Department of Materials Science and Engineering, Johns Hopkins University , Baltimore, Maryland 21218, United States.
Institute for NanoBioTechnology, Johns Hopkins University , Baltimore, Maryland 21218, United States.
J Am Chem Soc. 2017 Jan 18;139(2):937-945. doi: 10.1021/jacs.6b11447. Epub 2017 Jan 5.
pH-triggered membrane-permeabilizing peptides could be exploited in a variety of applications, such as to enable cargo release from endosomes for cellular delivery, or as cancer therapeutics that selectively permeabilize the plasma membranes of malignant cells. Such peptides would be especially useful if they could enable the movement of macromolecules across membranes, a rare property in membrane-permeabilizing peptides. Here we approach this goal by using an orthogonal high-throughput screen of an iterative peptide library to identify peptide sequences that have the following two properties: (i) little synthetic lipid membrane permeabilization at physiological pH 7 at high peptide concentration and (ii) efficient formation of macromolecule-sized defects in synthetic lipid membranes at acidic pH 5 and low peptide concentration. The peptides we selected are remarkably potent macromolecular sized pore-formers at pH 5, while having little or no activity at pH 7, as intended. The action of these peptides likely relies on tight coupling between membrane partitioning, α-helix formation, and electrostatic repulsions between acidic side chains, which collectively drive a sharp pH-triggered transition between inactive and active configurations with apparent pK values of 5.5-5.8. This work opens new doors to developing applications that utilize peptides with membrane-permeabilizing activities that are triggered by physiologically relevant decreases in pH.
pH 触发的膜通透性肽在多种应用中都可以得到利用，例如使货物从内体中释放出来以进行细胞递送，或者作为癌症治疗剂，选择性地使恶性细胞膜通透性增加。如果这些肽能够使大分子穿过细胞膜，那么它们将特别有用，因为这是膜通透性肽的罕见特性。在这里，我们通过使用迭代肽文库的正交高通量筛选来达到这一目标，以鉴定具有以下两种特性的肽序列：（i）在生理 pH 7 和高肽浓度下对合成脂质膜的通透性很小；（ii）在酸性 pH 5 和低肽浓度下在合成脂质膜中有效形成大分子大小的缺陷。我们选择的肽在 pH 5 时是非常有效的大分子大小的孔形成剂，而在 pH 7 时几乎没有或没有活性，这正是我们所期望的。这些肽的作用可能依赖于膜分配、α-螺旋形成和酸性侧链之间静电排斥之间的紧密耦合，这些因素共同驱动了一个在 pH 值为 5.5-5.8 之间的从非活性到活性的急剧 pH 触发转变。这项工作为开发利用受生理相关 pH 值降低触发的具有膜通透性的肽的应用开辟了新的途径。
