Structural insights into the allosteric activation mechanism of cGMP-dependent protein kinase I

Cyclic GMP-dependent protein kinase (PKG) is a key transducer in the NO-cGMP signaling pathway. In this line, PKG has been considered an important drug target for treating hypertensive cardiovascular and pulmonary diseases. However, the investigation of PKG’s allosteric activation mechanism has been hampered by a lack of structural information. One of the fundamental questions on the cGMP-dependent activation of PKG is how the enzyme can distinguish cGMP over cAMP and selectively respond to cGMP. To ensure proper signaling, PKG must have developed unique features to ensure its activation upon the right activation signal. In this thesis, the cGMP-selective activation mechanism of PKG was studied through determining crystal structures of three truncated constructs of the regulatory domain [CNB-A (92-227), CNB-B (271-369), and CNB-A/B (92-351)] of PKG Iβ in the absence or presence of cyclic nucleotides. Herein, two individual CNB domain structures with biochemical data revealed that the C-terminal CNB domain (CNB-B) is responsible for cGMP selectivity, while the N-terminal CNB-domain (CNB-A) has a higher binding affinity for both cGMP and cAMP without showing any selectivity. Based on these crystal structures, mutagenesis studies were performed in which the critical residues for cyclic nucleotide selectivity and activation were identified. Furthermore, we discovered that the conformational changes of the C-terminal helix of the CNB-B that bridges between the regulatory and catalytic domains including the hydrophobic capping interaction are crucial for PKG activation. In addition, to observe the global conformation of the activated R-domain, I solved a co-crystal structure of the CNB-A/B with cGMP. Although a monomeric construct was crystallized, the structure displays a dimer. Strikingly, the CNB-A domain and its bound cGMP provide a key interface for this dimeric interaction. Using small angle X-ray scattering (SAXS), the existence of the cGMP-mediated dimeric interface within the CNB domains was confirmed. Furthermore, measuring cGMP-binding affinities (EC50) of the dimeric interface mutants as well as determining activation constants (Ka) revealed that the interface formation is important for PKG activation. To conclude, this thesis study provides a new mechanistic insight in PKG activation along with a newly found interface that can be targeted for designing PKG-specific activity modulators.

An update of the mechanisms of resistance to EGFR-tyrosine kinase inhibitors in breast cancer: gefitinib (Iressatrade mark)-induced changes in the expression and nucleo-cytoplasmic trafficking of HER-ligands (Review)

Intrinsic resistance to the epidermal growth factor receptor (EGFR; HER1) tyrosine kinase inhibitor (TKI) gefitinib, and more generally to EGFR TKIs, is a common phenomenon in breast cancer. The availability of molecular criteria for predicting sensitivity to EGFR-TKIs is, therefore, the most relevant issue for their correct use and for planning future research. Though it appears that in non-small-cell lung cancer (NSCLC) response to gefitinib is directly related to the occurrence of specific mutations in the EGFR TK domain, breast cancer patients cannot be selected for treatment with gefitinib on the same basis as such EGFR mutations have been reported neither in primary breast carcinomas nor in several breast cancer cell lines. Alternatively, there is a general agreement on the hypothesis that the occurrence of molecular alterations that activate transduction pathways downstream of EGFR (i.e., MEK1/MEK2 - ERK1/2 MAPK and PI-3'K - AKT growth/survival signaling cascades) significantly affect the response to EGFR TKIs in breast carcinomas. However, there are no studies so far addressing a role of EGF-related ligands as intrinsic breast cancer cell modulators of EGFR TKI efficacy. We recently monitored gene expression profiles and sub-cellular localization of HER-1/-2/-3/-4 related ligands (i.e., EGF, amphiregulin, transforming growth factor-α, ß-cellulin, epiregulin and neuregulins) prior to and after gefitinib treatment in a panel of human breast cancer cell lines. First, gefitinibinduced changes in the endogenous levels of EGF-related ligands correlated with the natural degree of breast cancer cell sensitivity to gefitinib. While breast cancer cells intrinsically resistant to gefitinib (IC50 ≥15 μM) markedly up-regulated (up to 600 times) the expression of genes codifying for HERspecific ligands, a significant down-regulation (up to 106 times) of HER ligand gene transcription was found in breast cancer cells intrinsically sensitive to gefitinib (IC50 ≤1 μM). Second, loss of HER1 function differentially regulated the nuclear trafficking of HER-related ligands. While gefitinib treatment induced an active import and nuclear accumulation of the HER ligand NRG in intrinsically gefitinib-resistant breast cancer cells, an active export and nuclear loss of NRG was observed in intrinsically gefitinib-sensitive breast cancer cells. In summary, through in vitro and pharmacodynamic studies we have learned that, besides mutations in the HER1 gene, oncogenic changes downstream of HER1 are the key players regulating gefitinib efficacy in breast cancer cells. It now appears that pharmacological inhibition of HER1 function also leads to striking changes in both the gene expression and the nucleo-cytoplasmic trafficking of HER-specific ligands, and that this response correlates with the intrinsic degree of breast cancer sensitivity to the EGFR TKI gefitinib. The relevance of this previously unrecognized intracrine feedback to gefitinib warrants further studies as cancer cells could bypass the antiproliferative effects of HER1-targeted therapeutics without a need for the overexpression and/or activation of other HER family members and/or the activation of HER-driven downstream signaling cascades

