Identification of a Novel PSD-95/Dlg/ZO-1 (PDZ)-like Protein Interacting with the C Terminus of Presenilin-1

Abstract

Presenilin-1 (PS-1) is the most causative Alzheimer gene product, and its function is not well understood. In an attempt to elucidate the function of PS-1, we screened a human brain cDNA library for PS-1-interacting proteins using the yeast two-hybrid system and isolated a novel protein containing a PSD-95/Dlg/ZO-1 (PDZ)-like domain. This novel PS-1-associated protein (PSAP) shares a significant similarity with a Caenorhabditis elegans protein of unknown function. Northern blot analysis revealed that PSAP is predominantly expressed in the brain. Deletion of the first four C-terminal amino acid residues of PS-1, which contain the PDZ domain-binding motif (Gln-Phe-Tyr-Ile), reduced the binding activity of PS-1 toward PSAP 4-fold. These data suggest that PS-1 may associate with a PDZ-like domain-containing protein in vivo and thus may participate in receptor or channel clustering and intracellular signaling events in the brain.

Both the N-terminal fragment and the protein–protein interaction domain (PDZ domain) are required for the pro-apoptotic activity of presenilin-associated protein PSAP

“…Is the mitochondrial localization sufficient for the pro-apoptotic activity of PSAP? In this regard, it is notable that PSAP was thought to contain a putative PDZ domain [10] and that this putative PDZ domain remains intact in mutant NPDZ. Thus, we created a ΔCPDZ mutant in which, in addition to the Cterminal 67 amino acids, the PDZ domain was also deleted, and it was found that the proapoptotic activity of PSAP was completely abolished, though this mutant was still localized in mitochondria.…”

“…Interestingly, as in the case of PS2, the C-terminal fragment of PS1 was also found to inhibit Fas-induced apoptosis in Jurkat cells [9]. In an effort to understand the apoptotic regulatory effect of the C-terminal of PS1, we have identified a novel presenilin-associated protein (PSAP), which interacts with the C-terminal of PS1 [10]. Interestingly, in a subsequent study we found that PSAP is a pro-apoptotic protein that causes apoptosis when it is overexpressed [11].…”

CD47 and the 19 kDa Interacting Protein-3 (BNIP3) in T Cell Apoptosis

“…CD47ec-CD7 mutants and wild-type CD47 transfected cells showed comparable levels of Fas-induced apoptosis (result not shown). Note that the use of MMS domain as bait to perform the two-hybrid screen has already been successively performed (31)(32)(33)(34)(35)(36). In the present screen, five positive clones were selected of an estimated 5 ϫ 10 6 colonies, for their ability to reconstitute a functional Gal4 transcription complex.…”

Cellular FLICE-like Inhibitory Protein (c-FLIP) and PS1-associated Protein (PSAP) Mediate Presenilin 1-induced γ-Secretase-dependent and -independent Apoptosis, Respectively

“…This may be largely because, in contrast to PS1, PS2 does not interact with PSAP, as reported in our previous study (16).…”

“…Using a yeast two-hybrid system, our previous study identified PS1-associated protein (PSAP); this protein was subsequently found to be a mitochondrial proapoptotic molecule (16,17). This finding provides a direct molecular link between PS1 and the apoptotic pathway and opens a new avenue for studying the molecular mechanism by which PS-1 regulates apoptosis.…”