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Science News

Possible Link Between Genes Associated with Parkinson's, Heart Disease

Scientists have discovered an important step in a molecular pathway that may underlie the early stages of both Parkinson’s disease (PD) and heart disease. The new study shows how the actions of two genes already associated with PD are involved with a third gene, which is linked to heart disease. The results of this report appear in the April 26 issue of Science.

Although it is rare, there are cases in which people develop PD due to a genetic mutation. For example, mutations in genes known as Parkin and PINK1, are associated with developing PD at a young age. Recent studies have shown that these mutations disrupt the recycling of mitochondria in cells — the structures that transform nutrients into energy. Because the broken mitochondria become toxic, cells usually destroy them.

Gerald W. Dorn, II, M.D., and Yun Chen, Ph.D., at the Washington University School of Medicine, in St. Louis, MO, wanted to understand how cells know which mitochondria need to be destroyed. The scientists knew that proteins known as Mfn1 and Mfn2 somehow worked with PINK1 and Parkin. But they did not understand how. Because there are so many mitochondria in heart muscle cells, they carried out their studies using these cells as well as mouse and fruit fly hearts.

Results

  • The researchers discovered that in heart cells, the Mfn2 protein acts as an important middle-man between the two proteins associated with PD (PINK1 and Parkin). By interacting with both, it presence seems to permit the normal recycling of damaged mitochondria.
  • For the first time, scientists observed a basic sequence of events for the recycling process mentioned above.
  • Scientists observed several signs that Mfn2 was important not only for mitochondria recycling, but for heart health. For example, deleting the Mfn2 protein from fruit flies and mice caused both animals to show signs of heart failure. In mice, it caused the sequence of events that researchers had discovered, to be broken – mitochondria were not recycled and instead accumulated. Plus, their hearts hearts showed signs failure. Similarly, without Mfn2, fruit flies showed signs of heart failure when they lacked Mfn2.

What Does It Mean?

The important take-away in this study is its clarification of the steps in a molecular pathway that, when disrupted in brain cells, may underlie the development of PD. Surprisingly, the same molecular changes underlie some forms of heart disease.

In addition, the study authors suggest that some cases of inherited PD that are not explained by known genetic mutations may be caused by mutations in the gene Mfn2. 

It is important to note that there are very little data linking PD with heart failure, and it remains unknown whether heart failure risk is lower, same or increased in PD. Recent studies have suggested a link between the use of some PD medications (dopamine agonists) with heart failure.

Overall, identifying the Mfn2 protein may represent a potential new avenue of research to improve our understanding of PD.  And it is possible that medications, which improve the function of this biological pathway, may be helpful for both heart failure and PD.

Reference: Chen Y, Dorn GW (2013) PINK1-phosphorylated mitofusin 2 is a Parkin receptor for culling damaged mitochondria. Science 340:471–475

Source Date: May 07 2013