Figure 3.
The lysosomal degradation pathway of MVBs. (A) The microtubule system transports MVBs to the lysosome. The motor protein dynein at the plus end of the microtubule interacts with its regulatory factor, dynactin. At the same time, the p150Glued subunit of dynactin forms a complex with RILP, RAB7 and cholesterol-sensitive protein ORP1L in order to transport MVBs to the lysosomes located at the minus end of the microtubule. (B) The HOPS complex participates in the fusion of MVBs with lysosomes. The HOPS complex includes two RAB binding regions and a SNARE binding region. With the assistance of RILP, it can bind to RAB7 on both the MVBs and lysosomes and bring v-SNARE on the MVBs close to t-SNARE on the lysosomes. Once the two SNAREs are tightly tethered, MVBs fuse with the lysosome and are subsequently degraded.