scholarly journals Physical and Functional Interaction of Growth Hormone and Insulin-Like Growth Factor-I Signaling Elements

2004 ◽  
Vol 18 (6) ◽  
pp. 1471-1485 ◽  
Author(s):  
Yao Huang ◽  
Sung-Oh Kim ◽  
Ning Yang ◽  
Jing Jiang ◽  
Stuart J. Frank
Keyword(s):  
Growth Factor ◽  
Tyrosine Kinase ◽  
Tyrosine Phosphorylation ◽  
Intracellular Signaling ◽  
Kinase Inhibitor ◽  
Growth Factor Receptor ◽  
Janus Kinase ◽  
Intact Cells ◽  
Igf I

Abstract GH and IGF-I are critical regulators of growth and metabolism. GH interacts with the GH receptor (GHR), a cytokine superfamily receptor, to activate the cytoplasmic tyrosine kinase, Janus kinase 2 (JAK2), and initiate intracellular signaling cascades. IGF-I, produced in part in response to GH, binds to the heterotetrameric IGF-I receptor (IGF-IR), which is an intrinsic tyrosine kinase growth factor receptor that triggers proliferation, antiapoptosis, and other biological actions. Previous in vitro and overexpression studies have suggested that JAKs may interact with IGF-IR and that IGF-I stimulation may activate JAKs. In this study, we explore interactions between GHR-JAK2 and IGF-IR signaling pathway elements utilizing the GH and IGF-I-responsive 3T3-F442A and 3T3-L1 preadipocyte cell lines, which endogenously express both the GHR and IGF-IR. We find that GH induces formation of a complex that includes GHR, JAK2, and IGF-IR in these preadipocytes. The assembly of this complex in intact cells is rapid, GH concentration dependent, and can be prevented by a GH antagonist, G120K. However, it is not inhibited by the kinase inhibitor, staurosporine, which markedly inhibits GHR tyrosine phosphorylation. Moreover, complex formation does not appear dependent on GH-induced activation of the ERK or phosphatidylinositol 3-kinase signaling pathways or on the tyrosine phosphorylation of GHR, JAK2, or IGF-IR. These results suggest that GH-induced formation of the GHR-JAK2-IGF-IR complex is governed instead by GH-dependent conformational change(s) in the GHR and/or JAK2. We further demonstrate that GH and IGF-I can synergize in acute aspects of signaling and that IGF-I enhances GH-induced assembly of conformationally active GHRs. These findings suggest the existence of previously unappreciated relationships between these two hormones.

ARG tyrosine kinase activity is inhibited by STI571

Blood ◽  
2001 ◽  
Vol 97 (8) ◽  
pp. 2440-2448 ◽  
Author(s):  
Keiko Okuda ◽  
Ellen Weisberg ◽  
D. Gary Gilliland ◽  
James D. Griffin
Keyword(s):  
Growth Factor ◽  
Tyrosine Kinase ◽  
Tyrosine Kinase Inhibitor ◽  
Tyrosine Phosphorylation ◽  
Tyrosine Kinases ◽  
Kinase Inhibitor ◽  
Growth Factor Receptor ◽  
Kinase Domain ◽  
Fusion Partner ◽  
Induced Apoptosis

Abstract The tyrosine kinase inhibitor STI571 inhibits BCR/ABL and induces hematologic remission in most patients with chronic myeloid leukemia. In addition to BCR/ABL, STI571 also inhibits v-Abl, TEL/ABL, the native platelet-derived growth factor (PDGF)β receptor, and c-KIT, but it does not inhibit SRC family kinases, c-FMS, FLT3, the epidermal growth factor receptor, or multiple other tyrosine kinases. ARG is a widely expressed tyrosine kinase that shares substantial sequence identity with c-ABL in the kinase domain and cooperates with ABL to regulate neurulation in the developing mouse embryo. As described here, ARG has recently been implicated in the pathogenesis of leukemia as a fusion partner of TEL. A TEL/ARG fusion was constructed to determine whether ARG can be inhibited by STI571. When expressed in the factor-dependent murine hematopoietic cell line Ba/F3, the TEL/ARG protein was heavily phosphorylated on tyrosine, increased tyrosine phosphorylation of multiple cellular proteins, and induced factor-independent proliferation. The effects of STI571 on Ba/F3 cells transformed with BCR/ABL, TEL/ABL, TEL/PDGFβR, or TEL/ARG were then compared. STI571 inhibited tyrosine phosphorylation and cell growth of Ba/F3 cells expressing BCR/ABL, TEL/ABL, TEL/PDGFβR, and TEL/ARG with an IC50 of approximately 0.5 μM in each case, but it had no effect on untransformed Ba/F3 cells growing in IL-3 or on Ba/F3 cells transformed by TEL/JAK2. Culture of TEL/ARG-transfected Ba/F3 cells with IL-3 completely prevented STI571-induced apoptosis in these cells, similar to what has been observed with BCR/ABL- or TEL/ABL-transformed cells. These results indicate that ARG is a target of the small molecule, tyrosine kinase inhibitor STI571.

