Abstract
The protein tyrosine phosphatase SHP-2 has been proposed to serve as a regulator of leptin signaling, but its specific roles are not fully examined. To directly investigate the role of SHP-2, we employed dominant negative strategies in transfected cells. We show that a catalytically inactive mutant of SHP-2 blocks leptin-stimulated ERK phosphorylation by the long leptin receptor, ObRb. SHP-2, lacking two C-terminal tyrosine residues, partially inhibits ERK phosphorylation. We find similar effects of the SHP-2 mutants after examining stimulation of an ERK-dependent egr-1 promoter-construct by leptin. We also demonstrate ERK phosphorylation and egr-1 mRNA expression in the hypothalamus by leptin. Analysis of signaling by ObRb lacking intracellular tyrosine residues or by the short leptin receptor, ObRa, enabled us to conclude that two pathways are critical for ERK activation. One pathway does not require the intracellular domain of ObRb, whereas the other pathway requires tyrosine residue 985 of ObRb. The phosphatase activity of SHP-2 is required for both pathways, whereas activation of ERK via Tyr-985 of ObRb also requires tyrosine phosphorylation of SHP-2. SHP-2 is thus a positive regulator of ERK by leptin receptors, and both the adaptor function and the phosphatase activity of SHP-2 are critical for this regulation.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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CHO Cells
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Carrier Proteins / chemistry
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Carrier Proteins / metabolism*
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Cricetinae
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DNA-Binding Proteins / biosynthesis
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism
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Early Growth Response Protein 1
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Hypothalamus / metabolism
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Immediate-Early Proteins*
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Intracellular Signaling Peptides and Proteins
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Janus Kinase 2
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Leptin / pharmacology
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MAP Kinase Signaling System*
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Male
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Mice
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Mice, Inbred C57BL
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases / metabolism*
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Models, Biological
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Mutation
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Phosphorylation
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Promoter Regions, Genetic
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Protein Tyrosine Phosphatase, Non-Receptor Type 11
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Protein Tyrosine Phosphatase, Non-Receptor Type 6
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Protein Tyrosine Phosphatases / genetics
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Protein Tyrosine Phosphatases / physiology*
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Protein-Tyrosine Kinases / genetics
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Protein-Tyrosine Kinases / physiology
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Proto-Oncogene Proteins*
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RNA, Messenger / biosynthesis
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Receptors, Cell Surface*
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Receptors, Leptin
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STAT3 Transcription Factor
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Trans-Activators / metabolism
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Transcription Factors / biosynthesis
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Transcription Factors / genetics
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Transcription, Genetic
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Transfection
Substances
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Carrier Proteins
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DNA-Binding Proteins
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Early Growth Response Protein 1
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Egr1 protein, mouse
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Immediate-Early Proteins
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Intracellular Signaling Peptides and Proteins
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Leptin
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Proto-Oncogene Proteins
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RNA, Messenger
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Receptors, Cell Surface
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Receptors, Leptin
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STAT3 Transcription Factor
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Stat3 protein, mouse
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Trans-Activators
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Transcription Factors
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leptin receptor, mouse
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Protein-Tyrosine Kinases
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Jak2 protein, mouse
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Janus Kinase 2
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases
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Protein Tyrosine Phosphatase, Non-Receptor Type 11
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Protein Tyrosine Phosphatase, Non-Receptor Type 6
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Protein Tyrosine Phosphatases
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Ptpn11 protein, mouse
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Ptpn6 protein, mouse