Project Grant R01AI192712

PARSEC: PLASMODIUM FALCIPARUM ADAPTIVE RESPONSE TO SICKLE TRAIT ERYTHROCYTES - PROJECT ABSTRACT SICKLE-TRAIT HEMOGLOBIN CONFERS NEAR COMPLETE PROTECTION FROM SEVERE, LIFE-THREATENING PLASMODIUM FALCIPARUM MALARIA IN AFRICAN CHILDREN. THE MECHANISMS OF THIS PROTECTION REMAIN INCOMPLETELY UNDERSTOOD, BUT SEVERAL LINES OF EVIDENCE SUPPORT THE NOTION THAT SICKLE-TRAIT ATTENUATES THE CRITICAL PARASITE PATHOGENIC PHENOTYPE OF CYTOADHERENCE. WE HAVE REPORTED CONSERVED PARASITE TRANSCRIPTIONAL PROGRAMS IN SICKLE-TRAIT RBCS, SUPPORTING A MECHANISM OF THIS ATTENUATED CYTOADHESION THAT IS PRIMARILY POST-TRANSCRIPTIONAL. THIS HYPOTHESIS WAS AUGMENTED BY THE OBSERVATION THAT SOME P. FALCIPARUM PARASITES APPEAR TO HAVE ADAPTED TO INFECT SICKLE-TRAIT RBCS THROUGH MODULATION OF THE GENE PF3D7_1127000, ENCODING A PUTATIVE PROTEIN PHOSPHATASE. IN OUR RECENT PARASITE COMPARATIVE TRANSCRIPTOMIC STUDY IN MALIAN CHILDREN, PF3D7_1127000 WAS THE SINGLE MOST OVEREXPRESSED TRANSCRIPT IN SICKLE-TRAIT CHILDREN AT OVER 30-FOLD. IN AN ORTHOGONAL PARASITE GENOME-WIDE SCREEN, WE OBSERVED THIS GENE AS ENRICHED IN CHILDREN WITH SICKLE-TRAIT CODING MUTATIONS AND IDENTIFIED A STRUCTURAL REARRANGEMENT IN PF3D7_1127000 (AKA "PFSA3"). COLLECTIVELY, THESE DATA SUGGEST THAT A VARIANT LINKED TO OVEREXPRESSION OF PFSA3 IS A KEY PARASITE ADAPTATION TO GROWTH AND DISEASE IN SICKLE-TRAIT. WE WILL BUILD ON THESE CONVERGENT LINES OF EVIDENCE OF PARASITE ADAPTATION TO SICKLE-TRAIT RBCS WITH OUR EXPERIENCE WITH PARASITE EXPERIMENTAL GENETICS AND BIOCHEMISTRY TO INVESTIGATE THE CELLULAR FUNCTIONS OF WILDTYPE AND MUTANT PFSA3 AND ITS ASSOCIATION WITH CLINICAL DISEASE. OUR CENTRAL HYPOTHESIS IS THAT THE ADAPTIVE RESPONSE TO SICKLE-TRAIT RBCS OF PARASITE OVEREXPRESSION OF MUTANT PFSA3 NULLIFIES THE PROTECTION AGAINST CLINICAL DISEASE CONFERRED BY SICKLE- TRAIT. WE WILL TEST THIS HYPOTHESIS BY ENGINEERING TRANSGENIC PARASITES LINES EXPRESSING WILDTYPE AND MUTANT PFSA3 AND UNDERSTANDING THE NATIVE FUNCTIONS OF THE PROTEIN, ITS INTERACTING PARTNERS WITHIN THE PARASITE AND HOST CELL, AND THE EFFECTS OF PFSA3 EXPRESSION ON PATHOGENIC PARASITE PHENOTYPES, INVESTIGATE PFSA3 VARIATION IN A MOLECULAR EPIDEMIOLOGIC STUDY IN WESTERN KENYA, AND CHARACTERIZE THE BIOCHEMICAL ACTIVITY AND STRUCTURE OF PFSA3. THIS PROJECT BUILDS ON CONVERGENT LINES OF GENOMIC AND FUNCTIONAL GENOMIC EVIDENCE THAT IMPLICATE PFSA3 VARIATION IN ADAPTATION TO SICKLE-TRAIT RBCS. WITH OUR COMPLEMENTARY EXPERTISE IN PARASITE PATHOGENESIS, EXPERIMENTAL GENETICS, BIOCHEMISTRY, AND GENOMICS, WE WILL CHARACTERIZE THE NATIVE FUNCTION OF PFSA3 AND THE MECHANISMS BY WHICH IT MEDIATES PARASITE PHENOTYPES.