From the Department of Biochemistry and Molecular Biology.
J Biol Chem. 2014 Mar 28;289(13):9172-81. doi: 10.1074/jbc.M113.544890. Epub 2014 Feb 20.
Cytotoxic lymphocytes eliminate virally infected or neoplastic cells through the action of cytotoxic proteases (granzymes). The pore-forming protein perforin is essential for delivery of granzymes into the cytoplasm of target cells; however the mechanism of this delivery is incompletely understood. Perforin contains a membrane attack complex/perforin (MACPF) domain and oligomerizes to form an aqueous pore in the plasma membrane; therefore the simplest (and best supported) model suggests that granzymes passively diffuse through the perforin pore into the cytoplasm of the target cell. Here we demonstrate that perforin preferentially delivers cationic molecules while anionic and neutral cargoes are delivered inefficiently. Furthermore, another distantly related pore-forming MACPF protein, pleurotolysin (from the oyster mushroom), also favors the delivery of cationic molecules, and efficiently delivers human granzyme B. We propose that this facilitated diffusion is due to conserved features of oligomerized MACPF proteins, which may include an anionic lumen.
细胞毒性淋巴细胞通过细胞毒性蛋白酶（颗粒酶）的作用消除病毒感染或肿瘤细胞。穿孔蛋白是将颗粒酶递送到靶细胞细胞质中的必需蛋白；然而，其递呈机制尚不完全清楚。穿孔蛋白含有膜攻击复合物/穿孔素（MACPF）结构域，并寡聚形成质膜中的水性孔；因此，最简单（也是最受支持）的模型表明，颗粒酶通过穿孔素孔被动扩散进入靶细胞的细胞质。在这里，我们证明穿孔素优先递呈阳离子分子，而阴离子和中性货物的递呈效率较低。此外，另一种远缘相关的形成孔的 MACPF 蛋白，pleurotolysin（来自牡蛎蘑菇），也有利于阳离子分子的递呈，并有效地递呈人颗粒酶 B。我们提出，这种易化扩散是由于寡聚化 MACPF 蛋白的保守特征所致，这些特征可能包括阴离子腔。
