Ivane Beritashvili Center of Experimental Biomedicine, 14 Gotua Str, 0160, Tbilisi, Georgia.
Georgian National University, 9 Tsinandali Str, Tbilisi, Georgia.
J Bioenerg Biomembr. 2024 Jun;56(3):221-234. doi: 10.1007/s10863-024-10012-3. Epub 2024 Mar 22.
Na,K-ATPase is a crucial enzyme responsible for maintaining Na, K-gradients across the cell membrane, which is essential for numerous physiological processes within various organs and tissues. Due to its significance in cellular physiology, inhibiting Na,K-ATPase can have profound physiological consequences. This characteristic makes it a target for various pharmacological applications, and drugs that modulate the pump's activity are thus used in the treatment of several medical conditions. Cytochrome c (Cytc) is a protein with dual functions in the cell. In the mitochondria, it is essential for ATP synthesis and energy production. However, in response to apoptotic stimuli, it is released into the cytosol, where it triggers programmed cell death through the intrinsic apoptosis pathway. Aside from its role in canonical intrinsic apoptosis, Cytc also plays additional roles. For instance, Cytc participates in certain non-apoptotic functions -those which are less well-understood in comparison to its role in apoptosis. Within this in vitro study, we have shown the impact of Cytc on Na,K-ATPase for the first time. Cytc has a biphasic action on Na,K-ATPase, with activation at low concentrations (0.06 ng/ml; 6 ng/ml) and inhibition at high concentration (120 ng/ml). Cytc moreover displays isoform/subunit specificity and regulates the Na form of the enzyme, while having no effect on the activity or kinetic parameters of the K-dependent form of the enzyme. Changing the affinity of p-chloromercuribenzoic acid (PCMB) by Cytc is therefore both a required and sufficient condition for confirming that PCMB and Cytc share the same target, namely the thiol groups of cysteine in Na,K-ATPase.
钠钾-ATP 酶是一种至关重要的酶，负责维持细胞膜两侧的钠钾梯度，这对于各种器官和组织中的许多生理过程都是必不可少的。由于其在细胞生理中的重要性，抑制钠钾-ATP 酶会产生深远的生理后果。这一特性使其成为各种药理学应用的靶点，因此，调节泵活性的药物被用于治疗多种医学病症。细胞色素 c（Cytc）是一种在细胞中具有双重功能的蛋白质。在线粒体中，它是 ATP 合成和能量产生所必需的。然而，在响应凋亡刺激时，它会被释放到细胞质中，在那里通过内在凋亡途径引发程序性细胞死亡。除了在经典的内在凋亡中的作用外，Cytc 还发挥其他作用。例如，Cytc 参与某些非凋亡功能——与它在凋亡中的作用相比，这些功能不太为人所知。在这项体外研究中，我们首次展示了 Cytc 对钠钾-ATP 酶的影响。Cytc 对钠钾-ATP 酶具有双相作用，在低浓度（0.06ng/ml；6ng/ml）下激活，在高浓度（120ng/ml）下抑制。此外，Cytc 显示出同工酶/亚基特异性，调节酶的 Na 形式，而对酶的 K 依赖性形式的活性或动力学参数没有影响。因此，通过 Cytc 改变对氯汞苯甲酸（PCMB）的亲和力既是确认 PCMB 和 Cytc 具有相同靶标的必需和充分条件，即钠钾-ATP 酶中半胱氨酸的巯基。
