Protein synthesis has long been known to be required for associative learning to consolidate into long-term memory. Here we demonstrate that PKC isozyme activation on days before training can induce the synthesis of proteins necessary and sufficient for subsequent long-term memory consolidation. Bryostatin (Bryo), a macrolide lactone with efficacy in subnanomolar concentrations and a potential therapeutic for Alzheimer's disease, is a potent activator of PKC, some of whose isozymes undergo prolonged activation after associative learning. Under normal conditions, two training events with paired visual and vestibular stimuli cause short-term memory of the mollusc Hermissenda that lasts ≈7 min. However, after 4-h exposures to Bryo (0.25 ng/ml) on two preceding days, the same two training events produced long-term conditioning that lasted >1 week and that was not blocked by anisomycin (1 μg/ml). Anisomycin, however, eliminated long-term memory lasting at least 1 week after nine training events. Both the nine training events alone and two Bryo exposures plus two training event regimens caused comparably increased levels of the PKC α-isozyme substrate calexcitin in identified type B neurons and enhanced PKC activity in the membrane fractions. Furthermore, Bryo increased overall protein synthesis in cultured mammalian neurons by up to 60% for >3 days. The specific PKC antagonist Ro-32-0432 blocked much of this Bryo-induced protein synthesis as well as the Bryo-induced enhancement of the behavioral conditioning. Thus, Bryo-induced PKC activation produces those proteins necessary and sufficient for long-term memory on days in advance of the training events themselves.
Digital Commons Citation
Alkon, D. L.; Epstein, H.; Kuzirian, A.; Bennett, M. C.; and Nelson, T. J., "Protein Synthesis Required For Long-Term Memory Is Induced By Pkc Activation On Days Before Associative Learning" (2005). Faculty Scholarship. 641.
Alkon, D. L., Epstein, H., Kuzirian, A., Bennett, M. C., & Nelson, T. J. (2005). Protein Synthesis Required For Long-Term Memory Is Induced By Pkc Activation On Days Before Associative Learning. Proceedings Of The National Academy Of Sciences Of The United States Of America, 102(45), 16432-16437. http://doi.org/10.1073/Pnas.0508001102