Poster Sessions

Mol-23

Kempaiah Rayavara

K. Rayavara, S. A. Desai

Genetic disruption of a mechanosensitive ion channel in Plasmodium falciparum

Development of gametocytes is an essential step in the mosquito-based transmission of malaria parasites. Although a few gametocyte-specific proteins have been identified by genome-wide expression arrays and protein sequencing, little is known about their biological roles. Using the human malaria parasite P. falciparum, we determined that one of these gametocyte specific proteins has a conserved small conductance mechanosensitive channel domain (MscS). In other organisms, ion channels containing this domain open in response to lateral tension in membranes and play diverse physiological roles including osmotic regulation, cell division and motility. This parasite protein (Pf-MscS) is larger than most known MscS channels (calculated MW of 214 kDa) and has five predicted transmembrane domains. Quantitative RT-PCR confirmed diminishingly low expression in asexual blood stage forms that increases dramatically in gametocytes. Immunofluorescence assays using five specific antibodies raised in mice using both DNA vaccines and synthetic peptides reveal that the protein is expressed primarily at the gametocyte stage. To explore its physiological role, we disrupted the corresponding gene using double crossover homologous recombination. The phenotype of gene knockout parasites and approaches to targeting Pf-MscS for antimalarial drug or vaccine development will be discussed.