Functional interaction between native G protein-coupled purinergic receptors in Xenopus follicles
Por:
Arellano, RO, Garay, E, Vazquez-Cuevas, F
Publicada:
29 sep 2009
Categoría:
Multidisciplinary
Resumen:
Purinergic receptors are expressed in the membrane of the follicular cell layer that communicates with the Xenopus oocyte. Adenosine (Ado) generates a cAMP-dependent K+ current (IK,cAMP), whereas ATP activates a Cl- current (FCl) and has a dual effect on I K,cAMP, provoking both its activation and inhibition. Here, purinergic responses were studied electrophysiologically, first in the whole follicle (w.f.), and then in the same follicle after removal of its epithelium/theca layers (e.t.r. follicle). Responses were analyzed as the ratio of the current amplitudes (ietr/iwf) in the two preparations. For ATP activation of IK,cAMP and FCl, the ratios i etr/iwf were 0.053 and 22, respectively, whereas that for Ado was 0.75. Thus, epithelium/theca removal drastically altered the ATP response, suggesting a change in the signaling pathway that correlated with changes in the pharmacological characteristics: the half-maximal effective concentration for activation of the main current in w.f. (IK,cAMP) was 14 ± 3.8 µM [Hill coefficient (nH) = 2.7 ± 0.61], and that in e.t.r. follicles (FCl) was 1.8 ± 0.68 µM (nH = 0.76 ± 0.09), whereas Ado-response parameters did not change. Responses to UTP and ß,?-methylene-ATP, specific agonists for IK,cAMP inhibition and activation, respectively, indicated that in e.t.r. follicles inhibition increased and activation decreased drastically. Thus, purinergic responses were not independent; instead, they were functionally linked. We hypothesize that this property was due to direct interactions between receptors for Ado (A2 subtype) and ATP (P2Y subtype) in the Xenopus follicle.
Filiaciones:
Arellano, RO:
Univ Nacl Autonoma Mexico, Inst Neurobiol, Dept Neurobiol Celular & Mol, Juriquilla Queretaro 76230, Queretaro, Mexico
Garay, E:
Univ Nacl Autonoma Mexico, Inst Neurobiol, Dept Neurobiol Celular & Mol, Juriquilla Queretaro 76230, Queretaro, Mexico
Vazquez-Cuevas, F:
Univ Nacl Autonoma Mexico, Inst Neurobiol, Dept Neurobiol Celular & Mol, Juriquilla Queretaro 76230, Queretaro, Mexico
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