HDAC Inhibitors as Epigenetic Regulators

FACS analysis was carried out using Fpro0165 IgG, and a mouse and a mouse anti-human FPR2 antibody (unpublished in-house reagent) anti-human CXCR3 antibody (R&D Systems, MAB160) with detection using either a PE-labeled anti-human IgG (Sigma P8047) or a PE-labeled anti mouse IgG1(Jackson ImmunoResearch,115-116-146) as appropriate. amino acids and docking with a homology model of FPR1 suggests that this long VH CDR3 is critical to the predicted binding mode of the antibody. Antibody mutation studies identify the apex of the long VH CDR3 as important to mediating the species cross-reactivity profile of the antibody. This study illustrates an approach for antibody discovery and affinity engineering to typically intractable membrane proteins such as GPCRs. Keywords: antibody engineering, affinity maturation, phage display, antibody crystal structure, homology modeling, long CDR, G-protein coupled receptor, formyl peptide receptor-1 Abbreviations GPCRG-protein coupled receptorscFvsingle chain Fv fragmentIgGimmunoglobulin GCDRcomplementarity determining regionFPRformyl peptide receptorFMATfluorometric microvolume assay technologyFLIPRFluorescent Imaging Plate ReaderFvvariable domainMPLmagnetic proteoliposomeRIMMSrepetitive immunization at multiple sitesVHvariable heavyVLvariable light Introduction The formyl peptide receptor (FPR) family is a group of Class A G-protein coupled Sorafenib Tosylate (Nexavar) receptors (GPCRs) that mediate leukocyte responses during inflammation.1-4 In humans, the FPR receptor family is composed of 3 users: FPR1, FPR2/ALX and FPR3. Human FPR1 is usually primarily expressed in neutrophils, monocytes and macrophages and mediates effects such as degranulation and chemotaxis in response to a range of formyl-peptide ligands derived from bacteria and mitochondria. Therefore, FPR1 is usually a potential therapeutic target for the treatment of inflammation-related diseases that are exacerbated by bacterial infection and tissue damage.5 In addition, FPR1 was shown to be selectively expressed on highly malignant human glioma cells and contribute to tumor progression, and for that reason may be a potential therapeutic target for the treatment of malignant human glioblastoma.6 A significant advantage offered by monoclonal antibodies over other classes of therapeutic for targeting GPCRs is their high specificity that allows precise selectivity for desired GPCR family members and even desired conformations of a particular GPCR. Therefore, monoclonal antibodies offer the possibility for identifying GPCR-targeting therapeutics with very specific functions and correspondingly few unwanted effects.7 However, GPCRs and other complex integral membrane proteins are hard targets for antibody isolation and affinity maturation. A limiting factor is typically the availability of a suitable protein preparation for use as an immunogen or antigen in antibody generation Sorafenib Tosylate (Nexavar) and optimization methods. There are reports describing the use of purified GPCR preparations for antibody isolation, for example the immunization of animals with the rat neurotensin 1 receptor8 and the rat 5HT2c serotonin receptor;9 however, this is most often not the case and surrogate immunogens or antigens are usually required. 10 Peptides and proteins have been used successfully to mimic GPCR extracellular regions for antibody generation, but this approach is not relevant to all GPCRs because it depends on the size, the functional relevance and the sequence homology of these regions to other GPCRs in each case. Furthermore, the use of peptides is limited to mimicking linear epitopes rather than allowing the representation of conformational epitopes made up of multiple extracellular loops. Thyroid Sorafenib Tosylate (Nexavar) stimulating hormone receptor is an example of a class A GPCR very well suited to a peptide antigen approach since it possesses a large ectodomain that can be exploited for the design of immunogens, and, as a result, a panel of antibodies targeting this GPCR exist.11 Other successful examples of the use of peptides as antigens include the isolation of single chain Fv fragment (scFv) antibodies that are Ace able to recognize the native cholecystokinin-B receptor expressed on Sorafenib Tosylate (Nexavar) cells by panning of a phage display antibody library using a synthetic peptide corresponding to the second extracellular loop of the receptor,12 and isolation of a competitive antagonistic antibody for the class B GPCR glucose-dependent insulinotropic polypeptide receptor using phage display and ribosome display selections against a peptide comprising the receptor N-terminus.13 In cases where the use of extracellular domains or peptides as surrogate GPCR immunogens is not feasible, approaches that avoid the need for any purified GPCR have been used, such as the immunization of animals with DNA encoding the GPCR of interest14 or the use of GPCR over-expressing cell lines for the immunization of animals. The.