SUMOylation modulates the stability and function of PI3K-p110β

Area of Science:

• Biochemistry
• Molecular Biology
• Cancer Research

Background:

• Class I PI3K, crucial for cellular functions, comprises p85 regulatory and p110 catalytic subunits.
• The p110β catalytic subunit is increasingly recognized for its significant role in tumorigenesis.

Purpose of the Study:

• To investigate the potential regulation of the p110β subunit by SUMOylation.
• To understand the impact of SUMOylation on p110β activity and its role in cancer.

Main Methods:

• In vitro and in vivo experiments including transfected cells and endogenous conditions.
• Identification of the specific lysine residue responsible for SUMOylation.
• Assessment of protein stability and AKT activation.
• Evaluation of the interaction with the p85β regulatory subunit.

Main Results:

• p110β undergoes SUMOylation by SUMO1 and SUMO2, confirmed in vitro, in transfected cells, and endogenously.
• Lysine residue 952 in the p110β activation loop is essential for SUMOylation.
• SUMOylation stabilizes p110β, enhances AKT activation, and promotes cell growth and oncogenic transformation.
• The p85β regulatory subunit inhibits p110β SUMOylation.

Conclusions:

• SUMOylation is a novel regulatory mechanism for p110β.
• SUMOylation positively impacts PI3K pathway activation, contributing to p110β-driven cancers.
• The p85β subunit acts as a negative regulator of p110β SUMOylation.