Yeast Model Reveals How Organelle Movement Is Controlled

Researchers working with a yeast model have identified a mechanism that the cell uses to control the movement and placement of organelles during and after cell division. Their findings were published February 16, 2003, in the online edition of Nature.

Organelles are compartments and structures inside cells that perform varied and vital functions, including energy production, storage and transportation of important substances, and removal of waste products. Normal cellular function requires that they be positioned at specific locations.

Investigators from the University of Iowa (Iowa City, USA) studied the movement and placement of organelles in yeast. They found that the vacuole-specific Myo2p receptor, Vac17p, played a key role in this process. Vac17p bound simultaneously to Myo2p and to Vac8p, a vacuolar membrane protein. The transport complex, Myo2p–Vac17p–Vac8p, moved the vacuole to the bud, and was then disrupted through the degradation of Vac17p. The vacuole was ultimately deposited near the center of the bud. If the Vac17p protein was not degraded, then the release mechanism was disrupted and the vacuole was not deposited in the correct cellular location.

"We were just trying to figure out how the specific coupling mechanism worked and then we also discovered this protein turnover mechanism, which seems to be critical for depositing the cargo at the right place and time,” explained senior author Dr. Lois Weisman, associate professor of biochemistry at the University of Iowa. "The protein we have discovered is called Vac17p. We found that it is involved in the specific coupling of vacuoles to the motor protein. More surprisingly, we also found that regulation of the appearance and disappearance of this protein controls when that organelle moves and where it moves to.”

The authors believe that the mechanism elucidated in yeast cells probably also functions in the cells of higher animals, including humans.




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