The human malaria parasite, Plasmodium falciparum, remains a major public health issue in developing nations, with up to 300 million cases and up to 1 million deaths per year. Since drug resistant strains to common therapies can now be found worldwide, there is a dire need for novel antimalarial strategies to combat this disease. In P. falciparum, mechanisms involved in gene regulation remain poorly understood. Our laboratory recently found that there are significant dynamic changes of nucleosome occupancy throughout the parasite erythrocyte cycle. Nucleosomes are a component of chromatin and have been associated with regulating gene expression in eukaryotes. In the malaria parasite, a depletion of histone protein has been observed during the most transcriptionally active stage of the parasite cell cycle. Preliminary data in the lab indicate that autophagy may play a role in histone turnover. Autophagy is a process that engulfs cellular material into vesicles that fuse with lysosomes to degrade proteins. While this conserved process has been well characterized in higher eukaryotes, its function has been overlooked in the parasite. Autophagy is typically activated by nutrient starvation, but the malaria parasite resides in host cells with a consistent food source. From an evolutionary standpoint, the parasite may have adapted the autophagy machinery for an alternative function regulating part of the parasite cell cycle progression. To determine if autophagy plays a role in histone turnover, we incubated synchronized cultures with an activator, rapamycin, and inhibitor, bafilomycin, of the autophagy pathway. An accumulation of histone proteins at the most active transcriptional stage was displayed when treated with bafilomycin;conversely, we observed a depletion of histone protein and arrest of cell cycle progression when treated with rapamycin. To validate our preliminary data fluorescence imaging and biochemical assays will be performed. To further investigate autophagy in the parasite we will perform immunoprecipitations of autophagosomal membranes and identify proteins by mass spectrometry. Collectively, these experiments should confirm the role of the autophagy pathway in the malaria parasite and to identify the major regulatory proteins of this atypical pathway.

Public Health Relevance

The human malaria parasite remains a major public health issue in developing countries, resulting in one million deaths per year. Our preliminary data indicates that the autophagy pathway may regulate cell cycle progression in the parasite, and in this application, we propose to identify the molecular components that are involved in this pathway. The characterization of key regulatory elements of this parasite atypical autophagy pathway should provide new therapeutic strategies against this devastating disease.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Predoctoral Individual National Research Service Award (F31)
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Special Emphasis Panel (ZRG1-F13-C (20))
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Adger-Johnson, Diane S
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University of California Riverside
Anatomy/Cell Biology
Schools of Earth Sciences/Natur
United States
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Saraf, Anita; Cervantes, Serena; Bunnik, Evelien M et al. (2016) Dynamic and Combinatorial Landscape of Histone Modifications during the Intraerythrocytic Developmental Cycle of the Malaria Parasite. J Proteome Res 15:2787-801
Cervantes, Serena; Bunnik, Evelien M; Saraf, Anita et al. (2014) The multifunctional autophagy pathway in the human malaria parasite, Plasmodium falciparum. Autophagy 10:80-92