Overview: V-ATPase, a key enzyme that enables neurotransmission, can switch on and off at random, even with hours of rest.
sauce: University of Copenhagen
Researchers at the University of Copenhagen have made a startling discovery that marks another breakthrough in our understanding of the mammalian brain. That means the key enzymes that enable the brain to signal are switching on and off at random, even taking hours of “work breaks.”
These findings could have major implications for our understanding of the brain and drug development.
Today the find is on the cover Nature.
Millions of neurons are constantly sending messages to each other to form our thoughts and memories and keep us moving. When two neurons meet to exchange messages, neurotransmitters are transported from one neuron to another with the help of specific enzymes.
This process is critical for neurotransmission and the survival of all complex organisms. Until now, researchers around the world have assumed that these enzymes are always active and continuously transmit important signals. But this is not the case.
Using an innovative method, researchers from the Department of Chemistry at the University of Copenhagen have closely studied the enzyme and found that its activity switches on and off at random intervals. This contradicts our previous understanding.
“This is the first time we have studied these mammalian brain enzymes one molecule at a time, and we are in awe of the results. Unlike other enzymes, these enzymes can stop working within minutes to hours. Professor Dimitrios Stamou, who led the research at the Center for Engineering Cell Systems, said:
Until now, such studies have been performed with highly stable enzymes from bacteria.
Today, this research Nature.
Enzymatic switching can have far-reaching effects on neurotransmission
Neurons communicate using neurotransmitters. To transmit messages between two neurons, neurotransmitters are first pumped into small membrane sacs (called synaptic vesicles). The bladder acts as a container that stores neurotransmitters, and he only releases them between two neurons when transmitting a message.
The central enzyme in this study, known as V-ATPase, is responsible for providing energy to the neurotransmitter pumps within these vessels. , the container cannot send messages between neurons.
However, this study shows that there is only one enzyme in each container. When this enzyme is switched off, there is no energy to load the neurotransmitters into the reservoir. This is a completely new and unexpected discovery.
“It is almost incomprehensible that the very important process of loading the neurotransmitters into the containers is delegated to just one molecule per container. Even more so when it turns out that the
These findings raise many interesting questions.
“Does cutting off the energy source of a container mean that many of the containers are actually empty of neurotransmitters? If so, is it a “problem” that neurons evolved to avoid, or could it be an entirely new way to encode important information in the brain? Time will tell. ’ he says.
A breakthrough method for screening drugs for V-ATPase
The V-ATPase enzyme is an important drug target due to its critical role in cancer, cancer metastasis, and several other life-threatening diseases. Therefore, V-ATPase is a favorable target for anticancer drug development.
Existing assays for screening drugs for V-ATPase are based on averaging signals from billions of enzymes simultaneously. As long as the enzymes are always working in a given amount of time, or many enzymes working together, it is enough to know the average effect of the drug.
“However, we know that neither is necessarily true for V-ATPases. It suddenly became important ”, the University of Copenhagen, spearheading experiments in the lab.
The method developed here is the first to measure the effect of drugs on proton pumping of a single V-ATPase molecule. Detects one million times less current than the gold standard patch clamp method.
Facts about the V-ATPase enzyme:
- V-ATPase is an enzyme that breaks down ATP molecules and sends protons to the cell membrane.
- They are found in all cells and are essential for controlling intracellular and/or extracellular pH/acidity.
- In neurons, proton gradients established by V-ATPases provide energy for loading neurochemical messengers called neurotransmitters into synaptic vesicles for their subsequent release at synaptic junctions.
About this neuroscience research news
Original research: closed access.
“Regulation of mammalian brain V-ATPase by ultraslow mode switching” Dimitrios Stamou et al. Nature
Regulation of mammalian brain V-ATPase by ultraslow mode switching
Vacuolar-type adenosine triphosphatase (V-ATPase) is an electrogenic rotary mechanoenzyme structurally related to the F-type ATP synthase. They hydrolyze ATP and establish electrochemical proton gradients for numerous cellular processes.
In neurons, all neurotransmitter loading onto synaptic vesicles is activated by approximately one V-ATPase molecule per synaptic vesicle. To shed light on this bona fide single-molecule biological process, we investigated electromotive proton pumping by a single mammalian brain V-ATPase in a single synaptic vesicle.
Here, we observe the rotation of bacterial homologues and show that V-ATPase does not continuously pump in time, as suggested by assuming strict ATP–proton binding.
Instead, it stochastically switches between three ultralong-lived modes: proton pumping, inactivity, and proton leakage. Notably, direct observation of pumping revealed that physiologically relevant concentrations of ATP did not modulate the intrinsic pumping rate.
ATP regulates V-ATPase activity through proton pump mode switching probabilities. In contrast, the electrochemical proton gradient modulates pumping speed and switching between pumping and inactive modes.
A direct consequence of mode switching is the all-or-none stochastic variation of the synaptic vesicle electrochemical gradient, which is expected to introduce stochasticity into the proton-driven secondary active loading of neurotransmitters, thus It may have important implications for neurotransmission.
This study reveals and highlights the mechanistic and biological importance of ultraslow mode switching.