Date of Award

8-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Biological Sciences

Committee Member

Dr. Lesly Temesvari, Committee Chair

Committee Member

Dr. David Feliciano

Committee Member

Dr. Meredith Morris

Abstract

Entamoeba histolytica is a parasite responsible for amebic dysentery and liver abscess in humans. This pathogen causes ~100,000 deaths annually in regions that cannot prevent the fecal-oral route of transmission. Adhesion to host colonic epithelium is a hallmark of infection. The galactose/N-acetylgalactosamine (Gal/GalNAc) lectin is a parasite surface receptor that regulates adhesion to host cells. This lectin is a heterotrimer consisting of Heavy (Hgl), Light (Lgl) and Intermediate (Igl) subunits. Hgl and Lgl are covalently attached to each other by disulfide bonds and interact non-covalently with Igl. Little is known about how the trimer assembles, but lipid rafts, cholesterol- and sphingolipid-rich membrane domains, are thought to be involved. Hgl and Lgl transiently associate with rafts but Igl is constitutively localized to these domains. It is conceivable that Igl, of which there are two isoforms (Igl1 and Igl2), serves to anchor Hgl/Lgl in rafts. We used two techniques to knock down expression of Igl including a short hairpin RNA (shRNA) approach and ‘Trigger’ approach. Attempts to knock down individual isoforms were not successful. However, when the ‘Trigger’ approach was used to simultaneously target both isoforms (1A2A cell line), we obtained approximately 57% knock down of Igl2, but not Igl1. These data suggest that Igl1 is essential. The 1A2A cells were able to adhere to and lyse host cells, but could not phagocytose erythrocytes. This implicates Igl2 in erythrophagocytosis. Finally, the submembrane distribution of Hgl/Lgl in the 1A2A cell line was not altered suggesting that Igl2 is dispensable for the association of the dimer with rafts.

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