Illuminating Cholesterol: A Revolutionary Luminescent Mimic Unveils Cellular Secrets

Posted on July 01, 2024

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Thanks to constant developments in biochemistry and cell biology, scientists are ever-advancing towards novel approaches to study even the most complex cellular processes. One such example is the behaviour of cholesterol inside living cells. Cholesterol, as a vital component of every living cell, ensures membrane integrity and many other cell functions such as synaptic transmission. With traditional radioactive tracers and biochemical assays as commonly used, existing approaches used for studying cholesterol dynamics have significant weaknesses. These traditional methods often lack the required resolution to interrogate real-time interaction, not to mention safety concerns. A recent paper has presented a revolutionary approach to solve this problem, by designing, synthesizing, and evaluating a luminescent cholesterol mimic.

The goal of the study is to design, synthesize, and evaluate a molecule that exhibits biological activity akin to natural cholesterol in living cells, but that is easily amenable to fluorescence microscopy, allowing for the ability to track the molecule over time in a safer, more efficient, and dynamic manner. Designing, synthesising, and evaluating this mimic involves a multitude of steps.

The main features of the design of a luminescent cholesterol mimic are the retention of the steroidal backbone, mirroring the structure of natural cholesterol, and adding the luminescent group (an organic molecule that emits light called a fluorophore). This fluorophore must be photostable and non-toxic, and it must emit light which can be filtered by a fluorescence microscope in the visible wavelength range. The addition of a fluorophore typically lowers the quantum yield of the producing fluorescence. On the other hand, an excited fluorophore can readily transfer the energy, intermediate between the two states, by means of resonance to a nearby reducing agent and thus boost the lipophilicity of the molecule.

Just like real cholesterol, the synthesis of the mimic of cholesterol is not easy. First a luminescent group must be introduced into the molecule in the right way so that it has at least some of the properties of cholesterol – in particular, it must be able to fold into a similar shape rather than being a long strand that doesn’t associate with anything. Organic chemists use techniques that they have worked out for attaching many different types of groups, and these techniques must be verified at each step to ensure the correct attachment both to the core and to any other groups that might impair the critical folding process. Finally, the mimic must be thoroughly tested to ensure that it behaves like cholesterol should: really, the real part of the mimic must be a very good one.

This is assessed by seeing if the mimic can integrate into cellular membranes: it must localize in the same way as cholesterol in the lipid bilayers if the designer molecule is to ‘stand in’ for cholesterol’s behaviour. Second, it must undergo functional assays that would show that it does not interfere with typical cellular processes. This means making sure that the cholesterol mimic is incorporated into cellular processes and interactions in the same way as natural cholesterol. Third, it is checked to make sure that it exhibits the desired luminescent properties, through fluorescence microscopy. The signal should be clear and unambiguous so that it can be easily tracked in real time within living cells.

The biological implications of this luminescent cholesterol mimic are even more profound. It offers scientists a powerful way to track cholesterol’s movements and interactions with proteins in cells, particularly in relation to how cholesterol affects membrane fluidity and signalling. The new mimic opens up whole new fields of cholesterol research ­– particularly in regard to how cholesterol relates to cardiovascular and neurological diseases such as atherosclerosis and Alzheimer’s. This new family of molecular mimics could helps prevent heart disease, and may offer a much safer way to study cholesterol in laboratory experiments. In this way, our team is helping to advance cellular biochemistry by providing a safer way to indirectly study the most abundant steroid on Earth. Check out Avanti’s newest Fluoro azasterol!

The researchers envision that, in the future, they’ll create even more refined mimics of lipids such as cholesterol. A repository of different kinds of luminescent cholesterol analogues could eventually be developed, each with different properties or uses. It could lead to a toolkit for the clear-sighted study of lipid dynamics at the molecular level. However it develops from here, the research underscores the utility of interdisciplinary work. By using chemistry to address biological questions, the researchers were able to expand our understanding of a biomolecule that plays a vital role in health and disease.

In summary, this luminescent cholesterol mimic is a momentous breakthrough for cholesterol dynamics by potentially offering a safer, more efficient and dynamic method to visualize the dynamic properties of cholesterol in living cells. Looking ahead, this work raises new questions at the crossroads of lipid dynamics and cellular biochemistry. And as researchers improve and extend this approach, our ability to examine how cholesterol affects biological processes will guide new discoveries in health and disease.

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For the full research article click here: J. Org. Chem. 2021, 86, 2, 1612–1621Publication Date:December 28, 2020