Evidence that histidine protonation of receptor-bound anthrax protective antigen is a trigger for pore formation.

The protective antigen (PA) component of the anthrax toxin forms pores within the low pH environment of host endosomes through mechanisms that are poorly understood. It has been proposed that pore formation is dependent on histidine protonation. In previous work, we biosynthetically incorporated 2-fluorohistidine (2-FHis), an isosteric analogue of histidine with a significantly reduced pK(a) ( approximately 1), into PA and showed that the pH-dependent conversion from the soluble prepore to a pore was unchanged.

Vesicular monoamine transporter substrate/inhibitor activity of MPTP/MPP+ derivatives: a structure-activity study.

The active metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), N-methyl-4-phenylpyridinium (MPP(+)), selectively destroys the dopaminergic neurons and induces the symptoms of Parkinson's disease. Inhibition of mitochondrial complex I and/or the perturbation of dopamine metabolism through cellular and granular accumulation have been proposed as some of the major causes of neurotoxicity. In the present study we have synthesized and characterized a number of MPTP and MPP(+) derivatives that are suitable for the comparative neurotoxicity and complex I inhibition versus dopamine metabolism perturbation studies.

Effect of 2-fluorohistidine labeling of the anthrax protective antigen on stability, pore formation, and translocation.

The action of anthrax toxin relies in part upon the ability of the protective antigen (PA) moiety to form a heptameric pore in the endosomal membrane, providing a portal for entry of the enzymic moieties of the toxin into the cytosol. Pore formation is dependent on a conformational change in the heptameric prepore that occurs in the neutral to mildly acidic pH range, and it has been hypothesized that protonation of one or more histidine residues triggers this transition. To test this hypothesis, we used biosynthetic methods to incorporate the unnatural amino acid analogue 2-fluorohistidine (2-FHis) into PA.

Perturbation of dopamine metabolism by 3-amino-2-(4'-halophenyl)propenes leads to increased oxidative stress and apoptotic SH-SY5Y cell death.

We have recently characterized a series of 3-amino-2-phenyl-propene (APP) derivatives as reversible inhibitors for the bovine adrenal chromaffin granule vesicular monoamine transporter (VMAT) that have been previously characterized as potent irreversible dopamine-beta-monooxygenase (DbetaM) and monoamine oxidase (MAO) inhibitors. Halogen substitution on the 4'-position of the aromatic ring gradually increases VMAT inhibition potency from 4'-F to 4'-I, parallel to the hydrophobicity of the halogen. We show that these derivatives are taken up into both neuronal and non-neuronal cells, and into resealed chromaffin granule ghosts efficiently through passive diffusion.

Copper ions disrupt dopamine metabolism via inhibition of V-H+-ATPase: a possible contributing factor to neurotoxicity.

The involvement of copper in the pathophysiology of neurodegeneration has been well documented but is not fully understood. Commonly, the effects are attributed to increased reactive oxygen species (ROS) production due to inherent redox properties of copper ions. Here we show copper can have physiological effects distinct from direct ROS production.