FLRT3: mecanismes moleculars de senyalització en el desenvolupament dels axons talamocorticals

En aquest estudi hem trobat que FLRT3 (Fibronectin Leucine-Rich Transmembrane protein) interacciona amb el receptor de Slit, Robo1, de forma independent lligand. En cèl•lules HEK293T hem vist que FLRT3 i Robo1 interaccionen mitjançant els seus dominis intracel•lulars, que la co-expressió de FLRT3 amb Robo1 indueix el processament del receptor i que FLRT3 interacciona amb el fragment intracel•lular generat amb major afinitat i el segresta a la membrana. En presència de Slit, es produeix un increment en el processament de Robo1 i el fragment intracel•lular generat és captat per FLRT3. La interacció entre FLRT3-Robo1 i entre FLRT3-Robo1ICD es dóna en neurones talàmiques rostrals a E13.5. Slit indueix el processament de Robo1 per metaloproteases en aquestes neurones i FLRT3 captura el fragment generat. La interacció FLRT3-Robo1 i l'activació de ROCK són necessàries per la correcta guia axonal dels axons talamocorticals rostrals. FLRT3 regula directament i de forma negativa la senyalització repulsiva Slit/Robo i indirectament promou la senyalització atractiva Netrin/DCCEn este estudio hemos encontrado que FLRT3 (Fibronectin Leucine-Rich Transmembrane protein) interacciona con el receptor de Slit, Robo1, de forma independiente de ligando. En células HEK293T hemos visto que FLRT3 y Robo1 interaccionan mediante sus dominios intracelulares, que la co-expresión de FLRT3 con Robo1 induce el procesamiento del receptor y que FLRT3 interacciona con el fragmento intracelular generado con mayor afinidad y lo secuestra en la membrana. En presencia de Slit, se produce un incremento en el procesamiento de Robo1 y el fragmento intracelular generado es captado por FLRT3. La interacción entre FLRT3-Robo1 y entre FLRT3-Robo1ICD tiene lugar en neuronas talámicas rostrales a E13.5. Slit induce el procesamiento de Robo1 por metaloproteasas en estas neuronas y FLRT3 captura el fragmento generado. La interacción FLRT3-Robo1 i la activación de ROCK son necesarias para la correcta guía axonal de los axones talamocorticales rostrales. FLRT3 regula directamente y de forma negativa la señalización repulsiva Slit/Robo y indirectamente promueve la señalización atractiva Netrin/DCC.In this study we have found that FLRT3 (Fibronectin Leucine-Rich Transmembrane protein) interacts with the Slit receptor Robo1 ligand- independently. In HEK293T cells we have found that FLRT3 and Robo1 interact throught their intracellular domains, that the co-expression of FLRT3 with Robo1 triggers the shedding of the receptor and that FLRT3 interacts with the intracellular fragment generated with higher affinity and keeps it in the plasma membrane. The presence of Slit produces an increase in the shedding of Robo1 and the intracellular fragment that is generated is catched by FLRT3. The interaction between FLRT3-Robo1 and between FLRT3-Robo1ICD takes place in rostral thalamic neurons at E13.5. Slit triggers Robo1 shedding by metalloproteases in these neurons and FLRT3 catches the intracellular fragment generated. The interaction FLRT3-Robo1 and the activation of ROCK are necessary for the proper guidance of the rostral talamocortical axons. FLRT3 regulates directly and negatively the Slit/Robo repulsive signaling and indirectly promotes the Netrin/DCC attractive signalin

Alzheimer’s disease mutant mice exhibit reduced brain tissue stiffness compared to wild-type mice in both normoxia and following intermittent hypoxia mimicking sleep apnea

Background: Evidence from patients and animal models suggests that obstructive sleep apnea (OSA) may increase the risk of Alzheimer’s disease (AD) and that AD is associated with reduced brain tissue stiffness. Aim: To investigate whether intermittent hypoxia (IH) alters brain cortex tissue stiffness in AD mutant mice exposed to IH mimicking OSA. Methods: Six-eight month old (B6C3-Tg(APPswe,PSEN1dE9)85Dbo/J) AD mutant mice and wild-type (WT) littermates were subjected to IH (21% O2 40 s to 5% O2 20 s; 6 h/day) or normoxia for 8 weeks. After euthanasia, the stiffness (E) of 200-μm brain cortex slices was measured by atomic force microscopy. Results: Two-way ANOVA indicated significant cortical softening and weight increase in AD mice compared to WT littermates, but no significant effects of IH on cortical stiffness and weight were detected. In addition, reduced myelin was apparent in AD (vs. WT), but no significant differences emerged in the cortex extracellular matrix components laminin and glycosaminoglycans when comparing baseline AD and WT mice. Conclusion: AD mutant mice exhibit reduced brain tissue stiffness following both normoxia and IH mimicking sleep apnea, and such differences are commensurate with increased edema and demyelination in AD.This work was supported in part by Fundació Marató TV3 (20143231), the Spanish Ministry of Economy and Competitiveness—Instituto de Salud Carlos III (FIS-PI14/00004, FIS-PI14/00280) and SEPAR (139/2015). This work was partially funded by the CERCA Programme of Generalitat de Catalunya