Peter Bradley, Ph.D.



2610B MSB

Professor, Microbiology, Immunology & Molecular Genetics
Member, Cell & Developmental Biology GPB Home Area, Immunity, Microbes & Molecular Pathogenesis GPB Home Area


Research Interests

Toxoplasma gondii is an obligate intracellular parasite in the phylum Apicomplexa that causes severe central nervous system disorders of immunocompromised (AIDS/transplant/lymphoma) individuals and birth defects to congenitally infected neonates worldwide. In addition to being a globally important pathogen, Toxoplasma also serves as a model system for studying Apicomplexan parasites which cause a number of diseases of medical and veterinary importance including Plasmodium falciparum, the causative agent of malaria which kills 1-2 million people each year. Apicomplexans enter host cells by the active process of invasion that is driven by the parasite’s actin-myosin motor and involves the regulated release of the parasite’s specialized secretory organelles (the rhoptries, micronemes and dense granules). Invasion is coupled to the rhoptry-mediated formation of the parasitophorous vacuole in which the parasite resides in the cytoplasm of its host. While secretion of the rhoptries has long been implicated in the establishment of this vacuole, only a few rhoptry proteins have been reported and little is known about their precise role in this process. The Bradley lab is focusing on the role of the rhoptries in the invasion of host cells, creation of the parasitophorous vacuole in which the parasite resides, and host-parasite interaction. We have developed a method for obtaining highly purified rhoptries and analyzed this fraction using proteomic and monoclonal antibody approaches. Our proteomic analyses have identified 30 novel genes in the rhoptry fraction indicating we have identified the major proteins involved in rhoptry function. We have also produced a panel of monoclonal antibodies against the rhoptry fraction, one of which has been used to identify a rhoptry-localized protein that is targeted to the host cell nucleus, establishing a new role for the rhoptries in host-parasite interaction. Given that these proteins are present in organelles that are unique and intimately associated with infection, a complete understanding of their function promises to produce both interesting biology and important leads for ultimate control of these infections.



Back Peter S, O’Shaughnessy William J, Moon Andy S, Dewangan Pravin S, Reese Michael L, Bradley Peter J   Multivalent Interactions Drive the Toxoplasma AC9:AC10:ERK7 Complex To Concentrate ERK7 in the Apical Cap mBio, 2022; e0286421.


Mineo Tiago W P, Chern Jessica H, Thind Amara C, Mota Caroline M, Nadipuram Santhosh M, Torres Juan A, Bradley Peter J   Efficient Gene Knockout and Knockdown Systems in Neospora caninum Enable Rapid Discovery and Functional Assessment of Novel Proteins mSphere, 2022; e0089621.


Chern Jessica H, Pasquarelli Rebecca R, Moon Andy S, Chen Allan L, Sha Jihui, Wohlschlegel James A, Bradley Peter J   A Novel Toxoplasma Inner Membrane Complex Suture-Associated Protein Regulates Suture Protein Targeting and Colocalizes with Membrane Trafficking Machinery mBio, 2021; 12(5): e0245521.


Torres Juan A, Pasquarelli Rebecca R, Back Peter S, Moon Andy S, Bradley Peter J   Identification and Molecular Dissection of IMC32, a Conserved Toxoplasma Inner Membrane Complex Protein That Is Essential for Parasite Replication mBio, 2021; 12(1): .


Nadipuram Santhosh Mukund, Thind Amara Cervantes, Rayatpisheh Shima, Wohlschlegel James Akira, Bradley Peter John   Proximity biotinylation reveals novel secreted dense granule proteins of Toxoplasma gondii bradyzoites PloS One, 2020; 15(5): e0232552.


Bradley Peter J, Rayatpisheh Shima, Wohlschlegel James A, Nadipuram Santhosh M   Using BioID for the Identification of Interacting and Proximal Proteins in Subcellular Compartments in Toxoplasma gondii Methods in molecular biology (Clifton, N.J.), 2020; 2071: 323-346.


