Biology subjects

Germain, A.

Publications and source records attributed to Germain, A..

3 recordsLinked to original sources

bioRxiv2023

GAS6 and AXL promote insulin resistance by rewiring insulin signaling and increasing insulin receptor trafficking to late endosomes

Growth-arrest specific 6 (GAS6) is a secreted protein that acts as a ligand for TAM receptors (TYRO3, AXL and MERTK). In humans, GAS6 circulating levels and genetic variations in GAS6 are associated with hyperglycemia and increased risk of type 2 diabetes. However, the mechanisms by which GAS6 influences glucose metabolism are not understood. Here, we show that Gas6 deficiency in mice increases insulin sensitivity and protects from diet-induced insulin resistance. Conversely, increasing GAS6 circulating levels is sufficient to reduce insulin sensitivity in vivo. GAS6 inhibits the activation of the insulin receptor (IR) and reduces insulin response in muscle cells in vitro and in vivo. Mechanistically, AXL and IR fom a complex, while GAS6 reprograms signaling pathways downstream of IR. This results in increased IR endocytosis following insulin treatment. This study contributes to a better understanding of the cellular and molecular mechanisms by which GAS6 and AXL influence insulin sensitivity. ARTICLE HIGHLIGHTSO_LIGAS6 deficient mice are characterized by improved glucose tolerance, increased insulin sensitivity and are protected from diet-induced insulin resistance. C_LIO_LIThe GAS6 receptor AXL is expressed in muscle cells and forms a complex with the insulin receptor. C_LIO_LIGAS6 reprograms insulin signaling by modulating the phosphorylation of proteins implicated in endocytosis, vesicle-mediated transport, and membrane trafficking. C_LIO_LIAXL and GAS6 promotes insulin receptor endocytosis following insulin treatment. C_LI

physiology↗

bioRxiv2023

Dysregulation of extracellular vesicle protein cargo in female ME/CFS cases and sedentary controls in response to maximal exercise

In healthy individuals, physical exercise improves cardiovascular health and muscle strength, alleviates fatigue, and reduces risk of chronic diseases. Although exercise is suggested as a lifestyle intervention to manage various chronic illnesses, it negatively affects people with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), who suffer from exercise intolerance. We hypothesized that altered extracellular vesicle (EV) signaling in ME/CFS patients after an exercise challenge may contribute to their prolonged and exacerbated negative response to exertion (post-exertional malaise). EVs were isolated by size exclusion chromatography from the plasma of 18 female ME/CFS patients and 17 age- and BMI-matched female sedentary controls at three time points: before, 15 minutes, and 24 hours after a maximal cardiopulmonary exercise test. EVs were characterized using nanoparticle tracking analysis and their protein cargo was quantified using Tandem Mass Tag-based (TMT) proteomics. The results show that exercise affects the EV proteome in ME/CFS patients differently than in healthy individuals and that changes in EV proteins after exercise are strongly correlated with symptom severity in ME/CFS. Differentially abundant proteins in ME/CFS patients vs. controls were involved in many pathways and systems, including coagulation processes, muscle contraction (both smooth and skeletal muscle), cytoskeletal proteins, the immune system, and brain signaling.

molecular biology↗

bioRxiv2019

Systematic sequencing of chloroplast transcript termini from Arabidopsis thaliana reveals >200 transcription initiation sites and the extensive imprints of RNA-binding proteins and secondary structures

Chloroplast transcription requires numerous quality control steps to generate the complex but selective mixture of accumulating RNAs. To gain insight into how this RNA diversity is achieved and regulated, we systematically mapped transcript ends by developing a protocol called Terminome-Seq. Using Arabidopsis thaliana as a model, we catalogued >215 primary 5 ends corresponding to transcription start sites (TSS), as well as 1,628 processed 5 ends and 1,299 3 ends. While most termini were found in intergenic regions, numerous abundant termini were also found within coding regions and introns, including several major TSS at unexpected locations. A consistent feature was the clustering of both 5 and 3 ends, contrasting with the prevailing description of discrete 5 termini, suggesting an imprecision of the transcription and/or RNA processing machinery. Numerous termini correlated with the extremities of small RNA footprints or predicted stem-loop structures, in agreement with the model of passive RNA protection. Terminome-Seq was also implemented for pnp1-1, a mutant lacking the processing enzyme polynucleotide phosphorylase. Nearly 2,000 termini were altered in pnp1-1, revealing a dominant role in shaping the transcriptome. In summary, Terminome-Seq permits precise delineation of the roles and regulation of the many factors involved in organellar transcriptome quality control.

plant biology↗