Nature: Shocked! Revealing a new mechanism by which V-ATPases in mammalian brains transition between two different states

In a new study, researchers from the University of Copenhagen in Denmark have made a breakthrough in further understanding the mammalian brain, and they have made an incredible discovery: An important enzyme that activates brain signals is randomly turned on and off, and even subjected to "rest periods"
of up to several hours.
These findings could have a significant impact
on our understanding of the brain and drug development.
The findings were published in the Nov.
24, 2022 issue of Nature in the paper "Regulation of the mammalian-brain V-ATPase through ultraslow mode-switching.
"

Millions of neurons are constantly passing information to each other, forming thoughts and memories that allow us to move our bodies
as we please.
When two neurons meet to exchange information, neurotransmitters are transported from one neuron to another with the help of a unique enzyme
.

This process is essential
for neuronal communication and the survival of all complex organisms.
Until then, scientists around the world thought the enzyme was active at all times to constantly transmit basic signals
.
But this is far from the
case.

In the new study, the authors took a closer look at the enzyme using an innovative approach and found that its activity turned on and off at random intervals, contradicting
our previous understanding.

Corresponding author Professor Dimitrios Stamou, from the Centre for Geometric Engineering Cell Systems at the Department of Chemistry at the University of Copenhagen, said: "This is the first time that enzymes in mammalian brains have been studied individually, and we were shocked
by the results.
Contrary to popular belief, and unlike many other proteins, this enzyme can stop working for a few minutes to a few hours
.
Still, the brains of humans and other mammals are miraculously able to function
.
”

Previously, such studies were conducted
with very stable enzymes from bacteria.
Using this new method, the authors studied mammalian enzymes
isolated from rat brains for the first time.

Switching enzyme activity can have profound effects on neuronal communication

Neurons use neurotransmitters to communicate
.
To relay information between the two neurons, neurotransmitters are first pumped into
synaptic vesicles.
These synaptic vesicles act as containers to store neurotransmitters that are released between two neurons only when they are transmitting information
.

The new study focuses on a core enzyme called vacuole ATPase (V-ATPase), which is responsible for providing energy
for neurotransmitter pumps in synaptic vesicles.
Without it, neurotransmitters would not be pumped into synaptic vesicles, which would not be able to transmit information
between neurons.

Image from Nature, 2022, doi:10.
1038/s41586-022-05472-9
.

But the new study shows that in each synaptic vesicle there is only one enzyme; When this enzyme shuts down, there will be no more energy to drive neurotransmitters into synaptic vesicles
.
This is a new and unexpected discovery
.

Professor Stamou said, "It is almost incomprehensible that the extremely critical process of loading neurotransmitters into synaptic vesicles is entrusted to only one molecule in each synaptic vesicles
.
Especially when
we found that these molecules are off 40% of the time.
”

The findings, he says, raise a number of intriguing questions: "Does shutting down the energy source of synaptic vesicles mean that many synaptic vesicles really don't have neurotransmitters?" Does a large number of empty synaptic vesicles have a significant impact on communication between neurons? If so, could this become a 'problem' that neurons have evolved to circumvent, or could it be a whole new way of encoding important information in the brain? Only time will tell.

”

A revolutionary method for screening drugs targeting V-ATPase

V-ATPase is an important drug target because it plays a key role
in cancer, cancer metastasis, and several other life-threatening diseases.
Therefore, V-ATPase is a profitable target for anti-cancer drug development
.

Existing drug screening methods for V-ATPase are based on averaging
the signals of billions of enzymes simultaneously.
As long as an enzyme is constantly working in a timely manner, or when enzymes work together in large quantities, it is enough to know the average effect of a drug
.

Lead author Dr Elefterios Kosmidis, from the Department of Chemistry at the University of Copenhagen, said: "However, we now know that for V-ATPase, neither is necessarily true
.
Therefore, having a way to measure the behavior of individual V-ATPases in order to understand and optimize the desired effect of drugs suddenly becomes critical
.
”

The method developed by the new study is the first-ever method
capable of measuring the effect of a drug on proton pumping of a single V-ATPase molecule.
It can detect currents
that are more than 1 million times smaller than the gold-standard patch-clamp method.

Facts about V-ATPase: (1) V-ATPase is an enzyme that breaks down ATP molecules to pump protons across cell membranes; (2) they are present in all cells and are essential for controlling pH/acidity inside and/or outside the cell; (3) In neurons, the proton gradient established by V-ATPase provides energy
for loading neurochemical messenger molecules called neurotransmitters into synaptic vesicles for subsequent release at synaptic junctions.
(Biovalley Bioon.
com)

Resources:

Eleftherios Kosmidis et al.
 Regulation of the mammalian-brain V-ATPase through ultraslow mode-switching, Nature, 2022, doi:10.
1038/s41586-022-05472-9.