生物合成气囊：一种兼具成像与治疗性能的纳米级囊泡

Biosynthetic Gas Vesicle: A Kind of Nano-Scaled Vesicle with Imaging and Therapeutic Properties

摘要: 气囊是一种存在于蓝藻、古菌等多种原核微生物中的纳米级中空蛋白结构，其作用是为细胞提供浮力，赋予其在水环境中控制漂浮深度的能力。气囊壁厚约2 nm，内部疏水、外部亲水，气体可以自由通过气囊壁进行交换。目前已知的编码气囊的基因约8~20多个，其中编码气囊壁结构蛋白的基因GvpA和GvpC尤为关键。GvpA基因的表达是气囊合成所必须的，GvpC基因的表达对气囊的合成是非必须的，但表达GvpC蛋白可增强气囊外壳的抗压能力。通过去除、添加或修饰GvpC，气囊可以作为一个多功能分子平台实现疫苗研发、靶向治疗以及多模态医学成像等。在本篇综述中，我们介绍了气囊的结构与基本特性、编码基因及相关基因工程改造的研究进展，着重分享了气囊在超声成像等领域潜在的临床应用价值，并讨论了在应用过程中可能面临的问题。

Abstract: Gas vesicles (GVs) are nano-scaled, hollow proteinaceous structures found in numerous prokaryotic microorganisms such as cyanobacteria and archaea. Their function is to provide buoyancy to cells, giving them the ability to control their floating depth in the aqueous environment. The wall of GVs is about 2 nm thick, hydrophobic inside and hydrophilic outside, and gas molecules can be freely ex-changed through it. Presently, about 8~20 genes encoding GVs have been identified, among which GvpA and GvpC genes that encode wall structural proteins are particularly critical. The expression of the GvpA gene is necessary for synthesis, while the expression of the GvpC gene is not, but the ex-pression of the GvpC protein enhances the pressure resistance of the wall. By removing, adding or modifying GvpC, GVs can be used as a versatile molecular platform for vaccine research and devel-opment, targeted therapy, and multimodal medical imaging. In this review, we introduce the structure and basic features of GVs, coding genes and related genetic engineering advances. Poten-tial clinical applications of GVs in ultrasound imaging and other fields are shared, and the possible issues that may be faced in the applications are discussed.