Mechanisms of the ATP potentiation of hyposmotic taurine release in Swiss 3T3 fibroblasts

Rodrigo Franco-Cruz, Rafael Rodríguez, Herminia Pasantes-Morales

Research output: Contribution to journalArticle

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Abstract

Reducing osmolarity by 35% increased 3H-taurine efflux from Swiss 3T3 fibroblasts from 0.5% to a peak of 5.7%. The presence of ATP (10-100 μM; EC50 1.5 μM) increased taurine efflux up to 10%, and decreased the set point for hyposmotically stimulated taurine release (HTR). ATP potentiation was mimicked by UTP, reduced by addition of suramin and pyridoxal phosphate-6-azophenyl-2′,4′-disulphonic acid (PPADS) and unaffected by ADP, β,γ-methylene-ATP (β,γ-ATP) or 2-methylthio-ATP (Me-ATP), suggesting its mediation by purinergic P2Y2 and P2Y 4 metabotropic receptors. Under isosmotic conditions ATP increased the cytosolic [Ca2+] ([Ca2+]i) markedly, but did not increase taurine release. HTR was independent of external Ca 2+ but was reduced (by 56-59%) by BAPTA-AM, thapsigargin-induced depletion of intracellular Ca2+ stores, or phospholipase C (PLC) inhibition. Blockade of calmodulin (CaM) or calmodulin kinase II (CaMKII) reduced HTR by 54% and 76%, respectively. The ATP-mediated potentiation was prevented fully by all these treatments. HTR was reduced by 30-50% by blockers of protein tyrosine kinases (AG18), phosphoinositide 3-kinase (PI3K) (wortmannin), p21rho (toxin B), p21rho-kinase (Y27632) and the stress-activated kinase p38 (PD169316). ATP-mediated potentiation was reduced similarly by these blockers. Simultaneous inhibition of PI3K and CaMKII abolished HTR. Altogether, these results suggest a modulatory effect of ATP, probably exerted by a potentiation of the Ca2+-dependent fraction of HTR. This fraction has as signalling elements a PLC-dependent [Ca2+]i increase, resulting from Ca2+ released from thapsigargin-sensitive internal stores, followed by activation of CaM/CaMKII reactions. The Ca2+/ATP effect operates only when the Ca2+-independent, tyrosine kinase-mediated pathway is already activated. Suggested elements of cross-talk between the two pathways are PLC, PI3K and CaMKII.

Original languageEnglish (US)
Pages (from-to)159-169
Number of pages11
JournalPflugers Archiv European Journal of Physiology
Volume449
Issue number2
DOIs
StatePublished - Nov 1 2004

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Taurine
Fibroblasts
Adenosine Triphosphate
Calcium-Calmodulin-Dependent Protein Kinases
Phosphotransferases
1-Phosphatidylinositol 4-Kinase
Type C Phospholipases
Thapsigargin
Calmodulin
Phosphatidylinositols
Protein-Tyrosine Kinases
Phosphoinositide Phospholipase C
Suramin
Uridine Triphosphate
Pyridoxal Phosphate
Osmolar Concentration
Adenosine Diphosphate
Chemical activation
Acids

Keywords

  • Cell volume
  • Hyposmolarity
  • P2Y
  • Purinergic receptors

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Physiology (medical)

Cite this

Mechanisms of the ATP potentiation of hyposmotic taurine release in Swiss 3T3 fibroblasts. / Franco-Cruz, Rodrigo; Rodríguez, Rafael; Pasantes-Morales, Herminia.

In: Pflugers Archiv European Journal of Physiology, Vol. 449, No. 2, 01.11.2004, p. 159-169.

Research output: Contribution to journalArticle

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