近日，丹麦哥本哈根大学Dimitrios Stamou团队的最新研究阐明哺乳动物脑部V-ATP酶通过超低速模式切换的调节作用。2022年11月23日，国际知名学术期刊《自然》发表了这一成果。

研究人员表示，空泡型腺苷三磷酸酶（V-ATP酶）是结构上与F型ATP合成酶有关的生电型旋转机械酶。它们水解ATP，为大量的细胞过程建立电化学质子梯度。在神经元中，所有神经递质装入突触小泡是由每个突触小泡的一个V型ATP酶分子提供能量的。

为了阐明这一真正的单分子生物过程，研究人员揭示了单个哺乳动物脑V-ATP酶在单个突触小泡中的生电型质子泵作用。结果表明，V-ATP酶并不像观察到的细菌同源物旋转和被认为严格的ATP-质子耦合那样，在时间上连续泵送。相反，它们在三种超长寿命的模式之间随机切换：质子泵送、不活动和质子泄漏。值得注意的是，对泵送的直接观察显示，生理上相关浓度的ATP并不能调节内在的泵送速率。ATP通过质子泵送模式的切换概率调节V-ATP酶的活性。相反，电化学质子梯度调节泵送速率以及泵送模式和非活动模式的切换。

模式切换的一个直接后果是突触小泡的电化学梯度出现全或无的随机波动，这将有望在质子驱动的神经递质二次活性负荷中引入随机性，从而可能对神经递质产生重要影响。这项工作揭示并强调了超低速模式切换的机制和生物学重要性。

附：英文原文

Title: Regulation of the mammalian-brain V-ATPase through ultraslow mode-switching

Author: Kosmidis, Eleftherios, Shuttle, Christopher G., Preobraschenski, Julia, Ganzella, Marcelo, Johnson, Peter J., Veshaguri, Salome, Holmkvist, Jesper, Mller, Mads P., Marantos, Orestis, Marcoline, Frank, Grabe, Michael, Pedersen, Jesper L., Jahn, Reinhard, Stamou, Dimitrios

Issue&Volume: 2022-11-23

Abstract: Vacuolar-type adenosine triphosphatases (V-ATPases)1,2,3 are electrogenic rotary mechanoenzymes structurally related to F-type ATP synthases4,5. They hydrolyse ATP to establish electrochemical proton gradients for a plethora of cellular processes1,3. In neurons, the loading of all neurotransmitters into synaptic vesicles is energized by about one V-ATPase molecule per synaptic vesicle6,7. To shed light on this bona fide single-molecule biological process, we investigated electrogenic proton-pumping by single mammalian-brain V-ATPases in single synaptic vesicles. Here we show that V-ATPases do not pump continuously in time, as suggested by observing the rotation of bacterial homologues8 and assuming strict ATP–proton coupling. Instead, they stochastically switch between three ultralong-lived modes: proton-pumping, inactive and proton-leaky. Notably, direct observation of pumping revealed that physiologically relevant concentrations of ATP do not regulate the intrinsic pumping rate. ATP regulates V-ATPase activity through the switching probability of the proton-pumping mode. By contrast, electrochemical proton gradients regulate the pumping rate and the switching of the pumping and inactive modes. A direct consequence of mode-switching is all-or-none stochastic fluctuations in the electrochemical gradient of synaptic vesicles that would be expected to introduce stochasticity in proton-driven secondary active loading of neurotransmitters and may thus have important implications for neurotransmission. This work reveals and emphasizes the mechanistic and biological importance of ultraslow mode-switching.

DOI: 10.1038/s41586-022-05472-9

Source: https://www.nature.com/articles/s41586-022-05472-9