Many cellular delivery reagents enter the cytosolic space of cells by escaping the lumen of endocytic organelles and, more specifically, late endosomes. The mechanisms involved in endosomal membrane permeation remain largely unresolved, which impedes the improvement of delivery agents. Here, we investigate how 3TAT, a branched analog of the cell-penetrating peptide (CPP) TAT, achieves the permeabilization of bilayers containing bis(monoacylglycero)phosphate (BMP), a lipid found in late endosomes. We establish that the peptide does not induce the leakage of individual lipid bilayers. Instead, leakage requires contact between membranes. Peptide-driven bilayer contacts lead to fusion, lipid mixing, and, critically, peptide encapsulation within proximal bilayers. Notably, this encapsulation is a distinctive property of BMP that explains the specificity of CPP's membrane leakage activity. These results therefore support a model of cell penetration that requires both BMP and the vicinity between bilayers, two features unique to BMP-rich and multivesicular late endosomes.

许多细胞递送试剂通过逃离内吞细胞器的腔，更具体地说，是晚期内体而进入细胞的胞质空间。内体膜渗透所涉及的机制在很大程度上仍未得到解决，这阻碍了递送剂的改进。在这里，我们研究了 3TAT（细胞穿透肽（CPP）TAT 的分支类似物）如何实现含有双（单酰基甘油）磷酸酯（BMP）的双层的透化，这是一种在晚期内体中发现的脂质。我们确定肽不会诱导单个脂质双层的泄漏。相反，泄漏需要膜之间的接触。肽驱动的双层接触导致融合、脂质混合，关键是近端双层内的肽封装。尤其，这种封装是 BMP 的一个独特特性，它解释了 CPP 膜渗漏活动的特异性。因此，这些结果支持细胞渗透模型，该模型需要 BMP 和双层之间的附近，这是富含 BMP 和多泡晚期内体的两个独特特征。