Our lab is interested in the molecular events that enable apicomplexan parasites to remain widespread and deadly infectious agents. These single-celled eukaryotes comprise a phylum of organisms that parasitize diverse animal hosts. Many important human pathogens belong to this group, including the causative agents of malaria (Plasmodium spp.), cryptosporidiosis (Cryptosporidium spp.), and toxoplasmosis (Toxoplasma gondii). We use T. gondii to model features conserved throughout the phylum, such as their reliance on calcium signaling to regulate motility. We combine several approaches that span phospho-proteomics, chemical-genetics, and genome editing to investigate the unique biology of these organisms. Our work seeks to expand our understanding of eukaryotic diversity and identify specific features that can be targeted to treat parasite infections. For more information on our work, visit iBiology.org for Sebastian’s lectures on Toxoplasma and other stories of cutting-edge research in the life sciences, available for free to a global audience.


Lab News


Calcium Signaling

Changes in cytosolic calcium regulate eukaryotic cellular responses as diverse as membrane repair and muscle contraction. In apicomplexan parasites, calcium regulates motility in part through the regulation of adhesin exocytosis and myosin-motor function. We seek to understand the molecular details of these processes, examining both the events that lead to cytosolic calcium changes and the signaling events that follow them.



  • CDPK3 Immunofluorescence 


Protein Kinases

We are interested in how calcium signals are decoded by protein kinases, and in particular the role of calcium-dependent protein kinases (CDPKs) as the primary calcium-responsive kinases in parasites. Our work, and that of many others, has defined diverse roles for these kinases in regulating important events during the life cycle of apicomplexans. We have recently used alpaca-derived single-domain antibodies to probe the structure of CDPKs, defining a new mode of allosteric inhibition. We continue to develop biochemical methods to study these kinases, in addition to chemical-genetic approaches to study their function in vivo.

Chemical Genetics

We have engineered a panel of strains to study individual CDPKs. This approach relies on mutating the “gatekeeper” residue that restricts the depth of the ATP-binding pocket. This allows us to specifically inhibit or identify the targets of individual kinases. Using this approach, we have previously elucidated the distinct roles of TgCDPK1 and TgCDPK3 during the T. gondii lytic cycle. We continue to investigate the functions of these and other CDPKs, relying in part on phospho-proteomic methods to identify specific kinase targets.







Genome Engineering

Much of our work is made possible through a variety of genome-engineering methods. We are interested in developing new methods to enable efficient functional analysis of parasite genes and polymorphisms. Our lab was among the first to adapt CRISPR/Cas9 to engineer the T. gondii genome, and our plasmids are available to anyone through Addgene. We continue to improve these systems to enable genome-scale screening in parasites, which will allow­­ exploration of the multitude of apicomplexan genes with unknown functions.

