Inger Helene Madshus

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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)
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)
The fact that cytoplasmic pH is strictly regulated has only been appreciated during the last 10 years. Eukaryotic cells clamp cytoplasmic pH at 7.0-7.4 by ion transport mechanisms and a high buffering capacity of the cytosol. The values of internal pH observed (pH 7.0-7.4) are higher than expected if the protons had been passively distributed across 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)
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)
Mutation of the binding site for Cbl (Tyr1045) in the EGF receptor (EGFR) results in impaired ubiquitination but does not affect EGFR internalization. However, the Y1045F mutation resulted in strongly decreased degradation of the EGFR, as well as efficient recycling of EGFR to the plasma membrane. Significantly, more wild-type EGFR than Y1045F EGFR was(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)
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; also known as ErbB1) is one of four related receptor tyrosine kinases. These receptors (EGFR, ErbB2, ErbB3 and ErbB4) are frequently overexpressed in cancer and such overexpression is associated with poor clinical outcome. Understanding the mechanisms involved in growth-factor-receptor downregulation is medically(More)
By constructing stably transfected cells harboring the same amount of epidermal growth factor (EGF) receptor (EGFR), but with increasing overexpression of ErbB2, we have demonstrated that ErbB2 efficiently inhibits internalization of ligand-bound EGFR. Apparently, ErbB2 inhibits internalization of EGF-bound EGFR by constitutively driving EGFR-ErbB2(More)