40 research outputs found

    Refinement of the gonadotropin releasing hormone receptor I homology model by applying molecular dynamics

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    Sexual maturation of human cells in ovaries and prostate is linked to the biochemical cascade initiated by the activation of cell receptors through the binding of Gonadotropin Releasing Hormone (GnRH). The GnRH receptors (GnRHR) are part of the rhodopsin G-protein coupled receptor (GPCR) family and consist of seven trans–membrane helical domains connected via extra– and intra–cellular segments. The GnRH–GnRHR complex has been implicated in various forms of prostate and ovarian cancer. The lack of any structural data about the GnRH receptor impedes the design of antagonists for use in cancer treatment. The aim of the study is to devise a model of GnRHR to be used further for the design of improved peptide/non-peptide GnRH analogues and, to our knowledge provide new structural information regarding the extracellular loop 2 (ECL2) that acts a regulator of ligand entry to GnRHR. The common structural characteristics, of the members of the rhodopsin family of GPCRs, have been employed for the construction of a homology model for GnRHR. Structural information from the human β2–adrenergic receptor, as well as rhodopsins have been used in order to create a theoretical model for GnRHR. Furthermore, molecular dynamics (MD) simulations have been employed for the refinement of the model and to explore the impact of the bilayer membrane in GnRHR conformation

    Molecular dynamics at the receptor level of immunodominant myelin oligodendrocyte glycoprotein 35-55 epitope implicated in multiple sclerosis

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    Multiple Sclerosis (MS) is a common autoimmune disease whereby myelin is destroyed by the immune system. The disease is triggered by the stimulation of encephalitogenic T-cells via the formation of a trimolecular complex between the Human Leukocyte Antigen (HLA), an immunodominant epitope of myelin proteins and T-cell Receptor (TCR). Myelin Oligodendrocyte Glycoprotein (MOG) is located on the external surface of myelin and has been implicated in MS induction. The immunodominant 35–55 epitope of MOG is widely used for in vivo biological evaluation and immunological studies that are related with chronic Experimental Autoimmune Encephalomyelitis (EAE, animal model of MS), inflammatory diseases and MS. In this report, Molecular Dynamics (MD) simulations were used to explore the interactions of MOG35–55 at the receptor level. A detailed mapping of the developed interactions during the creation of the trimolecular complex is reported. This is the first attempt to gain an understanding of the molecular recognition of the MOG35–55 epitope by the HLA and TCR receptors. During the formation of the trimolecular complex, the residues Arg41 and Arg46 of MOG35–55 have been confirmed to serve as TCR anchors while Tyr40 interacts with HLA. The present structural findings indicate that the Arg at positions 41 and 46 is a key residue for the stimulation of the encephalitogenic T-cells

    Design And Synthesis of a Novel Potent Myelin Basic Protein Epitope 87−99 Cyclic Analogue:  Enhanced Stability and Biological Properties of Mimics Render Them a Potentially New Class of Immunomodulators †

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    A cyclic analogue, [cyclo(87−99)MBP87-99], of the human immunodominant MBP87-99 epitope, was designed based on ROESY/NMR distance information and modeling data for linear epitope 87−99, taking into account T-cell (Phe89, Lys91, Pro96) and HLA (His88, Phe90, Ile93) contact side-chain information. The cyclic analogue was found to induce experimental allergic encephalomyelitis (EAE), to bind HLA-DR4, and to increase CD4 T-cell line proliferation, like that of the conformationally related linear MBP87-99 epitope peptide. The mutant cyclic peptides, the cyclo(91−99)[Ala96]MBP87-99 and the cyclo(87−99)[Arg91Ala96]MBP87-99, reported previously for suppressing, to a varying degree, autoimmune encephalomyelitis in a rat animal model, were found in this study to possess the following immunomodulatory properties:  (i) they suppressed the proliferation of a CD4 T-cell line raised from a multiple sclerosis patient, (ii) they scored the best in vitro TH2/TH1 cytokine ratio in peripheral blood mononuclear cell cultures derived from 13 multiple sclerosis patients, inducing IL-10 selectively, and (iii) they bound to HLA-DR4, first to be reported for cyclic MBP peptides. In addition, cyclic peptides were found to be more stable to lysosomal enzymes and Cathepsin B, D, and H, compared to their linear counterparts. Taken together, these data render cyclic mimics as putative drugs for treating multiple sclerosis and potentially other Th1-mediated autoimmune diseases

    Peptides as therapeutic agents or drug leads for autoimmune, hormone dependent and cardiovascular diseases

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    Peptides regulate most physiological processes, mainly by binding to specific receptors located on the cell surface and inducing a series of signals, neurotransmissions or the release of growth factors. There has been a rapid expansion in the use of peptides as therapeutic agents after the 1960s, but a series of unfortunate side effects present in Phase I and II clinical studies combined with their low bioavailability, led to the introduction of the idea of peptidomimetics as alternative compounds that mimic the biological activity of peptides, while offering the advantages of increased bioavailability, biostability, bioefficiency, and bioselectivity. Since then new peptides with promising in vitro results, involving the monoclonal antibody expansion, as well as the newly launched research field for novel formulations for increasing peptides' bioavailability, redirected the interest on the peptide market. In this report we will highlight three areas where the use of peptides has shown promising results, with products that are either currently used as drugs or included into Phase III clinical studies

    Development of PLGA Nanoparticles with a Glycosylated Myelin Oligodendrocyte Glycoprotein Epitope (MOG35-55) against Experimental Autoimmune Encephalomyelitis (EAE)

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    Multiple sclerosis (MS) is one of the most common neurodegenerative diseases in young adults, with early clinical symptoms seen in the central nervous system (CNS) myelin sheaths due to an attack caused by the patient's immune system. Activation of the immune system is mediated by the induction of an antigen-specific immune response involving the interaction of multiple T-cell types with antigen-presenting cells (APCs), such as dendritic cells (DCs). Antigen-specific therapeutic approaches focus on immune cells and autoantigens involved in the onset of disease symptoms, which are the main components of myelin proteins. The ability of such therapeutics to bind strongly to DCs could lead to immune system tolerance to the disease. Many modern approaches are based on peptide-based research, as, in recent years, they have been of particular interest in the development of new pharmaceuticals. The characteristics of peptides, such as short lifespan in the body and rapid hydrolysis, can be overcome by their entrapment in nanospheres, providing better pharmacokinetics and bioavailability. The present study describes the development of polymeric nanoparticles with encapsulated myelin peptide analogues involved in the development of MS, along with their biological evaluation as inhibitors of MS development and progression. In particular, particles of poly(lactic-co-glycolic) acid (PLGA) loaded with peptides based on mouse/rat (rMOG) epitope 35-55 of myelin oligodendrocyte glycoprotein (MOG) conjugated with saccharide residues were developed. More specifically, the MOG(35-55) peptide was conjugated with glucosamine to promote the interaction with mannose receptors (MRs) expressed by DCs. In addition, a study of slow release (dissolution) and quantification on both initially encapsulated peptide and daily release in saline in vitro was performed, followed by an evaluation of in vivo activity of the formulation on mouse experimental autoimmune encephalomyelitis (EAE), an animal model of MS, using both prophylactic and therapeutic protocols. Our results showed that the therapeutic protocol was effective in reducing EAE clinical scores and inflammation of the central nervous system and could be an alternative and promising approach against MS inducing tolerance against the disease