Thierry Soldati

News

FebruarY 2024

A new visitor in the team for a few months! Screenshot_20240214-164141_Gallery.jpg

Carolina Panosso Schuindt, a bachelor student from the Freire Neto group in São Paulo, joined us for three months, thanks to the support of FAPESP, in order to work on the interaction between D. discoideum and a colorful opportunistic pathogen, Chromobacterium violaceum

"As part of my research at the University of São Paulo (Brazil), I characterized the role of ZntA and ZntR in the context of zinc and cadmium intoxication in the opportunistic pathogen Chromobacterium violaceum(Cv). Now I have joined the Soldati lab for a 3-month internship, and under the supervision of Dr. Lucas Ceseti, I will investigate what happens when Dicty meets Cv and whether ZntA and ZntR are essential for the bacterial virulence in the context of infection." - Carolina Panosso Schuindt

 

Congratulations to Crisalida for her successful master's defense !Sans titre.jpg

 

After a year with us, Crisalida successfully defended her master's work. She worked at investigating the role of lipophagy in lipid droplet dynamics in D. discoideum. She will continue her work with us for few months, before to start her PhD in another team at Unige Smile

January 2024

New paper out in mSystems: Temporal genome-wide fitness analysis of Mycobacterium marinum during infection reveals the genetic requirement of virulence and survival in amoebae and microglial cells

In this pivotal study, our lab, in collaboration with the team of Pr. Graham Stewart, has identified critical genes essential for mycobacterial survival during the infection. Tuberculosis, a persistent infectious disease, has become even more challenging with the rise of drug-resistant strains, necessitating improved treatment strategies. Utilizing transposon sequencing (Tn-Seq) on Mycobacterium marinum (a model pathogen for M. tuberculosis), we pinpointed genes crucial for infection survival. This unbiased genome-wide approach highlighted disruptions in 57% of TA sites and identified 568 essential genes (10.2%). Noteworthy pathways for M. marinum survival during infection in different host cells included DNA damage repair, lipid and vitamin metabolism, the type VII secretion system (T7SS) ESX-1, and the Mce1 lipid transport system. These findings, consistent with previous studies, provide valuable insights into tuberculosis pathogenesis, offering potential targets for more effective drug interventions. 

For the complete story, click here! 

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New collaborative paper with Philippe Dehio in the team of Prof. Christoph Hess: An evolutionary-conserved VPS34-PIKfyve-TRPML1-Myosin II axis regulates the speed of amoeboid cell migration

In this new collaborative work,  a crucial connection between ultrastructural polarization and T cell migration signaling have been unveiled. This study led by the team of Prof. Hess, identifies endo-lysosome-localized kinases, specifically VPS34–PIKfyve, as instrumental in regulating the speed of amoeboid migration in T cells. The research demonstrates the accumulation of these kinases at the uropod of polarized cells, influencing T cell velocity without altering directionality. The mechanism involves the generation of PI(3,5)P2, controlling Ca2+ efflux through TRPML1 and subsequently regulating myosin IIA activity and propulsive force via retrograde actin flow. Notably, the study also highlights the evolutionary conservation of the VPS34–PIKfyve axis in controlling migration speed in myeloid cells and Dictyostelium discoideum

Have a look here!

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OCTOBER 2023

An SNSF grant has been assigned to our group ! 

We are delighted to announce that our group has been granted an SNSF grant to work on the virulence strategies of pathogenic mycobacteria and cell-autonomous host defence mechanisms. We are happy to continue our strong contribution to the field with our unique model !

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New collaborative paper with the Wolfender group out in Frontiers in Natural Products: Targeted isolation of natural analogs of anti-mycobacterial hit compounds based on the metabolite profiling of a large collection of plant extracts

Antibiotics resistance is a clear threat to the future of current tuberculosis treatments like rifampicin, prompting the need for new treatment options in this field. While plants can offer a plethora of chemical diversity in their constitutive natural products to tackle this issue, finding potentially bioactive compounds in them has not always proven to be that simple. Classical bioactivity-guided fractionation approaches are still trendy, but they bear significant shortfalls, like their time-consuming nature as well as the ever-increasing risk of isolating known bioactive compounds. In this regard, we have developed an alternative method to the latter approach that allows for natural derivatives of a known bioactive scaffold to be efficiently targeted and isolated within a large library of plant extracts. Hence our approach allows for the anticipation of bioactive structure independently of preliminary bioassays. By relying on the chemical diversity of a set of 1,600 plant extracts analyzed by HRMS/MS, we were able to isolate and characterize several minor derivatives of a previously reported bioactive aza-anthraquinone compound from Cananga brandisiana, selected within the plant set. Assessment of bioactivity on these derivatives confirmed their expected activity on Mycobacterium marinum in our anti-infective assay. This proof-of-concept study has established an original path towards bioactive compounds isolation, with the advantage of potentially highlighting minor bioactive compounds, whose activity may not even be detectable at the extract level.

