March 2012
Volume 53, Issue 14
Free
ARVO Annual Meeting Abstract  |   March 2012
Towards a Novel Therapy for Uveal Melanoma: Targeting Oncogenic Gαq
Author Affiliations & Notes
  • Timothy W. Corson
    Glick Eye Institute, Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana
  • Kamakshi Sishtla
    Glick Eye Institute, Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana
  • Footnotes
    Commercial Relationships  Timothy W. Corson, None; Kamakshi Sishtla, None
  • Footnotes
    Support  IUPUI Research Support Funds Grant
Investigative Ophthalmology & Visual Science March 2012, Vol.53, 6877. doi:
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      Timothy W. Corson, Kamakshi Sishtla; Towards a Novel Therapy for Uveal Melanoma: Targeting Oncogenic Gαq. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6877.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: : To develop a peptide ligand for an oncoprotein found in uveal melanoma. Recently, oncogenic mutations were identified in more than 80% of uveal melanoma in the genes GNAQ or GNA11, encoding heterotrimeric G-protein α subunits Gαq and Gα11, respectively. These mutations "lock" the proteins in the active, GTP-bound conformation, causing constitutive mitogenic signaling. Selective blockade ofthe function of these oncoproteins offers an appealing route to inhibition of proliferation in uveal melanoma, a chemoresistant cancer currently lacking targeted therapies.

Methods: : Phage display was used to find peptide ligands selective for the common Q209L mutant of human Gαq. Recombinant wild type and Q209L Gαq-glutathione S-transferase fusions were expressed in E. coli, and folding of the wild type protein was confirmed by binding of BODIPY-GTPγS. Recombinant proteins were used for phage display panning using a 12-mer M13 phage library, and binding confirmed by anti-M13enzyme-linked immunosorbent assays.

Results: : Multiple phage clones were isolated that showed preferential binding to Gαq Q209L over wild-type protein, while several clones bound preferentially to wild-type Gαq. Sequencing and consensus peptide identification is underway, to be followed by validation with synthetic peptides.

Conclusions: : We have identified peptide-expressing phage that bind Gαq Q209L. Validated, selective peptide ligands for Gαq Q209L can be used in fluorescence polarization displacement assays to find small-molecule ligands with similar binding modes, tested for cytotoxicity in GNAQ mutant cells, and/or linked to signals for targeted protein degradation. Selective targeting of oncogenic Gαq Q209L will open an importantnew avenue for development of novel therapies for uveal melanoma.

Keywords: melanoma • mutations • proteins encoded by disease genes 
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