Decanoyl-RVKR-CMK

Mature pig oligodendrocytes rapidly process human recombinant pro-nerve growth factor and do not undergo cell death.[Pubmed:16805842]

J Neurochem. 2006 Jul;98(2):506-17.

The neurotrophin family with its first member, nerve growth factor (NGF), binds two classes of receptors, more specifically to Trk receptors and to a shared p75NTR receptor. It has been shown that proNGF rather than NGF is predominant in the mature central nervous system. A recent finding indicated that a furin-resistant proNGF preferentially binds to p75NTR, initiating a pro-apoptotic cascade even in the presence of TrkA. In this context, rodent oligodendrocytes were reported to undergo cell death when exposed to proNGF. We have investigated the effect of a non-mutated 32 kDa human recombinant proNGF (rhproNGF) on cultured pig oligodendrocytes which express TrkA, p75NTR and sortilin. Pig oligodendrocytes respond to rhproNGF (50 ng/mL) with an enhanced regeneration of their processes as already observed for NGF. Activity of mitogen-activated protein kinase (MAPK), which plays an important role in oligodendroglial process formation, was increased even when rhproNGF processing was inhibited by the furin inhibitor Decanoyl-RVKR-CMK. Similarly, a cleavage-resistant proNGF (R-1G) activated MAPK and promoted oligodendroglial process regeneration. High concentrations of rhproNGF (300 ng/mL) did not induce cell death. Sodium dodecyl sulfate - polyacrylamide gel electrophoresis and Western blotting revealed that oligodendrocytes process rhproNGF to NGF. NGF was detected in Western blots of oligodendroglial lysates already 10 min after rhproNGF exposure, followed by a release of NGF into the culture medium. Indirect evidence indicates that rhproNGF processing occurs via an endocytotic route.

Comparative study of the binding pockets of mammalian proprotein convertases and its implications for the design of specific small molecule inhibitors.[Pubmed:20151049]

Int J Biol Sci. 2010 Feb 3;6(1):89-95.

Proprotein convertases are enzymes that proteolytically cleave protein precursors in the secretory pathway to yield functional proteins. Seven mammalian subtilisin/Kex2p-like proprotein convertases have been identified: furin, PC1, PC2, PC4, PACE4, PC5 and PC7. The binding pockets of all seven proprotein convertases are evolutionarily conserved and highly similar. Among the seven proprotein convertases, the furin cleavage site motif has recently been characterized as a 20-residue motif that includes one core region P6-P2' inside the furin binding pocket. This study extended this information by examining the 3D structural environment of the furin binding pocket surrounding the core region P6-P2' of furin substrates. The physical properties of mutations in the binding pockets of the other six mammalian proprotein convertases were compared. The results suggest that: 1) mutations at two positions, Glu230 and Glu257, change the overall density of the negative charge of the binding pockets, and govern the substrate specificities of mammalian proprotein convertases; 2) two proprotein convertases (PC1 and PC2) may have reduced sensitivity for positively charged residues at substrate position P5 or P6, whereas the substrate specificities of three proprotein convertases (furin, PACE4, and PC5) are similar to each other. This finding led to a novel design of a short peptide pattern for small molecule inhibitors: [K/R]-X-V-X-K-R. Compared with the widely used small molecule dec-RVKR-cmk that inhibits all seven proprotein convertases, a finely-tuned derivative of the short peptide pattern [K/R]-X-V-X-K-R may have the potential to more effectively inhibit five of the proprotein convertases (furin, PC4, PACE4, PC5 and PC7) compared to the remaining two (PC1 and PC2). The results not only provide insights into the molecular evolution of enzyme function in the proprotein convertase family, but will also aid the study of the functional redundancy of proprotein convertases and the development of therapeutic applications.

A prohormone convertase cleavage site within a predicted alpha-helix mediates sorting of the neuronal and endocrine polypeptide VGF into the regulated secretory pathway.[Pubmed:16221685]

J Biol Chem. 2005 Dec 16;280(50):41595-608.

Distinct intracellular pathways are involved in regulated and constitutive protein secretion from neuronal and endocrine cells, yet the peptide signals and molecular mechanisms responsible for targeting and retention of soluble proteins in secretory granules are incompletely understood. By using confocal microscopy and subcellular fractionation, we examined trafficking of the neuronal and endocrine peptide precursor VGF that is stored in large dense core vesicles and undergoes regulated secretion. VGF cofractionated with secretory vesicle membranes but was not detected in detergent-resistant lipid rafts. Deletional analysis using epitope-tagged VGF suggested that the C-terminal 73-amino acid fragment of VGF, containing two predicted alpha-helical loops and four potential prohormone convertase (PC) cleavage sites, was necessary and sufficient with an N-terminal signal peptide-containing domain, for large dense core vesicle sorting and regulated secretion from PC12 and INS-1 cells. Further transfection analysis identified the sorting sequence as a compact C-terminal alpha-helix and embedded 564RRR566 PC cleavage site; mutation of the 564RRR566 PC site in VGF-(1-65): GFP:VGF-(545-617) blocked regulated secretion, whereas disruption of the alpha-helix had no effect. Mutation of the adjacent 567HFHH570 motif, a charged region that might enhance PC cleavage in acidic environments, also blocked regulated release. Finally, inhibition of PC cleavage in PC12 cells using the membrane-permeable synthetic peptide chloromethyl ketone (Decanoyl-RVKR-CMK) blocked regulated secretion of VGF. Our studies define a critical RRR-containing C-terminal domain that targets VGF into the regulated pathway in neuronal PC12 and endocrine INS-1 cells, providing additional support for the proposed role that PCs and their cleavage sites play in regulated peptide secretion.

Inhibition of convertase-related processing of proendothelin-1.[Pubmed:8587448]

J Cardiovasc Pharmacol. 1995;26 Suppl 3:S47-50.

The biologically inactive precursor proendothelin-1 (proET-1) is initially processed intracellularly to the intermediate big endothelin peptide (big ET-1) before its conversion to the endothelin-1 (ET-1) peptide by the endothelin-converting enzyme (ECE). We recently demonstrated that purified furin, a calcium-dependent serine endoprotease belonging to the family of mammalian convertases, cleaved proET-1 in vitro and hence produced the physiologically relevant big ET-1 peptide. Therefore, furin becomes a candidate proET-1-cleaving enzyme responsible for the initial biosynthetic processing steps of this precursor. In this study we examined the inhibitory properties of two convertase inhibitors, i.e., the decanoyl-Arg-Val-Lys-Arg-chloromethylketone (dec-RVKR-cmk) and the alpha 1-antitrypsin Portland (AT-PDX) on proET-1 processing. When purified furin or PACE4, another mammalian convertase, was incubated in the presence of dec-RVKR-cmk, proET-1 processing was completely abolished. In the presence of purified AT-PDX, furin-related cleavage of proET-1 was abolished but not PACE4 processing. In addition, incubation of endothelial cells with dec-RVKR-cmk inhibited production of ET-1 but did not significantly alter the levels of the prostanoid PGI2. These results indicate that convertase-related processing of proET-1 can be inhibited in vitro and in vivo, and that convertase-specific processing may be prevented with AT-PDX.