scholarly journals Platelet-Derived Growth Factor Receptor Association with Na+/H+ Exchanger Regulatory Factor Potentiates Receptor Activity

2000 ◽  
Vol 20 (22) ◽  
pp. 8352-8363 ◽  
Author(s):  
Stuart Maudsley ◽  
A. Musa Zamah ◽  
Nadeem Rahman ◽  
Jeremy T. Blitzer ◽  
Louis M. Luttrell ◽  
...  
Keyword(s):  
Growth Factor ◽  
Tyrosine Kinase ◽  
Intracellular Signaling ◽  
Pdz Domain ◽  
Growth Factor Receptor ◽  
Cell Types ◽  
Platelet Derived Growth Factor ◽  
Regulatory Factor ◽  
In Cells

ABSTRACT Platelet-derived growth factor (PDGF) is a potent mitogen for many cell types. The PDGF receptor (PDGFR) is a receptor tyrosine kinase that mediates the mitogenic effects of PDGF by binding to and/or phosphorylating a variety of intracellular signaling proteins upon PDGF-induced receptor dimerization. We show here that the Na+/H+ exchanger regulatory factor (NHERF; also known as EBP50), a protein not previously known to interact with the PDGFR, binds to the PDGFR carboxyl terminus (PDGFR-CT) with high affinity via a PDZ (PSD-95/Dlg/Z0-1 homology) domain-mediated interaction and potentiates PDGFR autophosphorylation and extracellular signal-regulated kinase (ERK) activation in cells. A point-mutated version of the PDGFR, with the terminal leucine changed to alanine (L1106A), cannot bind NHERF in vitro and is markedly impaired relative to the wild-type receptor with regard to PDGF-induced autophosphorylation and activation of ERK in cells. NHERF potentiation of PDGFR signaling depends on the capacity of NHERF to oligomerize. NHERF oligomerizes in vitro when bound with PDGFR-CT, and a truncated version of the first NHERF PDZ domain that can bind PDGFR-CT but which does not oligomerize reduces PDGFR tyrosine kinase activity when transiently overexpressed in cells. PDGFR activity in cells can also be regulated in a NHERF-dependent fashion by stimulation of the β2-adrenergic receptor, a known cellular binding partner for NHERF. These findings reveal that NHERF can directly bind to the PDGFR and potentiate PDGFR activity, thus elucidating both a novel mechanism by which PDGFR activity can be regulated and a new cellular role for the PDZ domain-containing adapter protein NHERF.

CHIR-258, a novel, multitargeted tyrosine kinase inhibitor for the potential treatment of t(4;14) multiple myeloma

Blood ◽  
2005 ◽  
Vol 105 (7) ◽  
pp. 2941-2948 ◽  
Author(s):  
Suzanne Trudel ◽  
Zhi Hua Li ◽  
Ellen Wei ◽  
Marion Wiesmann ◽  
Hong Chang ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Growth Factor ◽  
Tyrosine Kinase ◽  
Cell Lines ◽  
Kinase Inhibitor ◽  
Ectopic Expression ◽  
Growth Factor Receptor ◽  
Myeloma Cell ◽  
Class Iii

Abstract The t(4;14) translocation that occurs uniquely in a subset (15%) of patients with multiple myeloma (MM) results in the ectopic expression of the receptor tyrosine kinase (RTK), fibroblast growth factor receptor 3 (FGFR3). Inhibition of activated FGFR3 in MM cells induces apoptosis, validating FGFR3 as a therapeutic target in t(4;14) MM and encouraging the clinical development of FGFR3 inhibitors for the treatment of these patients, who have a poor prognosis. We describe here the characterization of a novel, small-molecule inhibitor of class III, IV, and V RTKs, CHIR-258, as an inhibitor of FGFR3. CHIR-258 potently inhibits FGFR3 with an inhibitory concentration of 50% (IC50) of 5 nM in in vitro kinase assays and selectively inhibited the growth of B9 cells and human myeloma cell lines expressing wild-type (WT) or activated mutant FGFR3. In responsive cell lines, CHIR-258 induced cytostatic and cytotoxic effects. Importantly, addition of interleukin 6 (IL-6) or insulin growth factor 1 (IGF-1) or coculture on stroma did not confer resistance to CHIR-258. In primary myeloma cells from t(4;14) patients, CHIR-258 inhibited downstream extracellular signal-regulated kinase (ERK) 1/2 phosphorylation with an associated cytotoxic response. Finally, therapeutic efficacy of CHIR-258 was demonstrated in a xenograft mouse model of FGFR3 MM. These studies support the clinical evaluation of CHIR-258 in MM.

