Department of Chemistry and Chemical Biology, Indian Institute of Technology (ISM) Dhanbad, Dhanbad 826004, India.
J Phys Chem B. 2023 Nov 16;127(45):9747-9758. doi: 10.1021/acs.jpcb.3c04217. Epub 2023 Sep 30.
Acidic tumor microenvironment (TME) presents a challenge for the action of antitumor drugs by acting as an additional barrier for the passive crossing of the cell membrane by chemotherapic agents playing a critical role in the proliferation of tumor cells. Anticancer lipopeptide C6-Pep dimer containing the leucine zipper motif shows an increased uptake into the model tumor membrane in TME, and application of external heat might lead to the uncoiling of the zipper, which could result in cell lysis. This work investigated the cause of this increased uptake of C6-Pep dimer into the bilayer model in TME. Accurate protonation states of all the titratable residues of the C6-Pep dimer in TME were determined using constant pH molecular dynamics. In TME, except for two terminal Glu5 residues, all other Glu residues in the C6-Pep dimer were permanently protonated. The remaining Glu5 residues had differential p values, leading to the construction of four possible dimers with different fixed protonation states, and molecular dynamics was used to study their interaction with the anionic bilayer. Except for the dimer at a physiological pH, the other dimers were positively charged and could readily adsorb on the membrane surface. The free energy of insertion of these dimers in the bilayer was lower for single and double protonated Glu5-containing dimers than for the others. After the insertion of the lipopeptides into the membrane, thinning of the bilayer in the vicinity of dimers and an increase in area per lipid of the bilayer were observed for all systems, indicating destabilization of the bilayer due to this intercalation. This study shows that the anticancer lipopeptide C6-Pep utilizes the TME around a tumor cell for insertion into the membrane.
酸性肿瘤微环境（TME）通过充当化疗药物被动穿过细胞膜的额外屏障，对肿瘤细胞的增殖起着关键作用，这给抗肿瘤药物的作用带来了挑战。含有亮氨酸拉链模体的抗癌脂肽 C6-Pep 二聚体在 TME 中显示出增加的模型肿瘤细胞膜摄取，外部加热可能导致拉链解卷，从而导致细胞裂解。这项工作研究了 C6-Pep 二聚体在 TME 中增加摄取到双层模型的原因。使用恒 pH 分子动力学确定了 TME 中 C6-Pep 二聚体所有可滴定残基的精确质子化状态。在 TME 中，除了两个末端 Glu5 残基外，C6-Pep 二聚体中的所有其他 Glu 残基都被永久质子化。其余的 Glu5 残基具有不同的 p 值，导致构建了具有不同固定质子化状态的四个可能的二聚体，并使用分子动力学研究它们与阴离子双层的相互作用。除了生理 pH 下的二聚体外，其他二聚体带正电荷，很容易吸附在膜表面上。这些二聚体在双层中的插入自由能对于单质子化和双质子化含 Glu5 的二聚体比其他二聚体低。在脂肽插入膜后，所有系统都观察到二聚体附近的双层变薄和双层每个脂质的面积增加，表明由于这种插入导致双层失稳。这项研究表明，抗癌脂肽 C6-Pep 利用肿瘤细胞周围的 TME 插入到膜中。