Back Peter S, O’Shaughnessy William J, Moon Andy S, Dewangan Pravin S, Hu Xiaoyu, Sha Jihui, Wohlschlegel James A, Bradley Peter J, Reese Michael L  Ancient MAPK ERK7 is regulated by an unusual inhibitory scaffold required for Toxoplasma apical complex biogenesis Proceedings of the National Academy of Sciences of the United States of America, 2020; .


Choi Charles Paul, Moon Andy Seong, Back Peter Sungmin, Jami-Alahmadi Yasaman, Vashisht Ajay Amar, Wohlschlegel James Akira, Bradley Peter John  A photoactivatable crosslinking system reveals protein interactions in the Toxoplasma gondii inner membrane complex PLoS Biology, 2019; 17(10): e3000475.


Suarez Catherine, Lentini Gaëlle, Ramaswamy Raghavendran, Maynadier Marjorie, Aquilini Eleonora, Berry-Sterkers Laurence, Cipriano Michael, Chen Allan L, Bradley Peter, Striepen Boris, Boulanger Martin J, Lebrun Maryse   A lipid-binding protein mediates rhoptry discharge and invasion in Plasmodium falciparum and Toxoplasma gondii parasites Nature communications, 2019; 10(1): 4041


Chen Allan L, Moon Andy S, Bell Hannah N, Huang Amy S, Vashisht Ajay A, Toh Justin Y, Lin Andrew H, Nadipuram Santhosh M, Kim Elliot W, Choi Charles P, Wohlschlegel James A, Bradley Peter J Novel insights into the composition and function of the Toxoplasma IMC sutures. Cellular Microbiology. 2016;


Mota Caroline M, Oliveira Ana C M, Davoli-Ferreira Marcela, Silva Murilo V, Santiago Fernanda M, Nadipuram Santhosh M, Vashisht Ajay A, Wohlschlegel James A, Bradley Peter J, Silva João S, Mineo José R, Mineo Tiago W P Neospora caninum Activates p38 MAPK as an Evasion Mechanism against Innate Immunity. Frontiers in microbiology. 2016; 7: 1456.


Nadipuram Santhosh M, Kim Elliot W, Vashisht Ajay A, Lin Andrew H, Bell Hannah N, Coppens Isabelle, Wohlschlegel James A, Bradley Peter J In Vivo Biotinylation of the Toxoplasma Parasitophorous Vacuole Reveals Novel Dense Granule Proteins Important for Parasite Growth and Pathogenesis. mBio. 2016; 7(4): .


Kim Elliot W, Nadipuram Santhosh M, Tetlow Ashley L, Barshop William D, Liu Philip T, Wohlschlegel James A, Bradley Peter J The Rhoptry Pseudokinase ROP54 Modulates Toxoplasma gondii Virulence and Host GBP2 Loading. mSphere. 2016; 1(2): .


Wang Kevin, Peng Eric D, Huang Amy S, Xia Dong, Vermont Sarah J, Lentini Gaelle, Lebrun Maryse, Wastling Jonathan M, Bradley Peter J Identification of Novel O-Linked Glycosylated Toxoplasma Proteins by Vicia villosa Lectin Chromatography. PloS one. 2016; 11(3): e0150561.


Silmon de Monerri Natalie C, Yakubu Rama R, Chen Allan L, Bradley Peter J, Nieves Edward, Weiss Louis M, Kim Kami The Ubiquitin Proteome of Toxoplasma gondii Reveals Roles for Protein Ubiquitination in Cell-Cycle Transitions. Cell host & microbe. 2015; 18(5): 621-33.


Rodriguez Jose A, Xu Rui, Chen Chien-Chun, Huang Zhifeng, Jiang Huaidong, Chen Allan L, Raines Kevin S, Pryor Alan, Nam Daewoong, Wiegart Lutz, Song Changyong, Madsen Anders, Chushkin Yuriy, Zontone Federico, Bradley Peter J, Miao Jianwei Three-dimensional coherent X-ray diffractive imaging of whole frozen-hydrated cells. IUCrJ. 2015; 2(Pt 5): 575-83.


