Peptides (v.83, #C)

Study on the molecular mechanism of antinociception induced by ghrelin in acute pain in mice by Fu-Yan Liu; Min-min Zhang; Ping Zeng; Wen-wen Liu; Jing-lei Wang; Bei Yang; Qun Dai; Jie Wei (1-7).
Ghrelin has been identified as the endogenous ligand for the GHS-R1α (growth hormone secretagogue receptor 1 alpha). Our previous experiments have indicated that ghrelin (i.c.v.) induces antinociceptive effects in acute pain in mice, and the effects were mediated through the central opioid receptors and GHS-R1α. However, which opioid receptor (OR) mediates the antinociceptive effects and the molecular mechanisms are also needed to be further explored. In the present study, the antinociceptive effects of ghrelin (i.c.v.) could be fully antagonized by δ-opioid receptor antagonist NTI. Furthermore, the mRNA and protein levels of δ-opioid peptide PENK and δ-opioid receptor OPRD were increased after i.c.v injection of ghrelin. Thus, it showed that the antinociception of ghrelin was correlated with the GHS-R1α and δ-opioid receptors. To explore which receptor was firstly activated by ghrelin, GHS-R1α antagonist [D-Lys3]-GHRP-6 was co-injection (i.c.v.) with deltorphin II (selective δ-opioid receptor agonist). Finally, the antinociception induced by deltorphin II wasn’t blocked by the co-injection (i.c.v.) of [D-Lys3]-GHRP-6, indicating that the GHS-R1α isn’t on the backward position of δ-opioid receptor. The results suggested that i.c.v. injection of ghrelin initially activated the GHS-R1α, which in turn increased the release of endogenous PENK to activation of OPRD to produce antinociception.
Keywords: Ghrelin; GHS-R1α; Opioid receptors; Antinociception; Transcriptional expression; Protein expression;

Human hemokinin-1 promotes migration of melanoma cells and increases MMP-2 and MT1-MMP expression by activating tumor cell NK1 receptors by Yixin Zhang; Xiaofang Li; Jingyi Li; Hui Hu; Xiaokang Miao; Xiaoyun Song; Wenle Yang; Qian Zeng; Lingyun Mou; Rui Wang (8-15).
Receptors and their regulatory peptides are aberrantly expressed in tumors, suggesting a potential tumor therapy target. Human hemokinin-1 (hHK-1) is a tachykinin peptide ligand of the neurokinin-1 (NK1) receptor which is overexpressed in melanoma and other tumor tissues. Here, we investigated the role of hHK-1 and the NK1 receptor in melanoma cell migration. NK1 receptor expression was associated with melanoma metastatic potential. Treatment with hHK-1 significantly enhanced A375 and B16F10 melanoma cell migration and an NK1 receptor antagonist L732138 blocked this effect. MMP-2 and MT1-MMP expression were up-regulated in hHK-1-treated melanoma cells and cell signaling data suggested that hHK-1 induced phosphorylation of ERK1/2, JNK and p38 by way of PKC or PKA. Kinase activation led to increased MMP-2 and MT1-MMP expression and melanoma cell migration induced by hHK-1. Thus, hHK-1 and the NK1 receptor are critical to melanoma cell migration and each may be a promising chemotherapeutic target.
Keywords: Hemokinin-1; Melanoma; Neurokinin-1 receptor; Cell migration; Matrix metalloproteinases;

