Signal transduction by the high-affinity GM-CSF receptor: two distinct cytoplasmic regions of the common beta subunit responsible for different signaling.

Abstract

The high‐affinity receptors for granulocyte‐macrophage colony stimulating factor (GM‐CSF), interleukin 3 (IL‐3) and IL‐5 consist of two subunits, alpha and beta. The alpha subunits are specific to each cytokine and the same beta subunit (beta c) is shared by these three receptors. Although none of these receptor subunits has intrinsic kinase activity, these cytokines induce protein tyrosine phosphorylation, activation of Ras, Raf‐1 and MAP kinase, and transcriptional activation of nuclear proto‐oncogenes such as c‐myc, c‐fos and c‐jun. In this paper, we describe a detailed analysis of the signaling potential of the beta c subunit by using a series of cytoplasmic deletion mutants. The human beta c consists of 881 amino acid residues. A C‐terminal deletion mutant of beta c at amino acid 763 (beta 763) induced phosphorylation of Shc and activation of Ras, Raf‐1, MAP kinase and p70 S6 kinase, whereas a deletion at amino acid 626 (beta 626) induced none of these effects. The beta 763 mutant, as well as the full‐length beta c, induced transcription of c‐myc, c‐fos and c‐jun. Deletions at amino acid 517 (beta 517) and 626 (beta 626) induced c‐myc and pim‐1, but no induction of c‐fos and c‐jun was observed. GM‐CSF increased phosphatidylinositol 3 kinase (PI3‐K) activity in anti‐phosphotyrosine immunoprecipitates from cells expressing beta 763 as well as beta c, whereas it was only marginally increased from cells expressing beta 517 or beta 626. Thus, there are at least two distinct regions within the cytoplasmic domain of beta c that are responsible for different signals, i.e. a membrane proximal region of approximately 60 amino acid residues upstream of Glu517 is essential for induction of c‐myc and pim‐1, and a distal region of approximately 140 amino acid residues (between Leu626 and Ser763) is required for activation of Ras, Raf‐1, MAP kinase and p70 S6 kinase, as well as induction of c‐fos and c‐jun.

IL-3 signaling and the role of Src kinases, JAKs and STATs: a covert liaison unveiled

“…Recent structure/function studies using the common b-chain of IL-3, GMCSF and IL-5 have shown that the cytoplasmic domain of this chain can be divided into two distinctive functional domains (Bagley et al, 1997;Woodcock et al, 1999). The membrane proximal intracellular portion of the receptor till amino-acid number 589, that includes the Box 1 region, was shown to be necessary and su cient for DNA synthesis mediated by several of these cytokines including IL-3 (Sato et al, 1993;Tian et al, 1996). This region was also found to be required for the induction of proliferation-associated genes such as c-myc, pim-1 and oncostatin M. Following cytokineinduced hetero-dimerization, this region of the receptor was found to bind to multiple signal-transducing proteins, which include JAKs, STATs, c-Src, phosphotidylinositol-3 kinase as well as Vav (Quelle et al, 1994;Jaster et al, 1997;Yoshimura et al, 1995Yoshimura et al, , 1998Rao and Mufson, 1995;Matsuguchi et al, 1995).…”

“…Upon IL-3 stimulation, the adaptor molecule Shc is rapidly phosphorylated and associates with the phosphorylated b c subunit of IL-3 (Sato et al, 1993;Pelicci et al, 1992;Blaikie et al, 1994). IL-3 stimulation also results in tyrosine phosphorylation of the inositol phosphatase (SHIP) which forms a complex with Shc, Grb2 and Sos, which are members of the Ras pathway (Lioubin et al, 1996).…”

“…The IL-3/IL-5 and GM-CSF cytokines induce a rapid activation of the lipid kinase phosphatidylinositol-3 kinase (PI3K) (Sato et al, 1993Co er et al, 1998a,b;Corey et al, 1993;Gold et al, 1994;al Shami et al, 1997). Interestingly, the same region of the b c chain that is responsible for the activation of the Ras pathway seems to be involved in signaling via the PI3K pathway (Sato et al, 1993).…”

Epidermal growth factor (EGF) suppresses staurosporine-induced apoptosis by inducing mcl-1 via the mitogen-activated protein kinase pathway

“…Phosphatidylinositol 3-kinase assay PI3-K assay was performed as described previously (Sato et al, 1993). In brief, 2.5610 6 cells were lysed in 0.5 ml lysis bu er (20 mM Tris, pH 8.0, 137 mM NaCl, 2.7 mM KCl, 1 mM MgCl 2 , 1 mM CaCl 2 , 1% NP-40, 10% glycerol, 1 mg/ ml bovine serum albumin, 1 mM phenylmethylsulfonyl uoride, 2 mg/ml aprotinin, and 2 mM sodium vanadate).…”

Recurring proviral integration suggests a role for proto-oncogene activation in thymomas induced with Mo-MuLV-rescued BCR/ABL virus

“…Cooperation between bcr-abl true, then this thymic transformation model may provide an and Pim-1 has not been previously demonstrated; however, important tool for identifying other genes that can influence the Pim-1-encoded serine kinase is an integral part of downthe pathogenesis of hematopoietic malignancies initiated by stream signaling from IL-2, IL-3 and GM-CSF receptors. [39][40][41] bcr-abl. Since expression of v-abl and bcr-abl kinases enables cells to survive and proliferate in the absence of these growth factors, …”