[Ressenya del llibre Ullastret: guía de las excavaciones y su museo, d'Aurora Martín Ortega]

Ressenya del llibre Ullastret: guía de las excavaciones y su museo. Ullastret és un dels pocs jaciments que reuneixen les condicions òptimes per a ésser visitat. Però, per tal que sigui ben profitosa, calia oferir al visitant una guia que expliqués les principals característiques del lloc i el llibre de l’Aurora Martín ho fa

Orientalisme, colonialisme i gènere. ‘El Marroc sensual i fanàtic’ d'Aurora Bertrana

Els autors s’endinsen en aquest article en l’estudi de les relacions entre geografia, orientalisme i colonialisme a Europa al tombant del segle passat, tot introduint la perspectiva de gènere i en el marc d'un interès més general per la història del pensament geogràfic contemporani. Ho fan a partir de l’anàlisi contextualitzada d'un text de l’època que fa referència al cas espanyol i a la seva aventura colonial africana. Es tracta del llibre El Marroc sensual i fanàtic (1936) d’Aurora Bertrana, una versió molt elaborada del discurs de la diferència i una bona il•lustració de la literatura de viatges de dones europees, força excepcional i atípica -això sí- en el context literari català i espanyol de l’època

Projecte Comènius a l'IES Aurora Picornell : diversitat a l'escola europea. 'Proyecto Comenius en el IES Aurora Picornell : diversidad en la escuela europea'.

Resumen tomado de la publicación. Incluye tablas de datos e imágenes de las actividades

El programa d'intervenció educativa (PIE) de l'IES Aurora Picornell (2003-2004). 'El programa de intervenció educativa (PIE) del IES Aurora Picornell (2003-2004)'.

Este capítulo forma parte del apartado dedicado a la investigación e innovación pedagógica en las Islas Baleares. Estudio realizado por el Grupo de Investigación y de Formación Educativa y Social (GIFES) del Departamento de Ciencias de la Educación de la Universitat de les Illes Balears. Resumen tomado de la publicación, disponible en castellano y catalán

Role of phosphatidylinositol 3-kinase pathway (PI3K/Akt) in humans

The signaling pathway of phosphatidylinositol 3-kinase (PI3K) is critical in many aspects of growth and cell survival. The path of PI3K is stimulated physiologically as a result of many growth factors and regulatory factors. Several genetic alterations such as amplification, mutation and chromosomal arrangements may compromise the PI3K pathway, generating permanent activation in different cancer types have found evidence of these deleterious genetic modifications. Abnormal activation of the PI3K pathway results in alteration of the control mechanisms of growth and cell survival, which favors the competitive growth, and frequently metastatic capacity, greater resistance to treatment. The aim of this paper is to review matters relating to the operation of the PI3K/Akt signaling pathway and its role in the process of carcinogenesis in humans.

Aurora Díaz-Plaja : una bibliotecària destacada. 'Aurora Díaz-Plaja : una bibliotecaria destacada'.

Resumen en catalán del autor

R. B. Cunninghame Graham's 'Aurora La Cujiñi' (1898) : an exploration. 'Aurora La Cujiñi (1998) de R. B. Cunninghame Graham : una indagación'.

Resumen en español

La luna y la aurora en poetas del siglo XIX.

Tratamiento que de la luna y la noche hacen los poetas decimonónicos, recurso frecuentemente utilizado en esta época para sus poemas, con muchas finalidades diferentes. Pueden representar a la amada, a la patria, como confidente del poeta, a modo de representación alegórica de inocencia, modestia o castidad, o las diferentes descripciones de la imagen de la luna según el paisaje. También es frecuente entre la poesía del siglo XIX el canto a la aurora, describiéndola de forma colorida, como contrapunto de las descripciones oscuras y azules de la noche, igualmente, es personificada por algunos líricos de la época. El tratamiento de la luna y la aurora refleja la psicología y el estilo de cada poeta.

La Bater??a Aurora : una nueva evaluaci??n de la inteligencia exitosa

Resumen basado en el de la publicaci??n

Aurora Bertrana, una dona extraordinaria

Resumen basado en el de la publicaci??n