Reconstitution of γ‐secretase by truncated presenilin (PS) fragments revealed that PS C‐terminal transmembrane domain is critical for formation of γ‐secretase complex

Abstract

The presenilin (PS) complex, including PS, nicastrin (NCT), APH-1 and PEN-2, is essential for gamma-secretase activity. Previously, the PS C-terminal tail was shown to be essential for gamma-secretase activity. Here, to further understand the precise mechanism underlying the activation of gamma-secretase regulated by PS cofactors, we focused on the role of the PS1 C-terminal region including transmembrane domain (TM) 8 in gamma-secretase activity. For this purpose, we co-expressed C-terminally truncated PS1 (PS1DeltaC) completely lacking gamma-secretase activity and the PS1 C-terminal short fragment in PS-null cells, because the successful reconstitution of gamma-secretase activity in PS-null cells by the co-expression of PS1DeltaC and the PS1 C-terminal short fragment would allow us to investigate the role of the PS1 C-terminal region in gamma-secretase activity. We found that the exogenous expression of the PS1 C-terminal short fragment with NCT and APH-1 completely rescued a defect of the gamma-secretase activity of PS1DeltaC in PS-null cells. With this reconstitution system, we demonstrate that both TM8 and the PS1 C-terminal seven-amino-acid-residue tail are involved in the formation of the active gamma-secretase complex via the assembly of PS1 with NCT and APH-1.