Unravel the interactome of the ND complex in the ciliate Tetrahymena thermophila as a tool to shed light on rhoptry secretion in Apicomplexa

ABSTRACT: Alveolates are a group of widespread microorganisms comprising Ciliates, Apicomplexa and Dinoflagellates, who have independently adapted their secretory pathways to interact at best with their own environments, in order to sustain a free-living or parasitic life-style. In fact, apicomplexan parasites which include Toxoplasma gondii and Plasmodium falciparum, upon contacting the host cell, secrete proteins from secretory organelles called rhoptries to invade and take control of the host. On the other hand, secretory organelles of free-living ciliates, called mucocysts in Tetrahymena thermophila, fulfill different functions than those of parasites since their contents are secreted in response to predators or preys, and maybe used for encystment. Despite this functional specialization, our recent comparative analysis between ciliates and apicomplexan parasites demonstrated that the mechanism for the exocytosis of their secretory organelles is conserved. This exocytic machinery involves unique structural features and molecular players, such as the ND (non-discharge) factors, which are essential for the fusion events leading to the discharge of the secretory organelles in both models. Additional evidences in support of this shared mechanism come from our recent work on a small GTPase in the Ras superfamily identified in ciliates and apicomplexans, with a conserved role in regulated exocytosis. Tetrahymena and Toxoplasma mutants depleted of this protein have significant defects in mucocyst and rhoptry secretion, respectively. The small GTPase is part of the ND complex, as shown by co-immunoprecipitation assays in Tetrahymena, and mass-spectrometry analyses of Toxoplasma ND9 and NDP1 proteins. Our data remark how valuable ciliates are as models to study essential processes in apicomplexan pathogens. Thus, to shed light on the molecular mechanisms regulating rhoptry secretion in Apicomplexa, we will continue to take advantage of ciliates biology and try to identify the interactome of the ND complex in the ciliate Tetrahymena, by using immunoprecipitation combined with mass spectrometry of the ND9 and NDP1 homologs, and also of the newly described small GTPase. This approach will uncover novel candidates, and those with homologs in apicomplexa will be pursued further in Toxoplasma.

INSTRUMENT(S):

ORGANISM(S): Eukaryota Tetrahymena Thermophila

TISSUE(S): Ciliated

SUBMITTER: valerie Rofidal  

LAB HEAD: Maryse Lebrun

PROVIDER: PXD069210 | Pride | 2026-10-26

REPOSITORIES: Pride