mu1A-adaptin-deficient mice: lethality, loss of AP-1 binding and rerouting of mannose 6-phosphate receptors |
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| Authors: | Meyer C Zizioli D Lausmann S Eskelinen E L Hamann J Saftig P von Figura K Schu P |
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| Affiliation: | Zentrum für Biochemie und Molekulare Zellbiologie, Dept. Biochemie II, Universit?t G?ttingen, Heinrich-Düker-Weg 12, D-37073 G?ttingen, Germany. |
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| Abstract: | The heterotetrameric AP-1 complex is involved in the formation of clathrin-coated vesicles at the trans-Golgi network (TGN) and interacts with sorting signals in the cytoplasmic tails of cargo molecules. Targeted disruption of the mouse mu1A-adaptin gene causes embryonic lethality at day 13.5. In cells deficient in micro1A-adaptin the remaining AP-1 adaptins do not bind to the TGN. Polarized epithelial cells are the only cells of micro1A-adaptin-deficient embryos that show gamma-adaptin binding to membranes, indicating the formation of an epithelial specific AP-1B complex and demonstrating the absence of additional mu1A homologs. Mannose 6-phosphate receptors are cargo molecules that exit the TGN via AP-1-clathrin-coated vesicles. The steady-state distribution of the mannose 6-phosphate receptors MPR46 and MPR300 in mu1A-deficient cells is shifted to endosomes at the expense of the TGN. MPR46 fails to recycle back from the endosome to the TGN, indicating that AP-1 is required for retrograde endosome to TGN transport of the receptor. |
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