Date of Award

January 2012

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Choukri Ben Mamoun

Second Advisor

Tim-Wolf Gilberger

Subject Area(s)

Medicine, Molecular biology

Abstract

GOLGI AND ERES BIOGENESIS IN THE MALARIA-CAUSING PARASITE PLASMODIUM FALCIPARUM. Michelle Morales, Susann Herrmann and Tim-Wolf Gilberger, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany. Sponsored by Choukri Ben Mamoun, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT.

Plasmodium falciparum, the parasite causing the most severe form of human malaria, continues to bear a global burden of morbidity and mortality. No vaccine is available and resistance is emerging and expanding to all classes of existing antimalarials. Relatively little is known about the secretory pathway of P. falciparum, which has the ability to export proteins to specialized parasite organelles and into the host erythrocyte to create the ideal environment for growth.

This thesis is focused on an understanding of the biogenesis of two critical organelleswithin P. falciparum's secretory pathway: endoplasmic reticulum exit sites (ERES) and the Golgi apparatus. This study cloned parasites containing fluorescently-labeled proteins to identify ERES (Sec13p) and the Golgi apparatus (GRASP). Time lapse 3D microscopy, photobleaching and photoconversions were used to visualize the process.

In this thesis, it was shown that Plasmodium falciparum ERES undergo recruitment at rapid rates of approximately 15.2 seconds following photobleaching experiments. Evidence gathered via time-lapse microscopy in conjunction with photoconversions of Sec13p fused to Dendra showed that ERES form de novo. Although conclusive evidence

on Golgi biogenesis was not obtained, given the close spatial and duplication time relationship between ERES and the Golgi and previous studies in Pichia pastoris and Trypanosoma brucei, it is speculated that the Golgi similarly forms de novo. Strides were made towards the creation of a GRASP knock-out and examination of GRASPinteraction partners in P. falciparum, which after optimization of methods, may allow for a more detailed study of Golgi biogenesis, GRASP affect on Golgi architecture and on alternative secretion of proteins. It is hoped these conclusions will further the understanding of the P. falciparum secretory pathway, which may ultimately lead to novel drug targets in the fight against malaria.

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