Abstract
Plasmodium, the malaria parasite, undergoes a complex life cycle alternating between a vertebrate host and a mosquito vector of the genus Anopheles In red blood cells of the vertebrate host, Plasmodium multiplies asexually or differentiates into gamete precursors, the male and female gametocytes, responsible for parasite transmission. Sexual stage maturation occurs in the midgut of the mosquito vector, where male and female gametes egress from the host erythrocytes to fuse and form a zygote. Gamete egress entails the successive rupture of two membranes surrounding the parasite, the parasitophorous vacuole membrane and the erythrocyte plasma membrane. In this study, we used the rodent model parasite Plasmodium berghei to design a label-free quantitative proteomic approach aimed at identifying gender-related proteins differentially released/secreted by purified mature gametocytes when activated to form gametes. We compared the abundance of molecules secreted by wild type gametocytes of both genders with that of a transgenic line defective in male gamete maturation and egress. This enabled us to provide a comprehensive data set of egress-related molecules and their gender specificity. Using specific antibodies, we validated eleven candidate molecules, predicted as either gender-specific or common to both male and female gametocytes. All of them localize to punctuate, vesicle-like structures that relocate to cell periphery upon activation, but only three of them localize to the gametocyte-specific secretory vesicles named osmiophilic bodies. Our results confirm that the egress process involves a tightly coordinated secretory apparatus that includes different types of vesicles and may put the basis for functional studies aimed at designing novel transmission-blocking molecules.
Highlights
Plasmodium, the malaria parasite, undergoes a complex life cycle alternating between a vertebrate host and a mosquito vector of the genus Anopheles
Proteomic Analysis of Gender-Related Proteins Released during P. berghei Gamete Egress from the Host red blood cell (RBC)—To define gender-related factors released during gametogenesis, we relied on a transgenic parasite line defective in male gamete maturation and egress, actII(-)
Enriched (.95%) mature gametocytes were recovered from peripheral blood of mice infected with synchronous P. berghei parasites, 30 hpi, when young asexual stages and mature gametocytes are the major parasite populations circulating
Summary
Authors Felicia Grasso, Stefania Mochi, Federica Fratini, Anna Olivieri, Chiara Currà, Inga Siden Kiamos, Elena Deligianni, Cecilia Birago, Leonardo Picci, Elisabetta Pizzi, Tomasino Pace, and Marta Ponzi. By a differential quantitative proteomic approach, we identified proteins released by Plasmodium gametocytes from a transgenic line defective in male gametogenesis and its parental line, when activated to form gametes. Gender specificity of gametocyte egress-secretome was defined by a comparative analysis of proteins quantified in the two lines. Candidate proteins selected for validation confirmed the predicted gender-specificity and showed that these secreted proteins localize to different types of vesicles, suggesting that emergence from the host cell involves a tightly coordinated secretory apparatus
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