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Proteasome activity in a naïve mosquito cell line infected with Wolbachia pipientis wAlbB

Fallon, Ann M., Witthuhn, Bruce A.
In vitro cellular & developmental biology 2009 v.45 no.8 pp. 460-466
Aedes albopictus, Western blotting, Wolbachia pipientis, biochemical pathways, cultured cells, cysteine, gels, inoculum, metabolism, methionine, monoclonal antibodies, proteasome endopeptidase complex, sodium dodecyl sulfate, tandem mass spectrometry, ubiquitin
We used Wolbachia pipientis strain wAlbB from Aedes albopictus Aa23 cells to infect clonal Ae. albopictus TK-6 cells, which are resistant to 5-bromodeoxyuridine. Infected TK-6 cells were cultured in medium containing 5-bromodeoxyuridine to select against Aa23 cells that might have persisted in the inoculum. Infected TK-6 lines retained the Wolbachia infection for 5 mo, indicating that their metabolic processes support Wolbachia growth and multiplication. To investigate early events after Wolbachia infection, we labeled infected cells with ³⁵S[methionine/cysteine]. Patterns of labeled proteins on sodium dodecyl sulfate gels were similar in control and infected cells, with the exception of a 29-kDa protein. Tandem mass spectrometry revealed that the 29-kDa band included α and β subunits of the 26S proteasome. Independent confirmation of the up-regulation of the proteasome was established by probing Western blots with a monoclonal antibody to the proteasome-associated co-factor, ubiquitin. Wolbachia's loss of metabolic pathways for the synthesis of most amino acids and retention of pathways for their uptake and metabolism suggest that proteasome activation provides a mechanism whereby controlled degradation of intracellular host proteins would increase availability of amino acids to support establishment and maintenance of the Wolbachia infection.