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
ISSN: 00278424





PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Editorial
NATL ACAD SCIENCES, 2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 USA, Estados Unidos America
Tipo de documento: Article
Volumen: 106 Número: 39
Páginas: 16680-16685
WOS Id: 000270305800027
ID de PubMed: 19805357