RESUMO
The impairment of the cystic fibrosis transmembrane conductance regulator (CFTR) activity induces intracellular chloride (Cl- ) accumulation. The anion Cl- , acting as a second messenger, stimulates the secretion of interleukin-1ß (IL-1ß), which starts an autocrine positive feedback loop. Here, we show that NLR family pyrin domain containing 3 (NLRP3) and caspase 1 (CASP1) are indirectly modulated by the intracellular Cl- concentration, showing maximal expression and activity at 75 mM Cl- , in the presence of the ionophores nigericin and tributyltin. The expression of PYD and CARD domain containing (PYCARD/ASC) remained constant from 0 to 125 mM Cl- . The CASP1 inhibitor VX-765 and the NLRP3 inflammasome inhibitor MCC950 completely blocked the Cl- -stimulated IL-1ß mRNA expression and partially the IL-1ß secretion. DCF fluorescence (cellular reactive oxygen species, cROS) and MitoSOX fluorescence (mitochondrial ROS, mtROS) also showed maximal ROS levels at 75 mM Cl- , a response strongly inhibited by the ROS scavenger N-acetyl-L-cysteine (NAC) or the NADPH oxidase (NOX) inhibitor GKT137831. These inhibitors also affected CASP1 and NLRP3 mRNA and protein expression. More importantly, the serum/glucocorticoid regulated kinase 1 (SGK1) inhibitor GSK650394, or its shRNAs, completely abrogated the IL-1ß mRNA response to Cl- and the IL-1ß secretion, interrupting the autocrine IL-1ß loop. The results suggest that Cl- effects are mediated by SGK1, in which under Cl- modulation stimulates the secretion of mature IL-1ß, in turn, responsible for the upregulation of ROS, CASP1, NLRP3 and IL-1ß itself, through autocrine signalling.
Assuntos
Caspase 1/metabolismo , Cloretos/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Proteínas Imediatamente Precoces/metabolismo , Interleucina-1beta/metabolismo , Espaço Intracelular/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Inibidores de Caspase/farmacologia , Linhagem Celular , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Dipeptídeos/farmacologia , Retroalimentação Fisiológica , Furanos/farmacologia , Humanos , Proteínas Imediatamente Precoces/genética , Indenos/farmacologia , Interleucina-1beta/genética , Mutação/genética , Nigericina/farmacologia , Proteínas Serina-Treonina Quinases/genética , RNA Interferente Pequeno/genética , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais , Sulfonamidas/farmacologia , para-Aminobenzoatos/farmacologiaRESUMO
Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. It has been postulated that reduced HCO3- transport through CFTR may lead to a decreased airway surface liquid pH. In contrast, others have reported no changes in the extracellular pH (pHe). We have recently reported that in carcinoma Caco-2/pRS26 cells (transfected with short hairpin RNA for CFTR) or CF lung epithelial IB3-1 cells, the mutation in CFTR decreased mitochondrial complex I activity and increased lactic acid production, owing to an autocrine IL-1ß loop. The secreted lactate accounted for the reduced pHe, because oxamate fully restored the pHe. These effects were attributed to the IL-1ß autocrine loop and the downstream signaling kinases c-Src and JNK. Here we show that the pHe of IB3-1 cells can be restored to normal values (â¼7.4) by incubation with the epidermal growth factor receptor (EGFR, HER1, ErbB1) inhibitors AG1478 and PD168393. PD168393 fully restored the pHe values of IB3-1 cells, suggesting that the reduced pHe is mainly due to increased EGFR activity and lactate. Also, in IB3-1 cells, lactate dehydrogenase A mRNA, protein expression, and activity are downregulated when EGFR is inhibited. Thus, a constitutive EGFR activation seems to be responsible for the reduced pHe in IB3-1 cells.
Assuntos
Regulador de Condutância Transmembrana em Fibrose Cística/genética , Fibrose Cística/patologia , Células Epiteliais/metabolismo , Lactato Desidrogenase 5/metabolismo , Ácido Láctico/metabolismo , Pulmão/metabolismo , Fibrose Cística/genética , Fibrose Cística/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Células Epiteliais/patologia , Receptores ErbB/metabolismo , Humanos , Concentração de Íons de Hidrogênio , Pulmão/patologiaRESUMO
Homo sapiens orphan G protein-coupling receptor PEIG-1 was first cloned and characterized by applying differential display to T84 colonic carcinoma cells incubated in the presence of phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) (GenBank AF506289.1). Later, Lotan's laboratory found the same gene product in response to retinoic acid analogues, naming it with the symbol RAIG1. Now the official HGNC symbol is GPRC5A. Here, we report the extension of its original cDNA fragment towards the 5' and 3' end. In addition, we show that TPA (100 ng/ml, 162 nM) strongly stimulated GPRC5A mRNA in T84 colonic carcinoma cells, with maximal expression at 4 h and 100 ng/ml (162 nM). Western blots showed several bands between 35 and 50 kDa, responding to TPA stimulation. Confocal microscopy confirmed its TPA upregulation and the location in the plasma membrane. The PKC inhibitor Gö 6983 (10 µM), and the Ca2+ chelator BAPTA-AM (150 µM), strongly inhibited its TPA induced upregulation. The PKA inhibitor H-89 (10 µM), and the MEK1/2 inhibitor U0126 (10 µM), also produced a significant reduction in the TPA response (~50%). The SGK1 inhibitor GSK650394 stimulated GPRC5A basal levels at low doses and inhibit its TPA-induced expression at concentrations ≥10 µM. The IL-1ß autocrine loop and downstream signalling did not affect its expression. In conclusion, RAIG1/RAI3/GPRC5A corresponds to the originally reported PEIG-1/TIG1; the inhibition observed in the presence of Gö 6983, BAPTA and U0126, suggests that its TPA-induced upregulation is mediated through a PKC/Ca2+ âMEK1/2 signalling axis. PKA and SGK1 kinases are also involved in its TPA-induced upregulation.