The mammalian target of rapamycin (mTOR) is a protein kinase whose primary purpose is to help in controlling the balance between protein synthesis and degradation according to the availability of various nutrients. mTOR has a variety of functions ranging from ribosome synthesis to translation to autophagy.
One research group set out to show how mTOR interacts with huntingtin protein aggregates. After showing that mTOR is indeed sequestered, or trapped, by huntingtin aggregates in cell cultures, they went on to show that mTOR does not function properly in cells that have huntingtin aggregates. To set off different cellular processes, mTOR signals to other molecules in the cell by working as a kinase, which is a molecule that adds a phosphate group onto another molecule (or "phosphorylates" it) in order to turn that molecule on or off. The researchers showed that certain molecules phosphorylated by mTOR were not phosphorylated to the same degree in cells that contained huntingtin aggregates. This finding indicates that the interaction between mTOR and the aggregates prevents mTOR from performing its usual functions. By phosphorylating these molecules, mTOR is supposed to stimulate the synthesis of certain proteins. The experiment also showed that in cells with huntingtin aggregates, these proteins were produced at lower levels, probably because mTOR was inactivated. The researchers found that increasing mTOR activity, which would prevent autophagy, increased aggregate levels and cell death.
Last Modified: 05/22/2009
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