Membrane Anchoring of the Diras3 N-terminal Extension Permits Tumor Suppressor Function

Authors

Xiaowen Liang
Sung Yun Jung
Lon Wolf Fong
Gamze Bildik
Joshua P Gray
Weiqun Mao
Shuxing Zhang
Steven W Millward
Alemayehu A Gorfe
Yong Zhou
Zhen Lu
Robert C Bast

Publication Date

11-17-2023

Journal

iScience

Abstract

DIRAS3 is an imprinted tumor suppressor gene encoding a GTPase that has a distinctive N-terminal extension (NTE) not found in other RAS proteins. This NTE and the prenylated C-terminus are required for DIRAS3-mediated inhibition of RAS/MAP signaling and PI3K activity at the plasma membrane. In this study, we applied biochemical, biophysical, and computational methods to characterize the structure and function of the NTE. The NTE peptide recognizes phosphoinositides PI(3,4,5)P3 and PI(4,5)P2 with rapid kinetics and strong affinity. Lipid binding induces NTE structural change from disorder to amphipathic helix. Mass spectrometry identified N-myristoylation of DIRAS3. All-atom molecular dynamic simulations predict DIRAS3 could adhere to the membrane through both termini, suggesting the NTE is involved in targeting and stabilizing DIRAS3 on the membrane by double anchoring. Overall, our results are consistent with DIRAS3's function as a tumor suppressor, whereby the membrane-bound DIRAS3 can effectively target PI3K and KRAS at the membrane.

Keywords

Cancer, Protein physics, Structural biology