RESUMEN
The ForMAX beamline at the MAX IV Laboratory provides multiscale and multimodal structural characterization of hierarchical materials in the nanometre to millimetre range by combining small- and wide-angle X-ray scattering with full-field microtomography. The modular design of the beamline is optimized for easy switching between different experimental modalities. The beamline has a special focus on the development of novel fibrous materials from forest resources, but it is also well suited for studies within, for example, food science and biomedical research.
RESUMEN
Cytohesin-1 is a regulatory interaction partner of the beta2 integrin alphaLbeta2 (LFA-1) and a guanine exchange factor (GEF) for ADP ribosylation factor (ARF)-GTPases. However, a functional role of cytohesin-1 in leukocyte adhesion to activated endothelium and subsequent transmigration in response to chemokines has not been defined. Overexpression of cytohesin-1 increased LFA-1-dependent arrest of leukocytic cells triggered by chemokines on cytokine-activated endothelium in flow while reducing the fraction of rolling cells. Conversely, a dominant-negative PH domain construct of cytohesin-1 but not a mutant deficient in GEF activity impaired arrest, indicating an involvement of the PH domain while GEF function is not required. Expression of these constructs and a beta2 mutant interrupting the interaction with cytohesin-1 indicated that shape change in flow and transendothelial chemotaxis involve both LFA-1 avidity regulation and GEF activity of cytohesin-1. As a potential downstream target, ARF6 but not ARF1 was identified to participate in chemotaxis. Our data suggest that cytohesin-1 and ARF6 are involved in the dynamic regulation of complex signaling pathways and cytoskeletal remodeling processes governing LFA-1 functions in leukocyte recruitment. Differential effects of cytohesin-1 and ARF6 mutants in our systems reveal that cytohesin-1 with its GEF activity controls both conversion of rolling into firm arrest and transmigration triggered by chemokines, whereas a cyclical activity of ARF6 plays a more important role in diapedesis.
Asunto(s)
Moléculas de Adhesión Celular/fisiología , Movimiento Celular/fisiología , Quimiocinas/fisiología , Leucocitos/citología , Antígeno-1 Asociado a Función de Linfocito/fisiología , Endotelio/citología , GTP Fosfohidrolasas/metabolismo , Factores de Intercambio de Guanina Nucleótido/fisiologíaRESUMEN
Children of psychiatrically ill parents have a high risk themselves to develop a psychiatric illness in adulthood. Prevention aims at strengthening the resilience of these children and reducing psychosocial risk factors. This article found and describes a theoretical concept of prevention groups for children in schoolage (7-16 years) whose parents are psychiatrically ill. First practical experiences are depicted. The Hamburgian model of prevention works with closed and temporary limited groups of children as well as with the parents. It is based on supporting the children's existing coping strategies and the children are encouraged to exchange their individual experiences of the relationships within their families. One conclusion was, that the main thematic emphasis varied considerably depending on the age of the children.
Asunto(s)
Hijo de Padres Discapacitados/psicología , Trastornos Mentales/prevención & control , Desarrollo de la Personalidad , Psicoterapia de Grupo , Adaptación Psicológica , Adolescente , Niño , Femenino , Humanos , Masculino , Trastornos Mentales/psicología , Grupo de Atención al Paciente , Factores de RiesgoRESUMEN
Cell adhesion mediated by integrin receptors is controlled by intracellular signal transduction cascades. Cytohesin-1 is an integrin-binding protein and guanine nucleotide exchange factor that activates binding of the leukocyte integrin leukocyte function antigen-1 to its ligand, intercellular adhesion molecule 1. Cytohesin-1 bears a carboxyl-terminal pleckstrin homology domain that aids in reversible membrane recruitment and functional regulation of the protein. Although phosphoinositide-dependent membrane attachment of cytohesin-1 is mediated primarily by the pleckstrin homology domain, this function is further strengthened by a short carboxyl-terminal polybasic amino acid sequence. We show here that a serine/threonine motif within the short polybasic stretch of cytohesin-1 is phosphorylated by purified protein kinase C delta in vitro. Furthermore, the respective residues are also found to be phosphorylated after phorbol ester stimulation in vivo. Biochemical and functional analyses show that phosphorylated cytohesin-1 is able to tightly associate with the actin cytoskeleton, and we further demonstrate that phosphorylation of the protein is required for maximal leukocyte function antigen-1-mediated adhesion of Jurkat cells to intercellular adhesion molecule 1. These data suggest that both phosphatidylinositol 3-kinase and protein kinase C-dependent intracellular pathways that stimulate beta(2)-integrin-mediated adhesion of T lymphocytes converge on cytohesin-1 as functional integrator.
