Design and characterisation of long-R3-insulin-like growth factor-I muteins which show resistance to pepsin digestion

Synthetic peptides derived from the sequence of a lasso peptide microcin J25 show antibacterial activity

Microcin J25 (MccJ25) is a plasmid-encoded, ribosomally synthesized antibacterial peptide with a unique lasso structure. The lasso structure, produced with the aid of two processing enzymes, provides exceptional stability to MccJ25. We report the synthesis of six peptides (1-6), derived from the MccJ25 sequence, that are designed to form folded conformation by disulfide bond formation and electrostatic or hydrophobic interactions. Two peptides (1 and 6) display good activity against Salmonella newport, and are the first synthetic derivatives of MccJ25 that are bactericidal. Peptide 1 displays potent activity against several Salmonella strains including two MccJ25 resistant strains. The solution conformation and the stability studies of the active peptides suggest that they do not fold into a lasso conformation and peptide 1 displays antimicrobial activity by inhibition of target cell respiration. Like MccJ25, the synthetic MccJ25 derivatives display minimal toxicity to mammalian cells suggesting that these peptides act specifically on bacterial cells.

Insulin-like growth factor I (IGF-I) and IGF binding protein-1 modulate prostate cancer cell growth and apoptosis: possible mediators for the effects of diet and exercise on cancer cell survival

Previous studies showed that serum from men consuming a low fat diet and undergoing exercise intervention (DE) reduced LNCaP cell growth and induced apoptosis in vitro. DE also decreased serum IGF-I and increased serum IGF binding protein-1 (IGFBP-1). The present study evaluates the effects of IGF-I and IGFBP-1 on growth and apoptosis of prostate cancer cells in vitro. When IGF-I was added to the post-DE serum, the reduction in LNCaP cell growth and the induction of apoptosis in medium containing post-DE serum alone were reversed. When IGFBP-1 was added to the pre-DE serum samples, LNCaP cell growth was reduced, and apoptosis was induced. IGF-I, long-R(3)-IGF-I (only binds IGF-I receptor), AL(31)Leu(60)-IGF-I (only binds IGFBPs), antihuman IGF-I receptor antibodies, and IGFBP-1 were then added to LNCaP cultures to determine the independent effects of IGF-I and IGFBP-1 on cell growth. Collectively, the results using these agents show that IGF-I and IGFBP-1 exert opposing effects on LNCaP cell growth and apoptosis, and IGFBP-1 acts mainly through an IGF-dependent mechanism. DE results in a decrease in serum IGF-I with increased IGFBP-1 in vivo that is associated with apoptosis and reduced LNCaP and LAPC-4 prostate cancer cell growth in vitro.

Pharmacokinetics, metabolic stability, and subcutaneous bioavailability of a genetically engineered analog of DcR3, FLINT [DcR3(R218Q)], in cynomolgus monkeys and mice

Decoy receptor 3 (DcR3) is a novel member of the tumor necrosis factor receptor superfamily, which binds to and blocks the activities of the ligands, FasL and LIGHT (a cellular ligand for herpes virus entry mediator and lymphotoxin receptor), that play an important role in regulating apoptosis in normal physiology. DcR3 was rapidly degraded to a major circulating metabolic fragment, DcR3(1-218), after subcutaneous administration in primates and mice. DcR3 was molecularly engineered by changing the arginine residue at position 218 to glutamine to generate a potentially stable analog, DcR3(R218Q), which we termed FasLigand inhibitor protein [FLINT (LY498919)]. The influence of this modification on the kinetics and bioavailability of DcR3 was evaluated in primates and mice. After i.v. administration of FLINT and DcR3, both compounds were cleared from the plasma in a bi-phasic manner, with the terminal phase half-life being somewhat longer for FLINT than for DcR3. After s.c. administration, the exposure to the full-length form of FLINT was 5.7- to 6-fold greater than for DcR3. In both primates and mice, greater than 90% of circulating immunoreactivity after s.c. administration of FLINT was associated with intact molecule, whereas only 17 to 37% was associated with intact molecule after administration of DcR3. The absolute s.c. bioavailability of intact FLINT was approximately 4- to 6-fold higher than for DcR3. The improved s.c. bioavailability of FLINT is related to the increased metabolic stability afforded to the molecule as a result of the amino acid mutation at position 218 of the primary sequence of DcR3 and may translate to the need for lower therapeutic doses in a number of disease indications.

Decoy receptor 3 (DcR3) is proteolytically processed to a metabolic fragment having differential activities against Fas ligand and LIGHT

Fas ligand (FasL) and Fas receptor are members of the tumor necrosis factor (TNF) receptor and ligand family that play an important role in regulating apoptosis in normal physiology. Decoy receptor 3 (DcR3) is a novel member of the TNF receptor superfamily, which binds to and blocks the activities of the ligands FasL and LIGHT. We have demonstrated that DcR3 was degraded rapidly to a major circulating metabolic fragment after subcutaneous administration in primates and mice. This fragment was also generated in subcutaneous tissue homogenate in vitro. Mass spectrometry and N-terminal sequencing indicated that DcR3 was proteolytically cleaved between R218 and A219 in the primary sequence to yield the fragment DcR3(1-218). While retaining its ability to bind LIGHT and inhibit LIGHT-mediated activities, DcR3(1-218) no longer bound FasL and did not inhibit FasL-mediated apoptosis in vitro. The primary sequence of DcR3 was molecularly engineered, changing the arginine residue at position 218 to glutamine to generate an analog, DcR3(R218Q), which we termed FLINT (LY498919). We demonstrated that FLINT was more stable to proteolytic degradation in vitro and in vivo and maintained its activity against both soluble FasL and soluble LIGHT in vitro. As a result, the modification in the sequence of DcR3 to produce FLINT (LY498919) should result in a pharmacologically superior molecule in the therapeutic intervention of diseases in which the pathogenesis is linked to FasL-mediated apoptotic or inflammatory events.

The porcine insulin-like growth factor system: at the interface of nutrition, growth and reproduction

The IGF system is implicated in the regulation of cellular response to protein- and energy-restriction. Although it is clear that the IGF and their binding proteins are profoundly influenced by dietary factors, a number of important questions remain about this relationship. In particular, although studies to date have focused on nutritional modulation of hepatic IGF gene expression, the molecular mechanisms underlying metabolic regulation of liver IGF and IGF binding protein genes remain relatively unknown. Moreover, the potential effects of altered nutrition on the expression and/or actions of IGF system components in tissues other than the liver have been examined only in cursory fashion. Many of these studies have used rats, an admittedly important model, but one which differs from the human in a potentially significant way: rats lack circulating IGF-II and IGFBP-2 during post-weaning and adult life. Here, we summarize current research on the porcine IGF system and highlight the particular usefulness this system may offer for unraveling the complex relationships of nutrition and systemic/local IGF expression and actions that are relevant to human nutritional physiology.