K128 ubiquitination constrains RAS activity by expanding its binding interface with GAP proteins

Area of Science:

• Oncology
• Molecular Biology
• Cell Signaling

Background:

• The RAS signaling pathway is frequently dysregulated in various cancers.
• Mechanisms controlling RAS activity in human pathologies require further elucidation.
• Lysine 128 (K128) ubiquitination of NRAS and KRAS is a prevalent modification decreased in cancer.

Purpose of the Study:

• To investigate the functional role of K128 ubiquitination in RAS signaling and cancer.
• To determine how K128 ubiquitination impacts RAS interactions with GTPase-activating proteins (GAPs).
• To explore the consequences of altered K128 ubiquitination in both wild-type and mutant RAS-driven cancers.

Main Methods:

• Investigated K128 ubiquitination in cancer cell lines and tissues.
• Utilized cell culture stimulation with growth factors and cytokines.
• Analyzed RAS-GAP interactions and downstream signaling pathways (RAL/TBK1).
• Assessed the impact on tumor growth and senescence-associated secretory phenotype.

Main Results:

• K128 ubiquitination enhances binding to GAPs (NF1, RASA1), promoting GTP hydrolysis and limiting wild-type RAS activation.
• Transient K128 ubiquitination restricts RAS activation upon growth factor stimulation.
• In KRAS mutant cells, K128 ubiquitination suppresses tumor growth by inhibiting RAL/TBK1 signaling and autocrine circuits.
• Reduced K128 ubiquitination activates both wild-type and mutant RAS, inducing a senescence-associated secretory phenotype and promoting pancreatic tumorigenesis.

Conclusions:

• K128 ubiquitination acts as a crucial negative regulator of RAS signaling.
• This modification influences RAS activity in both normal and cancerous conditions.
• Targeting K128 ubiquitination may offer therapeutic strategies for RAS-driven cancers, particularly pancreatic cancer.