Retroviral Glycoprotein-Mediated Immune Suppression via the potassium Channel KCa3.1- A new strategy for treatment of Inflammatory Bowel Diseases.

Background and Purpose: Peptides derived from retroviral envelope proteins have been shown to possess a wide range of immunosuppressive and anti-inflammatory activities. We have previously reported identification of such a peptide derived from the envelope protein coded by a human endogenous retrovirus (HERV). In this study we assessed effects of this peptide treatment on inhibition of immune response in the DSS-induced mice model of colitis. Furthermore, we identified that in vitro the peptide inhibits the KCa3.1 potassium channel, a potential target for therapy of immune diseases. Experimental Approach: We characterized an immunosuppressive peptide ENV59, from a specific HERV envelope protein, in vivo effects on inflammation control in acute colitis mice model and in vitro on the production of pro-inflammatory cytokines. Furthermore, we described in vitro ENV59-GP3 effects with respect to potency of inhibition on KCa3.1 channels and calcium influx. Key Results: ENV59-GP3 peptide treatment showed reduction of the disease score in the DSS-induced acute colitis mice model, which was comparable to effects of the KCa3.1 channel blocker NS6180. Analysis of cytokine production from DSS-mice model treated animals revealed equipotent inhibitory effects of the ENV59-GP3 and NS6180 compounds on the production of IL-6, TNF-α, IL-1β. Patch clamp studies show that the peptide ENV59-GP3 is a blocker of the potassium channel KCa3.1. Conclusion and Implications: Env59-GP3 represents KCa3.1 channel inhibitor underlining the implications of using virus derived channel blockers for treatment of autoimmune diseases. There are no drugs with a similar mechanism of action currently on the market.

Characterization of a novel peptide mined from the Red Sea brine pools and modified to enhance its anticancer activity

Peptide-based drugs have emerged as highly selective and potent cancer therapy. Cancer is one of the leading causes of death worldwide. Multiple approaches have been developed towards cancer treatment, including chemotherapy, radiation, and hormonal therapy; however, such procedures' non-specificity, toxicity, and inefficiency present a hurdle. In this study, we developed a support vector machine (SVM) model to detect the potential anticancer properties of novel peptides through scanning the American University in Cairo Red Sea metagenomics library. Further, we performed in silico studies on a novel 37-mer antimicrobial peptide mined from SVM pipeline analysis. This peptide was further modified to enhance its anticancer activity, analyzed for gene oncology, and subsequently synthesized. The anticancer properties of this 37-mer peptide were evaluated via cellular viability and cell morphology of SNU449, HepG2, SKOV3, and HeLa cells, using MTT assay. Furthermore, we assessed the migration capability of SNU449 and SKOV3 via scratch wound healing assay. Moreover, the targeted selectivity of the peptide for cancerous cells was assessed by testing its hemolytic activity on human erythrocytes. The peptide caused a significant reduction in cellular viability and critically affected the morphology of hepatocellular carcinoma (SNU449 and HepG2), ovarian cancer (SKOV3), and to a limited extent, cervical cancer cell lines (HeLa), in addition to decreasing viability of human fibroblast cell line (1Br-hTERT). Peptide treatment significantly affected the proliferation and migration ability of SNU449 and SKOV3 cells. Annexin V assay was used to evaluate induced cell death upon peptide treatment, attributing programmed cell death (Apoptosis) as the main cause of cell death in SNU449 cells. Finally, we established broad-spectrum antimicrobial properties of the peptide on both gram-positive and gram-negative bacterial strains. Thus, these findings infer the novelty of the peptide as a potential anticancer and antimicrobial agent.

A novel Calmodulin-interacting Domain of Unknown Function 506 protein represses root hair elongation in Arabidopsis

DUF506 proteins are omnipresent in higher plants. Phosphorus (P) stress-inducible AtRXR1/REPRESSOR OF EXCESSIVE ROOT HAIR ELONGATION 1 gene, as the first functionally characterized DUF506 gene, is proved to inhibit root hair elongation through interaction of RXR2/RabD2c GTPase. However, the knowledge of other P-responsive DUF506 genes is still limited. Here, we identify four additional P-inducible DUF506 genes and select two of candidates for functional investigation. Expression analysis results reveal that both of candidates are induced by auxin. At3g07350, the duplicated pair of RXR1, expresses ubiquitously in seedlings under P-stress, whereas At1g62420 is mainly induced in roots. Overexpression and knockout mutants of At1g62420, which is called RXR3, exhibit shorter or longer root hair length, respectively. Cellular imaging results demonstrate RXR3 localizes in root epidermal cells. ChIP, synthetic peptide treatment and qRT-PCR assay results indicate RXR3 is transcriptionally activated by RSL4 or RALF1. BiFC and CaM-binding assay suggest that RXR3 interacts with various CaMs in presence of Ca2+. Moreover, the frequencies of [Ca2+]cyt in rxr3 mutants are approximately 20% higher compared to that of wild type. Taken together, our results illustrate a divergent mechanism by which RSL4-directed RXR3 interacts with calmodulin and functions in parallel of RXR1, to prevent root hair excessive growth.

