AsianScientist (Mar. 1, 2018) – A team of researchers at the Center for Self-assembly and Complexity within the Institute for Basic Science (IBS) have directly observed the process by which cells recycle their components. Their findings are published in Angewandte Chemie International Edition.
The word autophagy comes from the Greek language and means ‘self-eating.’ As weird as it is sounds, it is an indispensable process used by cells to cleanse themselves of damaged organelles and proteins. Inside lysosomes, old cellular parts are broken down to their building blocks, which are then used to build new organelles.
One example of a cellular organelle that must be periodically recycled is the mitochondrion. If cells accumulate defective mitochondria, they can damage themselves. This occurs, for example, in Alzheimer’s and Parkinson’s diseases, where the build-up of damaged mitochondria and aggregated proteins leads to neuronal death.
In this study, a team of researchers led by Dr. Park Kyeng Min of IBS developed a technique to visualize how mitochondria fuse with lysosomes. The relatively simple and inexpensive technique uses hollow barrel-shaped synthetic molecules, known as cucurbituril (CB[7]), that bind exceptionally tightly to a molecule called adamantylamine (AdA) and cannot be degraded by the lysosomes.
CB[7] was decorated with a fluorescent dye (Cy3), while AdA with another dye (Cy5). Initially, CB[7]-Cy3 enters the lysosomes, while Ada-Cy5 enters the mitochondria. When the two organelles fuse in the recycling process, CB[7]-Cy3 and Ada-Cy5 bind together. Cy3 then donates energy to Cy5, which leads to a reduction in Cy3 fluorescence intensity in favor of an increase in Cy5 emission intensity. This process is known as fluorescence resonance energy transfer.
The research team was thus able to follow the behavior of different organelles and observe the mitophagy process occurring in live cells. Moreover, the experiments showed that the two compounds are not toxic for the cells below a 800 nanomolar dose.
“The most challenging part of the experiment was the choice of the chemicals. We chose chemicals with the right hydrophilicity, charge and molecular size to be selectively incorporated into mitochondria and lysosomes,” said Park.
In the future, a similar technique could be used to study autophagy processes that involve other cellular organelles, like the Golgi apparatus and the endoplasmic reticulum.
The article can be found at: Li et al. (2018) Autophagy Caught in the Act: A Supramolecular FRET Pair Based on an Ultrastable Synthetic Host–Guest Complex Visualizes Autophagosome–Lysosome Fusion.
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Source: Institute for Basic Science; Photo: Shutterstock.
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