Chen, AL Kim, EW Toh, JY Vashisht, AA Rashoff, AQ Van, C Huang, AS Moon, AS Bell, HN Bentolila, LA Wohlschlegel, JA Bradley, PJ Novel Components of the Toxoplasma Inner Membrane Complex Revealed by BioID. MBio. 2015; 6(1): e02357-14.


Gold DA Kaplan AD Lis A Bett GC Rosowski EE Cirelli KM Bougdour A Sidik SM Beck JR Lourido S Egea PF Bradley PJ Hakimi MA Rasmusson RL Saeij JP The Toxoplasma Dense Granule Proteins GRA17 and GRA23 Mediate the Movement of Small Molecules between the Host and the Parasitophorous Vacuole. Cell Host Microbe. 2015; 17(5): 642-52. .


Beck JR Chen AL Kim EW Bradley PJ RON5 Is Critical for Organization and Function of the Toxoplasma Moving Junction Complex. PLoS Pathogens. 2014; 10(3): e1004025.


Tonkin ML Beck JR Bradley PJ Boulanger M The inner membrane complex sub-compartment proteins critical for replication of the apicomplexan parasite Toxoplasma gondii adopt a Pleckstrin homology fold. J Biol Chem 2014; 289(20): 13962-73.


de Leon JC, Scheumann N, Beatty W, Beck JR, Tran JQ, Yau C, Bradley PJ, Gull K, Wickstead B, Morrissette NS. A SAS-6-like protein suggests that the Toxoplasma conoid complex evolved from flagellar components. Eukaryot Cell. 2013; 12(7): 1009-19.


Beck JR, Fung C, Straub KW, Coppens I, Vashisht AA, Wohlschlegel JA, Bradley PJ. A Toxoplasma palmitoyl acyl transferase and the palmitoylated Armadillo Repeat protein TgARO govern apical rhoptry tethering and reveal a critical role for the rhoptries in host cell invasion but not egress. PLoS Pathog. 2013; 9(2): e1003162.


Child MA, Hall CI, Beck JR, Ofori LO, Albrow VE, Garland M, Bowyer PW, Bradley PJ, Powers JC, Boothroyd JC, Weerapana E, Bogyo M. Small-molecule inhibition of a depalmitoylase enhances Toxoplasma host-cell invasion. Nat Chem Biol. 2013; 9(10): 651-6.


Anderson-White B. Beck, J.R. Chen, C.T. Meissner M. Bradley P.J. Gubbels M.J. Cytoskeleton Assembly in Toxoplasma gondii Cell Division. Int Rev Cell Mol Biol. 2012; 298: 1-31.


Hajagos, B.E. Turetzky, J.M. Peng, E.D. Cheng, S.J. Ryan, C.M. Souda, P. Whitelegge, J.P. Lebrun, M. Dubremetz, J.F. Bradley, P.J. Molecular Dissection of Novel Trafficking and Processing of the Toxoplasma gondii Rhoptry Metalloprotease Toxolysin-1. Traffic. 2012; 13(2): 292-304.


Tonkin M.L. Brown S. Beck J.R. Bradley P.J. Boulanger M.J. Purification, crystallization and preliminary X-ray diffraction analysis of inner membrane complex (IMC) subcompartment protein 1 (ISP1) from Toxoplasma gondii. . Acta Crystallogr Sect F Struct Biol Cryst Commun. 2012; 68(7): 832-4.


Fung, C* Beck, J.R.* Robertson SD Gubbels MJ Bradley PJ Toxoplasma ISP4 is a central IMC sub-compartment protein whose localization depends on palmitoylation but not myristoylation. Mol Biochem Parasitol. 2012; 184(2): 99-108.


Hajagos Bettina E, Turetzky Jay M, Peng Eric D, Cheng Stephen J, Ryan Christopher M, Souda Puneet, Whitelegge Julian P, Lebrun Maryse, Dubremetz Jean-Francois, Bradley Peter J Molecular dissection of novel trafficking and processing of the Toxoplasma gondii rhoptry metalloprotease toxolysin-1. Traffic (Copenhagen, Denmark). 2012; 13(2): 292-304.


