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


Undergraduate Students

Graduate Students

Postdoctoral Fellows


  • High-Resolution Mapping of Transcription Initiation in the Asexual Stages of Toxoplasma gondii

    Markus BM, Waldman BS, Lorenzi HA, Lourido S

    Front Cell Infect Microbiol. 2021 Jan 20;10:617998.

    PMID: 33553008

    Identifying the Target of an Antiparasitic Compound in Toxoplasma Using Thermal Proteome Profiling.

    Herneisen AL, Sidik SM, Markus BM, Drewry DH, Zuercher WJ, Lourido S.

    ACS Chem Biol. 2020 Jul 17;15(7):1801-1807.

    PMID: 32597628

    Functional and Computational Genomics Reveal Unprecedented Flexibility in Stage-Specific Toxoplasma Metabolism.

    Krishnan A, Kloehn J, Lunghi M, Chiappino-Pepe A, Waldman BS, Nicolas D, Varesio E, Hehl A, Lourido S, Hatzimanikatis V, Soldati-Favre D.

    Cell Host Microbe. 2020 Jan 27. pii: S1931-3128(20)30041-X.

    PMID: 31991093

    Identification of a master regulator of differentiation in Toxoplasma.

    Waldman BS, Schwarz D, Wadsworth II MS, Saeij JP, Shalek AK, Lourido S.

    Cell. 2020 Jan 10. pii: S0092-8674(19)31375-3. 

    PMID: 31955846

    Plate-Based Quantification of Stimulated Toxoplasma Egress.

    Shortt E, Lourido S.

    Methods Mol Biol. 2020;2071:171-186.

    PMID: 31758453

    High-Throughput Measurement of Microneme Secretion in Toxoplasma gondii.

    Brown KM, Sibley LD, Lourido S.

    Methods Mol Biol. 2020;2071:157-169.

    PMID: 31758452


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.