysis with an IC(50) of 24.8 ± 3.0 μM, (K(m) for Ins(1,3,4,5)P(4) is 215 ± 28 μM). Molecular dynamics simulations suggest that when BiPh(2,3',4,5',6)P(5) binds to SHIP2, a flexible loop folds over and encloses the ligand. Compounds targeting such a closed conformation might therefore deliver SHIP2-specific drugs.
    ACS Chemical Biology 02/2012; 7(5):822-8. · 5.44 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Protein kinase B/AKT plays a central role in cancer. The serine/threonine kinase is overexpressed or constitutively active in many cancers and has been validated as a therapeutic target for cancer treatment. However, targeting the kinase activity has revealed itself to be a challenge due to non-selectivity of the compounds towards other kinases. This review summarizes other approaches scientists have developed to inhibit the activity and function of AKT. They consist in targeting the pleckstrin homology (PH) domain of AKT. Indeed, upon the generation of 3-phosphorylated phosphatidylinositol phosphates (PI3Ps) by PI3-kinase (PI3K), AKT translocates from the cytosol to the plasma membrane and binds to the PI3Ps via its PH domain. Thus, several analogs of PI3Ps (PI Analogs or PIAs), alkylphospholipids (APLs), such as edelfosine or inositol phophates (IPs) have been described that inhibit the binding of the PH domain to PI3Ps. Recent allostertic inhibitors and small molecules that do not bind the kinase domain but affect the kinase activity of AKT, presumably by interacting with the PH domain, have been also identified. Finally, several drug screening studies spawned novel chemical scaffolds that bind the PH domain of AKT. Together, these approaches have been more or less sucessfull in vitro and to some extent translated in preclinical studies. Several of these new AKT PH domain inhibitors exhibit promising anti-tumor activity in mouse models and some of them show synergy with ionizing radiation and chemotherapy. Early clinical trials have started and results will attest to the validity and efficacy of such approaches in the near future.
    Current Medicinal Chemistry 01/2011; 18(18):2727-42. · 3.72 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Since its discovery in the late 1980s, phosphoinositide 3-kinase (PI3K), and its isoforms have arguably reached the forefront of signal transduction research. Regulation of this lipid kinase, its functions, its effectors, in short its entire signaling network, has been extensively studied. PI3K inhibitors are frequently used in biochemistry and cell biology. In addition, many pharmaceutical companies have launched drug-discovery programs to identify modulators of PI3Ks. Despite these efforts and a fairly good knowledge of the PI3K signaling network, we still have only a rudimentary picture of the signaling dynamics of PI3K and its lipid products in space and time. It is therefore essential to create and use novel biological and chemical tools to manipulate the phosphoinositide signaling network with spatial and temporal resolution. In this review, we discuss the current and potential future tools that are available and necessary to unravel the various functions of PI3K and its isoforms.
    ChemBioChem 09/2012; 13(14):2022-35. · 3.74 Impact Factor

Full-text (2 Sources)

View
35 Downloads
Available from
May 28, 2014