Biosynthesis, localization, and macromolecular arrangement of the Plasmodium falciparum translocon of exported proteins (PTEX).

To survive within its host erythrocyte, Plasmodium falciparum must export hundreds of proteins across both its parasite plasma membrane and surrounding parasitophorous vacuole membrane, most of which are likely to use a protein complex known as PTEX (Plasmodium translocon of exported proteins). PTEX is a putative protein trafficking machinery responsible for the export of hundreds of proteins across the parasitophorous vacuole membrane and into the human host cell. Five proteins are known to comprise the PTEX complex, and in this study, three of the major stoichiometric components are investigated including HSP101 (a AAA(+) ATPase), a protein of no known function termed PTEX150, and the apparent membrane component EXP2. We show that these proteins are synthesized in the preceding schizont stage (PTEX150 and HSP101) or even earlier in the life cycle (EXP2), and before invasion these components reside within the dense granules of invasive merozoites. From these apical organelles, the protein complex is released into the host cell where it resides with little turnover in the parasitophorous vacuole membrane for most of the remainder of the following cell cycle. At this membrane, PTEX is arranged in a stable macromolecular complex of >1230 kDa that includes an ∼600-kDa apparently homo-oligomeric complex of EXP2 that can be separated from the remainder of the PTEX complex using non-ionic detergents. Two different biochemical methods undertaken here suggest that PTEX components associate as EXP2-PTEX150-HSP101, with EXP2 associating with the vacuolar membrane. Collectively, these data support the hypothesis that EXP2 oligomerizes and potentially forms the putative membrane-spanning pore to which the remainder of the PTEX complex is attached.

The Idea of Deafness as Disability in Renaissance Germany.

This essay assesses the degree to which the deaf were regarded as a disabled population in medical, religious, and legal thought during the Renaissance, chronologically identified with the period between approximately 1500 and 1650. The primary geographic focus rests on the German-speaking lands of central Europe. Analysis shows that the idea of deafness as a disability here was composite one, making connections between inability to hear and intellectual impairment, moral deficiency, and disease. This contrasts with recent findings elsewhere in Europe, where intellectuals were more focused on sign languages as a means of integrating the deaf into hearing society.

Systematic analysis of FKBP inducible degradation domain tagging strategies for the human malaria parasite Plasmodium falciparum.

Targeted regulation of protein levels is an important tool to gain insights into the role of proteins essential to cell function and development. In recent years, a method based on mutated forms of the human FKBP12 has been established and used to great effect in various cell types to explore protein function. The mutated FKBP protein, referred to as destabilization domain (DD) tag when fused with a native protein at the N- or C-terminus targets the protein for proteosomal degradation. Regulated expression is achieved via addition of a compound, Shld-1, that stabilizes the protein and prevents degradation. A limited number of studies have used this system to provide powerful insight into protein function in the human malaria parasite Plasmodium falciparum. In order to better understand the DD inducible system in P. falciparum, we studied the effect of Shld-1 on parasite growth, demonstrating that although development is not impaired, it is delayed, requiring the appropriate controls for phenotype interpretation. We explored the quantified regulation of reporter Green Fluorescent Protein (GFP) and luciferase constructs fused to three DD variants in parasite cells either via transient or stable transfection. The regulation obtained with the original FKBP derived DD domain was compared to two triple mutants DD24 and DD29, which had been described to provide better regulation for C-terminal tagging in other cell types. When cloned to the C-terminal of reporter proteins, DD24 provided the strongest regulation allowing reporter activity to be reduced to lower levels than DD and to restore the activity of stabilised proteins to higher levels than DD29. Importantly, DD24 has not previously been applied to regulate proteins in P. falciparum. The possibility of regulating an exported protein was addressed by targeting the Ring-Infected Erythrocyte Surface Antigen (RESA) at its C-terminus. The tagged protein demonstrated an important modulation of its expression.