Cyclic cis-Locked Phospho-Dipeptides Reduce Entry of AβPP into Amyloidogenic Processing Pathway

Area of Science:

• Biochemistry
• Neuroscience
• Drug Discovery

Background:

• The cis/trans isomerization of X-Pro peptide bonds can function as a molecular switch in biological processes.
• The cis isomer of the phospho-Thr668-Pro669 motif in amyloid-β protein precursor (AβPP) correlates with increased amyloidogenic processing and production of neurotoxic amyloid-beta (Aβ) in Alzheimer's disease (AD).

Purpose of the Study:

• To design and evaluate cis-locked phospho-Thr-Pro (pCDP) cyclic dipeptides as mimics of the pathological cis isomer of AβPP.
• To investigate the effect of pCDP derivatives on amyloidogenic AβPP processing in AD cell models.

Main Methods:

• Design of a cis-locked cyclic dipeptide (pCDP) and three phosphate-blocked derivatives (pCDP-diBzl, pCDP-Bzl, pCDP-diPOM).
• Establishment of H4 neuroglioma cell lines overexpressing AβPP695 or BACE1 as AD models.
• Measurement of secreted AβPP fragment (sAβPPβ) as a proxy for BACE1 activity and amyloidogenic processing.
• Enzymatic assays to assess direct inhibition of BACE1 catalytic activity by pCDP derivatives.

Main Results:

• pCDP-diBzl significantly decreased sAβPPβ levels in both H4-AβPP695 and H4-BACE1 cells.
• pCDP-diPOM decreased sAβPPβ levels in H4-BACE1 cells but not in H4-AβPP695 cells.
• No pCDP derivatives directly inhibited BACE1 catalytic activity.
• The compounds affected proteolytic AβPP fragments in a dose-dependent manner.

Conclusions:

• pCDP-diBzl and pCDP-diPOM inhibit AβPP entry into the amyloidogenic pathway through distinct targets, not by direct BACE1 inhibition.
• These findings offer valuable insights for developing novel therapeutic strategies for Alzheimer's disease.