Sohn, C.S. Cheng, T.T. Drummond, M.L. Peng, E.D. Vermont, S.J. Xia, D. Cheng, S.J. Wastling J.M. Bradley, P.J. Identification of novel proteins in Neospora caninum using an organelle purification and monoclonal antibody approach. PLoS One. 2011; 6(4): e18383.


Liang, L., Döskaya, M., Juarez, S., Caner, A., Jasinskas, A., Tan, X., Hajagos, B.E., Bradley, P.J., Korkmaz, M., Güruz, Y., Felgner, P., Davies, D.H. Identification of potential serodiagnostic and subunit vaccine antigens by antibody profiling of toxoplasmosis cases in Turkey. Mol Cell Proteomics. 2011; 10(7): M110.006916.


Straub, K.W. Peng, E.D. Hajagos, B.E. Tyler, J.S. Bradley, P.J. The Moving Junction Protein RON8 Facilitates Firm Attachment and Host Cell Invasion in Toxoplasma gondii. PLoS Pathogens. 2011; 7(3): e1002007.


Beck, J.R., Rodriguez-Fernandez, I.A., de Leon, J.C., Huynh, M., Carruthers, V.B., Morrissette, N.S., Bradley, P.J. A Novel Family of Toxoplasma IMC Proteins Display a Hierarchical Organization and Function in Coordinating Parasite Division. PLoS Pathogens. 2010; 6(9): pii: e1001094.


Turetzky, J.M. Chu, D.K. Hajagos, B.E. Bradley, P.J. Processing and Secretion of ROP13: a unique Toxoplasma effector protein. Int J Parasitol. 2010; 40(9): 1037-44.


Breinich, M.S. Ferguson, D.J.P. Foth, B.J. van Dooren, G.G. Lebrun, M. Quon, D.V. Striepen, B. Bradley, P.J. Frischknecht, F. Carruthers, V.B. Meissner, M. A Dynamin is Required for the Biogenesis of Secretory Organelles in Toxoplasma gondii. Current Biology. 2009; 19(4): 277-86.


Straub, K.W. Cheng, S.J. Sohn, C.S. Bradley, P.J. Novel components of the Apicomplexan moving junction reveal conserved and coccidia-restricted elements. Cellular Microbiology. 2008; 11(40): 590-603.


Rome, M.E. Beck, J.R. Turetzky, J.M. Webster, P. Bradley, P.J. Intervacuolar transport and unique topology of GRA14, a novel dense granule protein in Toxoplasma gondii. Infection and Immunity. 2008; 76(11): 4865-75. Epub 2008 Sep 2..


Derocher AE, Coppens I, Karnataki A, Gilbert LA, Rome ME, Feagin JE, Bradley PJ, Parsons M. A thioredoxin family protein of the apicoplast periphery identifies abundant candidate transport vesicles in Toxoplasma. Eukaryot Cell. 2008; 7: 1518-1529.


Bradley, P.J. Sibley, L.D. Rhoptries: an arsenal of secreted virulence factors. . Curr Opin Microbiol. 2007; 10(6): 582-7.


Wastling, J.M. Bradley, P.J. Proteomic Analysis of the Rhoptry Organelles of Toxoplasma gondii. In “The biology of Toxoplasma gondii” 2007; D. Soldati and J. Ajioka (eds.): 455-474.


Gilbert L.A. Ravindran S. Turetzky J.M. Boothroyd J.C. Bradley P.J. Toxoplasma gondii Targets a Protein Phosphatase 2C to the Nucleus of Infected Host Cells. Eukaryot Cell. 2007; 6(1): 73-83. Epub 2006 Nov 3. .


Alexander, D.L., Mital, J., Ward, G.E., Bradley, P.J., Boothroyd, J.C. Identification of the Moving Junction Complex of Toxoplasma gondii: A Collaboration between Distinct Secretory Organelles. PLOS Pathogens. 2005; 1(2): e17.


