當人們遭受到天災人禍，由於突如其來的重大傷害，在事件過後可能會造成創傷性壓力症候群(Post Traumatic Stress Disorder, PTSD)，在心理及生理上都受到影響。然而如果我們對於恐懼記憶形成的過程更加了解，或許就能幫助PTSD患者走出陰影。在恐懼記憶形成的過程有許多分子機制參與其中，而protein kinase M zeta(PKM zeta)就是其中之一。PKM zeta是一個持續性活化的磷酸酶，與PKC zeta的差別在PKM zeta沒有調節片段(regulatory domain)。PKM zeta屬於PKC 異構物的一員，目前的研究主要集中在海馬迴腦區，認為PKM zeta參與在海馬迴相關長期增意現象以及記憶維持當中。因此本研究的主要目的PKM zeta是否參與在恐懼記憶中以及相關分子機制為何。
首先使用一種偽受質胜肽抑制劑(myristoylated ζ -pseudosubstrate inhibitory peptide ，ZIP)來選擇性抑制PKM zeta。SD大鼠經過制約學習後，在兩側杏仁核內投與ZIP，之後測其恐懼指數。結果發現ZIP組的恐懼指數相較於制約學習組有顯著的下降。隨後的實驗也證明沒有再復發(spontaneous recovery 或 reinstatement)的情形發生，顯示PKM zeta對於恐懼記憶的維持十分重要。最後探討PKM zeta參與在恐懼記憶中的分子機制為何。我們利用不同的biotin標定法，探討細胞膜上以及胞飲進入細胞膜內的GluR1/GluR2次體，經由西方點墨法得知ZIP組的細胞膜上GluR1/GluR2次體相較於制約學習組有明顯的降低，而胞飲進入細胞膜內的GluR1/GluR2次體則有顯著的增加。根據以上實驗結果，PKM zeta對恐懼記憶及LTP之維持扮演了重要的角色，並且可能透過調節GluR1/GluR2次體之運輸影響恐懼記憶及LTP。

People who have faced natural disasters or serious crime may get Post Traumatic Stress Disorder(PTSD), and develop not only physiological but also psychological trauma. However, if we know better about the formation, maintanance and storage of fear memory, we may help PTSD patient overcome the event. There are many signal cassade involved in memory formation, and protein kinase M zeta is one of them. PKM zeta is constitutively active, and catalytic fragment of PKC zeta. It’s an atypical form of protein kinase C, and has been proven to be important in maintenance of hippocampus-dependent memories and long-term potentiation. The purpose of this study is to investigate the involvement of PKM zeta in fear memory formation and the underlying mechanism of PKM zeta action.

First, we used a myristoylated ζ -pseudosubstrate inhibitory peptide (ZIP) to selectively inhibit PKM zeta. After fear-conditioning(CS-US) training, ZIP was injected bilaterally into the amygdala, and then fear response was analyzed. We found that fear response in ZIP-injection group was lower than that in CS-US group. Second, we used another behavior protocol to investigate if ZIP-treated rats showed spontaneous recovery or reinstatement after ZIP injection. The results showed none of these happened, which meant that PKM zeta was important for fear memory maintenance, and showed no spontaneous recovery or reinstatement.

Finally, we want to know how PKM zeta is involved in fear memory by using biotinylation and immunoprecipitation to detect the change of surface GluR1/GluR2 and internal GluR1/GluR2 after ZIP injection. Western blot data showed that surface GluR1/GluR2 were lower in ZIP-injection group than in CS-US group, and internal GluR1/GluR2 were both higher in ZIP-injection group.

Blockade of PKM zeta impaired fear memory, caused reduction of surface GluR1/GluR2 and increased internal GluR1/GluR2. Therefore we conclude that PKM zeta plays an important role in fear memory maintenance , and it may inference fear memory and LTP through the regulation of GluR1/GluR2 receptor trafficking.

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