PI3K functions as a hub in mechanotransduction.

Mammalian cells integrate different types of stimuli that govern their fate. These stimuli encompass biochemical as well as biomechanical cues (shear, tensile, and compressive stresses) that are usually studied separately. The phosphatidylinositol 3-kinase (PI3K) enzymes, producing signaling phosphoinositides at plasma and intracellular membranes, are key in intracellular signaling and vesicular trafficking pathways. Recent evidence in cancer research demonstrates that these enzymes are essential in mechanotransduction. Despite this, the importance of the integration of biomechanical cues and PI3K-driven biochemical signals is underestimated. In this opinion article, we make the hypothesis that modeling of biomechanical cues is critical to understand PI3K oncogenicity. We also identify known/missing knowledge in terms of isoform specificity and molecular pathways of activation, knowledge that is needed for clinical applications.

MEF2 and NR2F2 cooperate to regulate Akr1c14 gene expression in mouse MA-10 Leydig cells.

Leydig cells are essential for male reproductive development and health throughout life. Production of androgens [testosterone, dihydrotestosterone (DHT)] as well as intermediate steroids [progesterone, dihydroprogesterone (DHP)] is tightly regulated. In the mouse, the 3α-hydroxysteroid dehydrogenase enzyme (3α-HSD, AKR1C14) catalyses the interconversion of DHP and DHT into less potent steroids. Despite its importance, nothing is currently known regarding the regulation of Akr1c14 expression in Leydig cells. Recently, the transcription factors MEF2 and NR2F2 were identified in the mouse testis including in Leydig cells where they were found to regulate expression of genes involved in steroidogenesis. Analyses of transcriptomic data from MEF2- or NR2F2-deficient MA-10 Leydig cells revealed a significant decrease in Akr1c14 mRNA levels. Using qPCR, we confirmed that Akr1c14 mRNA levels were decreased in MEF2- and in NR2F2-deficient conditions. Conversely, overexpression of MEF2A or/and NR2F2 in MA-10 Leydig cells led to an increase in endogenous Akr1c14 mRNA levels. Recruitment of MEF2 and NR2F2 to the Akr1c14 promoter was confirmed by ChIP while DNA precipitation assays revealed direct binding of MEF2 but not NR2F2 to this region. In functional promoter studies, NR2F2 was found to activate the Akr1c14 promoter while MEF2A on its own had no effect. Combination of both NR2F2 and MEF2A led to a cooperative activation of the Akr1c14 promoter and this required intact MEF2 and NR2F2 elements. Finally, co-immunoprecipitation experiments showed that MEF2 and NR2F2 are present in the same protein complex. In conclusion, our results identify a novel cooperation between MEF2 factors and NR2F2 in the expression of the Akr1c14 gene involved in the regulation of DHP/DHT levels.