P2X7 receptor activates extracellular signal-regulated kinases ERK1 and ERK2 independently of Ca2+ influx.
P2X7 nucleotide receptors modulate a spectrum of cellular events in various cells including epithelia, such as exocrine pancreas. Although the pharmacology and channel properties of the P2X7 receptors have been studied intensively, signal transduction pathways are relatively unknown. In this study we applied a heterologous expression system of rat P2X7 receptors in HEK-293 cells. We followed the receptor expression and function using the enhanced green fluorescent protein (EGFP) tag, activation of intracellular proteins and increases in cellular Ca2+. EGFP-P2X7 receptors localized to the plasma membrane, clusters within the membrane and intracellularly. Stimulation of P2X7 receptors in HEK-293 cells led to an activation of extracellular signal-regulated kinases ERK1 and ERK2 and this activation was seen after just 1 min of stimulation with ATP. Using C- and N-terminal P2X7-receptor mutants we show that the N-terminus is important in activation of ERKs, whereas deletion of the last 230 amino acids in the C-terminus did not effect ERK activation. On the other hand, Ca2+ entry was impaired in C-terminal but not in N-terminal mutants. In cell suspensions prepared from rat pancreas we show that P2X7 receptors also activate ERK1 and ERK2, indicating that these signalling pathways are also turned on in native epithelium.
August Krogh Institute, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen, Denmark. JAmstrup@aki.ku.dk
Jan
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Amstrup
Ivana
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Novak
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002460:Cell Line; D004789:Enzyme Activation; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016296:Mutagenesis; D010179:Pancreas / Q000502:physiology; D010183:Pancreatic Ducts / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000502:physiology*; D058486:Receptors, Purinergic P2X7; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017384:Sequence Deletion; D015398:Signal Transduction; D014162:Transfection
D008164:Luminescent Proteins; C546468:P2RX7 protein, human; C546470:P2rx7 protein, rat; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium