Calcium/phospholipid-dependent protein kinase (PKC) was partially purified from P1798 lymphosarcoma. Phospholipid-dependence was specific for phosphatidylserine. PKC phosphorylated Histone 1, with an apparent K_m of 14.1 μM. Chlorpromazine, a lipid-binding drug, inhibited PKC activity by 100%. Further studies were undertaken to establish analytical conditions which could be applied to the study of PKC in intact cells. The conditions included (1) determining optimum cell concentration for measuring PKC activity, (2) recovering PKC into the soluble fraction of cell extracts, (3) evaluating calcium and phospholipid requirements of PKC in this fraction, and (4) inhibiting PKC in this fraction. Final studies involved treatment of intact cells with potential activators. Both phytohaemagglutinin and a phorbol ester increased PKC activation.

No description available.

Les acides gras à longue chaîne (AGLC) issus des graisses alimentaires exercent de<br />nombreuses fonctions au niveau de l'organisme (source d'énergie et d'acides gras<br />indispensables, synthèse d'eicosanoïdes, régulation de gènes). Leur biodisponibilité cellulaire<br />est donc un paramètre essentiel, principalement conditionné par la barrière intestinale. On sait<br />que l'absorption intestinale des AGLC est très efficace. En revanche, on ignore si ce<br />phénomène est inné ou adaptatif. La réponse à cette question est essentielle. Si l'intestin est<br />capable d'adapter son absorption au contenu en lipides du régime, on pourrait envisager de<br />nouvelles stratégies thérapeutiques visant à limiter la surcharge lipidique de l'organisme dont<br />les effets sont connus. Dans cette optique, nous avons soumis pendant 21 jours des souris à un<br />régime hyperlipidique (40% m/m). Nous avons constaté une induction : 1) du captage des<br />AGLC, 2) de l'activité proliférative qui s'accompagne d'une augmentation de la masse<br />relative de la muqueuse, 3) de l'expression des gènes impliqués dans le captage (Fatty Acid<br />Transport Protein 4, FATP-4), le trafic entérocytaire (Fatty Acid Transporter, FAT; Intestinal<br />and Liver Fatty Acid-Binding Protein, I et L-FABP) des AGLC, la synthèse et la sécrétion des<br />lipoprotéines (Microsomal Triglyceride transfer Protein, MTP et apolipoprotéine A-IV). Ce<br />phénomène est adaptatif puisque ces régulations retournent aux valeurs des témoins lorsque<br />les souris sont renourries avec un régime normolipidique. Ces modifications s'accompagnent<br />d'une augmentation de l'efficacité de clairance plasmatique des lipoprotéines riches en<br />triglycérides. Selon les données de la littérature, le Peroxisome Proliferator-Activated<br />Receptor β (PPARβ) pourrait occuper une place centrale dans cette adaptation intestinale.<br />C'est pourquoi l'impact de la sur-expression intestinale de ce récepteur nucléaire a été étudié<br />sur les capacités d'absorption chez la souris. Les données obtenues ont montré que la surexpression<br />intestinale de PPARβ engendre une adaptation moins efficace des capacités<br />d'absorption. Selon nos travaux, une moins bonne différenciation des entérocytes chez les<br />souris doubles trangéniques pourraient être à l'origine de ce défaut d'adaptation.

