We did not notice significantly different seizure stages in WT and AKAP150−/− mice as previously reported by Tunquist et al. (2008), except in response to the first dose of KA ( Figure S2). Hippocampi were isolated from mice 16–20 hr after intrapleural administration of either pilocarpine or KA, or only vehicle as a control, total RNA was extracted, and qPCR was performed. Indeed, a profound augmentation of both KCNQ2 and KCNQ3 mRNA was observed in mice after
buy Talazoparib seizures induced by pilocarpine (27.9 ± 6.7-fold and 9.3 ± 2.2-fold, n = 18) or KA (8.7 ± 2.3-fold and 3.1 ± 0.6-fold, n = 25), compared with control mice injected with vehicle (1.1 ± 0.05-fold and 1.1 ± 0.10-fold, n = 17) ( Figures 10D and 10E). This profoundly increased mRNA of both KCNQ2 and KCNQ3 in hippocampi from mice subjected to seizures is much greater than that seen from 50 K+ or ACh treatment in cultured sympathetic neurons, suggesting that seizures induce exaggeration of this transcriptional regulation and could be conserved throughout the nervous system as a protective mechanism against hyperexcitability disorders such as epilepsy. Our mechanism predicts that this profound increase induced by seizures should learn more likewise be dependent on AKAP150. Indeed, in AKAP150−/− mice, there was almost
no upregulation of KCNQ2 and KCNQ3 mRNA after pilocarpine-induced (1.5 ± 0.1 and 1.4 ± 0.1, n = 14) or KA-induced (1.8 ± 0.4 and 1.6 ± 0.2, n = 18) seizures ( Figures 10D and 10E), confirming the central role of
AKAP150 in this phenomenon. Here, we show neuronal activity all to closely regulate M-channel transcription, likely as a negative feedback loop that limits neuronal hyperexcitability. AKAP79/150 associates with L-type (CaV1.3) Ca2+ channels and orchestrates a signaling complex that includes bound PKA, CaM, and CaN in this microdomain. CaV1.3 channels serve as the critical “sensor” of activity and depolarization, and their opening creates an elevated local Ca2+i signal, which activates CaN bound to AKAP79/150 in the microdomain of elevated local [Ca2+]i. Upon Ca2+i/CaN signals, both NFATc1 and NFATc2 are dephosphorylated and translocate from the cytoplasm to the nucleus, where they act on KCNQ2 and KCNQ3 gene regulatory elements, upregulating IM, thus reducing excitability ( Figure 10F). In a variety of neurons, AKAP79/150 orchestrates PKA to phosphorylate and upregulate the activity of L-type Ca2+ channels, amplifying the responses to depolarization induced by neuronal activity. In the hippocampus, CaN counterbalances PKA actions since the Ca2+ ions that enter the cell through L channels participate in inactivating those same channels via CaN ( Hall et al., 2007; Oliveria et al., 2007).