Rosen Haim, Glukhman Vladimir, Feldmann Tomer, Fridman Eleonora, Lichtstein David
The Kuvin Center for the Study of Infectious and Tropical Diseases, Institute of Microbiology, Jerusalem, Israel.
Mol Biol Cell. 2004 Mar;15(3):1044-54. doi: 10.1091/mbc.e03-06-0391. Epub 2004 Jan 12.
Cardiac steroids (CSs) are specific inhibitors of Na+, K(+)-ATPase activity. Although the presence of CS-like compounds in animal tissues has been established, their physiological role is not evident. In the present study, treatment of human NT2 cells with physiological concentrations (nanomolar) of CSs caused the accumulation of large vesicles adjacent to the nucleus. Experiments using N-(3-triethylammonium propyl)-4-(dibutilamino)styryl-pyrodinum dibromide, transferrin, low-density lipoprotein, and selected anti-transferrin receptor and Rab protein antibodies revealed that CSs induced changes in endocytosis-dependent membrane traffic. Our data indicate that the CS-induced accumulation of cytoplasmic membrane components is a result of inhibited recycling within the late endocytic pathway. Furthermore, our results support the notion that the CS-induced changes in membrane traffic is mediated by the Na+, K(+)-ATPase. These phenomena were apparent in NT2 cells at nanomolar concentrations of CSs and were observed also in other human cell lines, pointing to the generality of this phenomenon. Based on these observations, we propose that the endogenous CS-like compounds are physiological regulators of recycling of endocytosed membrane proteins and cargo.
强心甾类化合物（CSs）是Na +，K（+）-ATP酶活性的特异性抑制剂。尽管已证实动物组织中存在类CS化合物，但其生理作用尚不明确。在本研究中，用生理浓度（纳摩尔）的CSs处理人NT2细胞会导致细胞核附近出现大量囊泡堆积。使用N-（3-三乙铵丙基）-4-（二丁氨基）苯乙烯基-吡啶鎓二溴化物、转铁蛋白、低密度脂蛋白以及选定的抗转铁蛋白受体和Rab蛋白抗体进行的实验表明，CSs会诱导依赖内吞作用的膜运输发生变化。我们的数据表明，CSs诱导的细胞质膜成分堆积是晚期内吞途径中回收过程受到抑制的结果。此外，我们的结果支持以下观点：CSs诱导的膜运输变化是由Na +，K（+）-ATP酶介导的。这些现象在纳摩尔浓度的CSs作用下在NT2细胞中很明显，在其他人类细胞系中也观察到了，这表明这种现象具有普遍性。基于这些观察结果，我们提出内源性类CS化合物是内吞膜蛋白和货物回收的生理调节因子。
