NMR structural studies of the ItchWW3 domain reveal that phosphorylation at T30 inhibits the interaction with PPxY-containing ligands.

In this work, we study the role of phosphorylation as a regulatory mechanism for the interaction between the E3 ubiquitin ligase ItchWW3 domain and two PPxY motifs of one of its targets, the Epstein-Barr virus latent membrane protein 2A. Whereas ligand phosphorylation only diminishes binding, domain phosphorylation at residue T30 abrogates it. We show that two ItchWW domains can be phosphorylated at this position, using CK2 and PKA kinases and/or with stimulated T lymphocyte lysates. To better understand the regulation process, we determined the NMR structures of the ItchWW3-PPxY complex and of the phosphoT30-ItchWW3 variant. The peptide binds the domain using both XP and tyrosine grooves. A hydrogen bond from T30 to the ligand is also detected. This hydrogen-bond formation is precluded in the variant, explaining the inhibition upon phosphorylation. Our results suggest that phosphorylation at position 30 in ItchWW domains can be a mechanism to inhibit target recognition in vivo.

Oral insulin-mimetic compounds that act independently of insulin.

The hallmarks of insulin action are the stimulation and suppression of anabolic and catabolic responses, respectively. These responses are orchestrated by the insulin pathway and are initiated by the binding of insulin to the insulin receptor, which leads to activation of the receptor's intrinsic tyrosine kinase. Severe defects in the insulin pathway, such as in types A and B and advanced type 1 and 2 diabetes lead to severe insulin resistance, resulting in a partial or complete absence of response to exogenous insulin and other known classes of antidiabetes therapies. We have characterized a novel class of arylalkylamine vanadium salts that exert potent insulin-mimetic effects downstream of the insulin receptor in adipocytes. These compounds trigger insulin signaling, which is characterized by rapid activation of insulin receptor substrate-1, Akt, and glycogen synthase kinase-3 independent of insulin receptor phosphorylation. Administration of these compounds to animal models of diabetes lowered glycemia and normalized the plasma lipid profile. Arylalkylamine vanadium compounds also showed antidiabetic effects in severely diabetic rats with undetectable circulating insulin. These results demonstrate the feasibility of insulin-like regulation in the complete absence of insulin and downstream of the insulin receptor. This represents a novel therapeutic approach for diabetic patients with severe insulin resistance.

New efficient substrates for semicarbazide-sensitive amine oxidase/VAP-1 enzyme: analysis by SARs and computational docking.

Structure activity relationships for semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 (SSAO/VAP-1) were studied using a library of arylalkylamine substrates, with the aim of contributing to the discovery of more efficient SSAO substrates. Experimental data were contrasted with computational docking studies, thereby allowing us to examine the mechanism and substrate-binding affinity of SSAO and thus contribute to the discovery of more efficient SSAO substrates and provide a structural basis for their interactions. We also built a model of the mouse SSAO structure, which provides several structural rationales for interspecies differences in SSAO substrate selectivity and reveals new trends in SSAO substrate recognition. In this context, we identified novel efficient substrates for human SSAO that can be used as a lead for the discovery of antidiabetic agents.

Structure-activity relationships of SSAO/VAP-1 arylalkylamine-based substrates.

Semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 (SSAO/VAP-1) substrates show insulin-mimetic effects and are therefore potentially valuable molecules for the treatment of diabetes mellitus. Herein we review several structural and electronic aspects of SSAO arylalkylamine-based substrates. Two main modifications directly affect amine oxidase (AO) activity: 1) variation in ring substitution modulates the biological activity of the arylalkylamine ligand by converting a substrate into a substrate-like inhibitor, and 2) variation in the number of methylene units between the aromatic ring and the ammonium groups of the arylalkylamine substrates dramatically alters the oxidation rate between species. Furthermore, we review relevant information about mammalian SSAO/VAP-1 substrate selectivity and specificity over monoamine oxidases (MAOs).

A novel protecting/activating strategy for beta-hydroxy acids and its use in convergent peptide synthesis.

beta-Hydroxy acids were reacted with hexafluoroacetone and carbodiimides to give carboxy-activated six-membered lactones in good yields. On reaction with amines, the corresponding amides were obtained. We demonstrate the following applications of this protecting/activating strategy: preparation of carboxamides in solution and on solid phase (both normal and reverse mode); recovery and reuse of the excess material in solid-phase synthesis; and convergent solid-phase peptide synthesis (CSPPS) with peptide segments bearing C-terminal Ser or Thr with very low levels of epimerization (<1%, HPLC).

Understanding the mechanism of action of the novel SSAO substrate (C7NH10)6(V10O28).2H2O, a prodrug of peroxovanadate insulin mimetics.

A new vanadium salt, hexakis(benzylammonium) decavanadate (V) dihydrate (C(7)NH(10))(6)(V(10)O(28)).2H(2)O (1), has been synthesized as well as characterized chemically and biologically. An in vitro enzyme assay revealed that compound 1 is oxidized to the same extent as a combination of benzylamine and vanadate by the enzyme semicarbazide-sensitive amine oxidase (SSAO), and therefore can be considered an SSAO substrate. It also stimulates glucose uptake in isolated rat adipocytes in a dose-dependent manner. We describe here the results of (51)V-NMR experiments that, combined with the in vitro results, corroborate that compound 1 could act as a prodrug of di-peroxovanadate ([V(OH)(2)(OO)(2)(OH)(2)](2-)) insulin mimetics.