Futter C E, Pearse A, Hewlett L J, Hopkins C R
Medical Research Council Laboratory for Molecular Cell Biology, University College, London, United Kingdom.
J Cell Biol. 1996 Mar;132(6):1011-23. doi: 10.1083/jcb.132.6.1011.
We have followed the transfer of EGF-EGF receptor (EGFR) complexes from endosomal vacuoles that contain transferrin receptors (TfR) to lysosome vacuoles identified by their content of HRP loaded as a 15-min pulse 4 h previously. We show that the HRP-loaded lysosomes are lysosomal-associated membrane protein-1 (LAMP-1) positive, mannose-6-phosphate receptor (M6PR) negative. and contain active acid hydrolase. EGF-EGFR complexes are delivered to these lysosomes intact and are then rapidly degraded. Preactivating the HRP contained within the preloaded lysosomes inhibits the delivery of EGFR and degradation of EGF, and results in the accumulation of EGFR-containing multivesicular bodies (MVB). With time these accumulating MVB undergo a series of maturation changes that include the loss of TfR, the continued recruitment of EGFR, and the accumulation of internal vesicles, but they remain LAMP-1 and M6PR negative. The mature MVB are often seen to make direct contact with lysosomes containing preactivated HRP, but their perimeter membranes remain intact. Together our observations suggest that the transfer of EGF-EGFR complexes from the TfR-containing endosome compartment to the lysosomes that degrade them employs a single vacuolar intermediate, the maturing MVB, and can be achieved by a single heterotypic fusion step.
我们追踪了表皮生长因子（EGF）-表皮生长因子受体（EGFR）复合物从含有转铁蛋白受体（TfR）的内体小泡向溶酶体小泡的转移过程，这些溶酶体小泡通过4小时前15分钟脉冲加载的辣根过氧化物酶（HRP）含量来鉴定。我们发现，加载HRP的溶酶体是溶酶体相关膜蛋白-1（LAMP-1）阳性、甘露糖-6-磷酸受体（M6PR）阴性，并且含有活性酸性水解酶。EGF-EGFR复合物完整地被递送至这些溶酶体，然后迅速降解。预激活预加载溶酶体内的HRP会抑制EGFR的递送和EGF的降解，并导致含有EGFR的多囊泡体（MVB）积累。随着时间推移，这些积累的MVB会经历一系列成熟变化，包括TfR的丢失、EGFR的持续募集以及内部小泡的积累，但它们仍然是LAMP-1和M6PR阴性。成熟的MVB常常被观察到与含有预激活HRP的溶酶体直接接触，但其周边膜保持完整。我们的观察结果共同表明，EGF-EGFR复合物从含TfR的内体区室向降解它们的溶酶体的转移利用了单一的液泡中间体，即成熟的MVB，并且可以通过单一的异型融合步骤实现。
