Prolyl oligopeptidase colocalizes with α-synuclein, ß-amyloid, tau protein and astroglia in the post-mortem brain samples with Parkinson's and Alzheimer's diseases.

Prolyl oligopeptidase (EC 3.4.21.26, PREP) is a serine protease that hydrolyzes proline-containing peptides shorter than 30-mer but it has also nonhydrolytic functions. PREP has been shown to accelerate aggregation of wild-type α-synuclein (α-syn) under cell-free conditions, and PREP inhibitors can block this aggregation both in vitro and in vivo. α-syn is the main component of Lewy bodies in Parkinson's disease (PD) and Lewy body dementia. To clarify the possible interaction of PREP with other markers of neurodegenerative diseases, we studied colocalizations of PREP and (1) α-syn, (2) ß-amyloid, (3) tau protein and (4) astroglial and microglial cells in human post-mortem brain samples from PD, Alzheimer's disease (AD) patients and in healthy control brain samples. In the substantia nigra of PD brains, an intense colocalization with PREP and α-syn was evident. PREP colocalized also with ß-amyloid plaques in AD brains and with tau protein in AD and in healthy brains. PREP was also found in astroglial cells in PD, AD and control brains, but not in the microglia. Our findings are the first ones to demonstrate colocalization of PREP and pathological proteins in the human brain and support the view that, at least in spatial terms, PREP could be associated with pathogenesis of neurodegenerative diseases.

Prolyl oligopeptidase induces angiogenesis both in vitro and in vivo in a novel regulatory manner.

BACKGROUND AND PURPOSE A serine protease, prolyl oligopeptidase (POP) has been reported to be involved in the release of the pro-angiogenic tetrapeptide acetyl-N-Ser-Asp-Lys-Pro (Ac-SDKP) from its precursor, 43-mer thymosin ß4 (Tß4). Recently, it was shown that both POP activity and the levels of Ac-SDKP are increased in malignant tumours. The aim of this study was to clarify the release of Ac-SDKP, and test if POP and a POP inhibitor, 4-phenyl-butanoyl-L-prolyl-2(S)-cyanopyrrolidine (KYP-2047), can affect angiogenesis. EXPERIMENTAL APPROACH We used HPLC for bioanalytical and an enzyme immunoassay for pharmacological analysis. Angiogenesis of human umbilical vein endothelial cells was assessed in vitro using a 'tube formation' assay and in vivo using a Matrigel plug assay (BD Biosciences, San Jose, CA, USA) in adult male rats. Moreover, co-localization of POP and blood vessels was studied. KEY RESULTS We showed the sequential hydrolysis of Tß4: the first-step hydrolysis by proteases to <30-mer peptides is followed by an action of POP. Unexpectedly, POP inhibited the first hydrolysis step, revealing a novel regulation system. POP with Tß4 significantly induced, while KYP-2047 effectively prevented, angiogenesis in both models compared with Tß4 addition itself. POP and endothelial cells were abundantly co-localized in vivo. CONCLUSIONS AND IMPLICATIONS We have now revealed that POP is a second-step enzyme in the release of Ac-SDKP from Tß4, and it has novel autoregulatory effect in the first step. Our results also advocate a role for Ac-SDKP in angiogenesis, and suggest that POP has a pro-angiogenic role via the release of Ac-SDKP from its precursor Tß4 and POP inhibitors can block this action.