5 research outputs found
Synthesis of Gly-ψ[(<i>Z</i>)CFCH]-Phe, a Fluoroalkene Dipeptide Isostere, and Its Incorporation into a Leu-enkephalin Peptidomimetic
A new
Leu-enkephalin peptidomimetic designed to explore the hydrogen
bond acceptor ability of the third peptide bond has been prepared
and studied. This new analog is produced by replacing the third amide
of Leu-enkephalin with a fluoroalkene. An efficient and innovative
synthesis of the corresponding dipeptide surrogate Fmoc-Gly-ψ[(<i>Z</i>)CFCH]-Phe-OH is described. The key step involves
the alkylation of a tin dienolate from the less hindered face of its
chiral sulfonamide auxiliary derived from camphor. Once its synthesis
was complete, its incorporation into the peptidomimetic sequence was
achieved on a solid support with chlorotrityl resin following the
Fmoc strategy. The peptidomimetic was characterized using competition
binding with [<sup>125</sup>I]-deltorphin I on membrane extracts of
HEK293 cells expressing the mouse delta opioid receptor (DOPr) and
based on its abilities to inhibit the electrically induced contractions
of the mouse <i>vas deferens</i> and to activate the ERK1/2
signaling pathway in DRGF11/DOPr-GFP cells. Together with our previous
observations, our findings strongly suggest that the third amide bond
of Leu-enkephalin primarily acts as a hydrogen bond acceptor in DOPr.
Consequently, this amide bond can be successfully replaced by an ester,
a thioamide, or a fluoroalkene without greatly impacting the binding
or biological activity of the corresponding analogs. The lipophilicity
(LogD<sub>7.4</sub>) of the active analog was also measured. It appears
that fluoroalkenes are almost as efficient at increasing the lipophilicity
as normal alkenes
Preparation and Evaluation at the Delta Opioid Receptor of a Series of Linear Leu-Enkephalin Analogues Obtained by Systematic Replacement of the Amides
Leu-enkephalin
analogues, in which the amide bonds were sequentially and systematically
replaced either by ester or <i>N</i>-methyl amide bonds,
were prepared using classical organic chemistry as well as solid phase
peptide synthesis (SPPS). The peptidomimetics were characterized using
competition binding, ERK1/2 phosphorylation, receptor internalization,
and contractility assays to evaluate their pharmacological profile
over the delta opioid receptor (DOPr). The lipophilicity (LogD<sub>7.4</sub>) and plasma stability of the active analogues were also
measured. Our results revealed that the last amide bond can be successfully
replaced by either an ester or an <i>N</i>-methyl amide
bond without significantly decreasing the biological activity of the
corresponding analogues when compared to Leu-enkephalin. The peptidomimetics
with an <i>N</i>-methyl amide function between residues
Phe and Leu were found to be more lipophilic and more stable than
Leu-enkephalin. Findings from the present study further revealed that
the hydrogen-bond donor properties of the fourth amide of Leu-enkephalin
are not important for its biological activity on DOPr. Our results
show that the systematic replacement of amide bonds by isosteric functions
represents an efficient way to design and synthesize novel peptide
analogues with enhanced stability. Our findings further suggest that
such a strategy can also be useful to study the biological roles of
amide bonds
Design, Synthesis, and Structure–Activity 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 structure–activity relationship studies.
A variety of ML-peptide analogues modified at the P8–P5 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