Stereochemical engineering yields a multifunctional peptide macrocycle inhibitor of Akt2 by fine-tuning macrocycle-cell membrane interactions.

Macrocycle peptides are promising constructs for imaging and inhibiting extracellular, and cell membrane proteins, but their use for targeting intracellular proteins is typically limited by poor cell penetration. We report the development of a cell-penetrant high-affinity peptide ligand targeted to the phosphorylated Ser474 epitope of the (active) Akt2 kinase. This peptide can function as an allosteric inhibitor, an immunoprecipitation reagent, and a live cell immunohistochemical staining reagent. Two cell penetrant stereoisomers were prepared and shown to exhibit similar target binding affinities and hydrophobic character but 2-3-fold different rates of cell penetration. Experimental and computational studies resolved that the ligands' difference in cell penetration could be assigned to their differential interactions with cholesterol in the membrane. These results expand the tool kit for designing new chiral-based cell-penetrant ligands.

Extracellular vimentin modulates human dendritic cell activation.

Vimentin is an intermediate filament protein traditionally considered to be an intracellular protein with a structural role. However, recent evidence suggests that vimentin can also be found outside the cell in disease conditions such as cancer, traumatic tissue injury, and inflammation. Extracellular vimentin was previously found to stimulate innate immunity by increasing monocyte and macrophage ability to kill bacteria. However, vimentin has also been previously found to decrease neutrophil infiltration into inflamed tissue. How extracellular vimentin affects the initiation of adaptive immune responses is unknown. Initiation of adaptive immunity involves priming of naïve T cells by antigen-presenting cells, the most effective of which are dendritic cells (DCs). In this study, we demonstrate how extracellular vimentin modulates lipopolysaccharide (LPS) - induced activation of human DCs. Using cytometric bead arrays, we show that extracellular vimentin decreases LPS-activated DC secretion of pro-inflammatory cytokines IL-6 and IL-12 while increasing secretion of the anti-inflammatory cytokine IL-10. Using flow cytometry, we show that extracellular vimentin does not significantly affect LPS-induced DC surface expression of MHC I (HLA-ABC) or MHC II (HLA-DR) presentation molecules, costimulatory factors (CD80, CD86), or the DC maturation marker (CD83). Further, LPS-stimulated DCs co-cultured with allogeneic naïve CD4 + T cells (Th0) induced less secretion of the pro-inflammatory Th1 effector cytokine IFN-γ in the presence of vimentin than in the presence of LPS alone. This result suggests that vimentin reduces Th1 differentiation. Taken together, our data suggest that extracellular vimentin may inhibit pro-inflammatory adaptive immune responses, by blocking DC secretion of pro-inflammatory cytokines. Thus, extracellular vimentin may play an important role in cancer or trauma-complications by inducing suppression of the adaptive immune response. In a positive sense, the presence of extracellular vimentin may prevent tissue-damage from contributing to the development of autoimmunity. Consequently, extracellular vimentin may become a novel drug target for treatment of a variety of pro- and anti-inflammatory disease conditions.

Predicting methotrexate resistance in rheumatoid arthritis patients.

Rheumatoid arthritis (RA) is an incurable, systemic autoimmune disease that decreases quality of life and can lead to severe disability. While there are many medications available to treat RA, the first-line of therapy is low-dose methotrexate (MTX), a small molecule disease-modifying anti-rheumatic drug (DMARD). MTX is the recommended therapy due to its affordability and efficacy in reducing symptoms in most RA patients. Unfortunately, there is great person-to-person variability in the physiological response to MTX, with up to 50% of patients showing little response to the medication. Thus, many RA patients initially placed on MTX do not experience an adequate reduction of symptoms, and could have benefited more in both the short and long terms if initially prescribed a different drug that was more effective for them. To combat this problem and better guide treatment decisions, many research groups have attempted to develop predictive tools for MTX response. Currently, there is no reliable, clinical-grade method to predict an individual's response to MTX treatment. In this review, we describe progress made in the area of MTX non-response/resistance in RA patients. We specifically focus on application of the following elements as predictive markers: proteins related to MTX transport and function, intracellular MTX concentration, immune cell frequencies, cytokines, and clinical factors.

The function of myeloid dendritic cells in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a systemic autoimmune disease that causes joint pain, inflammation, and loss of function. Disease pathogenesis involves activation and proliferation of autoreactive pro-inflammatory effector T cells. While the details of RA onset and progression remain controversial, dendritic cell (DC) numbers dramatically increase in the synovial joint tissues of RA patients. Based on their key functions as antigen-presenting cells and inducers of T cell differentiation, DCs may play an important role in the initiation of joint inflammation. Myeloid DC contributions are likely central to the development of RA, as they are more efficient at antigen presentation in comparison with their closely related cousins, plasmacytoid DCs. Synovial fluid in the joints of RA patients is enriched with pro-inflammatory cytokines and chemokines, which may stimulate or result from DC activation. Epidemiological evidence indicates that smoking and periodontal infection are major environmental risk factors for RA development. In this review, factors in the synovial environment that contribute to altered myeloid DC functions in RA and the effects of environmental risk factors on myeloid DCs are described.

A General Synthetic Approach for Designing Epitope Targeted Macrocyclic Peptide Ligands.

We describe a general synthetic strategy for developing high-affinity peptide binders against specific epitopes of challenging protein biomarkers. The epitope of interest is synthesized as a polypeptide, with a detection biotin tag and a strategically placed azide (or alkyne) presenting amino acid. This synthetic epitope (SynEp) is incubated with a library of complementary alkyne or azide presenting peptides. Library elements that bind the SynEp in the correct orientation undergo the Huisgen cycloaddition, and are covalently linked to the SynEp. Hit peptides are tested against the full-length protein to identify the best binder. We describe development of epitope-targeted linear or macrocycle peptide ligands against 12 different diagnostic or therapeutic analytes. The general epitope targeting capability for these low molecular weight synthetic ligands enables a range of therapeutic and diagnostic applications, similar to those of monoclonal antibodies.