Biochemists at the University of Zurich have determined the detailed structure of a volume-regulated chloride channel. This cellular valve is activated in response to swelling to prevent the cell from bursting. The protein also plays an important role in the uptake of chemotherapeutics and the release of neurotransmitters after a stroke. The controlled regulation of its activity thus opens up a promising strategy for novel therapies.
Human cells are enclosed by membranes and are in osmotic equilibrium with their environment. If the concentration of solute molecules (osmolarity) in the fluid surrounding the cells decreases, cells start to swell; in extreme cases, this can result in the cells bursting.
To avoid this, cells activate volume-regulated chloride channels (VRACs) of the LRRC8 protein family. If the cell volume increases as a result of inflowing water, these cellular valves open to allow the negatively charged chloride ions and uncharged osmolytes to flow out, returning the cell to its original state.
Structure of a volume-regulated anion channel
Although discovered only five years ago, important properties of these cellular valves have already been described. For example, it is known that, besides their role in volume regulation, VRACs play an important role for the uptake of drugs used in cancer therapy and that they are responsible for the uncontrolled release of neurotransmitters after a stroke.
Despite these advances, the molecular make-up of VRACs and the basis for their selectivity has remained elusive. Researchers at the Department of Biochemistry of the University of Zurich have now closed this gap in our understanding. Using cryo-electron microscopy and X-ray crystallography, the team led by Prof. Raimund Dutzler has determined the detailed molecular structure of a VRAC. In addition, the researchers analyzed the functional properties of the protein through electrophysiological techniques.
From form to function
VRACs consist of six subunits, which are arranged around an axis that defines the ion permeation pore. The protein, which is located in the membrane, contains a small extracellular and a large intracellular domain. The latter probably plays an important role in channel activation.
The extracellular domain constricts the channel and functions as selectivity filter. “The positive residues in this filter attract negatively charged chloride ions and allow their permeation while excluding larger molecules from entering the cell,” explains Raimund Dutzler.
Potential approaches for the treatment of ischemia and cancer
With their work, the UZH scientists have provided a foundation for a better understanding of the molecular mechanisms underlying cell volume control. “This knowledge provides a valuable basis for the development of potential novel drugs,” states Dutzler. In case of cerebral ischemia or stroke, the astrocytes in the brain swell.
The resulting uncontrolled outflow of the neurotransmitter glutamate, which is mediated by VRACs, has detrimental consequences for affected people. Such cases could benefit from the development of specific blockers. Another potential application relates to the role of VRACs in cancer therapy: A cell-specific activation of VRACs could improve the uptake of therapeutics into cancer cells.
Dawid Deneka, Marta Sawicka, Andy K. M. Lam, Cristina Paulino and Raimund Dutzler. Structure of a volume-regulated anion channel of the LRRC8 family. Nature. May 16, 2018. DOI: 10.1038/s41586-018-0134-y
The project was funded by a grant of the Swiss National Science Foundation (SNSF). The cryo-EM data were collected with electron microscopes of the Center for Microscopy and Image Analysis of UZH, which were acquired thanks to a substantial contribution of the Mäxi Foundation. X-ray data were collected at the Swiss Synchrotron Light Source of the Paul Scherrer Institute.
Prof. Raimund Dutzler, PhD
Department of Biochemistry
University of Zurich
Phone: +41 44 635 65 50
Kurt Bodenmüller | Universität Zürich
Research on TGN1412 – Fc:Fcγ receptor interaction: Strong binding does not mean strong effect
23.04.2019 | Paul-Ehrlich-Institut - Bundesinstitut für Impfstoffe und biomedizinische Arzneimittel
New eDNA technology used to quickly assess coral reefs
18.04.2019 | University of Hawaii at Manoa
Researchers led by Francesca Ferlaino from the University of Innsbruck and the Austrian Academy of Sciences report in Physical Review X on the observation of supersolid behavior in dipolar quantum gases of erbium and dysprosium. In the dysprosium gas these properties are unprecedentedly long-lived. This sets the stage for future investigations into the nature of this exotic phase of matter.
Supersolidity is a paradoxical state where the matter is both crystallized and superfluid. Predicted 50 years ago, such a counter-intuitive phase, featuring...
A stellar flare 10 times more powerful than anything seen on our sun has burst from an ultracool star almost the same size as Jupiter
A localization phenomenon boosts the accuracy of solving quantum many-body problems with quantum computers which are otherwise challenging for conventional computers. This brings such digital quantum simulation within reach on quantum devices available today.
Quantum computers promise to solve certain computational problems exponentially faster than any classical machine. “A particularly promising application is the...
The technology could revolutionize how information travels through data centers and artificial intelligence networks
Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers...
Physicists observe how electron-hole pairs drift apart at ultrafast speed, but still remain strongly bound.
Modern electronics relies on ultrafast charge motion on ever shorter length scales. Physicists from Regensburg and Gothenburg have now succeeded in resolving a...
17.04.2019 | Event News
15.04.2019 | Event News
09.04.2019 | Event News
18.04.2019 | Life Sciences
18.04.2019 | Physics and Astronomy
18.04.2019 | Life Sciences