scholarly journals Endosomal receptor kinetics determine the stability of intracellular growth factor signalling complexes

2007 ◽  
Vol 402 (3) ◽  
pp. 537-549 ◽  
Author(s):  
A. Rami Tzafriri ◽  
Elazer R. Edelman
Keyword(s):  
Growth Factor ◽  
Cell Surface ◽  
Dissociation Constant ◽  
Specific Binding ◽  
Ph Dependence ◽  
Growth Factor Receptor ◽  
Factor Binding ◽  
Receptor Complexes ◽  
Growth Factor Signalling ◽  
The Stability

There is an emerging paradigm that growth factor signalling continues in the endosome and that cell response to a growth factor is defined by the integration of cell surface and endosomal events. As activated receptors in the endosome are exposed to a different set of binding partners, they probably elicit differential signals compared with when they are at the cell surface. As such, complete appreciation of growth factor signalling requires understanding of growth factor–receptor binding and trafficking kinetics both at the cell surface and in endosomes. Growth factor binding to surface receptors is well characterized, and endosomal binding is assumed to follow surface kinetics if one accounts for changes in pH. Yet, specific binding kinetics within the endosome has not been examined in detail. To parse the factors governing the binding state of endosomal receptors we analysed a whole-cell mathematical model of epidermal growth factor receptor trafficking and binding. We discovered that the stability of growth factor–receptor complexes within endosomes is governed by three primary independent factors: the endosomal dissociation constant, total endosomal volume and the number of endosomal receptors. These factors were combined into a single dimensionless parameter that determines the endosomal binding state of the growth factor–receptor complex and can distinguish different growth factors from each other and different cell states. Our findings indicate that growth factor binding within endosomal compartments cannot be appreciated solely on the basis of the pH-dependence of the dissociation constant and that the concentration of receptors in the endosomal compartment must also be considered.

Kinetics and Regulation of Tyrosine Phosphorylation of the Platelet Derived Growth Factor Receptor

1989 ◽  
Vol 75 (4) ◽  
pp. 362-366
Author(s):  
Lilia Alberghina ◽  
Renata Zippel ◽  
Enzo Martegani ◽  
Emmapaola Sturani
Keyword(s):  
Growth Factor ◽  
Cell Surface ◽  
Tyrosine Phosphorylation ◽  
Growth Factor Receptor ◽  
Growth Conditions ◽  
Platelet Derived Growth Factor ◽  
Dependent Manner ◽  
Pdgf Receptor ◽  
Receptor Complexes ◽  
Phosphorylated Form

Platelet derived growth factor (PDGF) interaction with the cells induces rapid tyrosine phosphorylation of the PDGF receptor in a dose dependent manner. At 37 °C phosphorylation of the receptor is followed by its dephosphorylation and internalization. It is observed that the higher the ligand concentration, the more transient is the response, and the observed kinetics are explained by a simple kinetic model. At 4 °C the phosphorylated form of the receptor is more stable; however, if PDGF is dissociated from the cell surface-associated ligand-receptor complexes, the receptors are rapidly dephosphorylated, indicating that phosphatases specific for phosphotyrosine groups are very active within the cells. In fact, addition of orthovanadate stabilizes the phosphorylated form of the receptor and helps in recognizing possible physiological substrates of the PDGF receptor kinase. The expression of PDGF receptors on the cell surface has been investigated under different growth conditions: a positive correlation exists between the amount of PDGF receptors and the duplication times of exponentially growing cultures. Moreover, during exponential growth the PDGF receptors are scarcely expressed, and their number increases reaching a maximal value when the population enters the stationary phase.

scholarly journals Heparan Sulfate Acts as a Bone Morphogenetic Protein Coreceptor by Facilitating Ligand-induced Receptor Hetero-oligomerization

2010 ◽  
Vol 21 (22) ◽  
pp. 4028-4041 ◽  
Author(s):  
Wan-Jong Kuo ◽  
Michelle A. Digman ◽  
Arthur D. Lander
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Cell Surface ◽  
Heparan Sulfate ◽  
Bone Morphogenetic Proteins ◽  
Growth Factor Receptor ◽  
In Vivo Studies ◽  
Type I ◽  
Receptor Complexes

Cell surface heparan sulfate (HS) not only binds several major classes of growth factors but also sometimes potentiates their activities—an effect usually termed “coreception.” A view that coreception is due to the stabilization of growth factor–receptor interactions has emerged primarily from studies of the fibroblast growth factors (FGFs). Recent in vivo studies have strongly suggested that HS also plays an important role in regulating signaling by the bone morphogenetic proteins (BMPs). Here, we provide evidence that the mechanism of coreception for BMPs is markedly different from that established for FGFs. First, we demonstrate a direct, stimulatory role for cell surface HS in the immediate signaling activities of BMP2 and BMP4, and we provide evidence that HS–BMP interactions are required for this effect. Next, using several independent assays of ligand binding and receptor assembly, including coimmunoprecipitation, cross-linking, and fluorescence fluctuation microscopy, we show that HS does not affect BMP binding to type I receptor subunits but instead enhances the subsequent recruitment of type II receptor subunits to BMP-type I receptor complexes. This suggests a view of HS as a catalyst of the formation of signaling complexes, rather than as a stabilizer of growth factor binding.

