Localization of Leptin Binding Domain in the Leptin Receptor
- Tung Ming Fong1,
- Ruey-Ruey C. Huang1,
- Michael R. Tota1,
- Cheri Mao1,
- Tim Smith1,
- Jeff Varnerin1,
- Vladimir V. Karpitskiy2,
- James E. Krause1,2 and
- Lex H. T. Van der Ploeg1
- 1Merck Research Laboratories, Rahway, New Jersey 07065 (T.M.F., R.-R.C.H, M.R.T, C.M., T.S., J.V., L.H.T.V.d.P.), and 2Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110 (V.V.K., J.E.K)
Abstract
The leptin receptor is a member of the class I cytokine receptor family and is involved in the control of appetite and body weight. The predicted amino acid sequence of the extracellular region of the cloned leptin receptor differs from that of many other cytokine receptors in that it contains two homologous segments representing potential ligand binding sites. After the analysis of various deletion and substitution mutants of the leptin receptor, we found that the first potential binding motif is not required for leptin binding and receptor activation, whereas modification of the second potential binding motif can lead to inactive receptor mutants. Further deletion analysis generated a minimal binding domain that retains high affinity leptin binding. The leptin binding domain thus has been localized to residues 323–640, which contain the second segment of cytokine receptor domain/fibronectin type 3 domain (residues 428–635). Coexpression of the active isoform of leptin receptor (OB-Rb) with an inactive mutant lacking high affinity leptin binding site led to suppression of the activity mediated by OB-Rb, suggesting that the leptin receptor may exist as a multimeric complex in the absence of leptin.
Footnotes
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Send reprint requests to: Dr. T. M. Fong, Merck Research Laboratories, R80 M-213, P.O. Box 2000, Rahway, NJ 07065. E-mail: tung_fong{at}merck.com
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↵1 Current affiliation: Neurogen, Branford, CT 06405.
- Abbreviations:
- OB-Rb
- long form of leptin receptor
- C2
- immunoglobulin C2
- CK
- cytokine receptor
- ECD
- extracellular domain
- F3
- fibronectin type 3
- GH-R
- growth hormone receptor
- JAK
- Janus kinase
- OB-R
- leptin receptor
- OB-Ra
- the most common short form of leptin receptor
- min-BD
- minimal binding domain
- STAT
- signal transducer and activator of transcription
- EPO-R
- erythropoietin receptor
- GCSF-R
- granulocyte colony-stimulating factor receptor
- ELISA
- enzyme-linked immunosorbent assay
- CHO
- Chinese hamster ovary
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- Received May 2, 1997.
- Accepted October 24, 1997.
- The American Society for Pharmacology and Experimental Therapeutics
