Stimulation of c-Src by prolactin is independent of Jak2

1999 ◽  
Vol 345 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Juan Ángel FRESNO VARA ◽  
María Victoria CARRETERO ◽  
Haydée GERÓNIMO ◽  
Kurt BALLMER-HOFER ◽  
Jorge MARTÍN-PÉREZ
Keyword(s):  
Tyrosine Kinases ◽  
Kinase Domain ◽  
Receptor Phosphorylation ◽  
Kinase Activation ◽  
Cellular Targets ◽  
Juxtamembrane Region ◽  
Subsequent Activation ◽  
Src Family Tyrosine Kinases ◽  
Chicken Embryo Fibroblasts ◽  
Stimulation Of

Interaction of prolactin (PRL) with its receptor (PRLR) leads to activation of Jak and Src family tyrosine kinases. The PRL/growth hormone/cytokine receptor family conserves a proline-rich sequence in the cytoplasmic juxtamembrane region (Box 1) required for association and subsequent activation of Jaks. In the present work, we studied the mechanisms underlying c-Src kinase activation by PRL and the role that Jak2 plays in this process. PRL addition to chicken embryo fibroblasts (CEF) expressing the rat PRLR long form resulted in activation of c-Src and Jak2 and in tyrosine phosphorylation of the receptor. Receptor phosphorylation was due to associated Jak2, since in cells expressing either a Box 1 mutated PRLR (PRLR4P-A), which is unable to interact with Jak2, or a kinase-domain-deleted Jak2 (Jak2∆k), PRL did not stimulate receptor phosphorylation. Interestingly, addition of PRL to cells expressing PRLR4P-A resulted in an activation of c-Src equivalent to that observed with the wild-type receptor. These findings indicate that PRL-mediated stimulation of c-Src was independent of Jak2 activation and of receptor phosphorylation. Our results suggest that PRL-activated Src could send signals to downstream cellular targets independently of Jak2.

scholarly journals Phosphorylation of Tyrosine Residues in the Kinase Domain and Juxtamembrane Region Regulates the Biological and Catalytic Activities of Eph Receptors

2000 ◽  
Vol 20 (13) ◽  
pp. 4791-4805 ◽  
Author(s):  
Kathleen L. Binns ◽  
Paul P. Taylor ◽  
Frank Sicheri ◽  
Tony Pawson ◽  
Sacha J. Holland
Keyword(s):  
Tyrosine Kinases ◽  
Biological Activities ◽  
Phosphorylation Site ◽  
Kinase Domain ◽  
Kinase Assay ◽  
Eph Receptors ◽  
Amino Acid Homology ◽  
Tyrosine Residues ◽  
Juxtamembrane Region ◽  
Activation Segment

ABSTRACT Members of the Eph family of receptor tyrosine kinases exhibit a striking degree of amino acid homology, particularly notable in the kinase and membrane-proximal regions. A mutagenesis approach was taken to address the functions of specific conserved tyrosine residues within these catalytic and juxtamembrane domains. Ligand stimulation of wild-type EphB2 in neuronal NG108-15 cells resulted in an upregulation of catalytic activity and an increase in cellular tyrosine phosphorylation, accompanied by a retraction of neuritic processes. Tyrosine-to-phenylalanine substitutions within the conserved juxtamembrane motif abolished these responses. The mechanistic basis for these observations was examined using the highly related EphA4 receptor in a continuous coupled kinase assay. Tandem mass spectrometry experiments confirmed autophosphorylation of the two juxtamembrane tyrosine residues and also identified a tyrosine within the kinase domain activation segment as a phosphorylation site. Kinetic analysis revealed a decreased affinity for peptide substrate upon substitution of activation segment or juxtamembrane tyrosines. Together, our data suggest that the catalytic and therefore biological activities of Eph receptors are controlled by a two-component inhibitory mechanism, which is released by phosphorylation of the juxtamembrane and activation segment tyrosine residues.

scholarly journals Two Distinct Phosphorylation Pathways Have Additive Effects on Abl Family Kinase Activation

2003 ◽  
Vol 23 (11) ◽  
pp. 3884-3896 ◽  
Author(s):  
Keith Q. Tanis ◽  
Darren Veach ◽  
Henry S. Duewel ◽  
William G. Bornmann ◽  
Anthony J. Koleske
Keyword(s):  
Tyrosine Kinases ◽  
Kinase Activity ◽  
Intramolecular Interactions ◽  
Activation Loop ◽  
Additive Effects ◽  
Nonreceptor Tyrosine Kinase ◽  
Kinase Activation ◽  
Surface Receptors ◽  
Nonreceptor Tyrosine Kinases ◽  
Stimulation Of

