Regulation of G1 progression by the PTEN tumor suppressor protein is linked to inhibition of the phosphatidylinositol 3-kinase/Akt pathway

PTEN/MMAC1 is a tumor suppressor gene located on chromosome 10q23. Inherited PTEN/MMAC1 mutations are associated with a cancer predisposition syndrome known as Cowden’s disease. Somatic mutation of PTEN has been found in a number of malignancies, including glioblastoma, melanoma, and carcinoma of the prostate and endometrium. The protein product (PTEN) encodes a dual-specificity protein phosphatase and in addition can dephosphorylate certain lipid substrates. Herein, we show that PTEN protein induces a G1 block when reconstituted in PTEN-null cells. A PTEN mutant associated with Cowden’s disease (PTEN;G129E) has protein phosphatase activity yet is defective in dephosphorylating inositol 1,3,4,5-tetrakisphosphate in vitro and fails to arrest cells in G1. These data suggest a link between induction of a cell-cycle block by PTEN and its ability to dephosphorylate, in vivo, phosphatidylinositol 3,4,5-trisphosphate. In keeping with this notion, PTEN can inhibit the phosphatidylinositol 3,4,5-trisphosphate-dependent Akt kinase, a downstream target of phosphatidylinositol 3-kinase, and constitutively active, but not wild-type, Akt overrides a PTEN G1 arrest. Finally, tumor cells lacking PTEN contain high levels of activated Akt, suggesting that PTEN is necessary for the appropriate regulation of the phosphatidylinositol 3-kinase/Akt pathway.

Inositol hexakisphosphate is a physiological signal regulating the K+-inward rectifying conductance in guard cells

(RS)-2-cis, 4-trans-abscisic acid (ABA), a naturally occurring plant stress hormone, elicited rapid agonist-specific changes in myo-inositol hexakisphosphate (InsP6) measured in intact guard cells of Solanum tuberosum (n = 5); these changes were not reproduced by (RS)-2-trans, 4-trans-abscisic acid, an inactive stereoisomer of ABA (n = 4). The electrophysiological effects of InsP6 were assessed on both S. tuberosum (n = 14) and Vicia faba (n = 6) guard cell protoplasts. In both species, submicromolar concentrations of InsP6, delivered through the patch electrode, mimicked the inhibitory effects of ABA and internal calcium (Cai2+) on the inward rectifying K+ current, IK,in, in a dose-dependent manner. Steady state block of IK,in by InsP6 was reached much more quickly in Vicia (3 min at ≈1 μM) than Solanum (20–30 min). The effects of InsP6 on IK,in were specific to the myo-inositol isomer and were not elicited by other conformers of InsP6 (e.g., scyllo- or neo-). Chelation of Ca2+ by inclusion of 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid or EGTA in the patch pipette together with InsP6 prevented the inhibition of IK,in, suggesting that the effect is Ca2+ dependent. InsP6 was ≈100-fold more potent than Ins(1,4,5)P3 in modulating IK,in. Thus ABA increases InsP6 in guard cells, and InsP6 is a potent Ca2+-dependent inhibitor of IK,in. Taken together, these results suggest that InsP6 may play a major role in the physiological response of guard cells to ABA.

Characterization of Recombinant Rhamnogalacturonan α-l-Rhamnopyranosyl-(1,4)-α-d-Galactopyranosyluronide Lyase from Aspergillus aculeatus1 : An Enzyme That Fragments Rhamnogalacturonan I Regions of Pectin

The four major oligomeric reaction products from saponified modified hairy regions (MHR-S) from apple, produced by recombinant rhamnogalacturonan (RG) α-l-rhamnopyranosyl-(1,4)-α-d-galactopyranosyluronide lyase (rRG-lyase) from Aspergillus aculeatus, were isolated and characterized by 1H-nuclear magnetic resonance spectroscopy. They contain an alternating RG backbone with a degree of polymerization of 4, 6, 8, and 10 and with an α-Δ-(4,5)-unsaturated d-galactopyranosyluronic acid at the nonreducing end and an l-rhamnopyranose at the reducing end. l-Rhamnopyranose units are substituted at C-4 with β-galactose. The maximum reaction rate of rRG-lyase toward MHR-S at pH 6.0 and 31°C was 28 units mg−1. rRG-lyase and RG-hydrolase cleave the same alternating RG I subunit in MHR. Both of these enzymes fragment MHR by a multiple attack mechanism. The catalytic efficiency of rRG-lyase for MHR increases with decreasing degree of acetylation. Removal of arabinose side chains improves the action of rRG-lyase toward MHR-S. In contrast, removal of galactose side chains decreased the catalytic efficiency of rRG-lyase. Native RG-lyase was purified from A. aculeatus, characterized, and found to be similar to the rRG-lyase expressed in Aspergillus oryzae.

Identification of receptor-binding domains on human interleukin 5 and design of an interleukin 5-derived receptor antagonist.