For a complete reading, it's here.

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AUGUST 2023

2813367.png   Master internship 

   We are looking for two motivated master students to join our lab and collaborate on our most recent stories: TrafE and Vacuolins

    Don't hesitate to check our Job offers page ! 

 

June 2023

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Very exciting news! Our postdoc Sandra Guallar-Garrido has been awarded an SNF postdoctoral fellowship! 

This fellowship will allow here to keep deciphering the role of TrafE during M. marinum infection in Dicty. Huge congratulations to her!

New collaborative paper with the team of Jason King out in Journal of Cell Biology: A PI(3,5)P2 reporter reveals PIKfyve activity and dynamics on macropinosomes and phagosomes

Phosphoinositide signaling lipids (PIPs) are key regulators of membrane identity and trafficking. Of these, PI(3,5)P2 is one of the least well understood, despite key roles in many endocytic pathways including phagocytosis and macropinocytosis. PI(3,5)P2 is generated by the phosphoinositide 5-kinase PIKfyve, which is critical for phagosomal digestion and antimicrobial activity. However PI(3,5)P2 dynamics and regulation remain unclear due to lack of reliable reporters. Using the amoeba Dictyostelium discoideum we identify SnxA as a highly-selective PI(3,5)P2 -binding protein and characterise its use as a reporter for PI(3,5)P2 in both Dictyostelium and mammalian cells. Using GFP-SnxA we demonstrate that Dictyostelium phagosomes and macropinosomes accumulate PI(3,5)P2 three minutes after engulfment but is then retained differently, indicating pathway-specific regulation. We further find that PIKfyve recruitment and activity are separable, and that PIKfyve activation stimulates its own dissociation. SnxA is therefore a new tool for reporting PI(3,5)P2 in live cells that reveals key mechanistic details of the role and regulation of PIKfyve/PI(3,5)P2 .

Have a look here!

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APRIL 2023

New paper out in eLife: A TRAF-like E3 ubiquitin ligase TrafE coordinates ESCRT and autophagy in endolysosomal damage response and cell-autonomous immunity to Mycobacterium marinum

Cells are perpetually challenged by pathogens, protein aggregates or chemicals, that induce plasma membrane or endolysosomal compartments damage. This severe stress is recognised and controlled by the endosomal sorting complex required for transport (ESCRT) and the autophagy machineries, which are recruited to damaged membranes to either repair or to remove membrane remnants. Yet, insight is limited about how damage is sensed and which effectors lead to extensive tagging of the damaged organelles with signals, such as K63-polyubiquitin, required for the recruitment of membrane repair or removal machineries. To explore the key factors responsible for detection and marking of damaged compartments, we use the professional phagocyte Dictyostelium discoideum. We found an evolutionary conserved E3-ligase, TrafE, that is robustly recruited to intracellular compartments disrupted after infection with Mycobacterium marinum or after sterile damage caused by chemical compounds. TrafE acts at the intersection of ESCRT and autophagy pathways and plays a key role in functional recruitment of the ESCRT subunits ALIX, Vps32 and Vps4 to damage sites. Importantly, we show that the absence of TrafE severely compromises the xenophagy restriction of mycobacteria as well as ESCRT-mediated and autophagy-mediated endolysosomal membrane damage repair, resulting in early cell death.

 

For the complete story, click here! 

 

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MARCH 2023

We have a new postdoctoral fellow in the lab!justine.jpeg

Justine Toinon join us for a project on the exploration of the signaling cascades and transcriptional reprogramming in the course of Mycobacterium marinum infection both in Dictyostelium discoideum and in murine microglial cells. Let's give her a warm welcome! 

 

We have a new postdoctoral fellow in the lab!20230423_171619.jpg

After his stay last year, Lucas Ceseti decided to come back and join us as a postdoctoral fellow for a project on elucidating the strategies used by X. citri to resist predation by D. discoideum. Let's give him a warm welcome! 

