Sestrin2 is a leucine sensor for the mTORC1 pathway.

Area of Science:

• Cellular biology
• Molecular signaling
• Mammalian physiology

Background:

• Leucine, a key amino acid, regulates mammalian physiology by activating the mTOR complex 1 (mTORC1) pathway.
• Amino acid signaling to mTORC1 involves Rag GTPases, regulated by factors including GATOR1, GATOR2, and Sestrin2.
• Sestrin2 is known to inhibit mTORC1 signaling by interacting with GATOR2.

Purpose of the Study:

• To elucidate the precise mechanism by which leucine activates the mTORC1 pathway.
• To investigate the role of Sestrin2 in mediating leucine's effect on mTORC1 signaling.
• To determine if Sestrin2 functions as a direct sensor for leucine.

Main Methods:

• Biochemical assays to measure protein interactions and binding affinities.
• Cellular experiments to assess mTORC1 pathway activation in response to leucine.
• Mutational analysis to evaluate the importance of leucine-binding to Sestrin2.

Main Results:

• Leucine directly binds to Sestrin2 with a dissociation constant (Kd) of 20 micromolar.
• This leucine binding disrupts the interaction between Sestrin2 and GATOR2.
• The leucine-binding capability of Sestrin2 is critical for leucine-induced mTORC1 activation in cells.

Conclusions:

• Sestrin2 acts as a direct leucine sensor for the mTORC1 pathway.
• Leucine binding to Sestrin2 is the initiating event for mTORC1 activation.
• This finding reveals a novel mechanism in nutrient sensing and growth control.