Cross-talk among epidermal growth factor, Ap(5)A, and nucleotide receptors causing enhanced ATP Ca(2+) signaling involves extracellular kinase activation in cerebellar astrocytes.
In previous papers, we reported that ATP calcium responses in cerebellar astrocytes were strongly potentiated by preincubation with nanomolar concentrations of the diadenosine pentaphosphate Ap(5)A. However, the intracellular signaling pathway mediating this effect was not defined. We also showed that stimulation of astrocytes with the dinucleotide led to the activation of extracellular regulated kinases (ERKs). Here, we examined whether ERKs are involved in the potentiating mechanism and intracellular mechanism leading to their activation. Epidermal growth factor (EGF) exactly reproduced the potentiation displayed by the dinucleotide. Moreover, the potentiation of ATP responses by Ap(5)A and EGF was completely abolished by the MAP kinase (MEK) inhibitor U-0126, indicating that ERK activation is a required step for the potentiation event. Our data also indicated that ERK activation and the potentiation of ATP calcium responses were sensitive to the src-like kinase inhibitor herbimycin A, p21(ras) farnesyltransferase inhibitor peptide, and some PKC inhibitors. Taken together, our findings reveal that Ap(5)A triggers the potentiation of ATP calcium responses through an intracellular mechanism that is insensitive to pertussis toxin and that this potentiation requires src protein-mediated ERK activation and the participation of an atypical protein kinase C isoform activated downstream from ERK.
Delicado
Esmerilda G
EG
Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid, Spain. esmerild@vet.ucm.es
Jiménez
Ana I
AI
Carrasquero
Luz María G
LM
Castro
Enrique
E
Miras-Portugal
M Teresa
MT
D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D001253:Astrocytes / Q000201:enzymology* / Q000502:physiology*; D015153:Blotting, Western; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000201:enzymology / Q000502:physiology; D015226:Dinucleoside Phosphates / Q000502:physiology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000502:physiology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology*; D005470:Fluorometry; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000502:physiology; D009711:Nucleotides / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D020239:Receptor Cross-Talk / Q000502:physiology*; D020794:Receptor Protein-Tyrosine Kinases / Q000502:physiology; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000502:physiology
D015226:Dinucleoside Phosphates; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D009711:Nucleotides; C012275:P(1),P(5)-di(adenosine-5'-)pentaphosphate; D004815:Epidermal Growth Factor; D000255:Adenosine Triphosphate; D020794:Receptor Protein-Tyrosine Kinases; D019061:src-Family Kinases; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases