67 research outputs found
A biologically active peptide mimetic of N-acetylgalactosamine/galactose
No full textAbstract Background Glycosylated proteins and lipids are important regulatory factors whose functions can be altered by addition or removal of sugars to the glycan structure. The glycans are recognized by sugar-binding lectins that serve as receptors on the surface of many cells and facilitate initiation of an intracellular signal that changes the properties of the cells. We identified a peptide that mimics the ligand of an N-acetylgalactosamine (GalNAc)-specific lectin and asked whether the peptide would express specific biological activity. Findings A 12-mer phage display library was screened with a GalNAc-specific lectin to identify an amino acid sequence that binds to the lectin. Phage particles that were eluted from the lectin with free GalNAc were considered to have been bound to a GalNAc-binding site. Peptides were synthesized with the selected sequence as a quadravalent structure to facilitate receptor crosslinking. Treatment of human peripheral blood mononuclear cells for 24 h with the peptide stimulated secretion of interleukin-8 (IL-8) but not of IL-1β, IL-6, IL-10, or tumor necrosis factor-α (TNF-α). The secretion of IL-21 was stimulated as strongly with the peptide as with interferon-γ. Conclusion The data indicate that the quadravalent peptide has biological activity with a degree of specificity. These effects occurred at concentrations in the nanomolar range, in contrast to free sugars that generally bind to proteins in the micro- to millimolar range.</p
Abstract 170: An innovative immunotherapeutic strategy for ovarian cancer: Glycomimetic peptides
No full textAbstract
Successful treatment strategies for women with ovarian cancer remain elusive. We hypothesize that novel means of activating anti-cancer immune activity will be an important component of a multifaceted approach to successful treatment. The present set of studies tests the hypothesis that novel peptide mimetics of C-type lectin receptor ligands, sv4L and sv6D, enhance anti-cancer immune activity and limit the progression of ovarian cancer in a mouse model. We further test the hypothesis that sv6D will function in synergy with additional immune modulators and conventional cytotoxic therapy. C-Type lectin receptors were targeted that are specific for N-acetylgalactosamine (GalNAc). Both svL4 and sv6D bind GalNAc-specific C-type lectin receptors including CLEC10A/CD301 with a KD in the low nanomolar range. CLEC10A is a transmembrane, endocytic receptor expressed on dermal dendritic cells, macrophages and immature dendritic cells. Further, studies with the B16 mouse melanoma model and spontaneous tumors (histiocytic sarcoma and mammary gland tumor) in dogs showed that treatment with svL4 correlated with reduced tumor-associated Treg cells.
In the present studies subcutaneous injection of svL4 or sv6D every other day over 5 days stimulated a several-fold proliferation of immune cells in the peritoneal cavity of healthy mice. These results indicated that svL4 and/or sv6D might exhibit significant activity on peritoneal tumors. Efficacy of svL4 and sv6D each as a single agent and as a combination therapy with paclitaxel or anti-PD-1 was tested in C57BL6 female mice bearing ovarian ID8 intraperitoneal tumors. As a single agent, 0.1 nmole/g doses of svL4 or sv6D had a significant effect on suppressing ascites formation, a measure of tumor progression, and overall survival.
Drug combination studies revealed a positive therapeutic interaction with sv6D and the cytotoxic paclitaxel. As single agents, sv6D and paclitaxel each had a significant effect on extending survival (median survival 140.5 and 150 days, respectively, vs. 122 days with no treatment). Survival was extended further with combination treatment when sv6D was administered to mice previously treated with paclitaxel (median survival 169 days). Also, a positive interaction was observed with sv6D and the check-point inhibitor anti-PD-1. Administration of sv6D following anti-PD-1 treatment resulted in a significant survival advantage compared to treatment with either agent alone.
These data demonstrate 1) sv4L and sv6D mobilize immune cells in the peritoneal cavity, 2) svL4 or sv6D as single agents slow progression of ovarian cancer and enhance survival in a mouse model of ovarian cancer, 3) sv6D in combination with paclitaxel or anti-PD-1 extends survival past that of either agent alone. Taken together these date demonstrate the potential for this novel approach of harnessing lectin receptors as a means toward effective cancer treatment.
Citation Format: Katherine F. Roby, Laura L. Eggink, J. Kenneth Hoober. An innovative immunotherapeutic strategy for ovarian cancer: Glycomimetic peptides [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 170. doi:10.1158/1538-7445.AM2017-170</jats:p
The small CAB-like proteins of Synechocystis sp. PCC 6803 bind chlorophyll : In vitro pigment reconstitution studies on one-helix light-harvesting-like proteins
No full textThe large family of light-harvesting-like proteins contains members with one to four membrane spanning helices with significant homology to the chlorophyll a/b-binding antenna proteins of plants. From structural as well as evolutionary perspective, it is likely that the members of this family bind chlorophylls and carotenoids. However, undisputable evidence is still lacking. The cyanobacterial small CAB-like proteins (SCPs) are one-helix proteins with compelling similarity to the first and third transmembrane helix of LHCII (LHCIIb) including the chlorophyll-binding motifs. They have been proposed to act as chlorophyll-carrier proteins. Here, we analyze the in vivo absorption spectra of single scp deletion mutants in Synechocystis sp. PCC 6803 and compare the in vitro pigment binding ability of the SCP pairs ScpC/D and ScpB/E with the one of LHCII and a synthetic peptide containing the chlorophyll-binding motif (Eggink LL, Hoober JK (2000) J Biol Chem 275:9087–9090). We demonstrate that deletion of scpB alters the pigmentation in the cyanobacterial cell. Furthermore, we are able to show that chlorophylls and carotenoids interact in vitro with the pairs of ScpC/D and ScpB/E, demonstrated by fluorescence resonance energy transfer and circular dichroism.</p
ASGR1 and Its Enigmatic Relative, CLEC10A
No full textThe large family of C-type lectin (CLEC) receptors comprises carbohydrate-binding proteins that require Ca2+ to bind a ligand. The prototypic receptor is the asialoglycoprotein receptor-1 (ASGR1, CLEC4H1) that is expressed primarily by hepatocytes. The early work on ASGR1, which is highly specific for N-acetylgalactosamine (GalNAc), established the foundation for understanding the overall function of CLEC receptors. Cells of the immune system generally express more than one CLEC receptor that serve diverse functions such as pathogen-recognition, initiation of cellular signaling, cellular adhesion, glycoprotein turnover, inflammation and immune responses. The receptor CLEC10A (C-type lectin domain family 10 member A, CD301; also called the macrophage galactose-type lectin, MGL) contains a carbohydrate-recognition domain (CRD) that is homologous to the CRD of ASGR1, and thus, is also specific for GalNAc. CLEC10A is most highly expressed on immature DCs, monocyte-derived DCs, and alternatively activated macrophages (subtype M2a) as well as oocytes and progenitor cells at several stages of embryonic development. This receptor is involved in initiation of TH1, TH2, and TH17 immune responses and induction of tolerance in naïve T cells. Ligand-mediated endocytosis of CLEC receptors initiates a Ca2+ signal that interestingly has different outcomes depending on ligand properties, concentration, and frequency of administration. This review summarizes studies that have been carried out on these receptors
- …
