Direct evidence that the GPCR CysLTR2 mutant causative of uveal melanoma is constitutively active with highly biased signaling

J Biol Chem. 2021 Jan-Jun:296:100163. doi: 10.1074/jbc.RA120.015352. Epub 2020 Dec 11.

Abstract

Uveal melanoma is the most common eye cancer in adults and is clinically and genetically distinct from skin cutaneous melanoma. In a subset of cases, the oncogenic driver is an activating mutation in CYSLTR2, the gene encoding the G protein-coupled receptor cysteinyl-leukotriene receptor 2 (CysLTR2). The mutant CYSLTR2 encodes for the CysLTR2-L129Q receptor, with the substitution of Leu to Gln at position 129 (3.43). The ability of CysLTR2-L129Q to cause malignant transformation has been hypothesized to result from constitutive activity, but how the receptor could escape desensitization is unknown. Here, we characterize the functional properties of CysLTR2-L129Q. We show that CysLTR2-L129Q is a constitutively active mutant that strongly drives Gq/11 signaling pathways. However, CysLTR2-L129Q only poorly recruits β-arrestin. Using a modified Slack-Hall operational model, we quantified the constitutive activity for both pathways and conclude that CysLTR2-L129Q displays profound signaling bias for Gq/11 signaling pathways while escaping β-arrestin-mediated downregulation. CYSLTR2 is the first known example of a G protein-coupled receptor driver oncogene that encodes a highly biased constitutively active mutant receptor. These results provide new insights into the mechanism of CysLTR2-L129Q oncoprotein signaling and suggest CYSLTR2 as a promising potential therapeutic target in uveal melanoma.

Keywords: CysLTR2; G protein; G protein–coupled receptor; biased signaling; constitutive activity; signaling; uveal melanoma; β-arrestins.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • GTP-Binding Protein alpha Subunits, Gq-G11 / genetics*
  • GTP-Binding Protein alpha Subunits, Gq-G11 / metabolism
  • Gene Expression Regulation, Neoplastic*
  • Glutamine / metabolism
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • HEK293 Cells
  • Humans
  • Kinetics
  • Lysine / metabolism
  • Melanoma / genetics
  • Melanoma / metabolism
  • Melanoma / pathology
  • Models, Biological
  • Mutation
  • Protein Binding
  • Receptors, Leukotriene / genetics*
  • Receptors, Leukotriene / metabolism
  • Receptors, Vasopressin / genetics
  • Receptors, Vasopressin / metabolism
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction / genetics*
  • Uveal Neoplasms / genetics
  • Uveal Neoplasms / metabolism
  • Uveal Neoplasms / pathology
  • beta-Arrestin 2 / genetics*
  • beta-Arrestin 2 / metabolism

Substances

  • ARRB2 protein, human
  • AVPR2 protein, human
  • Receptors, Leukotriene
  • Receptors, Vasopressin
  • Recombinant Fusion Proteins
  • beta-Arrestin 2
  • Glutamine
  • Green Fluorescent Proteins
  • cysteinyl leukotriene receptor 2
  • GTP-Binding Protein alpha Subunits, Gq-G11
  • Lysine

Supplementary concepts

  • Uveal melanoma