Lab Members


  • Arranz-Solís D, Regidor-Cerrillo J, Lourido S, Ortega-Mora LM, Saeij JPJ. Toxoplasma CRISPR/Cas9 constructs are functional for gene disruption in Neospora caninum. Int J Parasitol. 2018 Jul;48(8):597-600. PMID: 29625127
  • Hara M, Lourido S, Petrova B, Lou HJ, Von Stetina JR, Kashevsky H, Turk BE, Orr-Weaver TL. Identification of PNG kinase substrates uncovers interactions with the translational repressor TRAL in the oocyte-to-embryo transition. Elife. 2018 Feb 26;7. PMID: 29480805
  • Sidik SM, Huet D, Lourido S. CRISPR-Cas9-based genome-wide screening of Toxoplasma gondii. Nat Protoc. 2018 Jan;13(1):307-323. PMID: 29323662
  • Bandini G, Haserick JR, Motari E, Ouologuem DT, Lourido S, Roos DS, Costello CE, Robbins PW, Samuelson J. O-fucosylated glycoproteins form assemblies in close proximity to the nuclear pore complexes of Toxoplasma gondii. Proc Natl Acad Sci USA. 2016 Oct 11;113(41):11567-11572. PMID: 27663739
  • Sidik SM, Huet D, Ganesan SM, Huynh MH, Wang T, Nasamu AS, Thiru P, Saeij JPJ, Carruthers VB, Niles JC, Lourido S. A Genome-wide CRISPR Screen in Toxoplasma Identifies Essential Apicomplexan Genes. Cell. 2016 Sep;166(6):1423–1435.e12. PMID: 27594426
  • Chahal JS, Khan OF, Cooper CL, McPartlan JS, Tsosie JK, Tilley LD, Sidik SM, Lourido S, Langer R, Bavari S, Ploegh HL, Anderson DG. Dendrimer-RNA nanoparticles generate protective immunity against lethal Ebola, H1N1 influenza, and Toxoplasma gondii challenges with a single dose. Proc Natl Acad Sci USA. 2016 Jul 19;113(29):E4133-42. PMID: 27382155
  • Sidik SM, Hortua Triana MA, Paul AS, El Bakkouri M, Hackett CG, Tran F, Westwood NJ, Hui R, Zuercher WJ, Duraisingh MT, Moreno SN, Lourido S. Using a genetically encoded sensor to identify inhibitors of Toxoplasma gondii Ca2+ signaling. J Biol Chem. 2016 Apr 29; 291(18):9566-80. PMID: 26933036
  • Brown KM, Lourido S, Sibley LD. Serum albumin stimulates protein kinase G-dependent microneme secretion in Toxoplasma gondiiJ Biol Chem. 2016 Apr 29; 291(18):9554-65. PMID: 26933037
  • Rothenberg DA, Gordon EA, White FM, Lourido S. Identification of Direct Kinase Substrates Using Analogue-Sensitive Alleles. Methods Mol Biol. 2016; 1355:71-84. PMID: 26584919 
  • Ingram JR, Knockenhauer KE, Markus BM, Mandelbaum J, Ramek A, Shan Y, Shaw DE, Schwartz TU, Ploegh HL, Lourido S. Allosteric activation of apicomplexan calcium-dependent protein kinases. Proc Natl Acad Sci U S A. 2015 Sep 8; 112(36):E4975-84. PMID: 26305940
  • 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 May 13; 17(5):642-52. PMID: 25974303
  • Lourido S, Moreno S. The calcium signaling toolkit of the apicomplexan parasites Toxoplasma gondii and Plasmodium spp. Cell Calcium. 2015 Mar; 57(3):186-93. Review. PMID: 25605521
  • Swee LK, Lourido S, Bell GW, Ingram JR, Ploegh HL. One-step enzymatic modification of the cell surface redirects cellular cytotoxicity and parasite tropism. ACS Chem Biol. 2015 Feb 20; 10(2):460-5. PMID: 25360987
  • Sidik SM, Hackett CG, Tran F, Westwood NJ, Lourido S. Efficient genome engineering of Toxoplasma gondii using CRISPR/Cas9. PLoS One. 2014 Jun 27; 9(6):e100450. PMID: 24971596
  • Lourido S, Jeschke GR, Turk BE, Sibley LD. Exploiting the unique ATP-binding pocket of Toxoplasma calcium-dependent protein kinase 1 to identify its substrates. ACS Chem Biol. 2013; 8(6):1155-62. PMID: 23530747
  • Lourido S, Zhang C, Lopez MS, Tang K, Barks J, Wang Q, Wildman SA, Shokat KM, Sibley LD. Optimizing small molecule inhibitors of calcium-dependent protein kinase 1 to prevent infection by Toxoplasma gondii. J Med Chem. 2013 Apr 11; 56(7):3068-77. PMID: 23470217
  • Lourido S, Tang K, Sibley LD. Distinct signalling pathways control Toxoplasma egress and host-cell invasion. EMBO J. 2012 Dec 12; 31(24):4524-34. PMID: 23149386
  • Lourido S, Shuman J, Zhang C, Shokat KM, Hui R, Sibley LD. Calcium-dependent protein kinase 1 is an essential regulator of exocytosis in Toxoplasma. Nature. 2010 May 20; 465(7296):359-62. PMID: 20485436
  • Wernimont AK, Artz JD, Finerty P Jr, Lin YH, Amani M, Allali-Hassani A, Senisterra G, Vedadi M, Tempel W, Mackenzie F, Chau I, Lourido S, Sibley LD, Hui R. Structures of apicomplexan calcium-dependent protein kinases reveal mechanism of activation by calcium. Nat Struct Mol Biol. 2010 May; 17(5):596-601. PMID: 20436473
  • Billker O, Lourido S, Sibley LD. Calcium-dependent signaling and kinases in apicomplexan parasites. Cell Host Microbe. 2009 Jun 18; 5(6):612-22. Review. PMID: 19527888


Lourido Lab

Whitehead Institute for Biomedical Research
Room 561D (Office), Room 555 (Lab)
455 Main Street
Cambridge, MA 02142-1479
Tel.: 617-324-4920 (Office), 617-324-5869 (Lab)

Administrative Lab Manager

Gabrielle McCauley
Tel.: 617-258-5251

Join Us

The Whitehead Institute is a world-renowned research institution doing cutting-edge biomedical research. We offer highly competitive salaries and benefits to postdoctoral fellows and associates. We welcome highly motivated individuals with training in molecular genetics, biochemistry, and cell biology. For additional information about ongoing research projects, please send inquiry to Sebastian Lourido, along with your CV and names of references.