ABSTRACT The activities of the related Abl and Arg nonreceptor tyrosine kinases are kept under tight control in cells, but exposure to several different stimuli results in a two- to fivefold stimulation of kinase activity. Following the breakdown of inhibitory intramolecular interactions, Abl activation requires phosphorylation on several tyrosine residues, including a tyrosine in its activation loop. These activating phosphorylations have been proposed to occur either through autophosphorylation by Abl in trans or through phosphorylation of Abl by the Src nonreceptor tyrosine kinase. We show here that these two pathways mediate phosphorylation at distinct sites in Abl and Arg and have additive effects on Abl and Arg kinase activation. Abl and Arg autophosphorylate at several sites outside the activation loop, leading to 5.2- and 6.2-fold increases in kinase activity, respectively. We also find that the Src family kinase Hck phosphorylates the Abl and Arg activation loops, leading to an additional twofold stimulation of kinase activity. The autoactivation pathway may allow Abl family kinases to integrate or amplify cues relayed by Src family kinases from cell surface receptors.

scholarly journals Proline Residues in Cd28 and the Src Homology (Sh)3 Domain of Lck Are Required for T Cell Costimulation

1999 ◽  
Vol 190 (3) ◽  
pp. 375-384 ◽  
Author(s):  
Amy D. Holdorf ◽  
Jonathan M. Green ◽  
Steven D. Levin ◽  
Michael F. Denny ◽  
David B. Straus ◽  
...  
Keyword(s):  
T Cell ◽  
T Cell Receptor ◽  
Tyrosine Kinases ◽  
Cell Receptor ◽  
Kinase Activation ◽  
Cd28 Costimulation ◽  
Cell Membrane Proteins ◽  
Src Homology ◽  
Src Family Tyrosine Kinases ◽  
T Cell Membrane

The Src family tyrosine kinases Lck and Fyn are critical for signaling via the T cell receptor. However, the exact mechanism of their activation is unknown. Recent crystal structures of Src kinases suggest that an important mechanism of kinase activation is via engagement of the Src homology (SH)3 domain by proline-containing sequences. To test this hypothesis, we identified several T cell membrane proteins that contain potential SH3 ligands. Here we demonstrate that Lck and Fyn can be activated by proline motifs in the CD28 and CD2 proteins, respectively. Supporting a role for Lck in CD28 signaling, we demonstrate that CD28 signaling in both transformed and primary T cells requires Lck as well as proline residues in CD28. These data suggest that Lck plays an essential role in CD28 costimulation.

scholarly journals Intramolecular Regulatory Switch in ZAP-70: Analogy with Receptor Tyrosine Kinases

2005 ◽  
Vol 25 (12) ◽  
pp. 4924-4933 ◽  
Author(s):  
Tomas Brdicka ◽  
Theresa A. Kadlecek ◽  
Jeroen P. Roose ◽  
Alexander W. Pastuszak ◽  
Arthur Weiss
Keyword(s):  
Tyrosine Kinases ◽  
Protein Tyrosine Kinase ◽  
Catalytic Domain ◽  
Receptor Tyrosine Kinases ◽  
Kinase Domain ◽  
Sh2 Domains ◽  
Downstream Signaling ◽  
Juxtamembrane Region ◽  
Activated T Cell ◽  
Regulatory Effects

ABSTRACT ZAP-70, a Syk family cytoplasmic protein tyrosine kinase (PTK), is required to couple the activated T-cell antigen receptor (TCR) to downstream signaling pathways. It contains two tandem SH2 domains that bind to phosphorylated TCR subunits and a C-terminal catalytic domain. The region connecting the SH2 domains with the kinase domain, termed interdomain B, has previously been shown to have striking regulatory effects on ZAP-70 function, presumed to be due to the recruitment of key substrates. Paradoxically, deletion of interdomain B preserves ZAP-70 function. Recent structural studies of several receptor tyrosine kinases (RTKs) revealed that their juxtamembrane regions negatively regulate their catalytic activities. In EphB2 and several other RTKs, this autoinhibition depends upon interaction between the kinase domain and tyrosine residues within the juxtamembrane region. Autoinhibition is released when these tyrosines become phosphorylated following receptor stimulation. Sequence homology suggested analogous regulation for ZAP-70. Based on mutagenesis analysis of ZAP-70 interdomain B, we find that this region downregulates ZAP-70 catalytic activity in a similar manner as the juxtamembrane region of EphB2. Similar regulation was also noted for the related Syk kinase. These findings suggest that a general autoinhibitory mechanism employed by RTKs is also used by some cytoplasmic tyrosine kinases.

scholarly journals Transactivation of the Insulin-Like Growth Factor-I Receptor by Angiotensin II Mediates Downstream Signaling from the Angiotensin II Type 1 Receptor to Phosphatidylinositol 3-Kinase

Endocrinology ◽  
2004 ◽  
Vol 145 (6) ◽  
pp. 2978-2987 ◽  
Author(s):  
Peter Zahradka ◽  
Brenda Litchie ◽  
Ben Storie ◽  
Gail Helwer
Keyword(s):  
Smooth Muscle ◽  
Angiotensin Ii ◽  
Growth Factor ◽  
Pi3 Kinase ◽  
Phosphatidylinositol 3 Kinase ◽  
Receptor Phosphorylation ◽  
Kinase Activation ◽  
Igf I ◽  
Stimulation Of