SPF (Supernatant Protein Factor) is a cytosolic protein that stimulates at least two enzymes in the cholesterol biosynthetic pathway: squalene monooxygenase and HMGCoA reductase. The mechanism of action has not been established but may be related to lipid transfer between intracellular membranes. There are three human genes for SPF: SEC14L2 (SPF1), SEC14L3 (SPF2) and SEC14L4 (SPF3). The present study differentiates these closely related genes by evaluating their tissue-specific and relative expression levels. SPF1 mRNA was found to be most abundant in liver, mammary gland and stomach. SPF2 showed negligible expression in all tissues tested; SPF3 expression pattern was similar to that of SPF1, but at 10-50-fold lower levels than SPF1. A cDNA to SPF3 was cloned and, upon transfection into rat hepatoma cells, was shown to increase cholesterol synthesis by approximately 50%, similar to that obtained with SPF1. However, in contrast to SPF1, SPF3 did not stimulate squalene monooxygenase activity in microsomal preparations, suggesting that it acts primarily through activation of HMG-CoA reductase. SPF possesses a lipid binding domain (Sec14) and a Golgi dynamics domain (GOLD). SPF resides in the cytosol and requires phosphorylation and the presence of Golgi in order to stimulate cholesterol synthesis. To determine if SPF associates with specific subcellular structures, cellular immunofluorescence studies were carried out. A phosphorylationdefective mutant, a protein lacking the GOLD domain, and the effect of protein kinase A-mediated phosphorylation of endogenous SPF were examined. No change in the subcellular location of SPF could be detected with either the phosphorylation mutant or the native SPF after protein kinase A activation. However, removal of the GOLD domain resulted in a protein that co-localized with large vesicular structures around nucleus. Studies with rat hepatoma cells showed that the expression of the two rat SPF genes is upregulated in response to serum deprivation, and is potentiated by removal of glucose. Lipid/cholesterol availability was demonstrated to be at least one of the serum components that affected SPF transcript levels. The oxysterol receptor LXR was shown not to be involved in SPF gene regulation, implicating SREBP and/or PPARα as the principal regulators of SPF gene transcription.

Serum amyloid A (SAA) is a small, evolutionarily well-conserved, acute-phase protein best known as the protein precursor for amyloid A amyloidosis. During acute injury, infection, or inflammation, SAA plasma concentration rapidly rises 1000-fold, but the benefit of this dramatic increase is unclear. SAA functions in the innate immune response, cell signaling, and lipid homeostasis. Most SAA circulates on plasma high-density lipoproteins (HDL), where it reroutes HDL for lipid recycling. The aim of this dissertation is to provide a structural basis for understanding SAA-lipid interactions and to elucidate the structure-function relationship in this ancient protein. SAA is an intrinsically disordered protein that acquires ~50% helical structure when bound to lipids, and is ~80% helical in three available atomic-resolution x-ray crystal structures. We took advantage of these crystal structures of lipid-free SAA to propose the binding site for various lipids, including lipids in HDL. We postulated that SAA, as a monomer, binds lipids via two amphipathic helices, h1 and h3, that form a concave hydrophobic surface, and that the curvature of this surface defines the binding preference of SAA for HDL versus larger lipoproteins. Next, we used murine SAA1.1 and a membrane-mimicking model phospholipid, palmitoyl-oleoyl phosphocholine (POPC), to reconstitute SAA-lipid complexes and characterize their overall structure, stability and stoichiometry using an array of spectroscopic, electron microscopic, and biochemical methods. We observed preferential formation of ~10 nm particles that mimic HDL size, accompanied by the α-helical folding. To probe the local protein conformation and dynamics in these SAA-POPC particles, we used hydrogen-deuterium exchange mass spectrometry. Analysis of the amount and the kinetics of deuterium uptake clearly established h1 and h3 as the lipid-binding site. Moreover, we determined that SAA binding to lipid follows a mixed model that combines induced fit, promoting α-folding in h3, with conformational selection, stabilizing pre-existing conformations in h1 and around the h2-h3 linker. Taken together, our results provided the structural basis necessary for understanding SAA-lipid interactions, which are central to beneficial functions of SAA as a housekeeping molecule, and to its misfolding in amyloid. This research sets the stage for understanding SAA interactions with its numerous other functional ligands.

Chronic exposure to the ubiqutious airborne fungus, Alternaria alternata, has long been implicated in the development and exacerbation of human allergy and asthma. Alt a 1 was identified previously by several groups as the major allergen secreted by A. alternata, due to its IgE-specific reactivity with sera from atopic patients. Despite the well-documented clinical importance of Alternaria and its major allergen, little knowledge exists regarding their role and interaction with the innate immune system. Here for the first time we characterize the innate immune response to A.alternata and verify the significance of Alt a 1 in contributing to this response in human airway cells and murine models. Our studies establish a baseline response for both a chronic and single-challenge murine inhalation model with Alternaria spores. Both models demonstrate live conidia induce a robust response, arguably more pathologically relevant compared to studies employing Alternaria extracts. We also elucidate the overall importance of Alt a 1 by utilizing recombinant Alt a 1 protein, A. alternata (Δalt a 1) deletion mutants, and an A.alternata (Alt a 1+) overexpression mutant. Both Alt a 1 protein and A. alternata conidia stimulated production of pro-inflammatory cytokines/chemokines in mice after a single intranasal challenge. Infiltration of effector cells (macrophages, neutrophils, eosinophils, and lymphocytes) into the lungs along with other hallmarks of airway inflammation was observed. In addition, Alt a 1 protein and conidia evoked secretion of pro-inflammatory cytokines in treated human airway epithelial cells while the Alt a 1+ overxpression mutant induced a significantly higher response. In contrast, spores of Δalt a 1 caused an attenuated response in both human cells and murine lungs suggesting that this single protein may play a major role in inducing the innate immune response in airway epithelium at the organismal level. Finally, we identified key biochemical properties of the Alt a 1 protein including a single histidine required for esterase activity and a unique RXLR-like motif which controls Alt a 1's ability to bind external lipids and enter human airway cells. Overall, these results improve our understanding of how Alternaria induces innate immunity and identifies possible therapeutic targets within allergenic proteins. / Ph. D.

