Thrombin Protease-activated Receptor-1 Signals through Gq- and G13-initiated MAPK Cascades Regulating c-Jun Expression to Induce Cell Transformation

Although the ability of G protein-coupled receptors to stimulate normal and aberrant cell growth has been intensely investigated, the precise nature of the molecular mechanisms underlying their transforming potential are still not fully understood. In this study, we have taken advantage of the potent mitogenic effect of thrombin and the focus-forming activity of one of its receptors, protease-activated receptor-1, to dissect how this receptor coupled to Gi, Gq/11, and G12/13 transduces signals from the membrane to the nucleus to initiate transcriptional events involved in cell transformation. Using endogenous and transfected thrombin receptors in NIH 3T3 cells, ectopic expression of muscarinic receptors coupled to Gq and Gi, and chimeric G protein subunits and murine fibroblasts deficient in Gq/11, and G12/13, we show here that, although coupling to Gi is sufficient to induce ERK activation, the ability to couple to Gq and/or G13 is necessary to induce c-jun expression and cell transformation. Furthermore, we show that Gq and G13 can initiate the activation of MAPK cascades, including JNK, p38, and ERK5, which in turn regulate the activity of transcription factors controlling expression from the c-jun promoter. We also present evidence that c-Jun and the kinases regulating its expression are integral components of the transforming pathway initiated by protease-activated receptor-1

Activació de les fosfolipases C i D per neurotransmissors

Els fosfolípids de les membranes cel·lulars compleixen un paper fonamental en el manteniment de 1'estructura i la compartició cel·lular, gràcies a la seva naturalesa molecular amfipàtica, i cada cop més són observats des de la perspectiva de la transducció de senyals com a precursors de missatgers intracel·lulars. Diverses fosfolipases, sensibles a l'activació per neurotransmissors i altres estímuls extracel·lulars, catalitzen la seva hidròlisi trencant enllaços ester o fosfoester, i l'acció, com a segons missatgers, dels productes que en poden derivar permet dibuixar una xarxa d'esdeveniments que se succeeixen i s'entrellacen configurant una part important del complex comandament del metabolisme i de les funcions cel·lulars. En aquest capítol tractarem alguns aspectes relacionats amb la intervenció de les fosfolipases C de fosfoinosítids (PLC) i de les fosfolipases D (PLD) en sistemes de transducció

Nurr1 protein is required for N-Methyl-d-aspartic Acid (NMDA) receptor-mediated neuronal survival

NMDA receptor (NMDAR) stimulation promotes neuronal survival during brain development. Cerebellar granule cells (CGCs) need NMDAR stimulation to survive and develop. These neurons differentiate and mature during its migration from the external granular layer to the internal granular layer, and lack of excitatory inputs triggers their apoptotic death. It is possible to mimic this process in vitro by culturing CGCs in low KCl concentrations (5 mm) in the presence or absence of NMDA. Using this experimental approach, we have obtained whole genome expression profiles after 3 and 8 h of NMDA addition to identify genes involved in NMDA-mediated survival of CGCs. One of the identified genes was Nurr1, a member of the orphan nuclear receptor subfamily Nr4a. Our results report a direct regulation of Nurr1 by CREB after NMDAR stimulation. ChIP assay confirmed CREB binding to Nurr1 promoter, whereas CREB shRNA blocked NMDA-mediated increase in Nurr1 expression. Moreover, we show that Nurr1 is important for NMDAR survival effect. We show that Nurr1 binds to Bdnf promoter IV and that silencing Nurr1 by shRNA leads to a decrease in brain-derived neurotrophic factor (BDNF) protein levels and a reduction of NMDA neuroprotective effect. Also, we report that Nurr1 and BDNF show a similar expression pattern during postnatal cerebellar development. Thus, we conclude that Nurr1 is a downstream target of CREB and that it is responsible for the NMDA-mediated increase in BDNF, which is necessary for the NMDA-mediated prosurvival effect on neurons

Late-stage differentiation of embryonic pancreatic β-cells requires Jarid2.

Jarid2 is a component of the Polycomb Repressor complex 2 (PRC2), which is responsible for genome-wide H3K27me3 deposition, in embryonic stem cells. However, Jarid2 has also been shown to exert pleiotropic PRC2-independent actions during embryogenesis. Here, we have investigated the role of Jarid2 during pancreas development. Conditional ablation of Jarid2 in pancreatic progenitors results in reduced endocrine cell area at birth due to impaired endocrine cell differentiation and reduced prenatal proliferation. Inactivation of Jarid2 in endocrine progenitors demonstrates that Jarid2 functions after endocrine specification. Furthermore, genome-wide expression analysis reveals that Jarid2 is required for the complete activation of the insulin-producing β-cell differentiation program. Jarid2-deficient pancreases exhibit impaired deposition of RNAPII-Ser5P, the initiating form of RNAPII, but no changes in H3K27me3, at the promoters of affected endocrine genes. Thus, our study identifies Jarid2 as a fine-tuner of gene expression during late stages of pancreatic endocrine cell development. These findings are relevant for generation of transplantable stem cell-derived β-cells

Activació de les fosfolipases C i D per neurotransmissors

Els fosfolípids de les membranes cel·lulars compleixen un paper fonamental en el manteniment de 1'estructura i la compartició cel·lular, gràcies a la seva naturalesa molecular amfipàtica, i cada cop més són observats des de la perspectiva de la transducció de senyals com a precursors de missatgers intracel·lulars. Diverses fosfolipases, sensibles a l'activació per neurotransmissors i altres estímuls extracel·lulars, catalitzen la seva hidròlisi trencant enllaços ester o fosfoester, i l'acció, com a segons missatgers, dels productes que en poden derivar permet dibuixar una xarxa d'esdeveniments que se succeeixen i s'entrellacen configurant una part important del complex comandament del metabolisme i de les funcions cel·lulars. En aquest capítol tractarem alguns aspectes relacionats amb la intervenció de les fosfolipases C de fosfoinosítids (PLC) i de les fosfolipases D (PLD) en sistemes de transducció

Ammonium quantification (AQua) in human plasma by 1 H‐NMR for staging of liver fibrosis in alcohol‐related liver disease and non‐alcoholic fatty liver disease

Liver fibrosis staging is a key element driving the prognosis of patients with chronic liver disease. Currently, biopsy is the only technique capable of diagnosing liver fibrosis in patients with alcohol‐related liver disease (ArLD) and nonalcoholic fatty liver disease (NAFLD) unequivocally. Noninvasive (e.g. plasma‐based) biomarker assays are attractive tools to diagnose and stage disease, yet must prove that they are reliable and sensitive to be used clinically. Here, we demonstrate proton nuclear magnetic resonance as a method to rapidly quantify the endogenous concentration of ammonium ions from human plasma extracts and show their ability to report upon early and advanced stages of ArLD and NAFLD. We show that, irrespective of the disease etiology, ammonium concentration is a more robust and informative marker of fibrosis stage than current clinically assessed blood hepatic biomarkers. Subject to validation in larger cohorts, the study indicates that the method can provide accurate and rapid staging of ArLD and NAFLD without the need for an invasive biopsy