scholarly journals Annexin A8 Regulates Late Endosome Organization and Function

2008 ◽  
Vol 19 (12) ◽  
pp. 5267-5278 ◽  
Author(s):  
Verena Goebeler ◽  
Michaela Poeter ◽  
Dagmar Zeuschner ◽  
Volker Gerke ◽  
Ursula Rescher
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Actin Filaments ◽  
Late Endosome ◽  
Endocytic Pathway ◽  
Mitogen Activated Protein Kinase ◽  
Late Endosomes ◽  
Endosomal Membranes ◽  
Epidermal Growth ◽  
And Function

Different classes of endosomes exhibit a characteristic intracellular steady-state distribution governed by interactions with the cytoskeleton. Late endosomes, organelles of the degradative lysosomal route, seem to require associated actin filaments for proper localization and function. We show here that the F-actin and phospholipid binding protein annexin A8 is associated specifically with late endosomes. Altering intracellular annexin A8 levels drastically affected the morphology and intracellular distribution of late endosomes. Trafficking through the degradative pathway was delayed in the absence of annexin A8, resulting in attenuated ligand-induced degradation of the epidermal growth factor receptor and prolonged epidermal growth factor-induced activation of mitogen-activated protein kinase. Depletion of annexin A8 reduced the association of late endosomal membranes with actin filaments. These results indicate that the defective cargo transport through the late endocytic pathway and the imbalanced signaling of activated receptors observed in the absence of annexin A8 results from the disturbed association of late endosomal membranes with the actin network, resulting in impaired actin-based late endosome motility.

scholarly journals The ESCRT-III Subunit hVps24 Is Required for Degradation but Not Silencing of the Epidermal Growth Factor Receptor

2006 ◽  
Vol 17 (6) ◽  
pp. 2513-2523 ◽  
Author(s):  
Kristi G. Bache ◽  
Susanne Stuffers ◽  
Lene Malerød ◽  
Thomas Slagsvold ◽  
Camilla Raiborg ◽  
...  
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Egf Receptor ◽  
Susceptibility Gene ◽  
Growth Factor Receptor ◽  
Mitogen Activated Protein Kinase ◽  
Endosomal Sorting ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Epidermal Growth

The endosomal sorting complexes required for transport, ESCRT-I, -II, and -III, are thought to mediate the biogenesis of multivesicular endosomes (MVEs) and endosomal sorting of ubiquitinated membrane proteins. Here, we have compared the importance of the ESCRT-I subunit tumor susceptibility gene 101 (Tsg101) and the ESCRT-III subunit hVps24/CHMP3 for endosomal functions and receptor signaling. Like Tsg101, endogenous hVps24 localized mainly to late endosomes. Depletion of hVps24 by siRNA showed that this ESCRT subunit, like Tsg101, is important for degradation of the epidermal growth factor (EGF) receptor (EGFR) and for transport of the receptor from early endosomes to lysosomes. Surprisingly, however, whereas depletion of Tsg101 caused sustained EGF activation of the mitogen-activated protein kinase pathway, depletion of hVps24 had no such effect. Moreover, depletion of Tsg101 but not of hVps24 caused a major fraction of internalized EGF to accumulate in nonacidified endosomes. Electron microscopy of hVps24-depleted cells showed an accumulation of EGFRs in MVEs that were significantly smaller than those in control cells, probably because of an impaired fusion with lyso-bisphosphatidic acid-positive late endosomes/lysosomes. Together, our results reveal functional differences between ESCRT-I and ESCRT-III in degradative protein trafficking and indicate that degradation of the EGFR is not required for termination of its signaling.

scholarly journals Activation of the Epidermal Growth Factor (EGF) Receptor Induces Formation of EGF Receptor- and Grb2-Containing Clathrin-Coated Pits

2006 ◽  
Vol 26 (2) ◽  
pp. 389-401 ◽  
Author(s):  
Lene E. Johannessen ◽  
Nina Marie Pedersen ◽  
Ketil Winther Pedersen ◽  
Inger Helene Madshus ◽  
Espen Stang
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Egf Receptor ◽  
Point Mutations ◽  
Adaptor Protein ◽  
Mitogen Activated Protein Kinase ◽  
Coated Pits ◽  
Α Subunit ◽  
Sh3 Domains ◽  
Epidermal Growth

