Differential use of two AP-3-mediated pathways by lysosomal membrane proteins
Differential use of two AP-3-mediated pathways by lysosomal membrane proteins
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DOI：
10.1111/j.1600-0854.2004.00236.x
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发表时间：
2004-12-01
期刊：
影响因子：
4.5
通讯作者：
Luzio, JP
中科院分区：
文献类型：
--
作者：
Ihrke, G;Kyttälä, A;Luzio, JP
衔接蛋白复合物AP-3参与溶酶体膜蛋白到晚期内体/溶酶体的分选。目前还不清楚是否AP-3含有囊泡形成的高尔基体网络（TGN）或早期内体。我们已经比较了endolyn/CD 164和“典型的”溶酶体膜糖蛋白（lgp 120/lamp-1和CD 63/lamp-3）的运输途径，这些蛋白分别含有天冬酰胺和甘氨酸之前的胞质YXXPhi靶向基序。具有NYHTL基序的Endolyn集中在溶酶体中，但也存在于内体和细胞表面。在酵母双杂交系统中，我们观察到AP-3的mu亚基与NYHTL基序的主要相互作用。Endolyn错误定位于AP-3缺陷型珍珠细胞的细胞表面，证实了AP-3在endolyn运输中的主要作用。然而，当在NRK和3 T3细胞中抑制AP-2介导的内吞作用或从早期到晚期内体的运输时，溶酶体递送内毒素（或NYHTL-报告基因）而不是含有GYXXPhi的蛋白质实际上被废除。这表明，内皮素主要是沿着间接溶酶体途径（经由细胞表面）沿着转运，而不是直接从TGN转运到晚期内体/溶酶体。我们的研究结果表明，AP-3介导的一些膜蛋白在早期内体的溶酶体分选除了与内在强大的AP-3相互作用的溶酶体靶向基序在TGN的蛋白质的分选。
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 YXXPhi-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 mu-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 GYXXPhi-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.