Biology subjects

Drin, G.

Publications and source records attributed to Drin, G..

5 recordsLinked to original sources

bioRxiv2026

Sfh3 is a sterol-modulated PI/PI4P transfer protein that confers azole resistance in yeast by specifically mediating lanosterol/PI exchange

Lipid transfer proteins precisely distribute lipids within eukaryotic cells, supporting functions such as vesicular trafficking and cellular signaling. Here, we analyzed whether Sfh3 (Sec14 homolog 3) functions as a sterol/phosphatidylinositol (PI) exchanger to clarify its role in neutral lipid mobilization from lipid droplets and in azole resistance in yeast. Using real-time assays, we found that its ergosterol transfer capacity is not activated by PI and is inhibited by ergosterol biosynthesis intermediates, such as lanosterol. Next, we found that Sfh3 exhibits both PI and PI4P transfer activities, which sterols can modulate. Through kinetic, structure-function, and thermal stability analyses, we identified remarkable Sfh3 mutants and ranked Sfh3's relative affinity for its lipid ligands. This allowed us to show that Sfh3 performs selective lanosterol/PI exchange, provided it recognizes PI, in the presence of ergosterol, and that this activity is necessary for yeast resistance to miconazole. Collectively, our data show that Sfh3 is a sterol-regulated PI/PI4P transfer protein, potentially linking sterol metabolism and PI4P signaling during lipid droplet utilization. In azole-treated yeast, elevated lanosterol levels may shift Sfh3 into an exclusive PI/lanosterol exchange mode, promoting cellular detoxification and conferring drug resistance. By revealing unanticipated Sfh-mediated lipid transfer mechanisms, our study provides new insights into the Sec14 family.

biochemistry↗

bioRxiv2024

Characterization of atypical BAR domain-containing proteins coded by Toxoplasma gondii

Toxoplasma gondii, the causative agent of toxoplasmosis, infects cells and replicates inside via the secretion of factors stored in specialized organelles (rhoptries, micronemes, dense granules) and the capture of host materials. The genesis of the secretory organelles and the processes of secretion and endocytosis depend on vesicular trafficking events whose molecular bases remain poorly known. Notably, there is no characterization of the BAR (Bin/Amphiphysin/Rvs) domain-containing proteins expressed by T. gondii and other apicomplexans, although such proteins are known to play critical roles in vesicular trafficking in other eukaryotes. Here, by combining structural analyses with in vitro assays and cellular observations, we have characterized TgREMIND (REgulators of Membrane Interacting Domains), involved in the genesis of rhoptries and dense granules, and TgBAR2 found at the parasite cortex. We establish that TgREMIND comprises an F-BAR domain that can bind curved neutral membranes with no strict phosphoinositide requirement and exert a membrane remodeling activity. Next, we establish that TgREMIND contains a new structural domain called REMIND, which negatively regulates the membrane-binding capacities of the F-BAR domain. In parallel, we report that TgBAR2 contains a BAR domain with an extremely basic membrane-binding interface able to deform anionic membranes into very narrow tubules. Our data show that T. gondii codes for two atypical BAR domain-containing proteins with very contrasting membrane-binding properties, allowing them to function in two distinct regions of the parasite trafficking system.

biochemistry↗

bioRxiv2023

Reconstitution of ORP-mediated lipid exchange process coupled to PI(4)P metabolism

Lipid distribution in the eukaryotic cells depends on tight couplings between lipid transfer and lipid metabolism. Yet these couplings remain poorly described. Notably, it is unclear to what extent lipid exchangers of the OSBP-related proteins (ORPs) family, coupled to PI(4)P metabolism, contribute to the formation of sterol and phosphatidylserine gradient between the endoplasmic reticulum (ER) and other cell regions. To address this question, we have examined in vitro the activity of Osh4p, a representative ORP, between Golgi mimetic membranes in which PI(4)P is produced by a PI 4-kinase and ER mimetic membranes in which PI(4)P is hydrolyzed by the phosphatase Sac1p. Using quantitative, real-time assays, we demonstrate that Osh4p creates a sterol gradient between the two membranes by sterol/PI(4)P exchange as soon as a PI(4)P gradient is generated at this interface following ATP addition, and define how much PI(4)P must be synthesized for this process. Then, using a kinetic model supported by our in vitro data, we estimate to what extent PI(4)P metabolism can drive lipid transfer in cells. Finally, we show that Sec14p, by transferring phosphatidylinositol between membranes, can support the synthesis of PI(4)P and the creation of a sterol gradient by Osh4p. These results indicate to what extent ORPs, under the control of PI(4)P metabolism, can distribute lipids in the cell.

biochemistry↗

bioRxiv2021

Functional analyses of phosphatidylserine/PI(4)P exchangers with diverse lipid species and membrane contexts set unanticipated rules on lipid transfer

Several members of the oxysterol-binding protein-related proteins (ORPs)/oxysterol-binding homology (Osh) family exchange phosphatidylserine (PS) and phosphatidylinositol 4-phosphate (PI(4)P) at the endoplasmic reticulum/plasma membrane (PM) interface. It is unclear whether they preferentially exchange PS and PI(4)P with specific acyl chains to tune the features of the PM, whether they use phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) instead of PI(4)P for exchange processes and whether their activity is influenced by the association of PS with sterol in the PM. Here, we measured in vitro how the yeast Osh6p and human ORP8 transported diverse PS and PI(4)P subspecies, including major cellular species, between membranes. We established how their activity is impacted by the length and unsaturation degree of these lipids. Surprisingly, the speed at which they individually transfer these ligands inversely depends on their affinity for them. To be fast, the transfer of high-affinity ligands requires their exchange for a counterligand of equivalent affinity. Besides, we determined that Osh6p and ORP8 cannot use PI(4,5)P2 for intracellular lipid exchange, as they have a low affinity for this lipid compared to PI(4)P, and do not transfer more PS into sterol-rich membranes. This study provides insights into PS/PI(4)P exchangers and sets unanticipated rules on how the activity of lipid transfer proteins relates to their affinity for ligands.

biochemistry↗

bioRxiv2020

Osh6 requires Ist2 for localization to the ER-PM contacts and efficient phosphatidylserine transport

Osh6 and Osh7 are lipid transfer proteins (LTPs) that move phosphatidylserine (PS) from the endoplasmic reticulum (ER) to the plasma membrane (PM). High PS level at the PM is key for many cellular functions. Intriguingly, Osh6/7 localize to ER-PM contact sites, although they lack membrane-targeting motifs, in contrast to multidomain LTPs that both bridge membranes and convey lipids. We show that Osh6 localization to contact sites depends on its interaction with the cytosolic tail of the ER-PM tether Ist2, a homologue of TMEM16 proteins. We identify a motif in the Ist2 tail, conserved in yeasts, as the Osh6-binding region, and we map an Ist2-binding surface on Osh6. Mutations in the Ist2 tail phenocopy osh6{Delta} osh7{Delta} deletion: they decrease cellular PS levels, and block PS transport to the PM. Our study unveils an unexpected partnership between a TMEM16-like protein and a soluble LTP, which together mediate lipid transport at contact sites.

cell biology↗