Fig. 7.

PKC activation potentiates heteromeric KARs. (A) AMPA steady-state currents were recorded from an oocyte three days after injection of GluK2/GluK5. Bath application of the phorbol ester PMA (50 nM) led to a biphasic response on AMPA elicited currents. (B) the time profile showed a fast potentiation followed by slow decrease in the currents. The specific PKC inhibitor Ro 320432 (2 μM) dramatically reduced PMA-mediated potentiation in oocytes injected with GluK2/GluK5 (n ≥ 8). (C) activation of PKC by PMA potentiated heteromeric GluK2/GluK5 (n = 12). Neither DMSO alone nor 4α-PMA (an inactive analog of PMA) mimicked the PMA induced potentiation of GluK2/GluK5 (n = 6 and n = 5, respectively). GluK2/GluK5 AMPA steady-state currents were also potentiated by exposure to 1 μM thymeleatoxin (an activator of the conventional PKC isoforms α, β, γ) (n = 6) (*P < 0.05; **P < 0.01; one-way ANOVA with Dunnett’s post-tests). (D) okadaic acid (20 nM) treatment enhanced PMA-induced potentiation of GluK2/GluK5 (n = 5). The filled squares indicate the normal level of potentiation (± S.E.M.) in the absence of okadaic acid. (E) genistein (Geni) (50 μM) pretreatment reduced the PMA induced potentiation of GluK2/GluK5 (n = 5). The specific PKC inhibitor Ro 320432 (2 μM) strongly attenuated the effect of 50 nM PMA. The effects of genistein and Ro 320432 were compared with GluK2/GluK5 exposed to PMA (C) and were found to be significantly different. Activation of PKC by PMA also potentiated heteromeric GluK2/GluK4 receptors, but failed to significantly potentiate homomeric GluK2 (*P < 0.05; **P < 0.01; ***P < 0.05; one-way ANOVA with Bonferroni’s post-tests).