Academic literature on the topic 'Microdomain organisation'

L'invasion de l'hôte par un pathogène induit une réponse immunitaire innée qui aboutit à l'activation cellulaire, à une réaction inflammatoire et parfois à l'initiation d'une immunité acquise. Des différences fondamentales existent dans l'organisation de la réponse immune innée à un pathogène, d'une cellule , d'un organe, ou d'un individu à l'autre. L'organisation de la réponse immune innée en réponse à l'invasion bactérienne, parasitaire ou fongique nécessitent la coopération du récepteur de type Toll 2 (TLR2) avec TLR1 ou TLR6 et la formation de complexes d'activation dans les radeaux lipidiques, qui déterminent une réponse spécifique et adaptée au pathogène. Cependant, les mécanismes de rapprochement moléculaire et la régulation des voies de signalisation impliqués dans la réponse inflammatoire sont encore mal compris. L'objectif de ce travail était d'investiguer les mécanismes impliqués dans la reconnaissance et la signalisation via TLR2, ainsi que dans la variabilité du phénotype inflammatoire. Par une méthode d'analyse protéomique différentielle, nous avons étudié la composition moléculaire du complexe d'activation et les modifications post-traductionnelles en fonction du dimère de TLR2 engagé. Cette approche a permis d'identifier et caractériser le rôle de la tyrosine kinase Lyn et d'IMPDHII dans la régulation de la signalisation de TLR2. Enfin, dans une approche translationnelle nous avons étudié le rôle d'un polymorphisme du gène IRAK1, dont la protéine est en aval de la majorité des TLRs, dans la variabilité du phénotype chez des patients septiques. Ce travail introduit des perspectives nouvelles sur l'organisation, la régulation et la variabilité de la réponse immunitaire innée<br>Host invasion by micro-organisms induces an innate immune response that leads to cell activation, inflammation and potentially to the initiation of an adaptative response. Major differences are found within the organisation of innate immune responses depending on the pathogen, the invaded cell-type and the host itself. Initiation and organisation of innate immune responses facing bacteria, parasites, or fungi need the cooperation of Toll-like receptor 2 (TLR2) with TLR1 or TLR6, and multimolecular complexes in lipid rafts that determine a specific response. However, our understanding of molecular interactions within lipid rafts remains cryptic. Specifically, little is known regarding the composition of signaling complexes induced by distinct pathogens and the activation mechanisms involved in the initiation and regulation of a potent inflammatory response. The aim of this research project was to investigate the mechanisms involved in recognition and signaling downstream TLR2, and factors that account for variability of the inflammatory phenotype. For this purpose, we established a differential proteomic strategy to identiy the composition of TLR2 activation cluster and post-translationnal modifications of proteins after the recruitment of TLR2 dimers to lipid rafts. This approach enabled us to identify tyrosine-kinase Lyn and IMPDHII as essential regulators of TLR2 signaling. In a translational approach, we studied the effect of an haplotype of IRAKI gene, which codes for a key signaling protein downstream TLRs, on clinical variability in patients with septic shock. Our results provide new insights in ogranisation, regulation and variability of innate imune response

Dans le but d’approfondir les connaissances fondamentales entre la structure des polymères associatifs intramoléculaires (polysavons) et leurs propriétés physico-chimiques en milieux aqueux, trois nouvelles familles de polymères amphiphiles cationiques ont été synthétisées par deux méthodes complémentaires permettant une grande variabilité de structure. Les polymères obtenus sont des poly(méth)acrylamides en peigne avec des groupes latéraux de type ammonium quaternaire portant une chaîne alkyle de taille variable. Une étude du comportement physico-chimique de ces polymères en solution, par viscosimétrie et spectroscopie de fluorescence avec deux sondes aux caractéristiques complémentaires, montre qu’ils présentent des propriétés de polysavons qui varient progressivement avec la structure des polymères amphiphiles étudiés, notamment la longueur de la chaîne alkyle latérale, la taille de l’espaceur entre les deux sites polaires amide et ammonium quaternaire et la masse molaire moyenne en nombre. En parallèle, la tensiométrie a montré que ces polyamphiphiles ont une très faible activité à l’interface eau/air confirmant la prédominance de l’effet hydrophobe, alors que les modèles moléculaires correspondants présentent d’excellentes propriétés tensio-actives. Des films de Langmuir ont ensuite été réalisés dans le cadre de la première étude de cette importance sur des polyamphiphiles cationiques. Dans ce domaine également, la grande variabilité de structure des polymères a permis des observations originales et de dégager de nouvelles relations entre la structure du polymère et les caractéristiques des isothermes de compression obtenues<br>In order to improve the fundamental knowledge of the relationships between the chemical structure of intramolecular associative polymers (polysoaps) and their physical chemical properties in aqueous media, three new families of cationic amphiphilic polymers were obtained by complementary methods offering great structure variability. The corresponding polymers were comb poly(meth)acrylamides with pendant ammonium groups with alkyl side chains of variable lengths. A first investigation of their physical chemical behaviour in aqueous solutions, by viscometry and fluorescence spectrometry with two complementary fluorescent probes, showed that they displayed polysoap properties which varied progressively with their chemical features, in particular the length of the alkyl side chain, the size of the spacer between the two polar amide and ammonium groups and the polymer molecular weight. Tensiometry confirmed the prevailing of the hydrophobic effect by showing that these polymers displayed a very weak activity at the water/air interface although the corresponding molecular models showed excellent tensio-active properties. Langmuir’s films were eventually obtained in the first study of this importance on cationic amphiphilic polymers. Here again, the great structural variability enabled original observations and new structure/properties relationships were obtained for the corresponding compression isotherms

