BPS2026 - Amyloid β suppression of Kv1.2 channels involves PYK2-dependent modulation of Y132

Aβ’s roles in Alzheimer’s disease (AD) include disruption of learning-memory-related synaptic communication and plasticity. How these abnormalities arise is not fully understood. We have focused on involvement of voltage-gated potassium channels in these processes, particularly Kv1.x family members, as they regulate Ca 2+ influx, neuronal excitability/neurotransmission, and their inhibition may lead to synapto-neuro-toxicity through hyperexcitability and excessive glutamate release. We’ve previously observed rapid, robust suppression (∼50% in 30 min) of macroscopic currents by Aβ(1-42) in Xenopus oocytes expressing homomeric Kv1.1, Kv1.2, or heteromeric Kv1.1/1.2 channels. The Ca 2+ chelator BAPTA-AM and PP2B inhibitor cyclosporin A each reduced Aβ-suppression to ∼20%. The broad spectrum PTK inhibitor genistein completely blocked suppression, indicating (endogenous) PTK(s)-involvement in Aβ-suppression. Here, we investigated the role of Kv1.2 Y132 in Aβ-suppression and whether PYK2, known to suppress Kv1.2, acts through this residue. Currents of (homomeric Kv1.2, and heteromeric 1.1/1.2) Y132F mutant channels were not obviously different in amplitudes/kinetics/voltage-dependencies from wt channels. However, currents of homomeric Y132F channels ( n = 10) showed only ∼17% suppression by Aβ(1–42) vs. ∼50% for wt channels ( n = 10), p < 0.007. Co-expression of PYK2 (gift from Prof Johannes Hell lab, UC Davis) and its activation by PMA, produced greater Aβ-suppression of wt Kv1.2 (∼84%, n = 7), as compared to PMA-alone/no exogenous PYK2 (58%, n = 6), p < .02. The additional suppression by PYK2 involved Y132, since suppression of Y132F channels by PMA+PYK2 (58%, n = 8) was significantly less than wt Kv1.2 and no different from suppression of either wt or Y132F Kv1.2 by PMA-alone (∼55%). Phosphorylation of Y132 may be important for Ca 2+ -, PP2B-, and PYK2-dependent suppression of Kv1.2 by Aβ(1–42) exposure. Suppression of Kv1.2-containing channels may lead to greater Ca 2+ influx into presynaptic terminals, enhanced glutamate release, increased depolarization of postsynaptic spines, and excitotoxicity in AD.