Isolation of IL-2 Receptor-|[beta]| cDNA Clones from AtT-20 Pituitary Cells: Constitutive Expression and Role in Signal Transduction

摘要

Interleukin-2 (IL-2) has been shown to stimulate ACTH secretion by anterior pituitary cells and has been implicated in pathophysiological processes of the pituitary and brain in several major neuropsychiatric disorders. The present study tested the hypothesis that IL-2 receptor-β (IL-2Rβ), a constitutively expressed and essential subunit for IL-2 signaling in lymphocytes, is expressed by AtT-20 pituitary cells and involved in transducing intracellular signals induced by IL-2. We isolated and sequenced three overlapping IL-2Rβ cDNA clones from AtT-20 pituitary cells representing key regions of the gene protein coding sequence. These cDNA clones included conserved sequences shared by growth hormone and prolactin as well as intracytoplasmic Src and JAK family homology domains of nonreceptor protein tyrosine kinases essential for IL-2 signaling in lymphocytes. Their nucleotide sequences were 100% homologous with those expressed by lymphocytes (together they comprised 70% of the full length coding sequence). The IL-2Rβ gene is constitutively expressed by AtT-20 pituitary cells, and its transcription was upregulated after CRF stimulation. Species-specific Il-2 induced intracellular signals in AtT-20 cells known to be mediated by Il-2Rβ, including a transient increase in c-myc nuclear proto-oncogene transcription and the dose-dependent induction of DNA replication as measured by [3H]thymidine incorporation. The IL-2-induced DNA replication signal was not delivered by heat inactivated IL-2 and was partially blocked by a murine anti-IL-2Rβ monoclonal antibody. These studies suggest that IL-2Rβ may be a critical target involved in mediating the neuroimmunological actions of this prototypical cytokine in endocrine cells.