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Updated: Jun 17, 2026
Inducible and Reversible Dominant-negative (DN) Protein Inhibition
Published on: January 7, 2019
A heterozygous mutation in the third transmembrane domain causes a dominant-negative effect on signalling capability
Patrick Tarnow1, Anne Rediger, Harald Brumm
1Department of Pediatric Endocrinology, Charité, Campus Virchow-Klinikum - Universitatsmedizin Berlin, Berlin, Germany.
Background:
Heterozygous MC4R mutation is the most frequent cause of monogenic obesity. For most MC4R mutations a gene dosage effect seems to be the underlying mechanism. However, a dominant negative effect of a heterozygous MC4R mutation was recently identified, pointing to an additional mechanism of MC4R inactivation.
Methods:
The complete loss-of-function mutation (Ser136Phe), identified in a cohort of obese Austrian patients, was characterized for cell surface expression, signal transduction and ligand binding properties. Co-transfection studies tested for a dominant negative effect. Dimerization was investigated by a sandwich ELISA and by fluorescence resonance energy transfer (FRET) approach. Potential intramolecular interactions of Ser136 were studied by homologous receptor modelling based on the crystal structure of the beta2-adrenergic receptor.
Results:
The Ser136Phe mutation showed a dominant negative effect. The sandwich ELISA and FRET approach demonstrated dimerization of mutant and wild type receptor. Receptor modelling revealed an essential function of Ser136 at transmembrane helix 3 (TMH3) for establishing H-bonds between TMH2, TMH3, and TMH7. The mutation Ser136Phe most likely disrupts this network and leads to an incompetent helix-helix arrangement in the mutated receptor.
Conclusion:
Identification of dominant negative MC4R mutations is important to fully understand receptor function and to determine receptor regions that are involved in MC4R dimer activation.
Insights
A specific mutation in the melanocortin 4 receptor (MC4R) causes obesity through a dominant negative effect, disrupting receptor function. This finding reveals new insights into MC4R inactivation mechanisms and therapeutic targets for obesity.
Area of Science:
- Endocrinology
- Molecular Biology
- Genetics
Background:
- Heterozygous MC4R mutations are a primary cause of monogenic obesity.
- While gene dosage is a common mechanism, dominant negative effects offer an alternative explanation for MC4R inactivation.
Observation:
- The Ser136Phe mutation, found in obese patients, exhibits a dominant negative effect.
- This mutation leads to dimerization of mutant and wild-type MC4R receptors.
Findings:
- The Ser136Phe mutation disrupts crucial hydrogen bonds within the MC4R, affecting its structural integrity.
- Receptor modeling indicates Ser136 is vital for the helix-helix interactions necessary for MC4R function.
Implications:
- Understanding dominant negative MC4R mutations is key to comprehending MC4R function.
- This research identifies specific receptor regions involved in MC4R dimer activation, potentially leading to new therapeutic strategies for obesity.
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