Rubimetide (Met-Arg-Trp), which had been isolated as an antihypertensive peptide from an enzymatic digest of spinach ribulose-bisphosphate carboxylase/oxygenase (Rubisco), showed anxiolytic-like activity prostaglandin (PG) D2-dependent manner in the elevated plus-maze test after administration at a dose of 0.1 mg/kg (ip.) or 1 mg/kg (p.o.) in male mice of ddY strain. In this study, we found that rubimetide has weak affinities for the FPR1 and FPR2, subtypes of formyl peptide receptor (FPR). The anxiolytic-like activity of rubimetide (0.1 mg/kg, ip.) was blocked by WRW4, an antagonist of FPR2, but not by Boc-FLFLF, an antagonist of FPR1, suggesting that the anxiolytic-like activity was mediated by the FPR2. Humanin, an endogenous agonist peptide of the FPR2, exerted an anxiolytic-like activity after intracerebroventricular (icv) administration, which was also blocked by WRW4. MMK1, a synthetic agonist peptide of the FPR2, also exerted anxiolytic-like activity. Thus, FPR2 proved to mediate anxiolytic-like effect as the first example of central effect exerted by FPR agonists. As well as the anxiolytic-like activity of rubimetide, that of MMK1 was blocked by BW A868C, an antagonist of the DP1-receptor. Furthermore, anxiolytic-like activity of rubimetide was blocked by SCH58251 and bicuculline, antagonists for adenosine A2A and GABAA receptors, respectively. From these results, it is concluded that the anxiolytic-like activities of rubimetide and typical agonist peptides of the FPR2 were mediated successively by the PGD2-DP1 receptor, adenosine-A2A receptor, and GABA-GABAA receptor systems downstream of the FPR2.
Keywords: Rubimetide; Rubisco; MMK1; Humanin; Anxiolytic-like activity; FPR2; Prostaglandin D2; DP1 receptor; Adenosine A2A receptor; GABAA receptor;

Overexpression of Leap2 impairs Xenopus embryonic development and modulates FGF and activin signals by Pierre Thiébaud; Bertrand Garbay; Patrick Auguste; Caroline Le Sénéchal; Zuzanna Maciejewska; Sandrine Fédou; Xavier Gauthereau; Patricia Costaglioli; Nadine Thézé (21-28).
Besides its widely described function in the innate immune response, no other clear physiological function has been attributed so far to the Liver-Expressed-Antimicrobial-Peptide 2 (LEAP2). We used the Xenopus embryo model to investigate potentially new functions for this peptide. We identified the amphibian leap2 gene which is highly related to its mammalian orthologues at both structural and sequence levels. The gene is expressed in the embryo mostly in the endoderm-derived tissues. Accordingly it is induced in pluripotent animal cap cells by FGF, activin or a combination of vegT/β-catenin. Modulating leap2 expression level by gain-of-function strategy impaired normal embryonic development. When overexpressed in pluripotent embryonic cells derived from blastula animal cap explant, leap2 stimulated FGF while it reduced the activin response. Finally, we demonstrate that LEAP2 blocks FGF-induced migration of HUman Vascular Endothelial Cells (HUVEC). Altogether these findings suggest a model in which LEAP2 could act at the extracellular level as a modulator of FGF and activin signals, thus opening new avenues to explore it in relation with cellular processes such as cell differentiation and migration.
Keywords: Leap2; Xenopus laevis; Embryo; FGF; Activin; Cell migration; HUVEC;

Identification of dipeptidyl peptidase 3 as the Angiotensin-(1–7) degrading peptidase in human HK-2 renal epithelial cells by Nildris Cruz-Diaz; Bryan A. Wilson; Nancy T. Pirro; K. Bridget Brosnihan; Allyson C. Marshall; Mark C. Chappell (29-37).
Angiotensin-(1–7) (Ang-(1–7)) is expressed within the kidney and exhibits renoprotective actions that antagonize the inflammatory, fibrotic and pro-oxidant effects of the Ang II-AT1 receptor axis. We previously identified a peptidase activity from sheep brain, proximal tubules and human HK-2 proximal tubule cells that metabolized Ang-(1–7); thus, the present study isolated and identified the Ang-(1–7) peptidase. Utilizing ion exchange and hydrophobic interaction chromatography, a single 80 kDa protein band on SDS-PAGE was purified from HK-2 cells. The 80 kDa band was excised, the tryptic digest peptides analyzed by LC–MS and a protein was identified as the enzyme dipeptidyl peptidase 3 (DPP 3, EC: 3.4.14.4). A human DPP 3 antibody identified a single 80 kDa band in the purified enzyme preparation identical to recombinant human DPP 3. Both the purified Ang-(1–7) peptidase and DPP 3 exhibited an identical hydrolysis profile of Ang-(1–7) and both activities were abolished by the metallopeptidase inhibitor JMV-390. DPP 3 sequentially hydrolyzed Ang-(1–7) to Ang-(3–7) and rapidly converted Ang-(3–7) to Ang-(5–7). Kinetic analysis revealed that Ang-(3–7) was hydrolyzed at a greater rate than Ang-(1–7) [17.9 vs. 5.5 nmol/min/μg protein], and the Km for Ang-(3–7) was lower than Ang-(1–7) [3 vs. 12 μM]. Finally, chronic treatment of the HK-2 cells with 20 nM JMV-390 reduced intracellular DPP 3 activity and tended to augment the cellular levels of Ang-(1–7). We conclude that DPP 3 may influence the cellular expression of Ang-(1–7) and potentially reflect a therapeutic target to augment the actions of the peptide.
Keywords: Renin angiotensin system; Angiotensin-(1–7); HK-2 cells; DPP 3;

