Structural basis for LZTR1 recognition of RAS GTPases for degradation

Area of Science:

• Molecular Biology
• Structural Biology
• Cellular Signaling

Background:

• RAS GTPases are crucial signaling proteins regulated by ubiquitination and proteolysis.
• Leucine Zipper-like Transcription Regulator 1 (LZTR1) acts as a substrate adapter for Cullin-3 RING E3 ubiquitin ligase, targeting specific RAS proteins for degradation.
• Dysregulation of RAS signaling is implicated in various cancers.

Purpose of the Study:

• To elucidate the structural basis of LZTR1's interaction with RAS GTPases.
• To understand how LZTR1 achieves RAS isoform selectivity and nucleotide specificity.
• To investigate the functional consequences of disease-associated LZTR1 mutations.

Main Methods:

• X-ray crystallography to determine the structures of LZTR1 Kelch domains bound to RIT1, MRAS, and KRAS.
• Biochemical assays to analyze substrate interactions and mutation effects.
• Cellular and mouse models to assess the in vivo impact of LZTR1 mutations.

Main Results:

• Detailed structures reveal the interfaces governing RAS isoform and nucleotide specificity.
• Disease-associated mutations in LZTR1's Kelch domain lead to impaired substrate binding, loop destabilization, or blade-blade repulsion.
• Mutations disrupting substrate binding phenocopy LZTR1 loss in cellular and mouse models, confirming LZTR1's substrate specificity.

Conclusions:

• LZTR1 recognizes specific RAS GTPases through defined structural interfaces.
• Understanding these recognition mechanisms provides a foundation for developing targeted therapies.
• The findings suggest a potential molecular glue strategy to degrade oncogenic KRAS.