title: Leptin receptor activation of SH2 domain containing protein tyrosine phosphatase 2 modulates Ob receptor signal transduction.
abstract: Leptin exerts its weight-reducing effects by binding to its receptor and activating signal transduction in hypothalamic neurons and other cell types. To identify the components of the leptin signal transduction pathway, an approach was developed in which bacterially expressed phosphorylated fragments of Ob receptor b (Ob-Rb) were used as affinity agents. Leptin binding to the Ob-Rb form of the leptin receptor leads to tyrosyl phosphorylation of the cytoplasmic domain of its receptor. Two of the three cytoplasmic tyrosines of Ob-Rb, at positions 985 and 1138, are phosphorylated after leptin treatment. Affinity chromatography using a tyrosine-phosphorylated fragment spanning Tyr 985 of Ob-Rb was used to identify proteins that bind to this site. The SH2 domain containing protein tyrosine phosphatase 2 (SHP-2) was isolated from bovine and mouse hypothalamus by using this method. After cotransfection of Ob-Rb, Janus kinase 2 (JAK2), and SHP-2 into 293T cells, leptin results in direct binding of SHP-2 to the phosphorylated Tyr 985. The bound SHP-2 is itself tyrosine phosphorylated after leptin treatment. SHP-2 is not phosphorylated after leptin treatment when a Y-->F 985 receptor mutant is cotransfected. In the absence of SHP-2 phosphorylation, the level of JAK2 phosphorylation was increased. Tyrosyl phosphorylation of the leptin receptor and signal transducer and activater of transcription 3 (STAT3) are not affected by phosphorylation of SHP-2. These data suggest that activation of SHP-2 by the leptin receptor results in a decreased phosphorylation of JAK2 and may act to attenuate leptin signal transduction. The method used in this report can in principle be used to isolate additional components of the leptin, or other, signal transduction pathway.
authors.affiliation: Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY, USA.
authors.forename: C
authors.initials: C
authors.lastname: Li
authors.forename: J M
authors.initials: JM
authors.lastname: Friedman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D047908:Intracellular Signaling Peptides and Proteins; D053614:Janus Kinase 2; D051379:Mice; D008969:Molecular Sequence Data; D009765:Obesity / Q000503:physiopathology*; D054648:Protein Phosphatase 2; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D015398:Signal Transduction; D014162:Transfection; D018909:src Homology Domains
chemical_list: D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; C515447:leptin receptor, mouse; D011505:Protein-Tyrosine Kinases; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D054648:Protein Phosphatase 2; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse; C509248:Ptpn6 protein, mouse; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases