title: The growth hormone receptor associates with Jak1, Jak2 and Tyk2 in human liver.
abstract: Studies in cell lines have shown that Jak2 is the primary tyrosine kinase involved in signal transduction by the growth hormone receptor (GHR). In addition, growth hormone (GH) stimulates tyrosine phosphorylation of Jak1 and Jak3 in certain cell lines, while the effect on Tyk2 has not been analysed. We have investigated the expression of Jak proteins in human liver and analysed their interactions with the GHR. Using Western blot analysis and immunohistochemistry, we demonstrate that Jak1, Jak2, Jak3 and Tyk2 are present in human liver. Immunoprecipitation by an antibody against the GHR (Mab 263) followed by immunoblotting with specific antibodies against Jak proteins showed that Jak1, Jak2 and Tyk2 were associated with the GHR in this tissue. We conclude that the GHR associates with Jak1, Jak2 and Tyk2 in human liver. Although experiments in vitro indicate that Jak2 mediates GH signalling, our results open the possibility that other Jak proteins may influence GHR signalling in human liver.
authors.affiliation: Research Center for Endocrinology and Metabolism, Department of Internal Medicine, Sahlgrenska University Hospital, Göteborg University, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Hellgren
authors.forename: J O
authors.initials: JO
authors.lastname: Jansson
authors.forename: L M
authors.initials: LM
authors.lastname: Carlsson
authors.forename: B
authors.initials: B
authors.lastname: Carlsson
mesh_terms: D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D006801:Humans; D007150:Immunohistochemistry; D018189:Immunomagnetic Separation; D053613:Janus Kinase 1; D053614:Janus Kinase 2; D008099:Liver / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000032:analysis / Q000378:metabolism*; D011506:Proteins / Q000032:analysis / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D011986:Receptors, Somatotropin / Q000378:metabolism*; D053634:TYK2 Kinase; D014162:Transfection
chemical_list: D011506:Proteins; D011518:Proto-Oncogene Proteins; D011986:Receptors, Somatotropin; D011505:Protein-Tyrosine Kinases; C507904:JAK1 protein, human; C507924:JAK2 protein, human; D053613:Janus Kinase 1; D053614:Janus Kinase 2; D053634:TYK2 Kinase; C070139:TYK2 protein, human