Adenylate cyclase toxin (ACT) from Bordetella hinzii: characterization and differences from ACT of Bordetella pertussis.

Bordetella hinzii is a commensal respiratory microorganism in poultry but is increasingly being recognized as an opportunistic pathogen in immunocompromised humans. Although associated with a variety of disease states, practically nothing is known about the mechanisms employed by this bacterium. In this study, we show by DNA sequencing and reverse transcription-PCR that both commensal and clinical strains of B. hinzii possess and transcriptionally express cyaA, the gene encoding adenylate cyclase toxin (ACT) in other pathogenic Bordetella species. By Western blotting, we also found that B. hinzii produces full-length ACT protein in quantities that are comparable to those made by B. pertussis. In contrast to B. pertussis ACT, however, ACT from B. hinzii is less extractable from whole bacteria, nonhemolytic, has a 50-fold reduction in adenylate cyclase activity, and is unable to elevate cyclic AMP levels in host macrophages (nontoxic). The decrease in enzymatic activity is attributable, at least in part, to a decreased binding affinity of B. hinzii ACT for calmodulin, the eukaryotic activator of B. pertussis ACT. In addition, we demonstrate that the lack of intoxication by B. hinzii ACT may be due to the absence of expression of cyaC, the gene encoding the accessory protein required for the acylation of B. pertussis ACT. These results demonstrate the expression of ACT by B. hinzii and represent the first characterization of a potential virulence factor of this organism.

The vesicular glutamate transporter 1 (xVGlut1) is expressed in discrete regions of the developing Xenopus laevis nervous system.

As the major excitatory neurotransmitter in the vertebrate nervous system, glutamate not only plays an essential role in adult neural signaling, but has also been implicated as a trophic factor in neuronal cell maturation, differentiation, and survival. An essential component of the glutamatergic neurotransmission system is the family of glutamate transporters, a multigene family that codes for plasma membrane-bound as well as vesicle-bound proteins responsible for the removal of glutamate from the cleft and its re-uptake into the synaptic vesicle. Here we describe the spatial and temporal expression of the vesicular glutamate transporter (xVGlut1) during the early developmental stages of the amphibian Xenopus laevis. RNAse protection analysis and in situ hybridization reveal that xVGlut1 is first expressed at late neurula stages in the developing spinal cord and trigeminal nerve. By tailbud stages xVGlut1 transcripts are detected in several of the cranial nerves, the pineal gland, and medial forebrain. By hatching stages xVGlut1 expression reappears in localized tracts within the spinal cord. Expression levels increase throughout development into adulthood.