scholarly journals Novel p62dok family members, dok-4 and dok-5, are substrates of the c-Ret receptor tyrosine kinase and mediate neuronal differentiation

2001 ◽  
Vol 154 (2) ◽  
pp. 345-354 ◽  
Author(s):  
Jan Grimm ◽  
Martin Sachs ◽  
Stefan Britsch ◽  
Silvana Di Cesare ◽  
Thomas Schwarz-Romond ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Neuronal Differentiation ◽  
Pc12 Cells ◽  
Receptor Tyrosine Kinase ◽  
Tyrosine Kinases ◽  
Family Members ◽  
Mitogen Activated Protein Kinase ◽  
New Family ◽  
Neuronal Tissues ◽  
Mitogen Activated Protein

Docking proteins are substrates of tyrosine kinases and function in the recruitment and assembly of specific signal transduction molecules. Here we found that p62dok family members act as substrates for the c-Ret receptor tyrosine kinase. In addition to dok-1, dok-2, and dok-3, we identified two new family members, dok-4 and dok-5, that can directly associate with Y1062 of c-Ret. Dok-4 and dok-5 constitute a subgroup of dok family members that is coexpressed with c-Ret in various neuronal tissues. Activated c-Ret promotes neurite outgrowth of PC12 cells; for this activity, Y1062 in c-Ret is essential. c-Ret/dok fusion proteins, in which Y1062 of c-Ret is deleted and replaced by the sequences of dok-4 or dok-5, induce ligand-dependent axonal outgrowth of PC12 cells, whereas a c-Ret fusion containing dok-2 sequences does not elicit this response. Dok-4 and dok-5 do not associate with rasGAP or Nck, in contrast to p62dok and dok-2. Moreover, dok-4 and dok-5 enhance c-Ret–dependent activation of mitogen-activated protein kinase. Thus, we have identified a subclass of p62dok proteins that are putative links with downstream effectors of c-Ret in neuronal differentiation.

scholarly journals Downregulation of the Ras–Mitogen-Activated Protein Kinase Pathway by the EphB2 Receptor Tyrosine Kinase Is Required for Ephrin-Induced Neurite Retraction

2001 ◽  
Vol 21 (21) ◽  
pp. 7429-7441 ◽  
Author(s):  
Sabine Elowe ◽  
Sacha J. Holland ◽  
Sarang Kulkarni ◽  
Tony Pawson
Keyword(s):  
Tyrosine Kinase ◽  
Receptor Tyrosine Kinase ◽  
Tyrosine Kinases ◽  
Receptor Tyrosine Kinases ◽  
Mapk Pathway ◽  
Neuronal Cells ◽  
Mitogen Activated Protein Kinase ◽  
Neurite Retraction ◽  
Mitogen Activated Protein ◽  
Stimulation Of

ABSTRACT Activation of the EphB2 receptor tyrosine kinase by clustered ephrin-B1 induces growth cone collapse and neurite retraction in differentiated NG108 neuronal cells. We have investigated the cytoplasmic signaling events associated with EphB2-induced cytoskeletal reorganization in these neuronal cells. We find that unlike other receptor tyrosine kinases, EphB2 induces a pronounced downregulation of GTP-bound Ras and consequently of the extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) pathway. A similar inhibition of the Ras-MAPK pathway was observed on stimulation of endogenous EphB2 in COS-1 cells. Inactivation of Ras, induced by ephrin B1 stimulation of NG108 neuronal cells, requires EphB2 tyrosine kinase activity and is blocked by a truncated form of p120-Ras GTPase-activating protein (p120-RasGAP), suggesting that EphB2 signals through the SH2 domain protein p120-RasGAP to inhibit the Ras-MAPK pathway. Suppression of Ras activity appears functionally important, since expression of a constitutively active variant of Ras impaired the ability of EphB2 to induce neurite retraction. In addition, EphB2 attenuated the elevation in ERK activation induced by attachment of NG108 cells to fibronectin, indicating that the EphB2 receptor can modulate integrin signaling to the Ras GTPase. These results suggest that a primary function of EphB2, a member of the most populous family of receptor tyrosine kinases, is to inactivate the Ras-MAPK pathway in a fashion that contributes to cytoskeletal reorganization and adhesion responses in neuronal growth cones.

scholarly journals Effects of epidermal growth factor and insulin on the activity of N-acetylglucosaminyltransferase V

1997 ◽  
Vol 324 (2) ◽  
pp. 543-545 ◽  
Author(s):  
Qiaohong WANG ◽  
Dapeng ZHOU ◽  
Dongmin SHAO ◽  
Zhonghou SHEN ◽  
Jianxin GU
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Tyrosine Kinase ◽  
Receptor Tyrosine Kinase ◽  
Protein Tyrosine Kinase ◽  
Kinase Activity ◽  
Mitogen Activated Protein Kinase ◽  
Receptor Protein ◽  
Mitogen Activated Protein ◽  
Epidermal Growth

When quiescent rat hepatocellular carcinoma 7919 cells were treated with epidermal growth factor (EGF) or insulin (stimulators of receptor tyrosine kinase activity), the activity of N-acetylglucosaminyltransferase V was increased. The effect of EGF reached a maximum after 10 min and remained high for 30 min, while the effect of insulin reached a maximum after 5 min and decreased after 15 min. Preincubation of the cells with 1-O-octadecyl-2-O-methylglycerophosphocholine (Et18-OH3), which blocked the activation of mitogen-activated protein kinase by EGF, also blocked the activation of N-acetylglucosamyltransferase V by this hormone, whereas the activation of N-acetylglucosamyltransferase V by insulin could not be blocked by Et18-OH3. Our results suggest that N-acetylglucosamyltransferase V may be regulated by different receptor protein tyrosine kinase pathways.

