Proteolytic processing of familial British dementia-associated BRI variants: evidence for enhanced intracellular accumulation of amyloidogenic peptides.
Different mutations in the BRI(2) gene cause rare neurodegenerative conditions, termed familial British dementia (FBD) and familial Danish dementia (FDD). The mutant genes encode BRI-L and BRI-D, the precursors of fibrillogenic ABri and ADan peptides, respectively. We previously reported that furin processes both BRI-L and its wild type counterpart, BRI, resulting in the secretion of C-terminal peptides; elevated levels of peptides were generated from BRI-L. In the present study, we show that inducible expression of alpha1-antitrypsin Portland, a furin inhibitor, inhibits the endoproteolysis of BRI and BRI-L in a dose-dependent manner. Moreover, comparison of the activities of several proprotein convertases reveals that furin is most efficient in endoproteolysis of BRI and BRI-L; PACE4, PC6A, PC6B, and LPC show much lower activities. Interestingly, LPC also exhibits enhanced cleavage of BRI-L compared with BRI. Finally, we demonstrate that BRI-D is also processed by furin and, like BRI-L, the cleavage of BRI-D is more efficient than that of BRI. Interestingly, while the ABri peptide is detected both intracellularly and in the medium, the ADan peptide accumulates predominantly in intracellular compartments. We propose that intracellular accumulation of amyloidogenic ADan or ABri peptides results in the neuronal damage leading to FDD and FBD, respectively.
Kim
Seong-Hun
SH
Department of Neurobiology, Pharmacology and Physiology, The University of Chicago, Chicago, Illinois 60637, USA.
Creemers
John W M
JW
Chu
Su
S
Thinakaran
Gopal
G
Sisodia
Sangram S
SS
D048868:Adaptor Proteins, Signal Transducing; D000682:Amyloid / Q000235:genetics / Q000378:metabolism*; D002451:Cell Compartmentation; D003704:Dementia / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009154:Mutation; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D000515:alpha 1-Antitrypsin / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D000682:Amyloid; C120083:ITM2B protein, human; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D010446:Peptide Fragments; D000515:alpha 1-Antitrypsin; C113421:alpha 1-antitrypsin Portland