3 research outputs found
Positional Scanning Identifies the Molecular Determinants of a High Affinity Multi-Leucine Inhibitor for Furin and PACE4
The proprotein convertase
family of enzymes includes seven endoproteases
with significant redundancy in their cleavage activity. We previously
described the peptide Ac-LLLLRVK-Amba that displays potent inhibitory
effects on both PACE4 and prostate cancer cell lines proliferation.
Herein, the molecular determinants for PACE4 and furin inhibition
were investigated by positional scanning using peptide libraries that
substituted its leucine core with each natural amino acid. We determined
that the incorporation of basic amino acids led to analogues with
improved inhibitory potency toward both enzymes, whereas negatively
charged residues significantly reduced it. All the remaining amino
acids were in general well tolerated, with the exemption of the P6
position. However, not all of the potent PACE4 inhibitors displayed
antiproliferative activity. The best analogues were obtained by the
incorporation of the Ile residue at the P5 and P6 positions. These
substitutions led to inhibitors with increased PACE4 selectivity and
potent antiproliferative effects
Design, Synthesis, and StructureāActivity Relationship Studies of a Potent PACE4 Inhibitor
PACE4 plays an important role in
the progression of prostate cancer
and is an attractive target for the development of novel inhibitor-based
tumor therapies. We previously reported the design and synthesis of
a novel, potent, and relatively selective PACE4 inhibitor known as
a Multi-Leu (ML) peptide. In the present work, we examined the ML
peptide through detailed structureāactivity relationship studies.
A variety of ML-peptide analogues modified at the P8āP5 positions
with leucine isomers (Nle, DLeu, and DNle) or substituted at the P1
position with arginine mimetics were tested for their inhibitory activity,
specificity, stability, and antiproliferative effect. By incorporating d isomers at the P8 position or a decarboxylated arginine mimetic,
we obtained analogues with an improved stability profile and excellent
antiproliferative properties. The DLeu or DNle residue also has improved
specificity toward PACE4, whereas specificity was reduced for a peptide
modified with the arginine mimetic, such as 4-amidinobenzylamide
The Multi-Leu Peptide Inhibitor Discriminates Between PACE4 and Furin And Exhibits Antiproliferative Effects On Prostate Cancer Cells
The proprotein convertases (PCs) play an important role
in protein precursor activation
through processing at paired basic residues. However, significant
substrate cleavage redundancy has been reported between PCs. The question
remains whether specific PC inhibitors can be designed. This study
describes the identification of the sequence LLLLRVKR, named Multi-Leu
(ML)-peptide, that displayed a 20-fold selectivity on PACE4 over furin,
two enzymes with similar structural characteristics. We have previously
demonstrated that PACE4 plays an important role in prostate cancer
and could be a druggable target. The present study demonstrates that
the ML-peptide significantly reduced the proliferation of DU145 and
LNCaP prostate cancer-derived cell lines and induced G<sub>0</sub>/G<sub>1</sub> cell cycle arrest. However, the ML-peptide must enter
the cell to inhibit proliferation. It is concluded that peptide-based
inhibitors can yield specific PC inhibitors and that the ML-peptide
is an important lead compound that could potentially have applications
in prostate cancer