Abstract
Ubiquitin-dependent protein degradation within malarial parasites is a burgeoning field of interest due to several encouraging reports of proteasome inhibitors that were able to confer antimalarial activity. Despite the growing interest in the Plasmodium proteasome system, relatively little investigation has been done to actually characterize the parasite degradation machinery. In this report, we provide an initial biological investigation of the ubiquitylating components of the endoplasmic reticulum-associated degradation (ERAD) system, which is a major pathway in targeting misfolded proteins from the ER to the cytosol for proteasome degradation. We are able to show that the ERAD system is essential for parasite survival and that the putative Plasmodium HRD1 (E3 ubiquitin ligase), UBC (E2 ubiquitin conjugating enzyme) and UBA1 (E1 ubiquitin activating enzyme) are able to mediate in vitro ubiquitylation. Furthermore, by using immunofluorescence, we report that Plasmodium HRD1 localizes to the ER membranes, while the Plasmodium UBC and UBA1 localize to the cytosol. In addition, our gene disruption experiments indicate that the Plasmodium HRD1 is likely essential. We have conducted an initial characterization of the ubiquitylating components of the Plasmodium ERAD system, a major pathway for protein degradation and parasite maintenance. In conjunction with promising proteasome inhibitor studies, we explore the possibility of targeting the Plasmodium ERAD system for future bottom-up drug development approaches.
Highlights
Malaria is one of the deadliest infectious diseases of the world, infecting up to half a billion and killing up to one million people each year [1]
To test the essentiality of the endoplasmic reticulumassociated degradation (ERAD) pathway in Plasmodium, we decided to test the inhibitory effects on P. falciparum cultures with Eeyarestatin I (ESI)
Proteasome inhibitor studies have shown promising antimalarial results and have ignited interest in studying how protein degradation in Plasmodium can be targeted for effective drug discovery and synthesis
Summary
Malaria is one of the deadliest infectious diseases of the world, infecting up to half a billion and killing up to one million people each year [1]. Though the protein degradation via the 26S proteasome closely involves ubiquitylation of target substrates, very little work has been done regarding the characterization of the parasite’s ubiquitylating machinery acting upstream of the proteasome, possibly leading to the discovery of parasite-specific divergences that can be exploited for drug targeting. Misfolded proteins are shuttled to the DER1 translocon complex, which forms a hydrophobic pore to allow the retrotranslocation of proteins through the ER membrane Within this translocon complex, the HRD1 E3 ubiquitin ligase interacts with membrane-bound proteins needed for retro-translocation and helps form the hydrophobic pore complex [15]. The HRD1 E3 enzyme catalyzes, with the intervention of other ubiquitylating enzymes, the ubiquitylation of the target misfolded protein that is the prerequisite for subsequent retro-translocation to the cytosol and destruction by the 26S proteasome [16,17,18]. While ubiquitin E1 and E2 enzymes seem to be well conserved across eukaryotic phyla, Plasmodium E3 ubiquitin ligases have been shown to have high levels of divergences that can be utilized for the development of new antimalarials [21]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