Salicylic acid binding protein 2 (SABP2) is known to play a key role in Salicylic acid mediated defense pathway. SBIP-470 is SABP2 interacting protein that might be putatively involved in transfer of lipids. SBIP-470 was cloned without the signal peptide and expressed in E. coli. In vitro lipid binding assay using recombinant SBIP-470 failed to detect lipid binding. In vitro lipid transfer assay showed recombinant SBIP-470 does not transfer phospholipid. Study has shown that SBIP-470 is highly inducible upon infection with viral as well as bacterial pathogens. Induction of SBIP-470 expression upon the TMV infection most likely depends upon the SABP2 while its expression upon non-host bacterial pathogens is most probably inhibited by the SABP2. A study of Arabidopsis knockout mutants (ltp12 mutant and ltp2 mutant) lacking the SBIP-470 homolog genes showed defects in growth phenotype, and they were found susceptible to bacterial pathogens.

[EN] ABSTRACT Abscisic acid (ABA) signaling plays a critical role in regulating root growth and root system architecture. ABA-mediated growth promotion and root tropic response under water stress are key responses for plant survival under limiting water conditions. In this work, we have explored the role of Arabidopsis (Arabidopsis thaliana) PYR/PYL/RCAR receptors (PYRABACTIN RESISTANCE1 (PYR1)/PYR1 LIKE (PYL)/REGULATORY COMPONENTS OF ABA RECEPTORS) for root ABA signaling. As a result, we discovered that PYL8 plays a nonredundant role for the regulation of root ABA sensitivity. Unexpectedly, given the multigenic nature and partial functional redundancy observed in the PYR/PYL family, the single pyl8 mutant showed reduced sensitivity to ABA-mediated root growth inhibition. This effect was due to the lack of PYL8-mediated inhibition of several clade A phosphatases type 2C (PP2Cs), since PYL8 interacted in vivo with at least five PP2Cs, namely HYPERSENSITIVE TO ABA1 (HAB1), HAB2, ABAINSENSITIVE1 (ABI1), ABI2, and PP2CA/ABA-HYPERSENSITIVE GERMINATION3 as revealed by tandem affinity purification and mass spectrometry proteomic approaches. Membrane-delimited abscisic acid (ABA) signal transduction plays a critical role in early ABA signaling, but the molecular mechanisms linking core signaling components to the plasma membrane are unclear. We show that transient calciumdependent interactions of PYR/PYL/RCAR ABA receptors with membranes are mediated through a 10-member family of C2-domain ABA-related (CAR) proteins in Arabidopsis thaliana. Specifically, we found that PYL4 interacted in an ABA-independent manner with CAR1 in both the plasma membrane and nucleus of plant cells. CAR1 belongs to a plant-specific gene family encoding CAR1 to CAR10 proteins, and bimolecular fluorescence complementation and coimmunoprecipitation assays showed that PYL4-CAR1 as well as other PYR/PYL-CAR pairs interacted in plant cells. The crystal structure of CAR4 was solved, which revealed that, in addition to a classical calcium-dependent lipid binding C2 domain, a specific CAR signature is likely responsible for the interaction with PYR/PYL/RCAR receptors and their recruitment to phospholipid vesicles. This interaction is relevant for PYR/PYL/RCAR function and ABA signaling, since different car triple mutants affected in CAR1, CAR4, CAR5, and CAR9 genes showed reduced sensitivity to ABA in seedling establishment and root growth assays. In summary, we identified PYR/PYL/RCAR-interacting partners that mediate a transient Ca2+-dependent interaction with phospholipid vesicles, which affects PYR/PYL/RCAR subcellular localization and positively regulates ABA signaling. / [ES] RESUMEN La señalización por la hormona vegetal ácido abscísico (ABA) desempeña un papel crítico en la