Targeting nucleotide exchange to inhibit constitutively active G protein α subunits in cancer cells

Area of Science:

• Molecular Biology
• Oncology
• Pharmacology

Background:

• Constitutively active G protein alpha (Gα) subunits are implicated in various diseases, including cancers like uveal melanoma (UM).
• Targeted inhibition of these aberrant Gα subunits remains a significant therapeutic challenge.
• Uveal melanoma (UM) driven by Gαq offers a specific context for investigating therapeutic interventions.

Purpose of the Study:

• To investigate the therapeutic potential of inhibiting constitutively active Gαq in UM.
• To elucidate the mechanism of action of the cyclic depsipeptide FR900359 (FR) on Gαq.
• To explore FR's effects on UM cell signaling, proliferation, differentiation, and apoptosis.

Main Methods:

• Utilized the cyclic depsipeptide FR900359 (FR) to inhibit constitutively active Gαq in UM cells.
• Assessed FR's allosteric inhibition of guanosine diphosphate-for-guanosine triphosphate (GDP/GTP) exchange.
• Examined FR's impact on second messenger signaling, cell proliferation, melanocytic differentiation, apoptosis, and polycomb repressive complex 2 (PRC2) activity.

Main Results:

• FR900359 effectively inhibited constitutively active Gαq in UM cells by trapping it in an inactive GDP-bound state.
• FR treatment arrested proliferation, promoted differentiation, and induced apoptosis in Gαq-driven UM cells, but not in BRAF-driven UM.
• FR reactivated PRC2-mediated gene silencing, revealing a novel effector pathway for Gαq in UM.

Conclusions:

• Constitutively active Gαq and PRC2 are viable therapeutic targets in UM.
• FR900359 demonstrates therapeutic promise for UM driven by Gαq.
• Development of FR analogs could offer new treatments for diseases involving aberrant Gα subunits or complex GPCR signaling.