John C. Samuelson, MD, PhD

Professor, Boston University Henry M. Goldman School of Dental Medicine

Biography

Our lab studies the glycobiology of protozoan parasites that cause diarrhea (Cryptosporidium and Giardia), dysentery (Entamoeba), birth defects (Toxoplasma), and blindness (Acanthamoeba). In particular, we use mass spectrometric, biochemical, and genetic methods to characterize sugars added to glycoproteins, as well as the enzymes that make or remove these sugars (glycosyltransferases and glycosyl hydrolases, respectively). For example, we showed that asparagine-linked glycans (N-glycans) of Cryptosporidium have a single mannose arm that is hardly modified and so is distinct from complex, highly modified N-glycans of the host. In contrast, Cryptosporidium vaccine candidates have mucin-like domains densely modified with O-GalNAc that resemble host intestinal mucins. We discovered a large set of nuclear proteins of Toxoplasma that are decorated with O-linked fucose and showed that O-fucosyltransferase is a homolog of plant Spindly. The host is lacking Spindly but has an O-GlcNAc transferase with a similar structure to Spindly that modifies an even larger set of nucleocytosolic proteins. We also identified a second Toxoplasma O-fucosyltransferase that modifies a secreted protein MIC2, which is essential for parasite adherence to and invasion into host cells.

The Samuelson lab also studies sugar polymers and glycoproteins present in cyst and oocyst walls of these parasites, which are critical for their transmission from person to person. The simple model we have developed is that these walls contain sugar polymers similar to those in fungal and plant walls: chitin (Entamoeba), glucan (Toxoplasma), and cellulose, chitin, and xylan (Acanthamoeba). In contrast to fungi and plants, glycoproteins in the parasite walls are few and are for the most part lectins (proteins that bind sugars), which bind the sugar polymers. These wall lectins are unique to each parasite and may be targets for diagnostic reagents. Finally, we have explored the potential use of alcohol-based hand sanitizers to prevent transmission of Giardia, Entamoeba, and Acanthamoeba.

Publications

  • Published 3/4/2025

    Kanakapura Sundararaj B, Goyal M, Samuelson J. Targets for the diagnosis of Acanthamoeba eye infections include four cyst wall proteins and the mannose-binding domain of the trophozoite mannose-binding protein. mSphere. 2025 Mar 25; 10(3):e0094824. PMID: 40035521.

    Read at: PubMed

  • Published 2/6/2025

    Tiwari M, Gas-Pascual E, Goyal M, Popov M, Matsumoto K, Grafe M, Gräf R, Haltiwanger RS, Olszewski N, Orlando R, Samuelson JC, West CM. Novel antibodies detect nucleocytoplasmic O-fucose in protist pathogens, cellular slime molds, and plants. mSphere. 2025 Feb 25; 10(2):e0094524. PMID: 39912628.

    Read at: PubMed

  • Published 8/13/2024

    Kanakapura Sundararaj B, Goyal M, Samuelson J. Cellulose binding and the timing of expression influence protein targeting to the double-layered cyst wall of Acanthamoeba. mSphere. 2024 Sep 25; 9(9):e0046624. PMID: 39136454.

    Read at: PubMed

  • Published 4/19/2023

    van der Wel H, Garcia AM, Gas-Pascual E, Willis MM, Kim HW, Bandini G, Gaye MM, Costello CE, Samuelson J, West CM. Spindly is a nucleocytosolic O-fucosyltransferase in Dictyostelium and related proteins are widespread in protists and bacteria. Glycobiology. 2023 Apr 19; 33(3):225-244. PMID: 36250576.

    Read at: PubMed

  • Published 10/17/2021

    Liu L, Veis J, Reiter W, Motari E, Costello CE, Samuelson JC, Ammerer G, Levin DE. Regulation of Pkc1 Hyper-Phosphorylation by Genotoxic Stress. J Fungi (Basel). 2021 Oct 17; 7(10). PMID: 34682295.

    Read at: PubMed

Other Positions

  • Professor, Virology, Immunology & Microbiology
    Boston University Chobanian & Avedisian School of Medicine
  • Faculty, National Emerging Infectious Disease Lab
    Boston University
  • Member, Genome Science Institute
    Boston University
  • Member, Bioinformatics Graduate Program
    Boston University
  • Graduate Faculty (Primary Mentor of Grad Students)
    Boston University Chobanian & Avedisian School of Medicine, Graduate Medical Sciences

Education

  • Harvard Medical School, MD
  • Harvard Medical School, PhD
  • Swarthmore College, BA