Exploring the role of three deubiquitinases – UCH54, UCHL3 and USP7 – in the biology of the malaria parasite

Abstract

Post-translational modification of proteins by ubiquitination serves as pivotal signals in the cell, exerting diverse effects ranging from degradation to modulating protein function, localization, and activity. Despite its fundamental role across eukaryotes, the involvement of ubiquitination in Plasmodium is poorly understood. Our project reveals key roles for three deubiquitinating enzymes in regulating the biology of the malaria parasite. Our data on PbUCHL3 and PbUCH54 reveal their role in the parasite's susceptibility to repeated artesunate exposure. These findings hold promise in combating artemisinin resistance, which is a growing cause for concern worldwide. Furthermore, our research highlights the indispensable role of PbUSP7 in malaria transmission biology. Within minutes of transmission to the mosquito vector, a sexual precursor male gametocyte replicates its DNA and differentiates to form eight flagellate male gametes. We have found an essential role for PbUSP7 in this process. USP7-deficient male gametocytes show aberrant nuclear characteristics and are unable to replicate their DNA in response to the mosquito environment. Whole-cell transcriptomic and proteomic data from USP7-knockout gametocytes reveal that the deubiquitinase alters the transcription as well as the stability of key proteins involved in DNA replication and flagella formation. Additionally, the deubiquitinase extensively regulates the stability of E3 ubiquitin ligases, key enzymes in the ubiquitin-proteasomal system that conjugate ubiquitin moieties to substrate cellular proteins. From stage-specific transcription to DNA replication and drug action, our studies on these three deubiquitinases unravel the complex biology of this age-old parasite while opening up new avenues for drug design and disease intervention.