Institute of Biochemistry, Biocenter, Goethe-University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany.
J Cell Sci. 2012 Sep 15;125(Pt 18):4230-40. doi: 10.1242/jcs.087346. Epub 2012 May 28.
TAPL (ABCB9) is a homodimeric polypeptide translocation machinery which transports cytosolic peptides into the lumen of lysosomes for degradation. Since the function of proteins is strongly dependent on the interaction network involved, we investigated the interactome of TAPL. A proteomic approach allowed identification of the lysosome-associated membrane proteins LAMP-1 and LAMP-2B as the most abundant interaction partners. Albeit with low frequency, major histocompatibility complex II subunits were also detected. The interaction interface with LAMP was mapped to the four-transmembrane helices constituting the N-terminal domain of TAPL (TMD0). The LAMP proteins bind independently to TAPL. This interaction has influence on neither subcellular localization nor peptide transport activity. However, in LAMP-deficient cells, the half-life of TAPL is decreased by a factor of five, whereas another lysosomal membrane protein, LIMP-2, is not affected. Reduced stability of TAPL is caused by increased lysosomal degradation, indicating that LAMP proteins retain TAPL on the limiting membrane of endosomes and prevent its sorting to intraluminal vesicles.
TAPL（ABCB9）是一种同二聚体多肽转运机制，可将胞质肽转运到溶酶体腔中进行降解。由于蛋白质的功能强烈依赖于所涉及的相互作用网络，因此我们研究了 TAPL 的相互作用组。一种蛋白质组学方法允许鉴定溶酶体相关膜蛋白 LAMP-1 和 LAMP-2B 作为最丰富的相互作用伙伴。尽管频率较低，但也检测到了主要组织相容性复合体 II 亚基。与 LAMP 的相互作用界面映射到构成 TAPL（TMD0）N 端结构域的四个跨膜螺旋。LAMP 蛋白独立地与 TAPL 结合。这种相互作用既不影响亚细胞定位也不影响肽转运活性。然而，在 LAMP 缺陷细胞中，TAPL 的半衰期减少了五倍，而另一种溶酶体膜蛋白 LIMP-2 不受影响。TAPL 的稳定性降低是由于溶酶体降解增加所致，表明 LAMP 蛋白将 TAPL 保留在内体膜上的限制膜上，并防止其分拣到腔内囊泡中。
