Properties of myelin altered peptide ligand cyclo(87-99)(Ala91,Ala96)MBP87-99 render it a promising drug lead for immunotherapy of multiple sclerosis.

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system, and it has been established that autoreactive T helper (Th) cells play a crucial role in its pathogenesis. Myelin basic protein (MBP) epitopes are major autoantigens in MS, and the sequence MBP87-99 is an immunodominant epitope. We have previously reported that MBP87-99 peptides with modifications at principal T-cell receptor (TCR) contact sites suppressed the induction of EAE symptoms in rats and SJL/J mice, diverted the immune response from Th1 to Th2 and generated antibodies that did not cross react with the native MBP protein. In this study, the linear and cyclic analogs of the MBP87-99 epitope, namely linear (Ala91,Ala96)MBP87-99 (P2) and cyclo(87-99)(Ala91,Ala96)MBP87-99 (P3), were evaluated for their binding to HLA-DR4, stability to lysosomal enzymes, their effect on cytokine secretion by peripheral blood mononuclear cells (PBMC) derived from MS patients or healthy subjects (controls), and their effect in rat EAE. P1 peptide (wild-type, MBP87-99) was used as control. P2 and P3 did not alter significantly the cytokine secretion by control PBMC, in contrast to P1 that induced moderate IL-10 production. In MS PBMC, P2 and P3 induced the production of IL-2 and IFN-γ, with a simultaneous decrease of IL-10, whereas P1 caused a reduction of IL-10 secretion only. The cellular response to P3 indicated that cyclization did not affect the critical TCR contact sites in MS PBMC. Interestingly, the cyclic P3 analog was found to be a stronger binder to HLA-DR4 compared to linear P2. Moreover, cyclic P3 was more stable to proteolysis compared to linear P2. Finally, both P2 and P3 suppressed EAE induced by an encephalitogenic guinea pig MBP74-85 epitope in Lewis rats whereas P1 failed to do so. In conclusion, cyclization of myelin altered peptide ligand (Ala91,Ala96)MBP87-99 improved binding affinity to HLA-DR4, resistance to proteolysis and antigen-specific immunomodulation, rendering cyclo(87-99)(Ala91,Ala96)MBP87-99 an important candidate drug for MS immunotherapy.

Insights into AT1 receptor activation through AngII binding studies.

This study investigates the binding of angiotensin II (AngII) to the angiotensin II type 1 receptor (AT1R), taking into consideration several known activation elements that have been observed for G-protein-coupled receptors (GPCRs). In order to determine the crucial interactions of AngII upon binding, several MD simulations were implemented using AngII conformations derived from experimental data (NMR ROEs) and in silico flexible docking methodologies. An additional goal was to simulate the induced activation mechanism and examine the already known structural rearrangements of GPCRs upon activation. Performing MD simulations to the AT1R - AngII - lipids complex, a series of dynamic changes in the topology of AngII and the intracellular part of the receptor were observed. Overall, the present study proposes a complete binding profile of AngII to the AT1R, as well as the key transitional elements of the receptor and the agonist peptide upon activation through NMR and in silico studies.