 

November 2022

New collaborative paper: 5-ethyl-2’-deoxyuridine fragilizes Klebsiella pneumoniae outer wall and facilitates intracellular killing by phagocytic cells

Our team collaborated with the team of Prof. Pierre Cosson on this work that allowed the identification of a new antibacterial compound targeting K. pneumoniae and facilitating its killing by Dicty. You can learn a bit more about this story here, or directly read the paper published in PLOS One here

Klebsiella pneumoniae is the causative agent of a variety of severe infections. Many K. pneumoniae strains are resistant to multiple antibiotics, and this situation creates a need for new antibacterial molecules. K. pneumoniae pathogenicity relies largely on its ability to escape phagocytosis and intracellular killing by phagocytic cells. Interfering with these escape mechanisms may allow to decrease bacterial virulence and to combat infections. In this study, we used Dictyostelium discoideum as a model phagocyte to screen a collection of 1,099 chemical compounds. Phg1A KO D. discoideum cells cannot feed upon K. pneumoniae bacteria, unless bacteria bear mutations decreasing their virulence. We identified 3 non-antibiotic compounds that restored growth of phg1A KO cells on K. pneumoniae, and we characterized the mode of action of one of them, 5-ethyl-2’-deoxyuridine (K2). K2-treated bacteria were more rapidly killed in D. discoideum phagosomes than non-treated bacteria. They were more sensitive to polymyxin and their outer membrane was more accessible to a hydrophobic fluorescent probe. These results suggest that K2 acts by rendering the membrane of K. pneumoniae accessible to antibacterial effectors. K2 was effective on three different K. pneumoniae strains, and acted at concentrations as low as 3 μM. K2 has previously been used to treat viral infections but its precise molecular mechanism of action in K. pneumoniae remains to be determined.

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September 2022

A new collaborative work with Dr. Cristina Alvarez-Martinez from the Universidade Estadual de Campinas (Brazil) supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and the Swiss National Science Foundation (SNSF)

Thanks to a research grant, the FAPESP and the SNSF will support a new collaborative work with Dr. Cristina Alvarez-Martinez. This project will aim at deciphering the molecular mechanisms of the Xanthomonas citri resistance to Dictyostelium discoideum predation and the role of the Type VI Secretion System (T6SS) (A) of X. citri in this resistance. Overall, this project will expand our understanding of the role of anti-eukaryotic T6SS and possibly reveal new effector functions and anti-host strategies. This will help to understand better the mechanisms used by X. citri to survive and disseminate in the environment (B).  

April 2022

We have a new postdoctoral fellow in the lab!

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Sandra Guallar-Garrido join us for a project on the machineries involved in damage sensing and repairing in Dictyostelium discoideum. Let's give her a warm welcome! 

 

January 2022

A new comer in the team for a few months! 

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Lucas Ceseti, a phD student from the group of Cristina Martinez (https://www.ib.unicamp.br/node/99), joined us for three months in order to work on the relationship between our favorite beast, Dictyostelium discoideum, and the phytopathogen Xanthomonas citri

"As part of my PhD research performed at Unicamp (Brazil), I went to the Soldati Lab for a 3-month internship to evaluate the phenotypes of Dicty expressing putative T6SS effectors that Xanthomonas citri (Xac) uses to resist against the amoeba. Also during this period, I worked together with the Senior postdoc Céline Michard to establish a potential tool for monitoring translocation from bacteria to Dicty, and much more aiming to understand what happens when Xac meets Dicty." - Lucas Ceseti

 

November 2021

New preprint from the lab: Disruption of vacuolin microdomains in the host Dictyostelium discoideum increases resistance to Mycobacterium marinum-induced membrane damage and infection

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis, manipulates the host phagosome maturation pathway to replicate intracellularly. Mycobacterium marinum, a closely-related species, and Dictyostelium discoideum, a social amoeba and alternative phagocytic host, have been used as models to study host-pathogen interactions occurring during mycobacterial infections. Vacuolins, functional homologues of the mammalian flotillins, organize membrane microdomains and play a role in vesicular trafficking. Various pathogens have been reported to manipulate their membrane association and function. During infection of D. discoideum with M. marinum, Vacuolin C was specifically and highly induced and all three vacuolin isoforms were enriched at the mycobacteria-containing-vacuole (MCV). In addition, absence of vacuolins reduced escape from the MCV and conferred resistance to M. marinum infection. Moreover, ESAT-6, the membrane-disrupting virulence factor of M. marinum, was less associated with membranes when vacuolins were absent. Together, these results suggest that vacuolins are important host factors that are manipulated by mycobacteria to inflict membrane damage and escape from their compartment.

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Read it here!