Ca2+-dependent ATP release from A549 cells involves synergistic autocrine stimulation by coreleased uridine nucleotides.
Extracellular ATP is a potent surfactant secretagogue but its origin in the alveolus, its mechanism(s) of release and its regulatory pathways remain unknown. Previously, we showed that hypotonic swelling of alveolar A549 cells induces Ca(2+)-dependent secretion of several adenosine and uridine nucleotides, implicating regulated exocytosis. In this study, we examined sources of Ca(2+) for the elevation of intracellular Ca(2+) concentration ([Ca(2+)](i)) evoked by acute 50% hypotonic stress and the role of autocrine purinergic signalling in Ca(2+)-dependent ATP release. We found that ATP release does not directly involve Ca(2+) influx from extracellular spaces, but depends entirely on Ca(2+) mobilization from intracellular stores. The [Ca(2+)](i) response consisted of slowly rising elevation, representing mobilization from thapsigargin (TG)-insensitive stores and a superimposed rapid spike due to Ca(2+) release from TG-sensitive endoplasmic reticulum (ER) Ca(2+) stores. The latter could be abolished by hydrolysis of extracellular triphospho- and diphosphonucleotides with apyrase; blocking P2Y(2)/P2Y(6) receptors of A549 cells with suramin; blocking UDP receptors (P2Y(6)) with pyridoxal phosphate 6-azophenyl-2',4'-disulfonic acid (PPADS); emptying TG-sensitive stores downstream with TG or caffeine in Ca(2+)-free extracellular solution; or blocking the Ca(2+)-release inositol 1,4,5-triphosphate receptor channel of the ER with 2-aminoethyldiphenylborinate. These data demonstrate that the rapid [Ca(2+)](i) spike results from the autocrine stimulation of IP(3)/Ca(2+)-coupled P2Y, predominantly P2Y(6), receptors, accounting for approximately 70% of total Ca(2+)-dependent ATP release evoked by hypotonic shock. Our study reveals a novel paradigm in which stress-induced ATP release from alveolar cells is amplified by the synergistic autocrine/paracrine action of coreleased uridine and adenosine nucleotides. We suggest that a similar mechanism of purinergic signal propagation operates in other cell types.
Tatur
Sabina
S
Centre hospitalier de l'Université de Montréal - Hôtel-Dieu, 3850 Saint-Urbain, Montréal, Québec, Canada.
Groulx
Nicolas
N
Orlov
Sergei N
SN
Grygorczyk
Ryszard
R
D000255:Adenosine Triphosphate / Q000378:metabolism*; D001081:Apyrase / Q000494:pharmacology; D019898:Autocrine Communication; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D045744:Cell Line, Tumor; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D006868:Hydrolysis; D007038:Hypotonic Solutions; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; D008175:Lung Neoplasms / Q000378:metabolism* / Q000473:pathology; D009997:Osmotic Pressure; D019899:Paracrine Communication; D058919:Purinergic P2 Receptor Antagonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D058473:Receptors, Purinergic P2Y2; D013498:Suramin / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors; D014500:Uracil Nucleotides / Q000378:metabolism*
D004791:Enzyme Inhibitors; D007038:Hypotonic Solutions; D053496:Inositol 1,4,5-Trisphosphate Receptors; C546385:P2RY2 protein, human; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; D014500:Uracil Nucleotides; C099845:purinoceptor P2Y6; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D002110:Caffeine; D011732:Pyridoxal Phosphate; D013498:Suramin; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D001081:Apyrase; D000252:Calcium-Transporting ATPases; D002118:Calcium
Mol Pharmacol. 1998 Dec;54(6):1118-23
9855642
Biochem Pharmacol. 2005 Apr 15;69(8):1177-86
15794938
J Physiol. 2004 Dec 1;561(Pt 2):499-513
15579539
Proc Natl Acad Sci U S A. 1997 Mar 18;94(6):2599-603
9122241
J Membr Biol. 2006;214(1):43-56
17598067
Cell Calcium. 2006 Nov-Dec;40(5-6):403-4
17027080
Annu Rev Physiol. 2005;67:595-621
15709972
J Physiol. 2001 May 1;532(Pt 3):759-69
11313444
Eur J Pharmacol. 2004 Feb 6;485(1-3):137-40
14757133
J Biol Chem. 2006 Aug 11;281(32):22992-3002
16754672
Cell Physiol Biochem. 2000;10(5-6):297-302
11125208
Cell Mol Life Sci. 2000 Mar;57(3):354-70
10823237
Physiol Rev. 1998 Jul;78(3):763-81
9674694
Am J Respir Cell Mol Biol. 2005 Dec;33(6):601-9
16109883
Proc Natl Acad Sci U S A. 1990 Apr;87(7):2466-70
2138778
FEBS Lett. 1996 Oct 21;395(2-3):137-42
8898081
J Vasc Res. 2004 Mar-Apr;41(2):166-73
15004436
J Microsc. 2004 Sep;215(Pt 3):302-12
15312195
J Membr Biol. 1997 Jul 15;158(2):127-36
9230090
Cell Calcium. 1996 Oct;20(4):339-46
8939353
Cell Calcium. 2002 Nov-Dec;32(5-6):343-54
12543094
Cell Calcium. 2006 Nov-Dec;40(5-6):423-39
17067670
J Physiol. 2001 May 1;532(Pt 3):582
11313430
Purinergic Signal. 2008 Jun;4(2):139-46
18368524
Am J Physiol Lung Cell Mol Physiol. 2003 Aug;285(2):L376-85
12691958
Am J Respir Cell Mol Biol. 1993 Sep;9(3):315-22
8398169
J Biochem. 2000 Aug;128(2):329-36
10920270
Am J Physiol Lung Cell Mol Physiol. 2000 Apr;278(4):L726-36
10749750
Physiol Rev. 1992 Oct;72(4):1037-61
1332089
J Biol Chem. 2001 Aug 31;276(35):33027-35
11402049
FASEB J. 2001 Aug;15(10):1727-38
11481220
Comp Biochem Physiol A Mol Integr Physiol. 2001 May;129(1):233-43
11369548
Am J Physiol. 1995 Jun;268(6 Pt 1):L1021-8
7611424
Trends Pharmacol Sci. 2006 Apr;27(4):211-7
16530853
J Neurochem. 2004 Jan;88(1):246-56
14675168
Gen Physiol Biophys. 2003 Dec;22(4):487-500
15113121
J Biol Chem. 2004 Aug 27;279(35):36855-64
15210701
J Cell Physiol. 1999 Jul;180(1):19-34
10362014
J Biol Chem. 1998 May 15;273(20):12281-7
9575179