Membrane anchoring of the DIRAS3 N-terminal extension permits tumor suppressor function

Area of Science:

• Molecular Biology
• Biochemistry
• Cell Biology

Background:

• DIRAS3 is an imprinted tumor suppressor gene encoding a GTPase.
• Its unique N-terminal extension (NTE) and prenylated C-terminus are crucial for inhibiting RAS/MAP signaling and PI3K activity.
• DIRAS3 functions at the plasma membrane.

Purpose of the Study:

• To characterize the structure and function of the DIRAS3 NTE.
• To investigate the role of the NTE in DIRAS3 membrane localization and activity.

Main Methods:

• Biochemical assays
• Biophysical techniques
• Computational methods (all-atom molecular dynamic simulations)
• Mass spectrometry

Main Results:

• The DIRAS3 NTE peptide binds PI(3,4,5)P3 and PI(4,5)P2 with high affinity and rapid kinetics.
• Lipid binding induces a structural change in the NTE from disordered to an amphipathic helix.
• Mass spectrometry confirmed N-myristoylation of DIRAS3.
• Molecular dynamics simulations suggest DIRAS3 is anchored to the membrane by both its N- and C-termini.

Conclusions:

• The NTE plays a key role in targeting and stabilizing DIRAS3 on the cell membrane.
• Membrane-bound DIRAS3 effectively targets PI3K and KRAS, consistent with its tumor suppressor function.