Skip to ContentSkip to Navigation
Part of University of Groningen
Science LinXScience Linx News

How a mitochondrial enzyme can trigger cell death

14 March 2019

Cytochrome c is a small enzyme that plays an important role in the production of energy by mitochondria. It is also involved in signalling dangerous problems that warrant apoptosis, or programmed cell death. Using solid-state NMR, University of Groningen Associate Professor Patrick van der Wel and colleagues from the University of Pittsburgh have discovered that the signal induced by cytochrome c is more controlled than expected. The results were published in the journal Structure on 14 March.

If cells malfunction, the body wants to get rid of them before they do more damage. Different signals can drive a cell to self-destruct through apoptosis. Widespread programmed cell death contributes to the progression of neurodegenerative diseases such as Huntington’s disease. A strong signal to trigger apoptosis is the oxidation of cardiolipin, a phospholipid that is only present in the membrane of mitochondria, the cell’s power stations. ‘Mitochondria have two membranes and this cardiolipin is primarily present in the inner membrane,’ explains Van der Wel. ‘When it is oxidized and moves to the outer membrane, it will trigger apoptosis.’

Patrick van der Wel | Photo Sylvia Germes
Patrick van der Wel | Photo Sylvia Germes

Atoms

Drugs that prevent the oxidization of cardiolipin also reduce cell death and can slow down the progression of Huntington’s disease in animal models. However, cells accelerate the oxidation process through the catalytic activity of cytochrome c, an enzyme that contains a reactive haem group. ‘This suggests that the oxidation event is not accidental but may also act as a useful and desirable signal for the cell,’ explains Van der Wel.

Van der Wel wanted to find out how the oxidization of the cardiolipin by cytochrome c takes place through studying the behaviour of the enzyme when it interacts with the mitochondrial membrane. To do this, he used solid-state NMR, a technique that allows scientists to study atoms in molecules such as proteins or lipids. ‘The signal from atoms that you measure by means of NMR is affected by the atoms’ surroundings. Therefore, a change in the shape of the protein would alter the signal.’ Van der Wel compared cytochrome c in solution with membrane-bound cytochrome c to see how interaction with the membrane altered its structure.

Cytochrome c
Cytochrome c

‘We expected that the protein would be inside the membrane, in an unfolded state that exposes the reactive haem group.’ The haem would then easily oxidize the cardiolipin. However, the results showed something different. ‘The enzyme doesn’t enter the membrane but is bound to membrane domains containing cardiolipin, and it remains folded. However, a protein loop covering the haem group will sometimes move aside, exposing the phospholipids to the haem group.’

When mitochondria are damaged, cytochrome c can induce a signal that leads to apoptosis. | Illustration Patrick van der Wel and Mingyue Li
When mitochondria are damaged, cytochrome c can induce a signal that leads to apoptosis. | Illustration Patrick van der Wel and Mingyue Li

Functional materials

This observation suggests that the action of cardiolipin in apoptosis is to a certain extent regulated, and not just a passive response to oxidative conditions. This could have implications for diseases in which cell death plays an important role. ‘If the active form of cytochrome c is still folded, it might be possible to develop drugs that stop it from oxidizing cardiolipin.’ Another possible point of intervention is the binding of the enzyme to specific membrane domains. And finally, problems with the mitochondria can either induce apoptosis or the less invasive removal of just the affected mitochondrion. ‘If we could understand how this choice is made, we might be able to influence this process.’

The experiments described in the paper in Structure were performed at the University of Pittsburgh, where Van der Wel worked prior to his transfer to the University of Groningen last year. He is now building a solid-state NMR group at the Zernike Institute for Advanced Materials, part of the Faculty of Science and Engineering. ‘This technique will also be used to study alternative ways of protein folding, for example the formation of amyloids. These protein aggregates play a role in neurodegenerative diseases but they could also be used to design new functional materials.’

Reference: Li M, Mandal A, Tyurin VA, DeLucia M, Ahn J, Kagan VE, van der Wel PCA: Surface-binding to Cardiolipin Nanodomains Triggers Cytochrome C Pro-apoptotic Peroxidase Activity via Localized Dynamics, Structure, 14 March 2019

Last modified:25 March 2019 4.58 p.m.
printView this page in: Nederlands

More news

  • 11 July 2019

    Major companies’ annual reports too vague about climate impact

    Many major Dutch companies publish extensive information about climate impact in their annual reports. However, very few companies provide concrete, detailed information about their own CO2 emissions, the impact of climate change on their business...

  • 08 July 2019

    UG permanently closes Yantai project

    The University of Groningen (UG) has permanently closed the project aimed at creating a branch campus in Yantai. Discussions were held with China Agricultural University, the city of Yantai and the Province of Shandong.

  • 03 July 2019

    Cheap train tickets boost public transport use but reduce customer satisfaction

    Offers of cheap single train tickets through retailers such as Kruidvat or Etos have a positive impact on the number of kilometres travelled by rail. This impact is much bigger than that of more general TV, newspaper or magazine advertising. However,...