Abstract
Mutations of the leptin receptor have been found to cause obesity in rodents. The fa mutation that is responsible for obesity in Zucker rats is a missense mutation (269 gln-->pro) in the extracellular domain of the leptin receptor. We have characterized the effects of this mutation on the two major isoforms of the leptin receptor, Ob-Rb and Ob-Ra, by studying cell-surface expression, leptin binding affinity, signaling capacity, and receptor-mediated internalization and degradation of leptin in transfected mammalian cell lines. Both Ob-Rb(269 gln-->pro) and Ob-Ra(269 gln-->pro) have decreased cell-surface expression and decreased leptin binding affinity. Ob-Rb(269 gln-->pro) was shown to have defective signaling to the JAK-STAT pathway and markedly diminished ability to activate transcription of the egr-1 promoter. Constitutive ligand-independent activation of Ob-Rb(269 gln-->pro) was observed for activation of egr-1-luc but only under conditions when JAK2 was coexpressed with Ob-Rb(269 gln-->pro), Finally, Ob-Ra(269 gln-->pro) has an increased ability to internalize leptin but is less efficient at degrading leptin, as compared with Ob-Ra. In conclusion, both Ob-Ra(269 gln-->pro) and Ob-Rb(269 gln-->pro) have multiple functional defects.
Publication types
-
Research Support, Non-U.S. Gov't
-
Research Support, U.S. Gov't, P.H.S.
MeSH terms
-
Amino Acid Sequence
-
Animals
-
Binding, Competitive
-
CHO Cells
-
Carrier Proteins / genetics*
-
Carrier Proteins / metabolism
-
Carrier Proteins / physiology*
-
Cricetinae
-
DNA-Binding Proteins / genetics
-
DNA-Binding Proteins / physiology
-
Early Growth Response Protein 1
-
Humans
-
Immediate-Early Proteins*
-
Isomerism
-
Janus Kinase 2
-
Leptin
-
Mice
-
Mutation / physiology*
-
Obesity / genetics*
-
Obesity / physiopathology*
-
Oxidation-Reduction
-
Phosphorylation / drug effects
-
Promoter Regions, Genetic / genetics
-
Protein-Tyrosine Kinases / metabolism
-
Proteins / pharmacology
-
Proto-Oncogene Proteins*
-
Rats
-
Rats, Zucker / genetics*
-
Rats, Zucker / physiology*
-
Receptors, Cell Surface*
-
Receptors, Leptin
-
Recombinant Proteins
-
STAT3 Transcription Factor
-
Trans-Activators / physiology
-
Transcription Factors / genetics
-
Tyrosine / metabolism
Substances
-
Carrier Proteins
-
DNA-Binding Proteins
-
EGR1 protein, human
-
Early Growth Response Protein 1
-
Egr1 protein, mouse
-
Egr1 protein, rat
-
Immediate-Early Proteins
-
LEPR protein, human
-
Leptin
-
Proteins
-
Proto-Oncogene Proteins
-
Receptors, Cell Surface
-
Receptors, Leptin
-
Recombinant Proteins
-
STAT3 Transcription Factor
-
STAT3 protein, human
-
Stat3 protein, mouse
-
Stat3 protein, rat
-
Trans-Activators
-
Transcription Factors
-
leptin receptor, mouse
-
Tyrosine
-
Protein-Tyrosine Kinases
-
JAK2 protein, human
-
Jak2 protein, mouse
-
Jak2 protein, rat
-
Janus Kinase 2