Tyrosine kinases regulate intracellular calcium during α2-adrenergic contraction in rat aorta

2002 ◽  
Vol 283 (4) ◽  
pp. H1673-H1680 ◽  
Author(s):  
Rebecca W. Carter ◽  
Nancy L. Kanagy
Keyword(s):  
Tyrosine Kinase ◽  
Tyrosine Kinases ◽  
Kinase Inhibitor ◽  
Growth Factor Receptor ◽  
Rat Aorta ◽  
Mitogen Activated Protein Kinase ◽  
Extracellular Signal ◽  
Mitogen Activated Protein ◽  
Intracellular Ca ◽  
Tyrphostin 23

We have demonstrated enhanced contractile sensitivity to the α2-adrenoreceptor (α2-AR) agonist UK-14304 in arteries from rats made hypertensive with chronic nitric oxide synthase (NOS) inhibition (LHR) compared with arteries from normotensive rats (NR); additionally, this contraction requires Ca2+ entry. We hypothesized that tyrosine kinases augment α2-AR contraction in LHR arteries by increasing Ca2+. The tyrosine kinase inhibitor tyrphostin 23 significantly attenuated UK-14304 contraction of denuded thoracic aortic rings from NR and LHR. However, tyrphostin 23 did not alter UK-14304 contraction in ionomycin-permeabilized aorta, which indicates that tyrosine kinases regulate intracellular Ca2+concentration. The Src family inhibitor PP1 and the epidermal growth factor receptor kinase inhibitor AG-1478 did not alter α2-AR contraction, whereas the mitogen-activated protein kinase extracellular signal-regulated kinase kinase inhibitor PD-98059 attenuated the contraction. Contraction to CaCl2 in ionomycin-permeabilized LHR rings was greater than in NR rings. UK-14304 augmented CaCl2 contraction in ionomycin-permeabilized rings from both groups but to a greater extent in LHR aorta. Together, these data suggest that α2-AR stimulates contraction via two pathways. One, which is enhanced with NOS inhibition hypertension, activates Ca2+ sensitivity and is independent of tyrosine kinases. The other is tyrosine kinase dependent and regulates intracellular Ca2+ concentration.

Tyrosine kinase-dependent calcium signaling in airway smooth muscle cells

2000 ◽  
Vol 278 (6) ◽  
pp. L1138-L1145 ◽  
Author(s):  
Barbara Tolloczko ◽  
Florence C. Tao ◽  
Mary E. Zacour ◽  
James G. Martin
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase ◽  
Tyrosine Kinase ◽  
Calcium Signaling ◽  
Tyrosine Phosphorylation ◽  
Airway Smooth Muscle ◽  
Tyrosine Kinases ◽  
Mitogen Activated Protein Kinase ◽  
Airway Smooth Muscle Cells ◽  
Mitogen Activated Protein

Contractile agonists may stimulate mitogenic responses in airway smooth muscle by mechanisms that involve tyrosine kinases. The role of contractile agonist-evoked activation of tyrosine kinases in contractile signaling is not clear. We addressed this issue using cultured rat airway smooth muscle cells. In these cells, serotonin (5-HT, 1 μM) caused contraction (quantitated by a decrease in cell area), which was blocked by the tyrosine kinase inhibitor genistein (40 μM). Genistein and tyrphostin 23 (40 and 10 μM, respectively) significantly decreased 5-HT-evoked peak Ca2+ responses, and the effect of genistein could be observed in the absence of extracellular Ca2+. The specific inhibitor of mitogen-activated protein kinase kinase PD-98059 (30 μM) had no significant effect on peak Ca2+ levels. Western analysis of cell extracts revealed that 5-HT caused a significant increase in tyrosine phosphorylation of proteins with molecular masses of ∼70 kDa within 10 s of stimulation but no measurable tyrosine phosphorylation of the γ isoform of phospholipase C (PLC-γ). Tyrosine phosphorylation was inhibited by genistein. Furthermore, genistein (40 μM) significantly attenuated 5-HT-induced inositol phosphate production. We conclude that in airway smooth muscle contractile agonists acting on G protein-coupled receptors may activate tyrosine kinase(s), which in turn modulate calcium signaling by affecting, directly or indirectly, PLC-β activity. It is unlikely that PLC-γ or the mitogen-activated protein kinase pathway is involved in Ca2+ signaling to 5-HT.

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