Biology subjects

Artavanis-Tsakonas, K.

Publications and source records attributed to Artavanis-Tsakonas, K..

3 recordsLinked to original sources

bioRxiv2023

A multistage Plasmodium CRL4-WIG1 ubiquitin ligase is critical for the formation of functional microtubule organisation centres in microgametocytes

Malaria is a mosquito-borne infectious disease caused by unicellular eukaryotic parasites of the Plasmodium genus. Protein ubiquitination by E3 ligases is a critical post-translational modification required for various cellular processes during the lifecycle of Plasmodium parasites. However, little is known about the repertoire and function of these enzymes in Plasmodium. Here we show that Plasmodium expresses a conserved cullin RING E3 ligase (CRL) complex that is functionally related to the eukaryotic CRL4. In P. falciparum asexual blood stages, a cullin-4 scaffold interacts with the RING protein RBX1, the adaptor protein DDB1 and a set of putative receptor proteins that may determine substrate specificity for ubiquitination. These receptor proteins contain WD40-repeat domains and include WD-repeat protein Important for Gametogenesis 1 (WIG1). This CRL4-related complex is also expressed in P. berghei gametocytes, with WIG1 being the only putative receptor detected in both schizont and gametocyte stages. While WIG1 is not required for the proliferation of P. berghei asexual blood stages, its disruption leads to a complete block in microgamete formation. Proteomic analyses indicate that WIG1 disruption alters proteostasis of ciliary proteins and components of the DNA replication machinery during gametocytogenesis. Further analysis by ultrastructure expansion microscopy (U-ExM) indicates that WIG1-dependent depletion of ciliary proteins is associated with impaired formation of the microtubule organisation centres that coordinate mitosis with axoneme formation and altered DNA replication during microgametogenesis. This work identifies a CRL4-related ubiquitin ligase in Plasmodium that is critical for the transmission of malaria parasites by regulating proteostasis of ciliary and DNA replication proteins.

microbiology↗

bioRxiv2022

Drug resistance-associated mutations in Plasmodium UBP-1 disrupt ubiquitin hydrolysis

Deubiquitinating enzymes function to cleave ubiquitin moieties from modified proteins, serving to maintain the pool of free ubiquitin in the cell while simultaneously impacting the fate and function of a target protein. Like all eukaryotes, Plasmodium parasites rely on the dynamic addition and removal of ubiquitin for their own growth and survival. While humans possess around 100 DUBs, Plasmodium contains [~]20 putative ubiquitin hydrolases, many of which bear little to no resemblance to those of other organisms. In this study, we characterize PfUBP-1, a large ubiquitin hydrolase unique to Plasmodium spp that has been linked to endocytosis and drug resistance. We demonstrate its ubiquitin activity, linkage specificity and assess the repercussions of point mutations associated with drug resistance on catalytic activity and parasite fitness.

microbiology↗

bioRxiv2022

Large-scale proteomic analysis of T. spiralis muscle-stage ESPs identifies a novel upstream motif for in silico prediction of secreted products

The Trichinella genus contains parasitic nematodes capable of infecting a wide range of hosts including mammals, birds and reptiles. Like other helminths, T. spiralis secretes a complex mixture of bioactive molecules capable of modulating its immediate surroundings and creating a hospitable environment for growth, survival and ultimately transmission. The constitution of these excretory-secretory products (ESPs) changes depending on the tissue niche and the specific stage of parasite development. Unique to T. spiralis is a true intracellular stage wherein larvae develop inside striated myotubes. Remarkably, the parasite larvae do not destroy the host cell but rather reprogram it to support their presence and growth. This transformation is largely mediated through stage-specific secretions released into the host cell cytoplasm. In this study, we apply state of the art proteomics and computational approaches to elucidate the composition and functions of muscle-stage T. spiralis ESPs. Moreover, we define a commonly-occurring, upstream motif that we believe is associated with the stichosome, the main secretory organ of this worm, and can thus be used to predict secreted proteins across experimentally less tractable T. spiralis life cycle stages. Author SummaryTrichinella spiralis is the only helminth parasite with a true intracellular stage. Newborn larvae penetrate the intestinal wall of the host, enter the circulation and preferentially infect muscle cells. Remarkably, they do not destroy the host cell but rather initiate a series of modulatory events that transform it into a nurse cell complex, a collagenated cyst that can persist for years. Each stage of T. spiralis development is guided by host-targeted secretions released by the worm directly into its immediate environment, mediating events such as immunoregulation, cell cycle control and angiogenesis. As such, these worm effectors hold therapeutic potential for chronic and autoimmune diseases. The composition of excretory-secretory products (ESPs) changes according to what the worm needs to accomplish and what tissue niche it is occupying at the time, with many deriving from the stichosome, the worms dedicated secretory organ. In this study, we characterise ESPs of muscle-stage T. spiralis larvae using proteomic and bioinformatic approaches and we define a regulatory motif associated with stichosome-derived proteins.

cell biology↗