title: The human prion octarepeat fragment prevents and reverses the inhibitory action of copper in the P2X4 receptor without modifying the zinc action.
abstract: Human prion protein fragments (PrP60-67 or PrP59-91) prevented and reversed the inhibition elicited by 5 micro m copper on the P2X4 receptor expressed in Xenopus laevis oocytes. A 60-s pre-application of 5 micro m copper caused a 69.2 +/- 2.6% inhibition of the 10 micro m adenosine triphosphate (ATP)-evoked currents, an effect that was prevented by mixing 5 micro m copper with 0.01-10 micro m of the PrP fragments 1-min prior to application. This interaction was selective, as PrP59-91 did not alter the facilitatory action of zinc. The EC50 of PrP60-67 and PrP59-91 for the reduction of the copper inhibition were 4.6 +/- 1 and 1.3 +/- 0.4 micro m, respectively. A synthetic PrP59-91 variant in which all four His were replaced by Ala was inactive. However, the replacement of Trp in each of the four putative copper-binding domains by Ala slightly decreased its potency. Furthermore, the application of 10 micro m PrP59-91 reversed the copper-evoked inhibition, restoring the ATP concentration curve to the same level as the non-inhibited state. Fragment 139-157 of betaA4 amyloid precursor protein also prevented the action of copper; its EC50 was 1.6 +/- 0.1 micro m; the metal chelator penicillamine was equipotent with PrP60-67, but carnosine was significantly less potent. Our findings highlight the role of PrP in copper homeostasis and hint at its possible role as a modulator of synapses regulated by this trace metal.
authors.affiliation: Centro de Regulación Celular y Patología, J. V. Luco Instituto MIFAB, Departamento de Fisiología, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago, Chile.
authors.forename: Ramón A
authors.initials: RA
authors.lastname: Lorca
authors.forename: Marcelo
authors.initials: M
authors.lastname: Chacón
authors.forename: María Inés
authors.initials: MI
authors.lastname: Barría
authors.forename: Nibaldo C
authors.initials: NC
authors.lastname: Inestrosa
authors.forename: J Pablo
authors.initials: JP
authors.lastname: Huidobro-Toro
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D019943:Amino Acid Substitution; D016564:Amyloid beta-Protein Precursor / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002614:Chelating Agents / Q000494:pharmacology; D003300:Copper / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008845:Microinjections; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010446:Peptide Fragments / Q000494:pharmacology*; D011328:Prions / Q000494:pharmacology*; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D058848:Receptors, Purinergic P2X4; D020449:Repetitive Sequences, Amino Acid / Q000502:physiology*; D013329:Structure-Activity Relationship; D014982:Xenopus laevis; D015032:Zinc / Q000494:pharmacology*
chemical_list: D016564:Amyloid beta-Protein Precursor; D002614:Chelating Agents; C548226:P2RX4 protein, human; D010446:Peptide Fragments; D011328:Prions; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058848:Receptors, Purinergic P2X4; C474326:betaA4 amyloid precursor protein (139-157), human; C474324:prion protein (59-91); C474325:prion protein (60-67); D003300:Copper; D000255:Adenosine Triphosphate; D015032:Zinc