FE65 as a link between VLDLR and APP to regulate their trafficking and processing
1 Department of Neuroscience, Georgetown University Medical Center, 3970 Reservoir Road NW, Washington, DC 20057-1464, USA
2 Department of Neurology, Georgetown University Medical Center, 3970 Reservoir Road NW, Washington, DC 20057-1464, USA
3 Department of Pharmacology, Georgetown University Medical Center, 3970 Reservoir Road NW, Washington, DC 20057-1464, USA
4 Laboratory of Neuroscience, Graduate School of Pharmaceutical Science, Hokkaido University, Sapporo, Japan
5 Nathan Kline Institute for Psychiatric Research, Orangeburg, New York, USA
6 Department of Pharmacology, College of Medicine, Neuroscience Research Institute, MRC, Seoul National University, Seoul, South Korea
7 Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju 500-757, Republic of Korea
8 Genetics and Aging Research Unit, Mass General Institute for Neurodegenerative Disease, Harvard Medical School, Charlestown, MA
Molecular Neurodegeneration 2012, 7:9 doi:10.1186/1750-1326-7-9Published: 19 March 2012
Several studies found that FE65, a cytoplasmic adaptor protein, interacts with APP and LRP1, altering the trafficking and processing of APP. We have previously shown that FE65 interacts with the ApoE receptor, ApoER2, altering its trafficking and processing. Interestingly, it has been shown that FE65 can act as a linker between APP and LRP1 or ApoER2. In the present study, we tested whether FE65 can interact with another ApoE receptor, VLDLR, thereby altering its trafficking and processing, and whether FE65 can serve as a linker between APP and VLDLR.
We found that FE65 interacted with VLDLR using GST pull-down and co-immunoprecipitation assays in COS7 cells and in brain lysates. This interaction occurs via the PTB1 domain of FE65. Co-transfection with FE65 and full length VLDLR increased secreted VLDLR (sVLDLR); however, the levels of VLDLR C-terminal fragment (CTF) were undetectable as a result of proteasomal degradation. Additionally, FE65 increased cell surface levels of VLDLR. Moreover, we identified a novel complex between VLDLR and APP, which altered trafficking and processing of both proteins. Furthermore, immunoprecipitation results demonstrated that the presence of FE65 increased the interaction between APP and VLDLR in vitro and in vivo.
These data suggest that FE65 can regulate VLDLR trafficking and processing. Additionally, the interaction between VLDLR and APP altered both protein's trafficking and processing. Finally, our data suggest that FE65 serves as a link between VLDLR and APP. This novel interaction adds to a growing body of literature indicating trimeric complexes with various ApoE Receptors and APP.