One-Trial In Vitro Conditioning of Hermissenda Regulates Phosphorylation of Ser-122 of Csp24
The regulation of the intrinsic excitability of a neuron is an important aspect of cellular and synaptic plasticity underlying learning and memory. Various voltage-dependent K+ channels have been shown to be critical for the modification of membrane excitability. Components of the cytoskeleton have been proposed to contribute to the location, distribution, and function of diverse K+ channels. However, the mechanisms underlying the regulation of the cytoskeleton by signaling pathways and the role of the cytoskeleton in the induction of intrinsic excitability is not understood. Hermissenda Csp24 is a beta-thymosin-like protein containing multiple actin-binding domains that contributes to intrinsic enhanced excitability produced by Pavlovian conditioning. One-trial in vitro conditioning produces a significant reduction in the A-type transient K+ current (IA) and a depolarized shift in the steady-state activation curve of IA. Intermediate and long-term enhanced excitability produced by one-trial conditioning is also dependent on the expression and phosphorylation of Csp24. Blocking the expression of Csp24 with an antisense oligonucleotide inhibits the development of intermediate-term enhanced excitability and the concomitant reduction in IA normally produced by one-trial in vitro conditioning. In this report using two-dimensional gel PAGE and electrospray mass spectrometry, we have identified two phosphorylation sites on Csp24. Using phospho-specific antibodies with Western blot analysis and immunoprecipitation procedures we show that one-trial in vitro conditioning results in an increase in the phosphorylation of Ser-122, but not Ser-49 of Csp24
hermissenda csp24 one-trial conditioning phosphoprotein actin ?-thymosin