My work in the Azad lab is focused on rickettsia-host interactions at the cellular level As an obligate intracellular pathogen, Rickettsia typhi must modulate normal host cell functions to create a replication niche and evade host immune defenses. Despite the importance of typhus group rickettsiae as pathogens, relatively little is known about how they establish infection in human host cells. We hypothesize that host and bacterial proteins interact to perform critical roles in rickettsial infection and that targeting these interactions can yield novel, effective anti-rickettsial therapies. Our studies examine host cell-pathogen interactions that are likely to be essential for establishment of successful R. typhi infection.

Using a bacterial pulldown assay and mass spectrometry analysis, we identified a number of proteins that bind to partially purified R. typhi but not a mock bacterial preparation. To test the role of these proteins as potentially critical host factors for R. typhi infection, we will knock down each protein in host cells using small interfering (si)RNAs and assess any effects on R. typhi invasion and replication. We will then identify and characterize the R. typhi factors that mediate interactions between rickettsiae and their host cells.

Among other proteins, Ku70, a subunit of the DNA-dependent protein kinase that serves as a receptor for R. conorii, was identified as a human binding partner of R. typhi. All methods for siRNA mediated knock down of host factors and assaying invasion and replication in host cells have been optimized and examination of the effects of knock-down of individual host proteins are underway. The fact that R. typhi binds to Ku70 suggests that this protein may be a human host cell receptor shared by both spotted fever and typhus group rickettsiae.

The techniques I have used extensively include: growth and purification of obligate intracellular bacteria, indirect immunofluorescence microscopy (both widefield and confocal), cell culture and transfection including generation of stably transfected cell lines, immunoblotting, metabolic radiolabeling of cells, protein-protein interaction assays, cell-based trafficking assays and siRNA-mediated protein knock-down.

My career at the bench started in the spring semester of 1997 in my freshman year of college, when I joined the lab of Dr. B. Franklin Pugh. The focus of the lab was on basal transcription initiation and my work centered on the interaction between the TATA-binding protein (TBP) and the TBP-associated Factor, TAF-172. I graduated with BS with honors in Microbiology in spring of 2000. My honors thesis was entitled: "Biochemical characterization of the TATA-binding protein associated factor, TAF-172".

In August 2000, I joined the Biochemistry Cell and Molecular Biology program at Johns Hopkins School of Medicine. I rotated through the laboratories of Dr. Janice Clements, studying retroviral pathogenesis, and Dr. Wade Gibson, studying human cytomegalovirus, eventually joining the lab of Dr. Carolyn Machamer in the Department of Cell Biology. Our lab focused on the structure and function of the Golgi complex, primarily focusing on the roles of Golgi-localized proteins, and coronavirus budding. My research was a bit of a new direction for the lab, combining the study of a Golgi protein, golgin-160 with apoptosis. We found that expression of a mutant version of golgin-160 that could not be cleaved by caspases rendered them resistant to certain pro-apoptotic stimuli including secretory pathway stress and death receptor ligation. We also observed a change in the localization of death receptors in cells expressing mutant golgin-160. My graduate work is published in 2 journal articles and a review, and my thesis entitled: "Apoptotic signaling at the Golgi Complex: insights from a caspase-resistant Golgi protein".

In November of 2007, I began work in Dr. Azad's lab, studying rickettsial phagosome escape. As an obligate intracellular pathogen, Rickettsia typhi, is a rewarding challenge to study. Upon entry into non-phagocytic cells by induced phagocytosis, R. typhi rapidly escapes from the phagosome to live freely in the cytoplasm of an infected cell. My research focuses on how bacterial interactions with human host cell proteins facilitates this infection process.

[1] Maag, R.S., Mancini, M., Rosen, A., and Machamer, C.E. (2005). Caspase-resistant golgin-160 disrupts apoptosis induced by secretory pathway stress and ligation of death receptors. Mol. Biol. Cell 16, 3019-3027.

[2] Maag, R.S., Hicks, S.W., and Machamer, C.E. (2003). Death from within: apoptosis and the secretory pathway. Curr. Opin. Cell Biol. 15, 1-6.

[3] Maag, R.S. and Machamer, C.E. (2006). Expression of caspase-resistant golgin-160 leads to mislocalization of Tumor Necrosis Factor Receptor. Manuscript in preparation.


Research Presentations:
[1] Maag, R.S. and Azad, A.F. (2007) Early host cell interactions and phagosome escape by Rickettsia typhi. 21st meeting of the American Society for Rickettsiology Meeting, p. 46. (poster).


[2] Maag, R.S. and Machamer, C.E. (2005). Caspase cleavage of golgin-160 is required for transduction of apoptotic signals initiated by secretory pathway stress and death receptor ligation. 2005 Cold Spring Harbor Meeting on Programmed Cell Death, p. 124 (poster).

[3] Maag, R.S. and Machamer, C.E. (2003). Caspase resistant golgin-160 impairs apoptosis in response to secretory pathway stress and ligation of death receptors. 2003 Cold Spring Harbor Meeting on Programmed Cell Death. p. 176 (poster).

[4] Maag, R.S. and Machamer, C.E. (2001). Caspase resistant golgin-160 delays Golgi disassembly during apoptosis. 41st American Society for Cell Biology Annual Meeting p. 508a (poster).