regulación del crecimiento de la raíz y en la arquitectura del sistema radical. La promoción de crecimiento de la raíz en condiciones de estrés hídrico mediada por ABA es clave para la supervivencia de las plantas bajo condiciones limitantes de agua. En este trabajo, hemos explorado el papel de los receptores PYR/PYL/RCAR (PYRABACTIN RESISTANCE1 (PYR1)/PYR1 LIKE (PYL)/ REGULATORY COMPONENTS OF ABA RECEPTORS) de Arabidopsis (Arabidopsis thaliana) en la ruta de señalización de ABA en raíz. Así, hemos descubierto que el receptor de ABA PYL8 juega un papel no redundante en la regulación de la percepción de ABA en raíz. Inesperadamente, dada la naturaleza multigénica y la redundancia funcional parcial observada en la familia PYR/PYL/RCAR, el mutante pyl8 fue el único mutante sencillo de pérdida de función de los receptores PYR/PYL/RCAR que mostraba una sensibilidad reducida a la inhibición del crecimiento mediada por ABA en raíz. Este efecto se debe a la falta de inhibición mediada por PYL8 de varias fosfatasas del grupo A tipo 2C (PP2Cs), ya que PYL8 es capaz de interactuar in vivo con al menos cinco PP2Cs, denominadas HYPERSENSITIVE TO ABA1 (HAB1), HAB2, ABAINSENSITIVE1 (ABI1), ABI2, and PP2CA/ABA-HYPERSENSITIVE GERMINATION3 según lo han revelado la purificación por afinidad en tándem (TAP por sus siglas en inglés) y estudios proteómicos de espectrometría de masas. La transducción de la señal del ABA localizada en la membrana plasmática celular juega un papel crucial en los pasos iniciales de la señalización de la fitohormona, pero los mecanismos moleculares que unen los componentes básicos de la señalización y la membrana plasmática no están claros. Estudiando las interacciones de los receptores del ABA PYR/PYL/RCAR con la membrana plasmática hemos encontrado que éstos pueden interaccionar transitoriamente con ella de forma dependiente de calcio gracias a una familia de proteínas con dominios C2 relacionadas con la ruta de señalización de ABA (denominadas C2-domain ABA-related (CAR) proteins). Específicamente, se encontró que PYL4 interacciona de manera independiente de ABA con CAR1 tanto en la membrana plasmática como en el núcleo de las células vegetales. La proteína CAR1 pertenece a una familia multigénica constituida por 10 miembros en Arabidopsis thaliana, desde CAR1 hasta CAR10, y que solo se encuentra en plantas. Los ensayos de complementación bi-molecular de fluorescencia y de co-immunoprecipitación confirmaron la interacción en células vegetales tanto de PYL4-CAR1 como de otras parejas de PYR/PYL-CAR. La cristalización de la proteína CAR4 reveló que, además de un dominio C2 clásico de unión a lípidos dependiente de calcio, las proteínas de la familia CAR presentan un dominio específico que probablemente es responsable de la interacción con los receptores PYR/PYL/RCAR y de su posterior reclutamiento a las vesículas de fosfolípidos. Esta interacción es relevante para la función de los receptores PYR/PYL/RCAR en la señalización del ABA, ya que diferentes mutantes triples car de pérdida de función, que tienen afectados los genes CAR1, CAR4, CAR5, y CAR9, demostraron una reducción de la sensibilidad al ABA en ensayos de establecimiento de plántula y crecimiento de la raíz. En resumen, hemos identificado nueva familia de proteínas que son capaces mediar las interacciones transitorias dependientes de Ca2+ con vesículas de fosfolípidos, lo que a su vez afecta localización de PYR/PYL/RCAR y regula positivamente la señalización de ABA. / [CA] RESUM La senyalització per l'hormona vegetal àcid abcíssic (ABA) exerceix un paper crític en la regulació del creixement de l'arrel i també en l'arquitectura del sistema radical. La promoció del creixement de l'arrel en condicions d'estrés hídric, regulada