The Leishmania LACK antigen is a ribosome-associated protein that facilitates expression of mitochondrial cytochrome c oxidase subunit IV (LmCOX4) to support parasite mitochondrial fitness and virulence within the vertebrate host. To further examine the relationship between LACK, its putative ribosome binding motif and LmCOX4, we compared the kinetics of LmCOX4 expression following temperature elevation in wildtype LACK (LACK WT) and LACK-putative ribosome-binding mutant (LACK^DDE) L. major. We found that, after initial exposure to mammalian temperature, LmCOX4 levels became undetectable in LACK^DDE L. major and also, surprisingly, in wild type (WT) control strains. Upon sustained exposure to mammalian temperature, LmCOX4 expression returned in WT control strains only. The initial loss of LmCOX4 in WT L. major was substantially reversed by treatment with the proteasome inhibitor MG132. Our findings indicate that initial loss of LmCOX4 under mammalian conditions is dependent upon proteasome degradation and LmCOX4 re-expression is dependent upon LACK possessing a WT putative ribosome binding motif.

在利什曼原虫LACK抗原是核糖体相关蛋白促进线粒体细胞色素的表达Ç氧化酶亚基IV（LmCOX4）支持脊椎动物宿主内寄生虫线粒体健身和毒力。为了进一步检查 LACK、其推定的核糖体结合基序和 LmCOX4 之间的关系，我们比较了野生型 LACK (LACK WT) 和 LACK 推定的核糖体结合突变体 ( LACK ^DDE ) L. Major 温度升高后 LmCOX4 表达的动力学。我们发现，在最初暴露于哺乳动物温度后，LACK ^DDE L. Major 中的 LmCOX4 水平变得无法检测到而且，令人惊讶的是，在野生型 (WT) 对照菌株中。在持续暴露于哺乳动物温度后，LmCOX4 表达仅在 WT 对照菌株中恢复。通过用蛋白酶体抑制剂 MG132 处理，WT L. Major 中 LmCOX4 的初始丢失被显着逆转。我们的研究结果表明，在哺乳动物条件下 LmCOX4 的初始丢失取决于蛋白酶体降解，而 LmCOX4 重新表达取决于 LACK 具有 WT 假定的核糖体结合基序。