Universität zu Köln 

Prof. Dr. Jonathan Howard

Institut für Genetik, Universität zu Köln
email: j.howard@uni-koeln.de
phone: +49-(0)221 470 4864
website

The immunity-related GTPases form a distinct family of large GTPases that are important resistance factors against vacuolar pathogens in vertebrates. During the previous two grant periods we have pioneered work on the biochemistry, structure and cell-autonomous function of this protein family against the protozoan pathogen, Toxoplasma gondii, in mice. Both as a resistance system and as a regulated protein complex the IRG proteins have remarkable properties. In the last round of this SFB 635 we wish to complete a structure-function analysis of the GTP hydrolysis cycle of this protein family, and to apply this knowledge to develop an understanding of the normal and abnormal behaviour of these proteins and their post-translational modifications in cellular contexts. In summary, our goals are:

1. To obtain crystallographic evidence to support a structural model of the activating interactions between IRG protein molecules in the GTP-bound state.
2. To measure the interactions between purified IRG proteins and lipid membranes, to investigate the roles of nucleotide binding status, myristoylation and phosphorylation.
3. To understand the mechanism by which mouse cells can inhibit the phosphorylation and inactivation of IRG resistance proteins by a parasite virulence factor.
4. To understand sterile activation of IRG proteins in cells, the formation of intracellular aggregates and their impact on cellular function.

Running time: 07/2003 – 06/2015

Recent publications:

Fentress, S., Steinfeldt, T., Howard, J.C. and Sibley L.D (2012). The arginine-rich N-terminal domain of ROP18 is necessary for vacuole targeting and virulence of Toxoplasma gondii. Cellular Microbiology. in press

Fleckenstein, M., Reese, M.L., Boothroyd, J.C., Howard, J.C. and Steinfeldt, T. (2012). A Toxoplasma gondii pseudokinase inhibits host IRG resistance proteins. PloS Biology. PLoS Biol 10(7): e1001358. doi:10.1371/journal.pbio.1001358

Traver M.K., Henry S.C., Cantillana V., Oliver T., Hunn J.P., Howard J.C., Beer S., Pfeffer K., Coers J., Taylor G.A. (2011). Immunity-related GTPase M (IRGM) proteins influence the localization of guanylate-binding protein 2 (GBP2) by modulating macroautophagy.

Pawlowski, N., Khaminets, A., Hunn, J.P., Papic, N., Schmidt, A., Uthaiah, R.C., Lange, R., Vopper, G., Martens, S., Wolf, E., and Howard, J.C. (2011). The activation mechanism of Irga6, an interferon-inducible GTPase contributing to mouse resistance against Toxoplasma gondii. BMC Biology 28, 7.

Steinfeldt, T., Könen-Waisman, S., Tong, L., Pawlowski, T., Lamkemeyer, T., Sibley, L. D., Hunn, J.P., Howard, J.C. (2010). Phosphorylation of mouse immunity-related GTPase (IRG) resistance proteins is an evasion strategy for virulent T. gondii. PLoS Biol. 8 (12), e1000576.

Pawlowski, N. (2010). Dynamin self-assembly and the vesicle fission mechanism: structural insights into the large atypical GTPases. BioEssays 32, 1033-1039. (B 2)

Hunn, J.P. and Howard, J.C. (2010). The mouse resistance protein, Irgm1 (LRG-47): a regulator or an effector of pathogen defense? PLoS Pathogens 6 (7), e1001008.

Khaminets, A., Hunn, J.P., Könen-Waisman, S., Zhao,, Y.O., Preukschat, D., Coers, J., Boyle, J.P., Ong,, Y.C., Boothroyd,, J.C., Reichmann,, G., Howard, J.C. (2010). Coordinated loading of multiple IRG resistance GTPases on to the Toxoplasma gondii parasitophorous vacuole. Cell. Microbiol. 12, 939-61.

Henry, S.C., Daniell, X.G., Burroughs, A.R., Indaram, M., Howell, D.N., Coers, J., Starnbach, M.N., Hunn, J.P., Howard, J.C., Feng, C.G., Sher, A., Taylor, G.A. (2009). Balance of Irgm protein activities determines IFN-? induced host defense. J. Leukoc. Biol. 85, 877-885.