Lysosome sorting of ?-glucocerebrosidase by LIMP-2 is targeted by the mannose 6-phosphate receptor.

ABSTRACT: The integral membrane protein LIMP-2 has been a paradigm for mannose 6-phosphate receptor (MPR) independent lysosomal targeting, binding to ?-glucocerebrosidase (?-GCase) and directing it to the lysosome, before dissociating in the late-endosomal/lysosomal compartments. Here we report structural results illuminating how LIMP-2 binds and releases ?-GCase according to changes in pH, via a histidine trigger, and suggesting that LIMP-2 localizes the ceramide portion of the substrate adjacent to the ?-GCase catalytic site. Remarkably, we find that LIMP-2 bears P-Man9GlcNAc2 covalently attached to residue N325, and that it binds MPR, via mannose 6-phosphate, with a similar affinity to that observed between LIMP-2 and ?-GCase. The binding sites for ?-GCase and the MPR are functionally separate, so that a stable ternary complex can be formed. By fluorescence lifetime imaging microscopy, we also demonstrate that LIMP-2 interacts with MPR in living cells. These results revise the accepted view of LIMP-2-?-GCase lysosomal targeting.

SUBMITTER: Zhao Y 

PROVIDER: S-EPMC4104448 | biostudies-literature | 2014 Jul

REPOSITORIES: biostudies-literature