scholarly journals Phosphorylation of iRhom2 at the plasma membrane controls mammalian TACE-dependent inflammatory and growth factor signalling

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Adam Graham Grieve ◽  
Hongmei Xu ◽  
Ulrike Künzel ◽  
Paul Bambrough ◽  
Boris Sieber ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Growth Factor ◽  
Cell Surface ◽  
Secretory Pathway ◽  
Inflammatory Responses ◽  
Growth Factor Receptor ◽  
Primary Mouse ◽  
Mouse Macrophages ◽  
Growth Factor Signalling ◽  
Intercellular Signalling

Proteolytic cleavage and release from the cell surface of membrane-tethered ligands is an important mechanism of regulating intercellular signalling. TACE is a major shedding protease, responsible for the liberation of the inflammatory cytokine TNFα and ligands of the epidermal growth factor receptor. iRhoms, catalytically inactive members of the rhomboid-like superfamily, have been shown to control the ER-to-Golgi transport and maturation of TACE. Here, we reveal that iRhom2 remains associated with TACE throughout the secretory pathway, and is stabilised at the cell surface by this interaction. At the plasma membrane, ERK1/2-mediated phosphorylation and 14-3-3 protein binding of the cytoplasmic amino-terminus of iRhom2 alter its interaction with mature TACE, thereby licensing its proteolytic activity. We show that this molecular mechanism is responsible for triggering inflammatory responses in primary mouse macrophages. Overall, iRhom2 binds to TACE throughout its lifecycle, implying that iRhom2 is a primary regulator of stimulated cytokine and growth factor signalling.

scholarly journals FRMD8 promotes inflammatory and growth factor signalling by stabilising the iRhom/ADAM17 sheddase complex

2018 ◽  
Author(s):  
Ulrike Künzel ◽  
Adam G. Grieve ◽  
Yao Meng ◽  
Sally A. Cowley ◽  
Matthew Freeman
Keyword(s):  
Growth Factor ◽  
Cell Surface ◽  
Inflammatory Cytokine ◽  
Egf Receptor ◽  
Receptor Ligands ◽  
Ferm Domain ◽  
Human Macrophages ◽  
Mouse Tissues ◽  
N Terminus ◽  
Growth Factor Signalling

AbstractMany intercellular signals are synthesised as transmembrane precursors that are released by proteolytic cleavage (‘shedding’) from the cell surface. ADAM17, a membrane-tethered metalloprotease, is the primary shedding enzyme responsible for the release of the inflammatory cytokine TNFα and several EGF receptor ligands. ADAM17 exists in complex with the rhomboid-like iRhom proteins, which act as cofactors that regulate ADAM17 substrate shedding. Here we report that the poorly characterised FERM domain-containing protein FRMD8 is a new component of iRhom2/ADAM17 sheddase complex. FRMD8 binds to the cytoplasmic N-terminus of iRhoms, and is necessary to stabilise the iRhoms and ADAM17 beyond the Golgi. In the absence of FRMD8, iRhom2 and ADAM17 are degraded via the endolysosomal pathway, resulting in the reduction of ADAM17-mediated shedding. We have confirmed the pathophysiological significance of FRMD8 in iPSC-derived human macrophages and mouse tissues, thus demonstrating its role in the regulated release of multiple cytokine and growth factor signals.

Kinetic analysis of the downregulation of epidermal growth factor receptors in rats in vivo

1990 ◽  
Vol 258 (4) ◽  
pp. C593-C598 ◽  
Author(s):  
S. Yanai ◽  
Y. Sugiyama ◽  
T. Iga ◽  
T. Fuwa ◽  
M. Hanano
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Cell Surface ◽  
Kinetic Analysis ◽  
Intravenous Administration ◽  
Recovery Rate ◽  
Specific Binding ◽  
Control Level ◽  
Epidermal Growth

We previously clarified the specific binding sites for epidermal growth factor (EGF) in several organs in rats based on in vivo kinetic analysis (D. C. Kim, Y. Sugiyama, H. Sato, T. Fuwa, T. Iga, and M. Hanano. J. Pharm. Sci. 77: 200-207, 1988). In the present study, we have determined the extent of the receptor downregulation and the recovery rate of the available receptors for EGF in several organs in vivo. At the specified times (30 min-24 h) after intravenous administration of excess unlabeled EGF (300 micrograms/kg), the early-phase (less than 3 min) uptake clearances (k1) of the tracer amount of 125I-EGF, which are proportional to the cell-surface available receptor densities, were determined in the liver, kidney, duodenum, jejunum, ileum, stomach, and spleen. As the result, the k1 value in each organ at 30 min after intravenous administration of unlabeled EGF was lowered close to the receptor-independent clearance value, indicating that the cell-surface receptors were almost completely downregulated, and thereafter, the k1 value showed gradual recovery to the control level. Furthermore, the recovery half-lives showed interorgan differences, namely the half-life (20 min) in the liver was much shorter than those (2-4.5 h) in other organs. These results were considered to reflect the processes of the recycling of internalized EGF receptors to the cell-surface or recruitment of new receptors. It was concluded that the recovery rate of the downregulated receptors in the liver, which is most responsible for the plasma clearance of EGF, is much faster than those in other organs.

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