Bradley, P.J., Ward, C., Cheng, S.J., Alexander, D.L., Coller, S., Coombs, G.H., Dunn, J.D., Ferguson, D.J., Sanderson, S.J., Wastling, J.M., Boothroyd, J.C. Proteomic analysis of rhoptry organelles reveals many novel constituents for host-parasite interactions in Toxoplasma gondii. The Journal of Biological Chemistry . 2005; 280(40): 34245-58.


Lebrun M., Michelin A., Hajj H.E., Poncet J., Bradley P.J., Vial H., Dubremetz J.F. The rhoptry neck protein RON4 relocalizes at the moving junction during Toxoplasma gondii invasion. Cellular Microbiology. 2005; 7(12): 1823-33.


Bradley, P.J., Li, N., Boothroyd, J.C. A GFP-based motif-trap reveals a novel mechanism of targeting for the Toxoplasma ROP4 protein. Molecular and Biochemical Parasitology. . 2004; 137(1): 111-20.


Bradley, P.J., Hsieh, C.L., Boothroyd, J.C. Unprocessed Toxoplasma ROP1 is effectively targeted and secreted into the nascent parasitophorous vacuole.Molecular and Biochemical Parasitology. 2002; 125(1-2): 189-93.


Bradley, P.J., Boothroyd, J.C. The pro region of Toxoplasma ROP1 is a rhoptry-targeting signal. International Journal for Parasitology. . 2001; 31(11): 1177-86.


Hehl, A.B., Lekutis, C., Grigg, M.E., Bradley, P.J., Dubremetz, J.F., Ortega-Barria, E., Boothroyd, J.C. Toxoplasma gondii homologue of plasmodium apical membrane antigen 1 is involved in invasion of host cells. Infection and Immunity. . 2000; 68(12): 7078-86.


Dyall S D, Koehler C M, Delgadillo-Correa M G, Bradley P J, Plümper E, Leuenberger D, Turck C W, Johnson P J Presence of a member of the mitochondrial carrier family in hydrogenosomes: conservation of membrane-targeting pathways between hydrogenosomes and mitochondria. Molecular and cellular biology. 2000; 20(7): 2488-97.


Plumper E, Bradley P J, Johnson P J Competition and protease sensitivity assays provide evidence for the existence of a hydrogenosomal protein import machinery in Trichomonas vaginalis. Molecular and biochemical parasitology. 2000; 106(1): 11-20.


Bradley, P.J., Boothroyd, J.C. Identification of the pro-mature processing site of Toxoplasma ROP1 by mass spectrometry. Molecular and Biochemical Parasitology. 1999; 100(1): 103-9.

Plumper E, Bradley P J, Johnson P J Implications of protein import on the origin of hydrogenosomes. Protist. 1998; 149(4): 303-11.


Bradley P J, Lahti C J, Plümper E, Johnson P J Targeting and translocation of proteins into the hydrogenosome of the protist Trichomonas: similarities with mitochondrial protein import. The EMBO journal. 1997; 16(12): 3484-93.


Bui E T, Bradley P J, Johnson P J A common evolutionary origin for mitochondria and hydrogenosomes. Proceedings of the National Academy of Sciences of the United States of America. 1996; 93(18): 9651-6.


Lahti C J, Bradley P J, Johnson P J Molecular characterization of the alpha-subunit of Trichomonas vaginalis hydrogenosomal succinyl CoA synthetase.Molecular and biochemical parasitology. 1994; 66(2): 309-18.


Johnson P J, Lahti C J, Bradley P J Biogenesis of the hydrogenosome in the anaerobic protist Trichomonas vaginalis. The Journal of parasitology. 1993; 79(5): 664-70.


Finlay D R, Meier E, Bradley P, Horecka J, Forbes D J A complex of nuclear pore proteins required for pore function. The Journal of cell biology. 1991; 114(1): 169-83.