Biology subjects

Gonnot, F.

Publications and source records attributed to Gonnot, F..

3 recordsLinked to original sources

bioRxiv2024

TRPM8 channels control Golgi morphology through an AR-dependent induction of the Scd1 gene and modulation of unsaturated lipid content

Transient receptor potential melastatin 8 (TRPM8), the cold and menthol receptor is essential to thermosensation, although its roles in organs within the body are still unclear. Besides TRPM8, we previously cloned several isoforms, like 4TM-TRPM8, which can be expressed with or without TRPM8. In this study, we characterize the human TRPM8(85) in ER membranes in the vicinity of Golgi apparatus (GA) and mitochondria in prostate epithelial cells. Silencing of TRPM8(85) induces lipid droplet accumulation, GA expansion and fragmentation associated with a drop in the vesicular trafficking to plasmalemma. Furthermore, lipidomic analysis reveals a strong shift in unsaturated fatty acids (UFAs), induced by TRPM8(85) silencing and to a lesser extent silencing of TRPM8. UFAs increase is caused by the induction of {Delta}9 stearoyl desaturase (Scd1) gene. Silencing SCD1 or palmitate incubation prevent GA expansion in TRPM8(85)-silenced cells. Finally, we demonstrated that TRPM8 regulates SCD1 via the androgen receptor.

cell biology↗

bioRxiv2022

High-sensitivity calcium biosensor on the mitochondrial surface reveals that IP3R channels participate in the reticular Ca2+ leak towards mitochondria

Genetically encoded biosensors based on fluorescent proteins (FPs) are widely used to monitor dynamics and sub-cellular spatial distribution of calcium ion (Ca2+) fluxes and their role in intracellular signaling pathways. The development of different mutations in the Ca2+-sensitive elements of the cameleon probes has allowed sensitive range of Ca2+ measurements in almost all cellular compartments. Region of the endoplasmic reticulum (ER) tethered to mitochondria, named as the mitochondrial-associated membranes (MAMs), has received an extended attention since the last 5 years. Indeed, as MAMs are essential for calcium homeostasis and mitochondrial function, molecular tools have been developed to assess quantitatively Ca2+ levels in the MAMs. However, sensitivity of the first generation Ca2+ biosensors on the surface of the outer-mitochondrial membrane (OMM)do not allow to measure M or sub-M changes in Ca2+ concentration which prevents to measure the native activity (unstimulated exogenously) of endogenous channels. In this study, we assembled a new ratiometric highly sensitive Ca2+ biosensor expressed on the surface of the outer-mitochondrial membrane (OMM). It allows the detection of smaller differences than the previous biosensor in or at proximity of the MAMs. Noteworthy, we demonstrated that IP3-receptors have an endogenous activity which participate to the Ca2+ leak channel on the surface of the OMM during hypoxia or when SERCA activity is blocked.

cell biology↗

bioRxiv2019

Regulation of Cyclin E by transcription factors of the naïve pluripotency network in mouse embryonic stem cells

Continuous, non-cell cycle-dependent expression of cyclin E is a characteristic feature of mouse embryonic stem cells (ESCs). We studied the 5 regulatory region of Cyclin E, also known as Ccne1, and identified binding sites for transcription factors of the naive pluripotency network, including Esrrb, Klf4, and Tfcp2l1 within 1 kilobase upstream of the transcription start site. Luciferase assay and chromatin immunoprecipitation-quantitative polymerase chain reaction (ChiP-qPCR) study highlighted one binding site for Esrrb that is essential to transcriptional activity of the promoter region, and three binding sites for Klf4 and Tfcp2l1. Knockdown of Esrrb, Klf4, and Tfcp2l1 reduced Cyclin E expression whereas overexpression of Esrrb and Klf4 increased it, indicating a strong correlation between the expression level of these factors and that of cyclin E. We observed that cyclin E overexpression delays differentiation induced by Esrrb depletion, suggesting that cyclin E is an important target of Esrrb for differentiation blockade. We observed that mESCs express a low level of miR-15a and that transfection of a miR-15a mimic decreases Cyclin E mRNA level. These results lead to the conclusion that the high expression level of Cyclin E in mESCs can be attributed to transcriptional activation by Esrrb as well as to the absence of its negative regulator, miR-15a.

cell biology↗