PT  - JOURNAL ARTICLE
AU  - Diancai Cai
AU  - Kaycey Pearce
AU  - Shanping Chen
AU  - David L. Glanzman
TI  - Protein Kinase M Maintains Long-Term Sensitization and Long-Term Facilitation in <em>Aplysia</em>
AID  - 10.1523/JNEUROSCI.4744-10.2011
DP  - 2011 Apr 27
TA  - The Journal of Neuroscience
PG  - 6421--6431
VI  - 31
IP  - 17
4099  - http://www.jneurosci.org/content/31/17/6421.short
4100  - http://www.jneurosci.org/content/31/17/6421.full
SO  - J. Neurosci.2011 Apr 27; 31
AB  - How the brain maintains long-term memories is one of the major outstanding questions in modern neuroscience. Evidence from mammalian studies indicates that activity of a protein kinase C (PKC) isoform, protein kinase Mζ (PKMζ), plays a critical role in the maintenance of long-term memory. But the range of memories whose persistence depends on PKMζ, and the mechanisms that underlie the effect of PKMζ on long-term memory, remain obscure. Recently, a PKM isoform, known as PKM Apl III, was cloned from the nervous system of Aplysia. Here, we tested whether PKM Apl III plays a critical role in long-term memory maintenance in Aplysia. Intrahemocoel injections of the pseudosubstrate inhibitory peptide ZIP (ζ inhibitory peptide) or the PKC inhibitor chelerythrine erased the memory for long-term sensitization (LTS) of the siphon-withdrawal reflex (SWR) as late as 7 d after training. In addition, both PKM inhibitors disrupted the maintenance of long-term (≥24 h) facilitation (LTF) of the sensorimotor synapse, a form of synaptic plasticity previously shown to mediate LTS of the SWR. Together with previous results (Bougie et al., 2009), our results support the idea that long-term memory in Aplysia is maintained via a positive-feedback loop involving PKM Apl III-dependent protein phosphorylation. The present data extend the known role of PKM in memory maintenance to a simple and well studied type of long-term learning. Furthermore, the demonstration that PKM activity underlies the persistence of LTF of the Aplysia sensorimotor synapse, a form of synaptic plasticity amenable to rigorous cellular and molecular analyses, should facilitate efforts to understand how PKM activity maintains memory.