Role of third intracellular loop of the melanocortin 4 receptor in the regulation of constitutive activity

Do Hun Kim, Seung Woo Shin, Ja Hyun Baik

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


The melanocortin 4 receptor (MC4R) has been reported to display constitutive activity, which is probably relevant to the maintenance of a normal energy balance. Among the clinically reported mutants of MC4R in human obesity patients, we investigated the functional characteristics of seven mutants characterized by mutations in the third intracellular (i3) loop of MC4R. Via a CRE (cAMP responsive element)-mediated luciferase reporter gene assay, we show that most of these mutants displayed significantly reduced basal activity with reduced reporter gene activity, whereas the P230L mutant manifested significantly increased basal activity. When the dominant negative Gs mutant was co-expressed, the majority of the mutants, including the P230L mutant, showed reduced basal activity. These results suggest that the i3 loop of MC4R is essential not only for the functional activity but also for the regulation and maintenance of an optimal constitutive activity of MC4R in association with G protein coupling, in the control of energy homeostasis.

Original languageEnglish
Pages (from-to)439-445
Number of pages7
JournalBiochemical and biophysical research communications
Issue number3
Publication statusPublished - 2008 Jan 18

Bibliographical note

Funding Information:
S.W. Shin and D.H. Kim are the recipients of a Brain Korea 21 program from the Korean Ministry of Education. This work was supported by a research grant from the 2003 Good Health R&D Project (Grant No. 03-PJ1-PG1-CH05-0005, A030078) from the Ministry of Health and Welfare, South Korea and by a grant from the Korea Science and Engineering Foundation (Grant R01-2007-000-20850-0) funded by the Research Program of the Korean Ministry of Science and Technology, South Korea.


  • Constitutive activity
  • G protein
  • Intracellular loop
  • Melanocortin
  • Melanocortin 4 receptor
  • Mutation
  • Obesity

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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