探討Lon蛋白酶在地塞米松誘導調節型樹突細胞之角色

Abstract

主要分布在粒線體基質的Lon蛋白酶扮演相當多角色，最主要的功能是分解粒線體中受損的蛋白。大多數關於Lon的研究顯示，過度表達Lon蛋白酶可以促使癌細胞增生、減緩細胞凋亡，甚至促使轉移的發生。然而，尚未有研究關注Lon如何調節免疫細胞。李岳倫老師團隊的初步數據顯示，具有抗發炎特性的M2a和M2c這兩類巨噬細胞中，Lon蛋白酶表現上升。根據此現象，我們認為Lon蛋白酶在調節型樹突細胞中，也會被誘導而表達。首先，我們透過篩選找出潛在的刺激物能夠同時培養出調節型樹突細胞，也能高度誘導Lon蛋白酶表現。其中，我們觀察到藥物地塞米松能達到上述的效果。接著，我們調整培養條件去確認骨髓衍生樹突細胞中，地塞米松能誘導Lon蛋白酶表現上升。我們列出了潛在的候選基因，來解答地塞米松和Lon蛋白酶之間的訊息路徑，發現GILZ和STAT3有參與其中。最後，我們使用粒線體電子傳遞鏈的抑制劑，發現抑制氧化磷酸化會降低抗發炎的指標。我們推測，經由地塞米松誘導的Lon蛋白酶促使樹突細胞改變代謝路徑，造成電子傳遞鏈中的氧化酶表現上升，而旺盛的氧化磷酸化則再影響了調節型的表現型和功能。

Lon protease, encoded by Lonp1 gene in nucleus, plays multiple roles in mitochondrial matrix. The main function of Lon protease is degradation of damaged proteins. The majority of Lon studies have demonstrated that overexpression of Lon protease promotes the proliferation, anti-apoptosis, and epithelial-mesenchymal transition (EMT) of cancer cells. However, the role of Lon in regulating immune cell has not been reported. Preliminary data from Dr. Lee group showed that Lonp1 expression was up-regulated in M2a and M2c macrophages, which possess anti-inflammatory phenotypes. Hence, we propose that Lon could also be induced in regulatory type of dendritic cells (regDCs). First of all, we managed to find the inducer for Lonp1 expression by screening different stimuli for regDC generation. Then, we observed that Lonp1 expression was highly induced in Dexamethasone (DEX)-treated bone marrow-derived dendritic cells (BMDCs). Next, we modified culturing protocol and confirmed the upregulation of Lon induced by DEX in BMDCs. In addition, we found that glucocorticoid-induced leucine zipper (GILZ) and signal transducer and activator of transcription 3 (STAT3) may take part in this signaling pathway. Last, we tried to study the role of Lon in the phenotype and function of DEX-induced regDCs. Inhibition of oxidative phosphorylation (OXPHOS) would affect M2/regDC-associated genes in DEX-induced regDCs, which suggests that metabolic pathway would affect regulatory phenotypes. We propose that the upregulation of Lon may promote OXPHOS through activation of different subunits of cytochrome c oxidase (COXs) and contribute to the regulatory phenotype.