Premium
Differential Use of Two AP‐3‐mediated Pathways by Lysosomal Membrane Proteins
Author(s) -
Ihrke Gudrun,
Kyttälä Aija,
Russell Matthew R. G.,
Rous Brian A.,
Luzio J. Paul
Publication year - 2004
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2004.00236.x
Subject(s) - endosome , microbiology and biotechnology , biology , endocytosis , golgi apparatus , protein targeting , lamp1 , lysosome , endocytic cycle , signal transducing adaptor protein , membrane protein , endoplasmic reticulum , cell , biochemistry , signal transduction , membrane , intracellular , enzyme
The adaptor protein complex AP‐3 is involved in the sorting of lysosomal membrane proteins to late endosomes/lysosomes. It is unclear whether AP‐3‐containing vesicles form at the trans ‐Golgi network (TGN) or early endosomes. We have compared the trafficking routes of endolyn/CD164 and ‘typical’ lysosomal membrane glycoproteins (lgp120/lamp‐1 and CD63/lamp‐3) containing cytosolic YXXΦ‐targeting motifs preceded by asparagine and glycine, respectively. Endolyn, which has a NYHTL‐motif, is concentrated in lysosomes, but also occurs in endosomes and at the cell surface. We observed predominant interaction of the NYHTL‐motif with the μ‐subunits of AP‐3 in the yeast two‐hybrid system. Endolyn was mislocalized to the cell surface in AP‐3‐deficient pearl cells, confirming a major role of AP‐3 in endolyn traffic. However, lysosomal delivery of endolyn (or a NYHTL‐reporter), but not GYXXΦ‐containing proteins, was practically abolished when AP‐2‐mediated endocytosis or traffic from early to late endosomes was inhibited in NRK and 3T3 cells. This indicates that endolyn is mostly transported along the indirect lysosomal pathway (via the cell surface), rather than directly from the TGN to late endosomes/lysosomes. Our results suggest that AP‐3 mediates lysosomal sorting of some membrane proteins in early endosomes in addition to sorting of proteins with intrinsically strong AP‐3‐interacting lysosomal targeting motifs at the TGN.