The Multi-Leu Peptide Inhibitor Discriminates Between PACE4 and Furin And Exhibits Antiproliferative Effects On Prostate Cancer Cells

Abstract

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 G0/G1 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.

PACE4 Undergoes an Oncogenic Alternative Splicing Switch in Cancer

“…These results demonstrate that GDF-15 is cleaved by PACE4 with very limited redundancy with the other endogenously coexpressed PCs, and are in line with a previous report showing that GDF-15 remained uncleaved in PACE4-deficient PC3 cells (10,33). Nevertheless, we also tested the in vitro cleavage of a GDF-15-spanning peptide incorporating the PC site (QAARGRRRAR#ARNG) with recombinant furin and PACE4 enzyme preparations (10). The GDF-15 peptide was cleaved correctly by both PCs (Fig.…”

“…In previous studies, we showed that when our ML-peptide inhibitor was modified by the addition of an N-terminal polyethylene glycol moiety, it lost its antiproliferative activity toward prostate cancer cells, which was correlated with a strong reduction of cell-penetrating properties (10). However, no apparent biological explanation could conciliate this phenomenon.…”

“…Activity assays were performed as described in ref. 10. Identical preparations from wild-type S2 cells were used as blanks.…”

The Paired Basic Amino Acid-cleaving Enzyme 4 (PACE4) Is Involved in the Maturation of Insulin Receptor Isoform B

“…The PC inhibitor multileucine peptide (ML) and its cell-impermeable PEGylated derivative (PEG8-ML) were previously described (27). Insulin receptor antibodies were purchased from Santa Cruz Biotechnology (Santa Cruz, CA) (␤ chain, sc711; ␣ chain, sc7953; phosphorylated ␤ chain (Tyr 1162/11636 ), sc25103).…”

Structure-Based Optimization of a Potent PACE4 Inhibitor Containing a Decarboxylated P1 Arginine Mimetic

“…Moreover, we developed a potent PACE4 inhibitor with considerable selectivity (20-fold over furin) known as the Multi-Leu (ML) peptide [2]. In order to improve its pharmacological profile, we performed structure-activity relationship (SAR) studies and determined that the incorporation of the decarboxylated arginine mimetic (4-amidinobenzylamide, Amba) at the P1 position led to a more potent and stable analog [3].…”