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EGF, but not TGF alpha, efficiently induces degradation of the EGF receptor (EGFR). We show that EGFR was initially polyubiquitinated to the same extent upon incubation with EGF and TGF alpha, whereas the ubiquitination was more sustained by incubation with EGF than with TGF alpha. Consistently, the ubiquitin ligase c-Cbl was recruited to the plasma(More)
After endocytosis, some membrane proteins recycle from early endosomes to the plasma membrane whereas others are transported to late endosomes and lysosomes for degradation. Conjugation with the small polypeptide ubiquitin is a signal for lysosomal sorting. Here we show that the hepatocyte growth factor-regulated tyrosine kinase substrate, Hrs, is involved(More)
Ligand binding causes the EGF receptor (EGFR) to become ubiquitinated by Cbl upon association with the adaptor protein Grb2. We have investigated the role of ubiquitin and Grb2 in ligand-induced endocytosis of the EGFR. Incubation of cells with EGF on ice caused translocation of Grb2 and Cbl from the cytosol to the rim of coated pits. Grb2 with point(More)
Diphtheria toxin B fragment is capable of forming cation-selective channels in the plasma membrane. Such channels may be involved in the translocation of the toxin A fragment to the cytosol. Seven negatively charged amino acids in the B fragment were replaced one by one by lysines, followed by studies of cytotoxicity and channel-forming ability of the(More)
We have investigated the localization and function of the epidermal growth factor receptor (EGFR) in normal cells, in cholesterol-depleted cells and in cholesterol enriched cells. Using immunoelectron microscopy we find that the EGFR is randomly distributed at the plasma membrane and not enriched in caveolae. Binding of EGF at 4 degrees C does not change(More)
Potassium depletion after a brief exposure of the cells to hypotonic medium was used to inhibit endocytosis from coated pits in Hep 2 cells. After such treatment the endocytic uptake of transferrin was arrested, and electron microscopy revealed that virtually no coated pits were present at the cell surface, while smooth (uncoated) pits were abundant. Under(More)
The anti-proliferative effect of the ErbB2 specific antibody Herceptin in cells overexpressing ErbB2 has previously been explained by endocytic downregulation of ErbB2. However, in the following, we demonstrate that Herceptin inhibited proliferation of ErbB2 overexpressing cells without downregulating ErbB2. Herceptin did also not induce endocytosis of(More)
The epidermal growth factor receptor (EGFR) and other members of the EGFR/ErbB receptor family of receptor tyrosine kinases (RTKs) are important regulators of proliferation, angiogenesis, migration, tumorigenesis and metastasis. Overexpression, mutations, deletions and production of autocrine ligands contribute to aberrant activation of the ErbB proteins.(More)
Epsin consists of an epsin NH(2)-terminal homology domain that promotes interaction with phospholipids, several AP-2-binding sites, two clathrin-binding sequences and several Eps15 homology domain-binding motifs. Epsin additionally possesses ubiquitin-interacting motifs (UIMs) and has been demonstrated to bind ubiquitinated cargo. We therefore investigated(More)