The extreme C terminus of presenilin 1 is essential for gamma-secretase complex assembly and activity.
The gamma-secretase complex catalyzes the cleavage of the amyloid precursor protein in its transmembrane domain resulting in the formation of the amyloid beta-peptide and the cytoplasmic APP intracellular domain. The active gamma-secretase complex is composed of at least four subunits: presenilin (PS), nicastrin, Aph-1, and Pen-2, where the presence of all components is critically required for gamma-cleavage to occur. The PS proteins are themselves subjected to endoproteolytic cleavage resulting in the generation of an N-terminal and a C-terminal fragment that remain stably associated as a heterodimer. Here we investigated the effects of modifications on the C terminus of PS1 on PS1 endoproteolysis, gamma-secretase complex assembly, and activity in cells devoid of endogenous PS. We report that certain mutations and, in particular, deletions of the PS1 C terminus decrease gamma-secretase activity, PS1 endoproteolysis, and gamma-secretase complex formation. We demonstrate that the N- and C-terminal PS1 fragments can associate with each other in mutants having C-terminal truncations that cause loss of interaction with nicastrin and Aph-1. In addition, we show that the C-terminal fragment of PS1 alone can mediate interaction with nicastrin and Aph-1 in PS null cells expressing only the C-terminal fragment of PS1. Taken together, these data suggest that the PS1 N- and C-terminal fragment intermolecular interactions are independent of an association with nicastrin and Aph-1, and that nicastrin and Aph-1 interact with the C-terminal part of PS1 in the absence of an association with full-length PS1 or the N-terminal fragment.
Bergman
Anna
A
Karolinska Institutet, Department of Neurotec, Section for Experimental Geriatrics, SE-141 86 Huddinge and Karolinska Institutet, Department of Cell and Molecular Biology, Medical Nobel Institute, SE-171 77 Stockholm, Sweden.
Laudon
Hanna
H
Winblad
Bengt
B
Lundkvist
Johan
J
Näslund
Jan
J
D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; D019281:Dimerization; D010450:Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008562:Membrane Glycoproteins / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry* / Q000502:physiology; D020125:Mutation, Missense; D053764:Presenilin-1; D014162:Transfection
D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C508853:PSEN1 protein, human; C469349:PSENEN protein, human; D053764:Presenilin-1; C413604:nicastrin protein; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human