Abstract Angiotensin II (AngII) activates phosphatidylinositol 3-kinase (PI3-kinase), a known effector of receptor tyrosine kinases. Treatment of smooth muscle cells with AngII has also been shown to promote phosphorylation of various tyrosine kinase receptors. We therefore investigated the relationship between AngII and IGF-I receptor activation in smooth muscle cells with a phosphorylation-specific antibody. Our experiments showed that IGF-I receptor phosphorylation was maximally stimulated within 10 min by AngII. Inclusion of an IGF-I-neutralizing antibody in the culture media did not prevent IGF-I receptor phosphorylation after AngII treatment, which argues that a paracrine/autocrine loop is not required. Furthermore, this process was blocked by losartan and 1-(1,1-dimethylethyl)-1-(4-methylphenyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine (PP-1), indicating stimulation of IGF-I receptor phosphorylation occurs via AngII type 1 receptor-dependent activation of Src kinase. The functional significance of IGF-I receptor transactivation was examined with selective inhibitors of the IGF-I receptor kinase (AG1024, AG538). When AngII-treated cells were incubated with AG1024 or AG538, phosphorylation of the regulatory p85 subunit of PI3-kinase was blocked. Furthermore, phosphorylation of the downstream factor p70S6K did not occur. In contrast, AG1024 did not prevent MAPK or Src kinase activation by AngII. AG1024 also did not inhibit AngII-dependent cell migration, although this process was blocked by inhibitors of the epidermal growth factor and platelet-derived growth factor receptors. Transactivation of the IGF-I receptor is therefore a critical mediator of PI3-kinase activation by AngII but is not required for stimulation of the MAPK cascade.

PDGF alpha-receptor mediated cellular responses are not dependent on Src family kinases in endothelial cells

1998 ◽  
Vol 111 (5) ◽  
pp. 607-614
Author(s):  
R. Hooshmand-Rad ◽  
K. Yokote ◽  
C.H. Heldin ◽  
L. Claesson-Welsh
Keyword(s):  
Endothelial Cells ◽  
Tyrosine Kinases ◽  
Src Family Kinases ◽  
Wild Type ◽  
Actin Reorganization ◽  
Aortic Endothelial Cells ◽  
Mutant Receptor ◽  
Juxtamembrane Region ◽  
Src Family Tyrosine Kinases ◽  
Type Receptor

Two novel autophosphorylation sites in the juxtamembrane region of the PDGF alpha-receptor, Tyr-572 and Tyr-574, were identified. A Y572/574F mutant PDGF (alpha)-receptor was generated and stably expressed in porcine aortic endothelial cells. In contrast to the wild-type receptor, the mutant receptor was unable to associate with or activate Src family tyrosine kinases. Tyrosine phosphorylated synthetic peptides representing the juxtamembrane sequence of the receptor dose-dependently inhibited the binding of Src family tyrosine kinases to the autophosphorylated PDGF alpha-receptor. The mutant receptor showed similar PDGF-induced kinase activity and ability to mediate mitogenicity, actin reorganization and chemotaxis as the wild-type receptor. Thus activation of Src family kinases by the PDGF alpha-receptor is not essential for PDGF-induced mitogenicity or actin reorganization.

scholarly journals Proapoptotic Function of the MET Tyrosine Kinase Receptor through Caspase Cleavage

2004 ◽  
Vol 24 (23) ◽  
pp. 10328-10339 ◽  
Author(s):  
David Tulasne ◽  
Julien Deheuninck ◽  
Filipe Calheiros Lourenco ◽  
Fabienne Lamballe ◽  
Zongling Ji ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Tyrosine Kinase ◽  
Cortical Neurons ◽  
Kinase Domain ◽  
Tyrosine Kinase Receptor ◽  
Caspase Cleavage ◽  
Cellular Targets ◽  
Juxtamembrane Region ◽  
Hepatocyte Growth

ABSTRACT The MET tyrosine kinase, the receptor of hepatocyte growth factor-scatter factor (HGF/SF), is known to be essential for normal development and cell survival. We report that stress stimuli induce the caspase-mediated cleavage of MET in physiological cellular targets, such as epithelial cells, embryonic hepatocytes, and cortical neurons. Cleavage occurs at aspartic residue 1000 within the SVD site of the juxtamembrane region, independently of the crucial docking tyrosine residues Y1001 or Y1347 and Y1354. This cleavage generates an intracellular 40-kDa MET fragment containing the kinase domain. The p40 MET fragment itself causes apoptosis of MDCK epithelial cells and embryonic cortical neurons, whereas its kinase-dead version is impaired in proapoptotic activity. Finally, HGF/SF treatment does not favor MET cleavage and apoptosis, confirming the known survival role of ligand-activated MET. Our results show that stress stimuli convert the MET survival receptor into a proapoptotic factor.

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