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Rescue of a pathogenic mutant human glucagon receptor by pharmacological chaperones

Run Yu1, Chun-Rong Chen, Xiaohong Liu

  • 1Division of Endocrinology and Carcinoid and Neuroendocrine Tumor Center, Cedars-Sinai Medical Center, B-131, 8700 Beverly Boulevard, Los Angeles, California 90048, USA. run.yu@cshs.org

Journal of Molecular Endocrinology
|June 14, 2012
PubMed

Insights

Mahvash disease, caused by a glucagon receptor (GCGR) mutation, may be treatable with pharmacological chaperones that partially restore normal receptor function. Novel glucagon analogs did not improve interaction with the mutant GCGR.

Area of Science:

  • Endocrinology
  • Molecular Biology
  • Genetics

Background:

  • A homozygous P86S mutation in the glucagon receptor (GCGR) causes Mahvash disease, characterized by hyperglucagonemia, alpha-cell hyperplasia, and neuroendocrine tumors.
  • The P86S mutant GCGR exhibits reduced activity due to mislocalization to the endoplasmic reticulum (ER) and impaired glucagon binding.

Purpose of the Study:

  • To investigate pharmacological chaperones for rescuing P86S mutant GCGR trafficking to the plasma membrane.
  • To develop novel glucagon analogs for improved interaction with the P86S mutant GCGR.

Main Methods:

  • Utilized enhanced green fluorescent protein-tagged P86S in HEK 293 cells for imaging and western blotting.
  • Employed molecular modeling to design novel glucagon analogs with alanine 19 substitutions (serine or asparagine).
  • Tested various compounds, including temperature shifts, osmotic chaperones, ER stressors (thapsigargin, curcumin), and a GCGR antagonist (L-168,049), for their rescue effects.

Main Results:

  • Incubation at 27°C and treatment with ER stressors partially restored P86S localization to the plasma membrane and improved processing.
  • The GCGR antagonist L-168,049 and compounds Cpd 13 and 15 also showed partial rescue effects.
  • Rescued P86S demonstrated increased glucagon-stimulated cAMP production and glucagon-induced internalization; however, novel glucagon analogs did not enhance cAMP production.

Conclusions:

  • Pharmacological chaperones, particularly temperature shifts and ER stressors, can partially rescue the P86S mutant GCGR.
  • These findings provide proof-of-principle for potential pharmacological chaperone therapy for Mahvash disease.
  • Novel glucagon analogs designed in this study failed to effectively interact with the P86S mutant GCGR.

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