Several disorders including pulmonary hypertension (PH) and heart failure (HF) could lead to right ventricle (RV) hypertrophy and failure. RV failure is one of the most important prognostic factors for morbidity and mortality in these disorders. However, there is still no therapy to prevent the RV hypertrophy in PH. Treatments developed for the left ventricle (LV) failure do not improve the survival in patients with RV failure probably due to the significant differences in the chambers physiology and hemodynamic function. A better understanding of the cellular and molecular mechanisms of RV hypertrophy is needed. Our focus lies into the alterations of cellular microarchitecture that promotes functional changes in Ca2+ handling. Recently our group showed that reorganisation of the transverse-axial tubular system (TATS) in HF are of particular importance for Ca2+ mishandling and contractile impairment of failing cells. Rationale: This study aims to establish the differences in membrane organisation of Ca2+ handling between healthy RV and LV myocytes, and to investigate the remodelling of RV during disease. Specifically, the objectives are: (1) To study the membrane organisation of RV and LV myocytes by revealing the surface topography using Scanning Ion Conductance Microscopy and by studying the TATS using confocal microscopy. (2) To assess the contraction and Ca2+ transients in RV and LV myocytes. (3) To determine the spatial distribution and properties of single L-type Ca2+ channels (LTCC) in RV myocytes using “smart patch clamp” technique. (4) To describe the changes occurring in the RV and LV in the two disease rat models: PH induced by monocrotaline injection and HF induced by chronic myocardial infarction (MI). This thesis showed that in healthy samples the TATS of RV myocytes has a different organization as compared to LV. Two main Ca2+ channels for the excitation-contraction coupling: LTCC and ryanodine receptors (RyR) were studied by immunofluorescence staining. The density of LTCC was lower in RV than in LV myocytes. However, the density of RyR was similar between the chambers. Contraction duration was longer in RV than in LV myocytes. The distribution of functional LTCCs in RV myocytes was uniform along the cell surface, in contrast to LV myocytes, where LTCCs were primarily located in the T-tubules. Secondly, PH rats showed a reduction of the conduction velocity anisotropy throughout the RV as well as prolongation of the refractoriness of the tissue. The hypertrophy of RV myocytes in PH was accompanied by the reduction of the TATS organisation. The amplitude of contraction of RV PH myocytes was higher, the activation of Ca2+ transients was more desynchronised than in controls, and the rate of spontaneous Ca2+ activity was significantly elevated. Functionally, in PH the open probability (Po) of LTCC located in the T-tubules was significantly higher. On the other hand, PH LV myocytes had preserved TATS but still showed prolonged Ca2+ transients that could influence increased refractoriness of LV tissue. Thirdly, by studying RV myocytes from the MI model, a significant hypertrophy was found, accompanied by a reduction of TATS organisation. The study reports a prolongation of Ca2+ transients with more frequent local Ca2+ waves in MI versus control RV myocytes. Higher Po of LTCCs was shown in MI RV myocytes could be associated with the PKA-mediated phosphorylation. In summary, RV myocytes have a lower TATS organisation than LV myocytes probably related to the lower workload of the RV chamber. Consequently, RV myocytes present several differences with LV myocytes, including changes in the Ca2+ handling or a more uniform distribution of LTCC on the membrane. Diseases induce reduction of TATS and Ca2+ mishandling in both chambers. Due to the intrinsic differences of RV versus LV myocytes, the RV could be more prone to pathological events in early stages of the diseases, which should be investigated further.