Insulin-like growth factor I-dependent tyrosine kinase activity in stromal cells of human endometrium in vitro

1992 ◽  
Vol 262 (6) ◽  
pp. E863-E868
Author(s):  
H. Von Eye Corleta ◽  
T. Strowitzki ◽  
M. Kellerer ◽  
H. U. Haring
Keyword(s):  
Growth Factor ◽  
Tyrosine Kinase ◽  
Stromal Cells ◽  
Kinase Activity ◽  
Insulin Like Growth Factor ◽  
Intact Cells ◽  
Factor I ◽  
Igf I ◽  
Stimulation Of

The study was undertaken to identify and characterize insulin-like growth factor I (IGF-I) receptors in human endometrial stromal cells in culture and to examine whether these receptors are modulated by estradiol (E2) and/or progesterone (P). We found that partially purified plasma membrane proteins from these cells contain specific high-affinity binding sites for IGF-I (10 fmol/micrograms protein). Chemical cross-linking with 125I-labeled IGF-I and autophosphorylation with [32P]ATP-labeled proteins of relative molecular weight 135,000 and 95,000 correspond to the known Mr values of the alpha- and the beta-subunits of IGF-I receptors. Receptor autophosphorylation and phosphorylation of the substrate poly(Glu,Na4Tyr1) was stimulated in vitro by IGF-I (half-maximally at 1 nM, maximally at 100 nM). After stimulation of intact cells with IGF-I (5 nM) and subsequent partial purification of receptors in the presence of phosphatase inhibitors, a 2.5- to 3.6-fold stimulation of the kinase activity toward poly(Glu,Na4Tyr1) was found. Preincubation of the cells for 16 h with E2, P, and E2 + P did not modify the IGF-I binding characteristics nor the effect of IGF-I (5 nM) on tyrosine kinase stimulation in intact cells. This suggests that, in isolated humans, endometrial cell modulation of IGF-I receptor function by estrogen and P does not occur.

Involvement of Shc in insulin- and epidermal growth factor-induced activation of p21ras

1994 ◽  
Vol 14 (3) ◽  
pp. 1575-1581
Author(s):  
G J Pronk ◽  
A M de Vries-Smits ◽  
L Buday ◽  
J Downward ◽  
J A Maassen ◽  
...  
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Egf Receptor ◽  
Growth Factor Receptor ◽  
Nucleotide Exchange ◽  
Similar Time ◽  
Epidermal Growth

Shc proteins are phosphorylated on tyrosine residues and associate with growth factor receptor-bound protein 2 (Grb2) upon treatment of cells with epidermal growth factor (EGF) or insulin. We have studied the role of Shc in insulin- and EGF-induced activation of p21ras in NIH 3T3 cells overexpressing human insulin receptors (A14 cells). A14 cells are equally responsive to insulin and EGF with respect to activation of p21ras. Analysis of Shc immunoprecipitates revealed that (i) both insulin and EGF treatment resulted in Shc tyrosine phosphorylation and (ii) Shc antibodies coimmunoprecipitated both Grb2 and mSOS after insulin and EGF treatment. The induction of tyrosine phosphorylation of Shc and the presence of Grb2 and mSOS in Shc immunoprecipitates followed similar time courses, with somewhat higher levels after EGF treatment. In mSOS immunoprecipitates, Shc could be detected as well. Furthermore, Shc immune complexes contained guanine nucleotide exchange activity toward p21ras in vitro. From these results, we conclude that after insulin and EGF treatment, Shc associates with both Grb2 and mSOS and therefore may mediate, at least in part, insulin- and EGF-induced activation of p21ras. In addition, we investigated whether the Grb2-mSOS complex associates with the insulin receptor or with insulin receptor substrate 1 (IRS1). Although we observed association of Grb2 with IRS1, we did not detect complex formation between mSOS and IRS1 in experiments in which the association of mSOS with Shc was readily detectable. Furthermore, whereas EGF treatment resulted in the association of mSOS with the EGF receptor, insulin treatment did not result in the association of mSOS with the insulin receptor. These results indicate that the association of Grb2-nSOS with Shc may be an important event in insulin-induced, mSOS-mediated activation of p21ras.

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