‘Power plants’ in cells linked to disease

U. COLORADO-BOULDER (US) — Close contact between mitochondria and the endoplasmic reticulum may be linked to a variety of degenerative diseases, including diabetes, cardiovascular disease, and stroke.

Mitochondria—tiny sausage-shaped organelles within cells that contain their own DNA—act like miniature power plants, providing cells with the energy to move and divide. The endoplasmic reticulum is a complex network of sacs and tubules that makes proteins and fats.

“This is the first time one cell organelle has been shown to shape another,” says Gia Voeltz, assistant professor of molecular, cellular, and developmental biology at the University of Colorado-Boulder.

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Enclosed by membranes, mitochondria vary vastly in numbers per individual cells depending on the organism and tissue type. While some single-cell organisms contain only a single mitochondrion, a human liver cell can contain up to 2,000 mitochondria and take up nearly one-quarter of the cell space.

The new research is published online in the journal Science.

Since numerous human diseases are associated with mitochondrial dysfunction, it is important to understand how the division process is regulated, Voeltz says.

“Our studies suggest the possibility that human mitochondrial diseases could result from disruption or excessive contact between the endoplasmic reticulum and the mitochondria.”

Previous work, including research in the lab of Jodi Nunnari, professor of molecular cell biology at the University of California, Davis, has shown that mitochondrial division is regulated by a protein known as “dynamin-related protein-1” that assembles into a noose-like ligature that tightens around individual mitochondrion, causing it to divide.

The team found that several additional proteins linked to mitochondrial division also were found where the endoplasmic reticulum and mitochondria touched.

“The new function for the endoplasmic reticulum expands and transforms our view of cell organization,” says Nunnari. “It’s a paradigm shift in cell biology.”

The study was funded in part by the National Institutes of Health, the Searle Scholar Program and CU-Boulder.

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