A detailed structure-function analysis of human interleukin 5 (hIL5) has been performed. The hIL5 receptor is composed of two different polypeptide chains, the alpha and beta subunits. The alpha subunit alone is sufficient for ligand binding, but association with the beta subunit leads to a 2- to 3-fold increase in binding affinity. The beta chain is shared with the receptors for IL3 and granulocyte/macrophage-colony-stimulating factor--hence the descriptor beta C (C for common). All hIL5 mutants were analyzed in a solid-phase binding assay for hIL5R alpha interaction and in a proliferation assay using IL5-dependent cell lines for receptor-complex activation. Most residues affecting binding to the receptor alpha subunit were clustered in a loop connecting beta-strand 1 and helix B (mutants H38A, K39A, and H41A), in beta-strand 2 (E89A and R91A; weaker effect for E90A) and close to the C terminus (T109A, E110A, W111S, and I112A). Mutations at one position, E13 (Glu13), caused a reduced activation of the hIL5 receptor complex. In the case of E13Q, only 0.05% bioactivity was detected on a hIL5-responsive subclone of the mouse promyelocytic cell line FDC-P1. Moreover, on hIL5-responsive TF1 cells, the same mutant was completely inactive and proved to have antagonistic properties. Interactions of this mutant with both receptor subunits were nevertheless indistinguishable from those of nonmutated hIL5 by crosslinking and Scatchard plot analysis of transfected COS-1 cells.

Congreso Internacional Museos Universitarios : tradición y futuro : Madrid, 3, 4, 5 de diciembre de 2014

Congreso Internacional de Museos Universitarios. Los Museos y Colecciones Universitarias: Tradición y Futuro. 3 al 5 de diciembre de 2014. Facultad de Odontología, Universidad Complutense de Madrid El Congreso fue organizado por el Campus de Excelencia Internacional (CEI), Campus de Moncloa, dentro de las líneas de actuación del Clúster de Patrimonio y fue financiado por el Ministerio de Educación, Cultura y Deporte. Las Universidades Complutense y Politécnica de Madrid fueron las responsables de confeccionar el programa y llevar a cabo todos los actos y actividades. El Congreso contó además con el respaldo del Consejo Internacional de Museos, ICOM España. A lo largo de tres días, personas vinculadas al patrimonio académico y universitario se dieron cita para presentar sus instituciones, debatir sobre los temas propuestos, compartir puntos de vista, y proponer iniciativas. No fue el primer congreso de museos universitarios en España, pero sí fue uno de los más importantes por la gran presencia de participantes, más de 200 asistentes, que procedían de la mayoría de comunidades autónomas. Un importante número de universidades españolas que tiene museos o colecciones estaba representado, y destacadas universidades europeas también presentaron sus trabajos. En la mesa inaugural participaron los representantes de las Universidades organizadoras, representantes de la Comunidad de Madrid y del Ayuntamiento de Madrid y el presidente de ICOM España. Además de resaltar la importancia de los museos y colecciones universitarias, los representantes de las instituciones se comprometieron a apoyar a las universidades en las tareas de investigación, conservación y difusión de su patrimonio. Las ponencias invitadas estuvieron a cargo de los representantes de las organizaciones internacionales más importantes relacionadas con el patrimonio universitario: el Consejo Internacional de Museos y Colecciones Universitarias (UMAC) y la Red del Patrimonio Académico Europeo (UNIVERSEUM). Las comunicaciones y pósters fueron numerosos agrupándose en las siguientes áreas temáticas:  La investigación en los museos y colecciones universitarias  La difusión de los museos y colecciones universitarias  Los proyectos de conservación y restauración en torno a museos y colecciones universitarias  Las colecciones universitarias como colecciones artísticas  La gestión de los museos y colecciones universitarias Las mesas redondas ahondaron en las áreas temáticas de las comunicaciones, centrándose en aspectos que hacían referencia a los retos a los que se enfrentan las instituciones: valor, documentación, gestión y difusión de los museos y colecciones. La realización de este Congreso permitió un extenso intercambio de experiencias y finalizó con la esperanza de que sirva de comienzo para dar visibilidad al patrimonio académico en el contexto fundamentalmente europeo intentando, a su vez, definir cuál es su papel en la nueva situación social, política y económica. Durante los tres días intensos se tuvo la oportunidad de darnos cuenta de las maravillas que atesoran nuestras universidades que están a la altura de muchas colecciones museísticas “tradicionales”. En este libro se recogen las interesantes iniciativas que nos sirven de modelo y nos animan a seguir trabajando para asegurar la conservación y difusión de tan destacado legado.

Y-box binding protein 1 (YB-1) relevance in estrogen receptor-positive (ER+) breast cancer

Tese de mestrado, Biologia Molecular e Genética, Universidade de Lisboa, Faculdade de Ciências, 2016