Biology subjects

Debayle, D.

Publications and source records attributed to Debayle, D..

3 recordsLinked to original sources

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↗

bioRxiv2019

Molecular and cellular dissection of the OSBP cycle through a fluorescent inhibitor

ORPphilins, natural molecules that strongly and selectively inhibit the growth of some cancer cell lines, are proposed to target intracellular lipid-transfer proteins of the Oxysterol-binding protein (OSBP) family. These conserved proteins exchange key lipids, such as cholesterol and phopsphatidylinositol-4-phosphate (PI(4)P), between organelle membranes. Among ORPphilins, molecules of the schweinfurthin family interfere with intracellular lipid distribution and metabolism, but their functioning at the molecular level is poorly understood. We report here that cell line sensitivity to schweinfurthin G (SWG) is inversely proportional to cellular level of OSBP. By taking advantage of the intrinsic fluorescence of SWG, we follow its fate in cell cultures and show that its incorporation at the TGN depends on OSBP cellular abundance. We report that SWG inhibits specifically the lipid exchange cycle of OSBP. As a consequence, post-Golgi trafficking, membrane cholesterol levels and PI(4)P turnover are affected. Finally, we demonstrate the direct binding of SWG into OSBP lipid-binding cavity by intermolecular FRET. Collectively these data describe for the first time a specific and intrinsically fluorescent pharmacological tool to dissect OSBP properties at the cellular and molecular levels.

cell biology↗

bioRxiv2019

Fat food exacerbates post-prandial hypothalamic inflammation involving GFAP+ cells and microglia

In humans, obesity was associated with brain inflammation and glial cell proliferation. Studies in rodents showed that glial cell proliferation occurs within 24 hours of high-fat diet (HFD) consumption, before obesity development. This proliferation was mainly observed in the hypothalamus (HT), a crucial brain structure for controlling body weight. Therefore, we sought to characterize the post-prandial HT inflammatory response to 1-3-6 hours exposure to a standard diet and HFD. HFD exposure increased gene expression of astrocyte and microglial marker (GFAP and Iba1) compare to standard treated mice and induced morphological modifications of microglial cells in HT. This remodeling was associated with higher expression of inflammatory genes and differential activation of hypothalamic neuropeptides involved in energy balance regulation. DREADD and PLX5622 technologies, used to modulate GFAP-positive or microglial cells activity respectively, showed that both glial cell types are involved in hypothalamic post-prandial inflammation, but in a different time frame and with a diet specificity Thus, an exacerbated post-prandial inflammation in brain might predispose individuals to obesity and needs to be characterized to address this worldwide crisis.

neuroscience↗