title: Multimeric growth hormone receptor complexes serve as signaling platforms.
abstract: Growth hormone (GH) signaling is required for promoting longitudinal body growth, stem cell activation, differentiation, and survival and for regulation of metabolism. Failure to adequately regulate GH signaling leads to disease: excessive GH signaling has been connected to cancer, and GH insensitivity has been reported in cachexia patients. Since its discovery in 1989, the receptor has served a pivotal role as the prototype cytokine receptor both structurally and functionally. Phosphorylation and ubiquitylation regulate the GH receptor (GHR) at the cell surface: two ubiquitin ligases (SCF(βTrCP2) and CHIP) determine the GH responsiveness of cells by controlling its endocytosis, whereas JAK2 initiates the JAK/STAT pathway. We used blue native electrophoresis to identify phosphorylated and ubiquitylated receptor intermediates. We show that GHRs occur as ∼500-kDa complexes that dimerize into active ∼900-kDa complexes upon GH binding. The dimerized complexes act as platforms for transient interaction with JAK2 and ubiquitin ligases. If GH and receptors are made in the same cell (autocrine mode), only limited numbers of ∼900-kDa complexes are formed. The experiments reveal the dynamic changes in post-translational modifications during GH-induced signaling events and show that relatively simple cytokine receptors like GHRs are able to form higher order protein complexes. Insight in the complex formation of cytokine receptors is crucially important for engineering cytokines that control ligand-induced cell responses and for generating a new class of therapeutic agents for a wide range of diseases.
authors.affiliation: From the Department of Cell Biology and Institute of Biomembranes, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Sedek
authors.forename: Lieke M
authors.initials: LM
authors.lastname: van der Velden
authors.forename: Ger J
authors.initials: GJ
authors.lastname: Strous
mesh_terms: D000818:Animals; D019898:Autocrine Communication / Q000502:physiology; D057809:HEK293 Cells; D019382:Human Growth Hormone / Q000235:genetics / Q000378:metabolism; D006801:Humans; D053614:Janus Kinase 2 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D055503:Protein Multimerization / Q000502:physiology*; D011986:Receptors, Somatotropin / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination / Q000502:physiology; D044844:beta-Transducin Repeat-Containing Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C471645:FBXW11 protein, human; C486774:Fbxw1b protein, mouse; D046912:Multiprotein Complexes; D011986:Receptors, Somatotropin; D044844:beta-Transducin Repeat-Containing Proteins; D019382:Human Growth Hormone; C467728:STUB1 protein, human; C492951:Stub1 protein, mouse; D044767:Ubiquitin-Protein Ligases; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2
keywords: Blue Native Electrophoresis; Cell Signaling; Cell Surface Receptor; Cytokine Action; Cytokine Receptor; Growth Hormone; Hexamers; JAK Kinase; JAK2; SCFβTrCP2