Investigating plasmepsin flexibility as a function of the flap region : a unique structural and dynamic feature of aspartic protease.

Ph. D. in Pharmaceutical Chemistry. University of KwaZulu-Natal, Durban 2015.Malaria is one of the most deadly infectious protozoan diseases known to man. It is spread by the Plasmodium parasite through the bite of the female Anopheles mosquito. Increasing resistance to currently available antimalarial drugs is a growing concern. Plasmepsins are malarial aspartic proteases, due to their characteristic mechanism of action, the fact that they are found in all Plasmodium species and are essential to parasitic survival they represent novel targets in the design of antimalarials. A unique structural feature of aspartic proteases and plasmepsins is the flap region lying perpendicular to the catalytic aspartic acid active, partially covering the active site. The flap region plays an important structural (and kinetic) role in regulating access to the active site, thereby regulating ligand binding. The present study focused on the flap dynamics of Plm I – V, proposing and validating parameters to accurately quantify the dynamic behaviour of the flap region. The catalytic aspartic acids is highly conserved in the plasmepsin family; sequence analysis revealed that although all plasmepsins are similar in structure, they differ greatly in the residues in the flap region. The heterogeneity in this region gives each plasmepsin unique substrate specificity and response to inhibitors. The parameters proposed in the present study gives a detailed account for the twisting of the flaps which move away from the active site in the absence of an inhibitor. Upon inhibitor binding, residues in the flap region form hydrogen bonds with the inhibitor pulling it inward towards the active site rendering the enzyme inactive. The parameters proposed in the present study will be of great value in the design of novel plasmepsin inhibitors, with increased efficacy and potency

WD40-repeat 47 is essential for brain development via microtubule-mediated processes and autophagy

Erreur dates et n° de conférence dans l'url https://hal.archives-ouvertes.fr/hal-02378786.International audienc

WD40-repeat 47 is essential for brain development via microtubule-mediated processes and autophagy

International audienc

WD40-repeat 47, a microtubule-associated protein, is essential for brain development and autophagy.

The family of WD40-repeat (WDR) proteins is one of the largest in eukaryotes, but little is known about their function in brain development. Among 26 WDR genes assessed, we found 7 displaying a major impact in neuronal morphology when inactivated in mice. Remarkably, all seven genes showed corpus callosum defects, including thicker (Atg16l1, Coro1c, Dmxl2, and Herc1), thinner (Kif21b and Wdr89), or absent corpus callosum (Wdr47), revealing a common role for WDR genes in brain connectivity. We focused on the poorly studied WDR47 protein sharing structural homology with LIS1, which causes lissencephaly. In a dosage-dependent manner, mice lacking Wdr47 showed lethality, extensive fiber defects, microcephaly, thinner cortices, and sensory motor gating abnormalities. We showed that WDR47 shares functional characteristics with LIS1 and participates in key microtubule-mediated processes, including neural stem cell proliferation, radial migration, and growth cone dynamics. In absence of WDR47, the exhaustion of late cortical progenitors and the consequent decrease of neurogenesis together with the impaired survival of late-born neurons are likely yielding to the worsening of the microcephaly phenotype postnatally. Interestingly, the WDR47-specific C-terminal to LisH (CTLH) domain was associated with functions in autophagy described in mammals. Silencing WDR47 in hypothalamic GT1-7 neuronal cells and yeast models independently recapitulated these findings, showing conserved mechanisms. Finally, our data identified superior cervical ganglion-10 (SCG10) as an interacting partner of WDR47. Taken together, these results provide a starting point for studying the implications of WDR proteins in neuronal regulation of microtubules and autophagy