| Abstrakt: |
ABSTRACTIn mammals, the natural resistance-associated macrophage protein 1 gene, Nramp1, plays a major role in resistance to mycobacterial infections. Chesapeake Bay striped bass (Morone saxatilis) is currently experiencing an epizootic of mycobacteriosis that threatens the health of this ecologically and economically important species. In the present study, we characterized an Nrampgene in this species and obtained evidence that there is induction following Mycobacteriumexposure. The striped bass Nrampgene (MsNramp) and a 554-amino-acid sequence contain all the signal features of the Nrampfamily, including a topology of 12 transmembrane domains (TM), the transport protein-specific binding-protein-dependent transport system inner membrane component signature, three N-linked glycosylation sites between TM 7 and TM 8, sites of casein kinase and protein kinase C phosphorylation in the amino and carboxy termini, and a tyrosine kinase phosphorylation site between TM 6 and TM 7. Phylogenetic analysis most closely grouped MsNrampwith other teleost Nrampgenes and revealed high sequence similarity with mammalian Nramp2. MsNrampexpression was present in all tissues assayed by reverse transcription-PCR. Within 1 day of injection of Mycobacterium marinum, MsNrampexpression was highly induced (17-fold higher) in peritoneal exudate (PE) cells compared to the expression in controls. The levels of MsNrampwere three- and sixfold higher on days 3 and 15, respectively. Injection of Mycobacterium shottsiiresulted in two-, five-, and threefold increases in gene expression in PE cells over the time course. This report is the first report of induction of an Nrampgene by mycobacteria in a poikilothermic vertebrate. |
