Distinct Pharmacological Effects of Inhibitors of Signal Peptide Peptidase and γ-Secretase

Abstract

Signal peptide peptidase (SPP) and γ-secretase are intramembrane aspartyl proteases that bear similar active site motifs but with opposite membrane topologies. Both proteases are inhibited by the same aspartyl protease transition-state analogue inhibitors, further evidence that these two enzymes have the same basic cleavage mechanism. Here we report that helical peptide inhibitors designed to mimic SPP substrates and interact with the SPP initial substrate-binding site (the “docking site”) inhibit both SPP and γ-secretase, but with submicromolar potency for SPP. SPP was labeled by helical peptide and transition-state analogue affinity probes but at distinct sites. Nonsteroidal anti-inflammatory drugs, which shift the site by SPP and γ-secretase, the SPP γ-secretase by the helical peptide transition-state analogue the γ-secretase inhibited SPP by SPP by the helical peptide but SPP by the transition-state analogue to γ-secretase, the by the transition-state analogue but the helical peptide the to the both SPP and that the inhibitors helical anti-inflammatory drugs, and are distinct and and with SPP and Signal peptide peptidase (SPP) and γ-secretase are intramembrane aspartyl proteases that bear similar active site motifs but with opposite membrane topologies. Both proteases are inhibited by the same aspartyl protease transition-state analogue inhibitors, further evidence that these two enzymes have the same basic cleavage mechanism. Here we report that helical peptide inhibitors designed to mimic SPP substrates and interact with the SPP initial substrate-binding site (the “docking site”) inhibit both SPP and γ-secretase, but with submicromolar potency for SPP. SPP was labeled by helical peptide and transition-state analogue affinity probes but at distinct sites. Nonsteroidal anti-inflammatory drugs, which shift the site by SPP and γ-secretase, the SPP γ-secretase by the helical peptide transition-state analogue the γ-secretase inhibited SPP by SPP by the helical peptide but SPP by the transition-state analogue to γ-secretase, the by the transition-state analogue but the helical peptide the to the both SPP and that the inhibitors helical anti-inflammatory drugs, and are distinct and and with SPP and the for the and anti-inflammatory peptide anti-inflammatory peptide the the the the the and to the the membrane by and membrane and with for the the and and the the and the the the the and the the to by γ-secretase, aspartyl protease for the peptide peptidase (SPP) intramembrane aspartyl protease with to SPP membrane with the for and for the the the that SPP for to SPP and motifs that the active site and the these motifs the membrane and with the opposite opposite membrane the these two proteases are the the SPP inhibited by transition-state analogue inhibitors for γ-secretase and to γ-secretase, which cleavage by SPP cleavage the by peptidase we SPP which membrane and and we that anti-inflammatory the cleavage site SPP. shift the SPP cleavage site by was similar to that for γ-secretase cleavage that the site the γ-secretase at site the are SPP and γ-secretase, SPP with and SPP and the and to active SPP active γ-secretase the at SPP at site and SPP and γ-secretase for inhibitors for by intramembrane aspartyl we the inhibitors SPP and γ-secretase probes helical peptide transition-state analogue these two we with two γ-secretase and and that helical and SPP and γ-secretase distinct and peptide inhibitors by and by and by probes by peptide with to that SPP the two that the SPP was to the to SPP and with helical peptide and and and membrane for with the and cleavage was and are the two the SPP. 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