Namkoong Sim, Lee Kang Il, Lee Jin I, Park Rackhyun, Lee Eun-Ju, Jang Ik-Soon, Park Junsoo
a Division of Biological Science and Technology; Yonsei University ; Wonju , Korea.
Autophagy. 2015;11(5):756-68. doi: 10.1080/15548627.2015.1034412.
The PKA-CREB signaling pathway is involved in many cellular processes including autophagy. Recent studies demonstrated that PKA-CREB inhibits autophagy in yeast; however, the role of PKA-CREB signaling in mammalian cell autophagy has not been fully characterized. Here, we report that the integral membrane protein ITM2A expression is positively regulated by PKA-CREB signaling and ITM2A expression interferes with autophagic flux by interacting with vacuolar ATPase (v-ATPase). The ITM2A promoter contains a CRE element, and mutation at the CRE consensus site decreases the promoter activity. Forskolin treatment and PKA expression activate the ITM2A promoter confirming that ITM2A expression is dependent on the PKA-CREB pathway. ITM2A expression results in the accumulation of autophagosomes and interferes with autolysosome formation by blocking autophagic flux. We demonstrated that ITM2A physically interacts with v-ATPase and inhibits lysosomal function. These results support the notion that PKA-CREB signaling pathway regulates ITM2A expression, which negatively regulates autophagic flux by interfering with the function of v-ATPase.
PKA-CREB信号通路参与包括自噬在内的许多细胞过程。最近的研究表明，PKA-CREB在酵母中抑制自噬；然而，PKA-CREB信号在哺乳动物细胞自噬中的作用尚未完全阐明。在此，我们报道整合膜蛋白ITM2A的表达受PKA-CREB信号正向调控，且ITM2A的表达通过与液泡ATP酶（v-ATPase）相互作用干扰自噬流。ITM2A启动子包含一个CRE元件，CRE共有位点的突变会降低启动子活性。福斯高林处理和PKA表达激活ITM2A启动子，证实ITM2A的表达依赖于PKA-CREB途径。ITM2A表达导致自噬体积累，并通过阻断自噬流干扰自溶酶体形成。我们证明ITM2A与v-ATPase发生物理相互作用并抑制溶酶体功能。这些结果支持PKA-CREB信号通路调节ITM2A表达这一观点，即ITM2A通过干扰v-ATPase的功能对自噬流起负向调节作用。
