The two-hydrophobic domain tertiary structure of reticulon proteins is critical for modulation of beta-secretase BACE1.
beta-Site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) is a membrane-bound protease that is essential for the production of beta-amyloid protein (Abeta). Given the crucial role of Abeta accumulation in Alzheimer's disease (AD), inhibition of BACE1 activity may represent a feasible therapeutic strategy in the treatment of AD. Recently, we and others identified reticulon 3 (RTN3) and reticulon 4-B/C (RTN4-B/C or Nogo-B/C) as membrane proteins that interact with BACE1 and inhibit its ability to produce Abeta. In this study, we employed various mutants of RTN3 and RTN4-C and C. elegans RTN to investigate the molecular mechanisms by which RTNs regulate BACE1. We found that RTN3 mutants lacking the N-terminal or C-terminal or loop domain as well as a RTN4-C mutant lacking the C-terminal domain bound to BACE1 comparably to wild-type RTN3 and RTN4-C. Furthermore, overexpression of wild-type RTN3, RTN4-C, and these RTN mutants similarly reduced Abeta40 and Abeta42 secretion by cells expressing Swedish mutant APP. C. elegans RTN, which has low homology to human RTNs, also interacted with BACE1 and inhibited Abeta secretion. In contrast, two RTN3 mutants containing deletions of the first or second potential transmembrane domains and an RTN3 swap mutant of the second transmembrane domain bound BACE1 but failed to inhibit Abeta secretion. Collectively, these results suggest that the two-transmembrane-domain tertiary structure of RTN proteins is critical for the ability of RTNs to modulate BACE1 activity, whereas N-terminal, C-terminal and loop regions are not essential for this function.
Kume
Hideaki
H
Department of Demyelinating Disease and Aging, National Institute of Neuroscience, NCNP, Tokyo, Japan.
Murayama
Kiyoko S
KS
Araki
Wataru
W
D000544:Alzheimer Disease / Q000235:genetics; D053829:Amyloid Precursor Protein Secretases / Q000737:chemistry* / Q000502:physiology; D016229:Amyloid beta-Peptides / Q000235:genetics / Q000378:metabolism; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000737:chemistry* / Q000502:physiology; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry* / Q000502:physiology; D002352:Carrier Proteins / Q000737:chemistry* / Q000502:physiology; D002460:Cell Line; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007668:Kidney; D008565:Membrane Proteins / Q000737:chemistry* / Q000502:physiology; D009154:Mutation; D009185:Myelin Proteins / Q000737:chemistry* / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000502:physiology; D000070798:Nogo Proteins; D010446:Peptide Fragments / Q000378:metabolism; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000502:physiology; D017384:Sequence Deletion; D013329:Structure-Activity Relationship
D016229:Amyloid beta-Peptides; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D008565:Membrane Proteins; D009185:Myelin Proteins; D009419:Nerve Tissue Proteins; D000070798:Nogo Proteins; D010446:Peptide Fragments; C476198:RTN3 protein, human; C000603199:RTN4 protein, human; D011993:Recombinant Fusion Proteins; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42); D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human