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Journal of Bacteriology, December 2007, p. 8651-8659, Vol. 189, No. 23
0021-9193/07/$08.00+0     doi:10.1128/JB.00881-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Anaplasma phagocytophilum p44 mRNA Expression Is Differentially Regulated in Mammalian and Tick Host Cells: Involvement of the DNA Binding Protein ApxR{triangledown} ,{dagger}

Xueqi Wang,{ddagger} Zhihui Cheng,{ddagger} Chunbin Zhang,{ddagger} Takane Kikuchi,§ and Yasuko Rikihisa*

Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio 43210

Received 5 June 2007/ Accepted 26 August 2007

The natural life cycle of Anaplasma phagocytophilum, an obligatory intracellular bacterium that causes human granulocytic anaplasmosis, consists of alternate infection of two distinct hosts, ticks and mammals, in which bacterial surface proteins are expected to have a critical role. The present study investigated regulation of A. phagocytophilum p44 genes, which encode the P44 major surface proteins. Quantitative real-time reverse transcription-PCR analysis revealed that the amount of p44 mRNA obtained from spleens of A. phagocytophilum-infected SCID mice was approximately 10-fold greater than the amount obtained from salivary glands of A. phagocytophilum-infected Ixodes scapularis nymphs. Similarly, the amount of p44 mRNA obtained from A. phagocytophilum-infected HL-60 cells per bacterium was significantly greater than the amount obtained from infected ISE6 tick cells. The relative amount of p44 mRNA was approximately threefold higher in A. phagocytophilum-infected HL-60 cells cultured at 37°C than in A. phagocytophilum-infected HL-60 cells cultured at 28°C. Although there are more than 100 p44 paralogs, we observed expression mainly from the p44 expression locus (p44E) in various host environments. Interestingly, transcription of the A. phagocytophilum gene encoding the DNA binding protein ApxR was also significantly greater in A. phagocytophilum-infected HL-60 cells than in infected ISE6 tick cells. Gel mobility shift and DNase I protection assays revealed recombinant ApxR binding to the promoter regions of p44E and apxR. ApxR also transactivated the p44E and apxR promoter regions in a lacZ reporter assay. These results indicate that p44 genes and apxR are specifically up-regulated in the mammalian host environment and suggest that ApxR not only is positively autoregulated but also acts as a transcriptional regulator of p44E.

* Corresponding author. Mailing address: Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, 1925 Coffey Road, Columbus, OH 43210-1093. Phone: (614) 292-5661. Fax: (614) 292-6473. E-mail: rikihisa.1{at}osu.edu

{triangledown} Published ahead of print on 28 September 2007.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

{ddagger} X.W., Z.C., and C.Z. contributed equally to this work.

§ Present address: Department of Microbiology and Immunology, Teikyo University School of Medicine, Tokyo, 173-8605, Japan.

Journal of Bacteriology, December 2007, p. 8651-8659, Vol. 189, No. 23
0021-9193/07/$08.00+0     doi:10.1128/JB.00881-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



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  • Scorpio, D. G., Leutenegger, C., Berger, J., Barat, N., Madigan, J. E., Dumler, J. S. (2008). Sequential Analysis of Anaplasma phagocytophilum msp2 Transcription in Murine and Equine Models of Human Granulocytic Anaplasmosis. CVI 15: 418-424 [Abstract] [Full Text]  


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