John C. Samuelson, MD, PhD

Professor, Molecular & Cell Biology

John Samuelson
(617) 414-1054
75 E. Newton St Evans Building

Biography

Entamoeba histolytica, Giardia lamblia, and Trichomonas are simple eukaryotes, which cause dysentery, diarrhea, and vaginitis, respectively. Our laboratory uses molecular biological methods to study the biochemistry, cell biology, pathogenesis, and evolution of these important human pathogens.

One project attempts to determine the composition of the walls of Entamoeba cysts, which are the infectious and diagnostic form. Chitin in cyst wall is made by stage-specific chitin synthases and is modified by endogenous chitin deacetylases and chitinases. Chitin fibrils in the wall are held together unique lectins , which have multiple chitin-binding domains. Post-translation modifications of the cyst wall lectins include addition of unusual O-phosphodiester-linked sugars and cleavages between chitin-binding domains. Identification of these cyst wall-associated lectins may lead to better diagnostic reagents for distinguishing pathogenic from non-pathogenic amebae.

A second project, which is performed in collaboration with my colleague Phillips Robbins, attempts to understand Asn-linked glycosylation in Entamoeba, Giardia, and other protists . In particular, we use bioinformatics to predict lipid-linked N-glycan precursors, as well as N-glycan associated proteins involved in quality control in the ER lumen. We test our predictions using biochemical methods, which include determinations of carbohydrate structures and purification of glycoproteins by lectin columns. These studies suggest 1) the present diversity of N-glycans derives in part from secondary loss of genes encoding enzyme involved in N-glycan precursor synthesis, 2) protists with short N-glycans lack N-glycan-dependent quality control, and 3) there is Darwinian selection for sites of N-glycans in secreted proteins of diverse eukaryotes and viruses. Unique parasite sugars may be novel vaccine candidates or targets for anti-microbial lectins.

A third project is concerned with how Entamoeba, Giardia, and Trichomonas adapt to the anaerobic environment in the intestinal lumen. We have identified an atrophic mitochondrion-derived organelle, which lacks enzymes of oxidative phosphorylation in Entamoeba. We have also identified numerous bacterium-like fermentation enzymes in these protists, which appear to have been obtained by lateral gene transfer (LGT). Although LGT is frequent between bacteria, it is unusual between bacteria and eukaryotes. Two of the bacterial genes acquired by LGT appear to be important for activating and inactivating metronidazole, the best drug against these organisms.

Other Positions

  • Professor, Microbiology, Boston University School of Medicine
  • Graduate Faculty (Primary Mentor of Grad Students), Boston University School of Medicine, Division of Graduate Medical Sciences
  • Member, Bioinformatics Graduate Program, Boston University

Education

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

Publications

  • Published on 10/18/2017

    Dubey R, Harrison B, Dangoudoubiyam S, Bandini G, Cheng K, Kosber A, Agop-Nersesian C, Howe DK, Samuelson J, Ferguson DJP, Gubbels MJ. Differential Roles for Inner Membrane Complex Proteins across Toxoplasma gondii and Sarcocystis neurona Development. mSphere. 2017 Sep-Oct; 2(5). PMID: 29062899.

    Read at: PubMed
  • Published on 8/8/2017

    Haserick JR, Klein JA, Costello CE, Samuelson J. Cryptosporidium parvum vaccine candidates are incompletely modified with O-linked-N-acetylgalactosamine or contain N-terminal N-myristate and S-palmitate. PLoS One. 2017; 12(8):e0182395. PMID: 28792526.

    Read at: PubMed
  • Published on 2/9/2017

    Aqeel Y, Rodriguez R, Chatterjee A, Ingalls RR, Samuelson J. Killing of diverse eye pathogens (Acanthamoeba spp., Fusarium solani, and Chlamydia trachomatis) with alcohols. PLoS Negl Trop Dis. 2017 Feb; 11(2):e0005382. PMID: 28182670.

    Read at: PubMed
  • Published on 2/8/2017

    Haserick JR, Leon DR, Samuelson J, Costello CE. Asparagine-Linked Glycans of Cryptosporidium parvum Contain a Single Long Arm, Are Barely Processed in the Endoplasmic Reticulum (ER) or Golgi, and Show a Strong Bias for Sites with Threonine. Mol Cell Proteomics. 2017 Apr; 16(4 suppl 1):S42-S53. PMID: 28179475.

    Read at: PubMed
  • Published on 11/16/2016

    Sanz S, López-Gutiérrez B, Bandini G, Damerow S, Absalon S, Dinglasan RR, Samuelson J, Izquierdo L. The disruption of GDP-fucose de novo biosynthesis suggests the presence of a novel fucose-containing glycoconjugate in Plasmodium asexual blood stages. Sci Rep. 2016 Nov 16; 6:37230. PMID: 27849032.

    Read at: PubMed
  • Published on 9/23/2016

    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 U S A. 2016 10 11; 113(41):11567-11572. PMID: 27663739.

    Read at: PubMed
  • Published on 8/17/2015

    Chatterjee A, Bandini G, Motari E, Samuelson J. Ethanol and isopropanol in concentrations present in hand sanitizers sharply reduce excystation of Giardia and Entamoeba and eliminate oral infectivity of Giardia cysts in gerbils. Antimicrob Agents Chemother. 2015 Nov; 59(11):6749-54. PMID: 26282413.

    Read at: PubMed
  • Published on 8/7/2015

    Chatterjee A, Ratner DM, Ryan CM, Johnson PJ, O'Keefe BR, Secor WE, Anderson DJ, Robbins PW, Samuelson J. Anti-Retroviral Lectins Have Modest Effects on Adherence of Trichomonas vaginalis to Epithelial Cells In Vitro and on Recovery of Tritrichomonas foetus in a Mouse Vaginal Model. PLoS One. 2015; 10(8):e0135340. PMID: 26252012.

    Read at: PubMed
  • Published on 12/2/2014

    Samuelson J, Robbins PW. Effects of N-glycan precursor length diversity on quality control of protein folding and on protein glycosylation. Semin Cell Dev Biol. 2015 May; 41:121-8. PMID: 25475176.

    Read at: PubMed
  • Published on 10/4/2013

    Samuelson J, Bushkin GG, Chatterjee A, Robbins PW. Strategies to discover the structural components of cyst and oocyst walls. Eukaryot Cell. 2013 Dec; 12(12):1578-87. PMID: 24096907.

    Read at: PubMed

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