A Screen for Endocytic Motifs |
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| Authors: | Patrycja Kozik Richard W Francis Matthew N J Seaman Margaret S Robinson |
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| Institution: | 1. University of Cambridge, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK;2. Telethon Institute for Child Health Research, Centre for Child Health Research, The University of Western Australia, PO Box 855, West Perth, WA 6872, Australia |
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| Abstract: | Sorting signals for cargo selection into coated vesicles are usually in the form of short linear motifs. Three motifs for clathrin‐mediated endocytosis have been identified: YXXΦ, D/E]XXXLL/I] and FXNPXY. To search for new endocytic motifs, we made a library of CD8 chimeras with random sequences in their cytoplasmic tails, and used a novel fluorescence‐activated cell sorting (FACS)‐based assay to select for endocytosed constructs. Out of the five tails that were most efficiently internalized, only one was found to contain a conventional motif. Two contain dileucine‐like sequences that appear to be variations on the D/E]XXXLL/I] motif. Another contains a novel internalization signal, YXXXΦN, which is able to function in cells expressing a mutant µ2 that cannot bind YXXΦ, indicating that it is not a variation on the YXXΦ motif. Similar sequences are present in endogenous proteins, including a functional YXXXΦN (in addition to a classical YXXΦ) in cytotoxic T‐lymphocyte‐associated protein 4 (CTLA‐4). Thus, the repertoire of endocytic motifs is more extensive than the three well‐characterized sorting signals. |
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| Keywords: | AP‐2 cargo clathrin endocytosis sorting signals |
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