The cyclin-dependent kinase inhibitor p21CIP1/WAF1 (p21) is highly expressed in the adult heart. However, in response to stress, its expression is downregulated. Therefore, we investigated the role of p21 in the regulation of cardiac hypertrophic growth. At 2 months of age, p21 knockout mice (p21KO) lack an overt cardiac phenotype. In contrast, by 10 months of age, p21KO developed age-dependent cardiac hypertrophy and heart failure. After 3 weeks of trans-aortic banding (TAB), the heart/body weight ratio in 11 week old p21KO mice increased by 57%, as compared to 42% in wild type mice indicating that p21KO have a higher susceptibility to pressure overload-induced cardiac hypertrophy. We then chronically infused 8 week old wild type mice with Angiotensin II (2.0 mg/kg/min) or saline subcutaneously by osmotic pumps for 14 days. Recombinant TAT conjugated p21 protein variants (10 mg/kg body weight) or saline were intraperitoneally injected once daily for 14 days into Angiotensin II and saline-infused animals. Angiotensin II treated mice developed pathological cardiac hypertrophy with an average increase of 38% in heart/body weight ratios, as compared to saline-treated controls. Reconstitution of p21 function by TAT.p21 protein transduction prevented Angiotensin II-dependent development of cardiac hypertrophy and failure. Taken together, our genetic and biochemical data show an important function of p21 in the regulation of growth-related processes in the heart.
Keywords: p21; Cdkn1a; p27; Cdkn1b; Myc; Retinoblastoma; Cyclin D2; Cdk; Cell cycle; Cardiac hypertrophy; Heart failure; Cardiac fibrosis; Angiotensin;

The 5-amino acid N-terminal extension of non-sulfated drosulfakinin II is a unique target to generate novel agonists by M. Leander; J. Heimonen; T. Brocke; M. Rasmussen; C. Bass; G. Palmer; J. Egle; M. Mispelon; K. Berry; R. Nichols (49-56).
The ability to design agonists that target peptide signaling is a strategy to delineate underlying mechanisms and influence biology. A sequence that uniquely characterizes a peptide provides a distinct site to generate novel agonists. Drosophila melanogaster sulfakinin encodes non-sulfated drosulfakinin I (nsDSK I; FDDYGHMRF-NH2) and nsDSK II (GGDDQFDDYGHMRF-NH2). Drosulfakinin is typical of sulfakinin precursors, which are conserved throughout invertebrates. Non-sulfated DSK II is structurally related to DSK I, however, it contains a unique 5-residue N-terminal extension; drosulfakinins signal through G-protein coupled receptors, DSK-R1 and DSK-R2. Drosulfakinin II distinctly influences adult and larval gut motility and larval locomotion; yet, its structure-activity relationship was unreported. We hypothesized substitution of an N-terminal extension residue may alter nsDSK II activity. By targeting the extension we identified, not unexpectedly, analogs mimicking nsDSK II, yet, surprisingly, we also discovered novel agonists with increased (super) and opposite (protean) effects. We determined [A3] nsDSK II increased larval gut contractility rather than, like nsDSK II, decrease it. [N4] nsDSK II impacted larval locomotion, although nsDSK II was inactive. In adult gut, [A1] nsDSK II, [A2] nsDSKII, and [A3] nsDSK II mimicked nsDSK II, and [A4] nsDSK II and [A5] nsDSK II were more potent; [N3] nsDSK II and [N4] nsDSK II mimicked nsDSK II. This study reports nsDSK II signals through DSK-R2 to influence gut motility and locomotion, identifying a novel role for the N-terminal extension in sulfakinin biology and receptor activation; it also led to the discovery of nsDSK II structural analogs that act as super and protean agonists.
Keywords: Cholecystokinin; DSK; FaRP; FMRF-NH2; Gut motility; Locomotion; Molecular docking; Sulfakinin;