Identification and characterization of vasoactive intestinal peptide receptor antagonists with high-affinity and potent anti-leukemia activity.

Vasoactive intestinal peptide (VIP) is a neuropeptide involved in tumor growth and immune modulating functions. Previous research indicated that a VIP antagonist (VIPhyb) enhances T-cell activation and induces T-cell-dependent anti-leukemic activity in mice. We created a combinatorial library of VIPhyb C-terminal sequence variations to develop a more potent VIP-receptor (VIP-R) antagonist, hypothesizing that specific amino acid substitutions would improve receptor binding and plasma stability.

Chemical Modifications to Enhance the Drug Properties of a VIP Receptor Antagonist (ANT) Peptide.

Antagonist peptides (ANTs) of vasoactive intestinal polypeptide receptors (VIP-Rs) are shown to enhance T cell activation and proliferation in vitro, as well as improving T cell-dependent anti-tumor response in acute myeloid leukemia (AML) murine models. However, peptide therapeutics often suffer from poor metabolic stability and exhibit a short half-life/fast elimination in vivo. In this study, we describe efforts to enhance the drug properties of ANTs via chemical modifications.

α-catenin middle- and actin-binding domain unfolding mutants differentially impact epithelial strength and sheet migration.

α-catenin (α-cat) displays force-dependent unfolding and binding to actin filaments through direct and indirect means, but features of adherens junction structure and function most vulnerable to loss of these allosteric mechanisms have not been directly compared. By reconstituting an α-cat F-actin-binding domain unfolding mutant known to exhibit enhanced binding to actin (α-cat-H0-FABD) into α-cat knockout Madin Darby Canine Kidney (MDCK) cells, we show that partial loss of the α-cat catch bond mechanism (via an altered H0 α-helix) leads to stronger epithelial sheet integrity with greater colocalization between the α-cat-H0-FABD mutant and actin. α-cat-H0-FABD -expressing cells are less efficient at closing scratch-wounds, suggesting reduced capacity for more dynamic cell-cell coordination.

α-catenin mechanosensitivity as a route to cytokinesis failure through sequestration of LZTS2.

Epithelial cells can become polyploid upon tissue injury, but mechanosensitive cues that trigger this state are poorly understood. Using α-catenin (α-cat) knock-out Madin Darby Canine Kidney (MDCK) cells reconstituted with wild-type and mutant forms of α-cat as a model system, we find that an established α-cat actin-binding domain unfolding mutant designed to reduce force-sensitive binding to F-actin (α-cat-H0-FABD) can promote cytokinesis failure, particularly along epithelial wound-fronts. Enhanced α-cat coupling to cortical actin is neither sufficient nor mitotic cell-autonomous for cytokinesis failure, but critically requires the mechanosensitive Middle-domain (M1-M2-M3) and neighboring cells.

CD2AP links actin to PI3 kinase activity to extend epithelial cell height and constrain cell area.

Maintaining the correct ratio of apical, basal, and lateral membrane domains is important for epithelial physiology. Here, we show that CD2AP is a critical determinant of epithelial membrane proportions. Depletion of CD2AP or phosphoinositide 3-kinase (PI3K) inhibition results in loss of F-actin and expansion of apical-basal domains, which comes at the expense of lateral membrane height in MDCK cells.

Akt/Nox2/NF-κB signaling pathway is involved in Tat-induced HIV-1 long terminal repeat (LTR) transactivation.

Human immunodeficiency virus (HIV) regulatory protein Tat has pro-oxidant property, which might contribute to Tat-induced long terminal repeat region (LTR) transactivation. However, the intracellular mechanisms whereby Tat triggers ROS production, and the relationship between Tat-induced ROS production and LTR transactivation, are still subject to debate. The present study was undertaken to evaluate the specific effects of Tat on nicotinamide adenine denucleotide phosphate (NADPH) oxidase in MAGI cells, and to determine the specific role of NADPH oxidase in Tat-induced LTR transactivation.

Nicotinamide phosphoribosyltransferase/sirtuin 1 pathway is involved in human immunodeficiency virus type 1 Tat-mediated long terminal repeat transactivation.

Tat is a multifunctional transactivator encoded by human immunodeficiency virus type 1 (HIV-1). Tat transactivating activity is controlled by nicotinamide adenine nucleotide(+) (NAD(+))-dependent deacetylase sirtuin 1 (SIRT1). Nicotinamide phosphoribosyltransferase (Nampt) is a rate-limiting enzyme in the conversion of nicotinamide into NAD(+), which is crucial for SIRT1 activation.