Asunto(s)
Actinas/metabolismo , Moléculas de Adhesión Celular/metabolismo , Citoesqueleto/metabolismo , Animales , Células COS , Carcinógenos/farmacología , Adhesión Celular/efectos de los fármacos , Moléculas de Adhesión Celular/química , Moléculas de Adhesión Celular/fisiología , Citoesqueleto/efectos de los fármacos , Factores de Intercambio de Guanina Nucleótido , Humanos , Molécula 1 de Adhesión Intercelular/metabolismo , Células Jurkat , Fosforilación/efectos de los fármacos , Estructura Terciaria de Proteína , Acetato de Tetradecanoilforbol/farmacologíaRESUMEN
Beta3 integrin adhesion molecules play important roles in wound repair and the regulation of vascular development and three beta3 integrin isoforms (beta3-A, -B, -C) have been described so far. Surface expression of beta3 integrins is dynamically regulated through internalization of beta3 integrins, however, the molecular mechanisms are understood incompletely. To evaluate the role of the cytoplasmic domain of beta3 integrins for internalization, we have generated single chain chimeras with variant and mutated forms of beta3 cytoplasmic domains. Upon transient transfection into chinese hamster ovary cells, it was found that the beta3-A chimera had strongly reduced cell surface expression compared with the corresponding beta3-B, or beta3-C fusion proteins, or the tail-less constructs, whereas steady state levels of all chimeras were near identical. Studies employing cytoplasmic domain mutants showed that the NITY motif at beta3-A 756-759 is critical for plasma membrane expression of beta3-A. Furthermore, delivery of beta3-A to the cell surface was specifically modulated by the cytoplasmic protein beta3-endonexin, a previously described intracellular protein. Coexpression of the native, long form of beta3-endonexin, which does not interact with the beta3 tail, acted as a dominant negative inhibitor of beta3-A-internalization and enhanced steady-state surface expression of the beta3-A-chimera. Furthermore, anti-beta3 antibody-induced internalization of the native beta3 integrin (alpha(IIb)beta3 was dramatically reduced for the Tyr(759)-Ala substitution mutant (alpha(IIb)beta3) (Y759A) and expression of the long isoform of beta3-endonexin substantially decreased the internalization of wild-type alpha(IIb)beta3. Thus, the NITY motif of the beta-chain cytoplasmic domain is involved in stimulated internalization of the beta3 integrin A isoform and beta3-endonexin appears to couple the beta3-A isoform to a specific receptor-recycling pathway.
Asunto(s)
Antígenos CD/metabolismo , Endocitosis/fisiología , Glicoproteínas de Membrana Plaquetaria/metabolismo , Secuencia de Aminoácidos , Animales , Antígenos CD/genética , Sitios de Unión , Células CHO , Membrana Celular/metabolismo , Cricetinae , Citoplasma/metabolismo , Regulación de la Expresión Génica , Proteínas Fluorescentes Verdes , Inmunoglobulinas/genética , Inmunoglobulinas/metabolismo , Integrina beta3 , Proteínas Luminiscentes/genética , Datos de Secuencia Molecular , Mutagénesis , Complejo GPIIb-IIIa de Glicoproteína Plaquetaria/genética , Complejo GPIIb-IIIa de Glicoproteína Plaquetaria/metabolismo , Glicoproteínas de Membrana Plaquetaria/genética , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismoRESUMEN
Intracellular signaling pathways, which regulate the interactions of integrins with their ligands, affect a wide variety of biological functions. Here we provide evidence of how cytohesin-1, an integrin-binding protein and guanine-nucleotide exchange factor (GEF) for ARF GTPases, regulates cell adhesion. Mutational analyses of the beta-2 cytoplasmic domain revealed that the adhesive function of LFA-1 depends on its interaction with cytohesin-1, unless the integrin is activated by exogenous divalent cations. Secondly, cytohesin-1 induces expression of an extracellular activation epitope of LFA-1, and the exchange factor function is not essential for this activity. In contrast, LFA-1-mediated cell adhesion and spreading on intercellular cell adhesion molecule 1 is strongly inhibited by a cytohesin-1 mutant, which fails to catalyze ARF GDP-GTP exchange in vitro. Thus, cytohesin-1 is involved in the activation of LFA-1, most probably through direct interaction with the integrin, and induces cell spreading by its ARF-GEF activity. We therefore propose that both direct regulation of the integrin and concomitant changes in the membrane topology of adherent T cells are modulated by dissectable functions of cytohesin-1.
Asunto(s)
Factores de Ribosilacion-ADP/fisiología , Antígenos CD18/fisiología , Moléculas de Adhesión Celular/fisiología , Adhesión Celular/fisiología , Antígeno-1 Asociado a Función de Linfocito/fisiología , Linfocitos T/citología , Animales , Moléculas de Adhesión Celular/genética , Tamaño de la Célula , Epítopos/química , Factores de Intercambio de Guanina Nucleótido , Guanosina Difosfato/metabolismo , Guanosina Trifosfato/metabolismo , Células HeLa , Humanos , Molécula 1 de Adhesión Intercelular/fisiología , Sustancias Macromoleculares , Ratones , Modelos Moleculares , Ratas , Proteínas Recombinantes de Fusión/fisiología , Técnicas del Sistema de Dos HíbridosRESUMEN
The phosphorylation state of the putative signal transduction protein P(II) from the cyanobacterium Synechococcus sp. strain PCC 7942 depends on the cellular state of nitrogen and carbon assimilation. In this study, dephosphorylation of phosphorylated P(II) protein (P[II]-P) was investigated both in vivo and in vitro. The in vivo studies implied that P(II)-P dephosphorylation is regulated by inhibitory metabolites involved in the glutamine synthetase-glutamate synthase pathway of ammonium assimilation. An in vitro assay for P(II)-P dephosphorylation was established that revealed a Mg2+-dependent P(II)-P phosphatase activity. P(II)-P phosphatase and P(II) kinase activities could be separated biochemically. A partially purified P(II)-P phosphatase preparation also catalysed the dephosphorylation of phosphoserine/phosphothreonine residues on other proteins in a Mg2+-dependent manner. However, only dephosphorylation of P(II)-P was regulated by synergistic inhibition by ATP and 2-oxoglutarate. As the same metabolites stimulate the P(II) kinase activity, it appears that the phosphorylation state of P(II) is determined by ATP and 2-oxoglutarate-dependent reciprocal reactivity of P(II) towards its phosphatase and kinase.