Global impact of protein arginine phosphorylation on the physiology of Bacillus subtilis

Reversible protein phosphorylation is an important and ubiquitous protein modification in all living cells. Here we report that protein phosphorylation on arginine residues plays a physiologically significant role. We detected 121 arginine phosphorylation sites in 87 proteins in the Gram-positive model organism Bacillus subtilis in vivo. Moreover, we provide evidence that protein arginine phosphorylation has a functional role and is involved in the regulation of many critical cellular processes, such as protein degradation, motility, competence, and stringent and stress responses. Our results suggest that in B. subtilis the combined activity of a protein arginine kinase and phosphatase allows a rapid and reversible regulation of protein activity and that protein arginine phosphorylation can play a physiologically important and regulatory role in bacteria

Supplementary Material for: Expression and Functional Activity of the Bitter Taste Receptors TAS2R1 and TAS2R38 in Human Keratinocytes

Recent studies have shown that human bitter taste receptors (TAS2Rs) are not only expressed in mucous epithelial cells of the tongue, but also in epithelial cells of the colon, stomach and upper respiratory tract. These cell types come in close contact with external bitter compounds by ingestion or breathing. In the present work we addressed the question whether bitter taste receptors might also be expressed in cornified epithelial cells of the skin. Here, we show for the first time the expression of TAS2R1 and TAS2R38 in human skin. Double staining of HaCaT cells and primary keratinocytes demonstrated the colocalization of TAS2R1 and TAS2R38 with the adaptor protein α-gustducin that is essential for signal transduction upon ligand binding. To test if TAS2Rs in keratinocytes are functional, we stimulated HaCaT cells with diphenidol, a clinically used bitter-tasting antiemetic, or amarogentin, the bitterest plant substance, that binds TAS2Rs, including TAS2R1 and TAS2R38. Diphenidol and amarogentin induced calcium influx. Furthermore, in keratinocytes diphenidol and amarogentin stimulated the expression of the differentiation markers keratin 10, involucrin and transglutaminase. Therefore, apart from the known role in mucous membranes of the gastrointestinal tract, TAS2Rs are expressed in the epidermis and might play a role in keratinocyte differentiation