Biology subjects

Le Berre, M.

Publications and source records attributed to Le Berre, M..

4 recordsLinked to original sources

bioRxiv2025

Molecular and functional dissection of the AP2-I/BDP1 transcriptional complex of the malaria parasite reveals a role beyond the red blood cell stages

The transcription factor AP2-I and the bromodomain protein BDP1 of the malaria parasite bind upstream of several genes implicated in red blood cell invasion. Here, we demonstrate that they form a complex and that AP2-I recruits BDP1 to the target genes. The ACDC domain of AP2-I interacts with a BDP1 region called BAAS, located between the ankyrin and the bromodomain. The ankyrin, in turn, binds to a conserved AP2-I specific region called ASAIR. Three of the interacting domains are parasite-specific, allowing inhibition without affecting the host. We further show that AP2-I is essential for asexual blood stage development, playing multiple roles, and that AP2-I and BDP1 function beyond invasion, binding to the promoters of the gametocytogenesis regulators gdv1 and ap2-g, suggesting a role for the AP2-I/BDP1 complex in parasite sexual commitment. Overall, our study highlights the essential and unique nature of the AP2-I/BDP1 complex and its potential as a novel antimalarial drug target. Author summaryThe transcription factor AP2-I and the bromodomain protein BDP1 of the malaria parasite have previously been shown to be implicated in red blood cell invasion by the human malaria parasite. Here we show that they form a complex and identify the interacting domains on each protein. Three of these are parasite-specific, allowing inhibition without affecting the human host. We also show that AP2-I is essential for parasite survival in the blood and that the protein is implicated in other processes beyond red blood cell invasion. Namely, AP2-I, but also BDP1, bind to the promoters of the gametocytogenesis regulators gdv1 and ap2-g, suggesting a role for the AP2-I/BDP1 complex in parasite sexual commitment, without which the parasite cannot be transmitted.

microbiology↗

bioRxiv2024

The monomer/dimer switch modulates the activity of plant adenosine kinase

HighlightThe switch from active monomers to inactive dimers in plant ADKs impacts overall enzyme activity and represents a novel negative feedback-loop mechanism to maintain steady levels of adenosine and AMP. Adenosine undergoes ATP-dependent phosphorylation catalyzed by adenosine kinase (ADK). In plants, ADK also phosphorylates cytokinin ribosides, transport forms of the hormone. Here, we investigated the substrate preferences, oligomeric states and structures of ADKs from moss (Physcomitrella patens) and maize (Zea mays) alongside metabolomic and phenotypic analyses. We showed that dexamethasone-inducible ZmADK overexpressor lines in Arabidopsis can benefit from a higher number of lateral roots and larger root areas under nitrogen starvation. We discovered that maize and moss enzymes can form dimers upon increasing protein concentration, setting them apart from the monomeric human and protozoal ADKs. Structural and kinetic analyses revealed a catalytically inactive unique dimer. Within the dimer, both active sites are mutually blocked. The activity of moss ADKs, exhibiting a higher propensity to dimerize, was tenfold lower compared to maize ADKs. Two monomeric structures in a ternary complex highlight the characteristic transition from an open to a closed state upon substrate binding. This suggests that the oligomeric state switch can modulate the activity of moss ADKs and likely other plant ADKs. Moreover, dimer association represents a novel negative feedback mechanism, helping to maintain steady levels of adenosine and AMP.

plant biology↗

bioRxiv2024

Structural characterization of the ACDC domain from ApiAP2 proteins of the malaria parasite

The Apicomplexan AP2 (ApiAP2) proteins are the best characterized family of DNA-binding proteins in the malaria parasite. Apart from the AP2 DNA-binding domain, there is little sequence similarity between ApiAP2 proteins and no other functional domains have been extensively characterized. One protein domain, which is present in a subset of the ApiAP2 proteins, is the conserved AP2-coincident domain mostly at the C-terminus (ACDC domain). Here we solved for the first time the crystal structure of the ACDC domain from two distinct Plasmodium falciparum ApiAP2 proteins and one orthologue from P. vivax, revealing a non-canonical four-helix bundle. Despite little sequence conservation between the ACDC domains from the two proteins, the structures are remarkably similar and do not resemble that of any other known protein domains. Due to their unique protein architecture and lack of homologues in the human genome, we performed in silico docking calculations against a library of known antimalarial compounds and we identified a small molecule that can potentially bind to any Apicomplexan ACDC domain within a pocket highly conserved amongst ApiAP2 proteins. Inhibitors based on this compound would disrupt the function of the ACDC domain and thus of the ApiAP2 proteins containing it, providing a new therapeutic window for targeting the malaria parasite and other Apicomplexans.

biochemistry↗

bioRxiv2023

A versatile high-throughput assay based on 3D ring-shaped cardiac tissues generated from human induced pluripotent stem cell derived cardiomyocytes

We developed a 96-well plate assay which allows fast, reproducible and high-throughput generation of 3D cardiac rings around a deformable optically transparent hydrogel (PEG) pillar of known stiffness. Human induced pluripotent stem cell-derived cardiomyocytes, mixed with normal human adult dermal fibroblasts in an optimized 3:1 ratio, self-organized to form ring-shaped cardiac constructs. Immunostaining showed that the fibroblasts form a basal layer in contact with the glass, stabilizing the muscular fiber above. Tissues started contracting around the pillar at D1 and their fractional shortening increased until D7, reaching a plateau at 25{+/-}1%, that was maintained up to 14 days. The average stress, calculated from the compaction of the central pillar during contractions, was 1.4{+/-}0.4 mN/mm2. The cardiac constructs recapitulated expected inotropic responses to calcium and various drugs (isoproterenol, verapamil) as well as the arrhythmogenic effects of dofetilide. This versatile high-throughput assay allows multiple in situ mechanical and structural read-outs.

bioengineering↗