Equipe d’Accueil :Lipid Trafficking and Membrane Contact Sites


Intitulé de l’Unité : UMR9198

Nom du Responsable de l’Unité : Frederic Boccard

Nom du Responsable de l’Équipe : Francesca Giordano

Adresse :  1, Avenue de la Terrasse, 91190, Gif-sur-Yvette

Responsable de l’encadrement : Francesca Giordano

Tél : +33 1 69 82 62 91  Fax : ……………………… E-mail:  francesca.giordano@i2bc.paris-saclay.fr

Résumé du projet (environ une demi-page)

Cholesterol is a vital lipid for cellular structure and function, ensuring cell membranes remain strong and flexible, which is crucial for overall health. Howeveer, excess cholesterol can lead to various health issues, including metabolic and aging-related diseases. Therefore, cells have complex regulatory systems to manage cholesterol levels, including its synthesis, uptake, transport, and storage. While the liver and brain are major cholesterol producers, the mechanisms maintaining cholesterol homeostasis in these cells are not well understood. In particular, the movements of cholesterol between different cellular organelles and membranes, and how its transport is coordinated with its storage and use, remain largely unknown.

The endoplasmic reticulum (ER) is the primary site for cholesterol synthesis and storage. However, cholesterol mainly resides in other cellular membranes, such as the plasma membrane (PM), where it plays a crucial role in membrane composition and function. Recent research has shown that membrane contact sites (CS), regions where cellular membranes are in close proximity, are essential for controlling lipid movement and storage within cells. It has been shown that cholesterol can be transported at these CS when PM cholesterol levels increase, leading to its storage in lipid droplets (LDs) via the ER. However, the specific proteins involved and their mechanisms are still not well understood.

Our team has recently discovered that ER-mitochondria CS are physically and functionally connected to LDs, forming a three-way mitochondria-ER-LD communication system in the cell. We have also shown that Oxysterol-binding proteins-related proteins ORP5 and ORP8, originally identified at ER-PM CS, orchestrate LD biogenesis at ER-mitochondria contacts. Interestingly, these proteins can transport cholesterol in vitro, but their role in cellular cholesterol transport has not been explored.

Our preliminary data reveal a novel role of ORP5 and ORP8 in cholesterol sensing, suggesting they may regulate cholesterol transport from the PM to ER and subsequently to LDs, in response to fluctuations in PM cholesterol levels.

We propose a project to study the role of ORP5 and ORP8 in cholesterol transport at ER-PM and mitochondria-ER-LD contact sites using a combination of imaging and biochemical approaches. The student will analyse fluorescent-cholesterol fluxes using confocal microscopy and live-cell imaging in human hepatocytes with ORP5 and ORP8 either overexpressed or downregulated. He/her will also examine their localization and the reorganization of the CS involved under various cholesterol perturbation conditions, such as inhibition of cholesterol synthesis and storage. These experiments aim to advance our understanding of the regulatory mechanisms linking cellular cholesterol trafficking and storage at CS, contributing valuable insights to the fields of cell biology and neurobiology.


Dernières Publications en lien avec le projet :

Monteiro-Cardoso VF* and Giordano F* (2024). Emerging functions of the mitochondria–ER–lipid droplet three-way junction in coordinating lipid transfer, metabolism, and storage in cells. FEBS Letters, Vol 598, 10:1252-1273.   doi: 10.1002/1873-3468.14893

Monteiro-Cardoso VF, Le Bars R, Giordano F*. (2023). Visualization and quantification of endogenous intra-organelle protein interactions at ER-mitochondria contacts sites by Proximity Ligation Assays. J Vis Exp Oct 20:(200). doi: 10.3791/64750

Monteiro-Cardoso VF, Rochin L, Arora A, Houcine A, Jääskeläinen E, Kivelä AM., Sauvanet C, Le Bars R, Marien E, Dehairs J, Neveu J, El Khallouki N, Santonico E, Swinnen JV, Tareste D,  Olkkonen MV, Giordano F*. (2022). ORP5/8 and MIB/MICOS Link ER-mitochondria and intermitochondrial contacts for non-vesicular transport of phosphatidylserine. Cell Reports, Sep 20;40(12):111364. doi: 10.1016/j.celrep.2022.111364

Guyard V, Monteiro-Cardoso VF, Omrane M, Sauvanet C, Houcine A, Boulogne C, Ben Mbarek K, Vitale N, Facklaris O, El Khallouki N, Thiam AR*, Giordano F*. (2022).ORP5 and ORP8 orchestrate lipid droplet biogenesis and maintainance at ER-mitochondria contact sites. Journal of Cell Biology, Sep 5;221(9):e202112107. doi: 10.1083/jcb.202112107

 Ce projet s’inscrit-il dans la perspective d’une thèse :

                                                       oui   X                                                           non o

 si oui type de financement prévu :  Paris Saclay or ANR


Ecole Doctorale de rattachement :  SDSV