Abrogation of Interleukin-3 Dependence of Myeloid Cells by the v-src Oncogene Requires SH2 and SH3 Domains Which Specify Activation of STATs

Abstract

The v-src oncogene encodes a nonreceptor tyrosine kinase. When this gene was expressed in the myeloblastic cell line 32Dcl3, it was found to abrogate interleukin-3 (IL-3) dependence of this cell line and to block its ability to terminally differentiate into granulocytes in response to granulocyte colony-stimulating factor (GCSF). In contrast, a highly related tyrosine kinase gene, v-fgr, fails to render this cell line IL-3 independent for growth or to block its ability to undergo terminal differentiation in the presence of GCSF. The active structural domains of v-src that are responsible for the abrogation of IL-3 dependence of myeloid cells and the mechanisms by which v-src transforms these cells are at present unclear. To identify the domains in v-src which are responsible for this activity, we constructed several chimeric recombinants between the v-src and the related It is becoming increasingly clear that hematopoietic cell growth and differentiation are mediated by a group of soluble factors known as cytokines (14,17,35). These molecules bind to their cognate receptors and mediate intracellular signal transduction events which result in the modulation of gene expression (13). During the past few years, new evidence has emerged to indicate that most cytokines transmit their signals via a new family of tyrosine kinases termed JAK kinases (7,31,35,38). To date, this family consists of four members, i.e., JAK-1, JAK-2, JAK-3, and TYK-2. These kinases, either alone or in conjunction with each other, appear to be responsible for effects mediated by several cytokines and neurokines (2,12,17,22,30,31,35). Current models suggest that interaction of cytokines with their receptors induces receptor dimerization, which increases the affinity of the cytoplasmic domain of the receptor for JAK kinases, resulting in a ligand-dependent increase of a complex that contains the receptors and JAK kinases. This results in activation of the JAK kinases through an event associated with tyrosine phosphorylation. The activated kinases appear to subsequently phosphorylate the receptors as well as cellular substrates, the most important of which are the STATs (signal transducers and activators of transcription). These transcription factors were originally described by Darnell et al. (7) as transcription factors associated with an interferon-mediated signaling mechanism. To date, six different STATs have been discovered, all of which seem to participate in cytokine-or growth hormone-mediated signal transduction (13,23).It is now well-established that several of the oncogenic tyrosine kinases belonging to the Src family have a profound effect on the cytokine dependence of hematopoietic cell lines (1, 26). Most notably, it has been demonstrated that constitutive expression of v-src and v-abl oncogenes in interleukin-3 (IL-3)-dependent myeloid cell lines renders them cytokine independent for growth (1,26,28,29). This alteration in growth factor dependence had suggested that these oncogenes might interfere with signal transduction pathways ...

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

“…IL-3/IL-5/GMCSF activation of hematopoietic cells appears to result predominantly in the activation of JAK-2, although JAK-1 and TYK-2 have also been found to be activated in certain cell systems Quelle et al, 1994;Lutticken et al, 1994;Chaturvedi et al, 1997Chaturvedi et al, , 1998Jaster et al, 1997). The membrane proximal region of the IL-3R b c chain is involved in association with the N-terminal region of JAK2.…”

“…These two proteins were originally discovered by Darnell's group in association with STAT-2 and a fourth protein termed p48, which constituted the multicomponent transcription factor ISGF3 (Darnell et al, 1994). STAT-3 also exists in two forms termed STAT3a and STAT3b with di erent transcriptional activation functions (Schaefer et al, 1995;Chaturvedi et al, 1997Chaturvedi et al, , 1998. STAT5 exists in two isoforms, termed as STAT5A and STAT5B (Mui et al, 1995a,b), which are encoded by two separate genes, which are tandemly linked on human chromosome 17 and mouse chromosome 11 (Lin et al, 1996;Copeland et al, 1995).…”

JAK-STAT signaling activated by Abl oncogenes

“…A recent report has suggested that the mechanism of BCR-Abl-induced STAT activation may be similar to Src (Chaturvedi et al, 1997). Like Src-induced STAT activation, the SH2 and SH3 domains of BCR-Abl are required for constitutive activation of STAT 5 by this oncoprotein (Chaturvedi et al, 1997;NieborowskaSkorska et al, 1999).…”

“…Like Src-induced STAT activation, the SH2 and SH3 domains of BCR-Abl are required for constitutive activation of STAT 5 by this oncoprotein (Chaturvedi et al, 1997;NieborowskaSkorska et al, 1999). These same studies did not explore the e ect of mutations in the carboxyl terminal portion of BCR-Abl on STAT activation.…”

STAT activation by the PDGF receptor requires juxtamembrane phosphorylation sites but not Src tyrosine kinase activation

“…Src family members may also regulate expression of genes through phosphorylation and activation of transcription factors known as STATs. Recently it was shown that an activated mutant of Src, v-Src, constitutively phosphorylates and activates STAT3, and that STAT3 phosphorylation is necessary for e cient transformation of cells by v-Src (Yu et al, 1995;Cao et al, 1996;Chaturvedi et al, 1997;Bromberg et al, 1998;Turkson et al, 1998). The phosphorylation of STAT3 by v-Src suggests that normal cellular Src may also phosphorylate STAT3 and directly regulate transcription.…”