per ABA és clau per la supervivència de les plantes sota condicions limitants d'aigua. Amb aquest treball, hem investigat el paper dels receptors PYR/PYL/RCAR (PYRABACTIN RESISTANCE1 (PYR1)/PYR1 LIKE (PYL)/ REGULATORY COMPONENTS OF ABA RECEPTORS) d'Arabidopsis (Arabidopsis thaliana) en el camí de senyalització d'ABA en arrel. Així, hem descobert que el receptor d'ABA PYL8 exerceix un paper no redundant en la regulació de la percepció d'ABA en arrel. Inesperadament, donada la naturalesa multigènica i la redundància funcional parcial que s'observa en la família PYR/PYL/RCAR, el mutant pyl8 va ser l'únic mutant senzill de pèrdua de funció dels receptors PYR/PYL/RCAR que mostrava una sensibilitat reduïda a la inhibició del creixement mitjançada per l'ABA en l'arrel. Doncs aquest efecte es deu a la falta d'inhibició regulada per PYL8 de diverses fosfatases del grup A tipus 2C (PP2Cs), ja que PYL8 té la capacitat d'interactuar in vivo almenys amb cinc PP2Cs, anomenades HYPERSENSITIVE TO ABA1 (HAB1), HAB2, ABAINSENSITIVE1 (ABI1), ABI2, and PP2CA/ABAHYPERSENSITIVE GERMINATION3 segons ho han revelat per una banda la purificació per afinitat en tàndem (TAP són les seues sigles en anglés) i per altra banda, estudis proteòmics d'espectrometria de masses. Pel que fa a la transducció del senyal del l'ABA, la qual es localitza en la membrana plasmàtica cel¿lular, juga un paper molt important en els primers instants de la senyalització de la fitohormona, no obstant això els mecanismes moleculars que uneixen els components bàsics d'aquesta senyalització amb la membrana plasmàtica, no es troben del tot clars. Per tant, s'han estudiat les interaccions que tenen els receptors del ABA PYR/PYL/RCAR amb la membrana plasmàtica, i hem trobat que aquests tenen la capacitat d'interaccionar transitòriament amb la membrana de forma dependent al calci, gràcies a una família de proteïnes amb domini C2, les quals es troben relacionades amb la ruta de senyalització d'ABA(anomenades C2domain ABArelated (CAR) proteins).Específicament, es va trobar que PYL4 interacciona d'una manera independent al ABA amb CAR1, tant en la membrana plasmàtica, com en el nucli de les cèl¿lules vegetals. La proteïna CAR1 pertany a la família multigènica constituïda per 10 components en Arabidopsis thaliana, des de CAR1 fins CAR10, que tan sols es troba en plantes. Els assajos de complementació bimolecular de fluorescència i de co-immunoprecipitació, van confirmar la interacció en cèl¿lules vegetals, tant de PYL4CAR1 com d'altres parelles de PYR/PYL-CAR. La cristal¿lització de la proteïna CAR4 va revelar que, a més d'un domini C2 clàssic de unió a lípids dependent del calci, les proteïnes de la família CAR presenten un domini PYR/PYL/RCAR, i del seu posterior reclutament a les vesícules fosfolipídiques. Doncs, aquesta interacció és rellevant en la funció dels receptors PYR/PYL/RCAR, ja que participa en la senyalització del l'ABA. Aquesta interacció es clau per a la funció dels receptors, ja que diferents mutants triples car de pèrdua de funció, els quals posseïxen afectats els gens CAR1, CAR4, CAR5 i CAR9, van mostrar una reducció de la sensibilitat a l'ABA en assajos d'establiment de plàntula i creixement de l'arrel. En conclusió, hem identificat una nova família de proteïnes amb la capacitat d'organitzar les interaccions transitòries dependents del calci amb vesícules de fosfolípids, fet que al seu torn afecta la localització de PYR/PYL/RCAR i regula positivament la senyalització d'ABA. / Rodríguez Solovey, LN. (2015). IDENTIFICATION OF TARGETS AND AUXILIARY PROTEINS OF PYR/PYL/RCAR ABA RECEPTORS: PROTEIN PHOSPHATASES TYPE 2C (PP2Cs) AND C2-DOMAIN ABA-RELATED PROTEINS (CARs) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/58862