The effects of a mitochondrial targeted peptide (elamipretide/SS31) on BAX recruitment and activation during apoptosis

Objective Elamipretide (SS31) is a mitochondria-targeted peptide that has reported functions of stabilizing mitochondrial cristae structure and improving mitochondrial bioenergetics. Several studies have documented cell protective features of this peptide, including impairment of intrinsic apoptosis by inhibiting the recruitment and activation of the pro-apoptotic BAX protein. We used live-cell imaging of ARPE-19 cells expressing fluorescently labeled BAX, cytochrome c, and a mitochondrial marker to investigate the effect of elamipretide on the kinetics of BAX recruitment, mitochondrial outer membrane permeabilization (as a function of cytochrome c release), and mitochondrial fragmentation, respectively. Result In nucleofected and plated ARPE-19 cells, elamipretide accelerated the formation of larger mitochondria. In the presence of the apoptotic stimulator, staurosporine, cells treated with elamipretide exhibited moderately slower rates of BAX recruitment. Peptide treatment, however, did not significantly delay the onset of BAX recruitment or the final total amount of BAX that was recruited. Additionally, elamipretide showed no impairment or delay of cytochrome c release or mitochondrial fragmentation, two events associated with normal BAX activation during cell death. These results indicate that the protective effect of elamipretide is not at the level of BAX activity to induce pro-apoptotic mitochondrial dysfunction after the initiation of staurosporine-induced apoptosis.

The Effects of a Mitochondrial Targeted Peptide (Elamipretide/SS31) on BAX Recruitment and Activation During Apoptosis

Objective: Elamipretide (SS31) is a mitochondria-targeted peptide that has reported functions of stabilizing mitochondrial cristae structure and improving mitochondrial bioenergetics. Several studies have documented cell protective features of this peptide, including impairment of intrinsic apoptosis by inhibiting the recruitment and activation of the pro-apoptotic BAX protein. We used live-cell imaging of ARPE-19 cells expressing fluorescently labeled BAX, cytochrome c, and a mitochondrial marker to investigate the effect of elamipretide on the kinetics of BAX recruitment, mitochondrial outer membrane permeabilization (as a function of cytochrome c release), and mitochondrial fragmentation, respectively. Result: In nucleofected and plated ARPE-19 cells, elamipretide accelerated the formation of larger mitochondria. In the presence of the apoptotic stimulator, staurosporine, cells treated with elamipretide exhibited moderately slower rates of BAX recruitment. Peptide treatment, however, did not significantly delay the onset of BAX recruitment or the final total amount of BAX that was recruited. Additionally, elamipretide showed no impairment or delay of cytochrome c release or mitochondrial fragmentation, two events associated with normal BAX activation during cell death. These results indicate that the protective effect of elamipretide is not at the level of BAX activity to induce pro-apoptotic mitochondrial dysfunction after the initiation of staurosporine-induced apoptosis.

NHERF1/EBP50 as a Target for Modulation of MRP Function in HepG2 Cells

As increased expression and activities of efflux transporters (ETs) often cause drug resistance in cancers, we tried modulating ET activity in cancer cells, using scaffold proteins such as ezrin/radixin/moesin (ERM) proteins, and Na+/H+ exchanger regulatory factor-1 (NHERF1)/ERM-binding phosphoprotein of 50 kDa (EBP50). To see whether EBP50 modulated ET activities in human liver cancer HepG2 cells, we used EBP50 siRNA and a designed TAT-PDZ1 peptide. The EBP50 knockdown (EBP50KD) cells had significantly higher intracellular accumulations of Rho123 and carboxy-dichlorofluorescein (CDF), but not H33342 (i.e., the respective substrates of P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP), and breast cancer resistance protein (BCRP)), compared with control HepG2, suggesting that EBP50 knockdown in HepG2 cells decreased activity of P-gp and MRP but not BCRP. Treatment with TAT-PDZ1 peptide (>1 pM) resulted in significantly higher CDF accumulation in HepG2 cells, which persisted for ≥180 min after TAT-PDZ1 peptide treatment. These results imply that EBP50 can modulate ET activities. To our knowledge, this is the first report on using a competitive peptide to modulate interactions between MRP and EBP50.

Mechanisms of action of the anti-diabetic peptide [S4K]CPF-AM1 in db/db mice

The anti-diabetic effects and mechanisms of action of an analogue of a frog skin host-defence peptide belonging to the caerulein-precursor fragment family, [S4K]CPF-AM1 were investigated in db/db mice with a genetically inherited form of degenerative diabetes-obesity. Twice-daily treatment with the peptide (75 nmol/kg body weight) for 28 days significantly decreased blood glucose (P<0.01) and HbA1c (P<0.05) and increased plasma insulin (P<0.05) concentrations with no effect on body weight, energy intake, body composition or plasma lipid profile. Peptide administration improved insulin sensitivity and intraperitoneal glucose tolerance. Elevated biomarkers of liver and kidney function associated with the db/db phenotype were significantly lowered by [S4K]CPF-AM1 administration. Peptide treatment significantly (P<0.05) increased pancreatic insulin content and improved the responses of isolated islets to established secretagogues. Elevated expression of genes associated with insulin signalling (Slc2a4, Insr, Irs1, Akt1, Pik3ca, Ppm1b) in the skeletal muscle of db/db mice were significantly downregulated by peptide treatment. Genes associated with insulin secretion (Abcc8, Kcnj11, Slc2a2, Cacn1c, Glp1r, Gipr) were significantly upregulated by treatment with [S4K]CPF-AM1. Studies with BRIN-BD1I clonal β-cells demonstrated that the peptide evoked membrane depolarization, increased intracellular Ca2+ and cAMP and activated the protein kinase C pathway. The data indicate that the anti-diabetic properties of [S4K]CPF-AM1 mice are mediated by direct insulinotropic action and by regulation of transcription of genes involved in both the secretion and action of insulin.