Substrate-based design of reversible Pin1 inhibitors

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• Human Pin1 is a peptidyl-prolyl cis/trans isomerase crucial for cell cycle progression.
• Pin1 specifically recognizes and acts on -Ser/Thr(PO(3)H(2))-Pro- motifs.
• Developing reversible Pin1 inhibitors is a therapeutic goal.

Purpose of the Study:

• To design reversible Pin1 inhibitors using a substrate structure-based approach.
• To systematically analyze the minimal structural requirements for Pin1 substrate recognition.
• To evaluate the inhibitory potential and stability of novel substrate analogue inhibitors.

Main Methods:

• Peptide-based substrate analysis to determine Pin1 recognition requirements.
• Direct UV-visible spectrophotometry to monitor prolyl isomerization kinetics.
• Enzyme kinetics (kcat/Km, Ki) and inhibition assays (IC50) were performed.
• Assessment of inhibitor stability in cell lysate against phosphatase activity.

Main Results:

• Pin1 exhibits catalysis for Ala-Pro, Ser-Pro, and Ser(PO(3)H(2))-Pro, with weak competitive inhibition.
• Optimal Pin1 and Ess1 substrate recognition involves five amino acid residues, with Ser(PO(3)H(2)) centrally located.
• A substrate analogue, Ac-Ala-Ala-Ser(PO(3)H(2))-Pro-Arg-NH-4-nitroanilide, showed efficient catalysis by Pin1 and Ess1.
• Substitutions like D-Ser(PO(3)H(2)) or thioxo amide bonds yielded potent reversible inhibitors with IC50 in the low micromolar range.
• The D-amino acid inhibitor demonstrated stability against phosphatase activity in cell lysate.

Conclusions:

• Minimal structural requirements for Pin1 substrate recognition were elucidated.
• Novel substrate analogue inhibitors of Pin1 were successfully designed and synthesized.
• These inhibitors exhibit potent reversible activity and enhanced stability, suggesting therapeutic promise.
• The findings provide a foundation for developing Pin1-targeted therapeutics for cell cycle-related diseases.