ABSTRACT In HeLa cells depleted of adaptor protein 2 complex (AP2) by small interfering RNA (siRNA) to the μ2 or α subunit or by transient overexpression of an AP2 sequestering mutant of Eps15, endocytosis of the transferrin receptor (TfR) was strongly inhibited. However, epidermal growth factor (EGF)-induced endocytosis of the EGF receptor (EGFR) was inhibited only in cells where the α subunit had been knocked down. By immunoelectron microscopy, we found that in AP2-depleted cells, the number of clathrin-coated pits was strongly reduced. When such cells were incubated with EGF, new coated pits were formed. These contained EGF, EGFR, clathrin, and Grb2 but not the TfR. The induced coated pits contained the α subunit, but labeling density was reduced compared to control cells. Induction of clathrin-coated pits required EGFR kinase activity. Overexpression of Grb2 with inactivating point mutations in N- or C-terminal SH3 domains or in both SH3 domains inhibited EGF-induced formation of coated pits efficiently, even though Grb2 SH3 mutations did not block activation of mitogen-activated protein kinase (MAPK) or phosphatidylinositol 3-kinase (PI3K). Our data demonstrate that EGFR-induced signaling and Grb2 are essential for formation of clathrin-coated pits accommodating the EGFR, while activation of MAPK and PI3K is not required.

Interaction of epidermal growth factor with receptors on human and porcine thyroid membranes

1984 ◽  
Vol 102 (1) ◽  
pp. 57-61 ◽  
Author(s):  
H. Humphries ◽  
S. MacNeil ◽  
D. S. Munro ◽  
S. Tomlinson
Keyword(s):  
Enzyme Activity ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Binding Sites ◽  
Affinity Constant ◽  
Maximal Inhibition ◽  
High Affinity ◽  
Epidermal Growth ◽  
And Function ◽  
Bovine Tsh

ABSTRACT Recent evidence suggests that epidermal growth factor (EGF) may play an important role in the regulation of thyroid growth and function. We have examined the interaction of murine EGF (mEGF) with human and porcine thyroid membranes and compared this with the binding of bovine TSH (bTSH) using 125I-labelled hormones as tracers. The characteristics of the binding of mEGF were found to be similar for human and porcine thyroid membranes. Epidermal growth factor bound with high affinity (affinity constant = 1·4 × 109 l/mol); the density of binding sites was low compared with the TSH receptor. At 37 °C, the binding of 125I-labelled EGF was maximal at 1 h and was saturable in the presence of unlabelled EGF; half-maximal inhibition was at 1 ng EGF/tube (0·5 nmol/l) using 0·5 mg membrane protein/tube. Unlabelled bTSH had no effect on the binding of labelled EGF. Similarly, unlabelled EGF did not affect the binding of labelled TSH; hence it was concluded that mEGF and bTSH bound to independent sites. Epidermal growth factor had no effect on adenylate cyclase activity in membranes prepared from human non-toxic goitre; increasing concentrations of EGF did not affect basal, TSH-stimulated or fluoride-stimulated enzyme activity. J. Endocr. (1984) 102, 57–61

Epidermal Growth Factor Modulates Thyroid Growth and Function in Culture*

Endocrinology ◽  
1983 ◽  
Vol 112 (5) ◽  
pp. 1680-1686 ◽  
Author(s):  
K. WESTERMARK ◽  
F. A. KARLSSON ◽  
B. WESTERMARK
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Epidermal Growth ◽  
And Function

Lack of effect of epidermal growth factor treatment in late-pregnant ewes on subsequent lactation

1991 ◽  
Vol 58 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Christine B. Gow ◽  
Debbi J. Singleton ◽  
Mervyn J. Silvapulle ◽  
G. Philip M. Moore
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Mammary Gland Development ◽  
Epidermal Growth Factor Treatment ◽  
Epidermal Growth ◽  
And Function ◽  
And Control ◽  
Gland Development ◽  
Mean Concentration ◽  
Growth Factor Treatment

SummaryTwin-bearing ewes were treated with epidermal growth factor (EGF) to determine its effect on mammogenesis and resultant milk production and composition. The EGF was infused intravenously at a dose rate of O5 mg/d in 300 ml saline between days 117 and 139 of gestation; control animals received placebo infusions of saline. All animals then received continuous infusions of 300 ml/d saline on days 139–144. Following parturition 1–5 d later, ewes were milked by hand for 10 d and thereafter were machine-milked until day 16 of lactation. At this level of treatment, EGF was not detected in the circulation during infusion and feed intake was not affected. All ewes gave birth to healthy twin lambs. There were no effects of EGF on birth weights of lambs, live weights of ewes or lengths of gestation. An EGF immunoreactive material was detected in the mammary secretions of control ewes at a mean concentration of 2 μg/l on day 1 of lactation. Two ewes had detectable levels on day 2, but none was found in the milk thereafter. In the EGF-infused group, concentrations of EGF in colostrum were ñ 10 times higher than in the control ewes on day 1 of lactation and EGF was detected in mammary secretions on day 2 but not in subsequent milk samples. A range of 0·3–0·5% of the EGF infused appeared in mammary secretions over the first 2 d of lactation. No other differences were observed for colostrum composition, subsequent milk yield or composition between the two groups of ewes indicating that mammary gland development and function were unaffected. The levels of EGF observed in the mammary secretions of treated and control ewes indicate that the mammary glands accumulate and store EGF in the pre partum period.

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