Background: Tau aggregation is a multistep process. The identity of Tau species compromising cell viability remains largely unknown. Results: Analysis of Tau aggregation dynamic identifies oligomeric Tau aggregates as toxic species that impair viability. Conclusion: Membrane leakage induced by oligomeric Tau is a mechanism for toxicity. Significance: Tau belongs to the class of amyloidogenic proteins that share a common toxicity-mediating mechanism.

Zn2+, Mg2+ and Ca2+ are essential divalent cations implicated in many metabolic processes and signalling pathways. An emerging new paradigm is that the organismal balance of these cations predominantly depends on a common gatekeeper, the channel-kinase TRPM7. Despite extensive electrophysiological studies and recent cryo-EM analysis, an open question is how the channel activity of TRPM7 is activated. Here, we performed site-directed mutagenesis of mouse TRPM7 in conjunction with patch-clamp assessment of whole-cell and single-channel activity and molecular dynamics (MD) simulations to show that the side chains of conserved N1097 form an inter-subunit Mg2+ regulatory site located in the lower channel gate of TRPM7. Our results suggest that intracellular Mg2+ binds to this site and stabilizes the TRPM7 channel in the closed state, whereas the removal of Mg2+ favours the opening of TRPM7. Hence, our study identifies the structural underpinnings through which the TRPM7 channel is controlled by cytosolic Mg2+, representing a new structure–function relationship not yet explored among TRPM channels.

A series of seven oxyprenylated phenylpropanoids and naphthoquinones were tested regarding their ability to activate transient receptor potential ankyrin subtype 1 channel (TRPA1). Three of the assayed compounds, namely, boropinal (3), juglone (5), and plumbagin (7), acted as strong modulators of TRPA1 channels with EC50 values of 9.8, 1.7, and 0.5 μM, respectively, as assessed by Ca(2+) assays. Moreover, the compounds elicited TRPA1 currents in electrophysiological whole cell recordings. We additionally provide evidence that plumbagin activated TRPA1-positive neurons isolated from mouse dorsal root ganglion neurons but did not affect sensory neurons from TRPA1-deficient mice. The high potencies of plumbagin and juglone to activate TRPA1 channels may explain the molecular basis of the mucosal irritant properties of these compounds as well as of related naphthoquinones and phytopreparations, as widely reported in the literature.

G protein-coupled receptors (GPCR) constitute the most versatile family of pharmacological target proteins. For some "orphan" GPCR, no ligand or drug-like modulator is known. In this study, we have established and applied a parallelized assay to co-screen 29 different human GPCR. Three compounds, chlorhexidine, Lys-05, and 9-aminoacridine triggered transient Ca 2+ signals linked to the expression of GPR30. GPR30, also named G protein-coupled estrogen receptor 1 (GPER1), was reported to elicit increases in cAMP in response to 17βestradiol, 4-hydroxytamoxifen, or G-1. These findings could, however, not be reproduced by other groups, and the de-orphanisation of GPR30 is, therefore, intensely disputed. The unbiased screen and following experiments in transiently or stably GPR30-overexpressing HEK293 cells did not show responses to 17β-estradiol, 4-hydroxytamoxifen or G-1. A thorough analysis of the activated signalling cascade revealed a canonical G q -coupled pathway, including phospholipase C, protein kinase C and ERK activation, receptor internalisation, and sensitivity to the G q inhibitor YM-254890. When expressed in different cell lines, the localisation of a fluorescent GPR30 fusion protein appeared variable. An efficient integration into the plasma membrane and stronger functional responses were found in HEK293 and in MCF-7 cells, whereas GPR30 appeared mostly retained in endomembrane compartments in Cos-7 or HeLa cells. Thus, conflicting findings may result from the use of different cell lines. The newly identified agonists and the finding that GPR30 couples to G q are expected to serve as starting point for identifying physiological responses that are controlled by this GPCR. Significance StatementWe have identified and thoroughly characterized novel and reliably acting agonists of the G protein-coupled receptor GPER1/GPR30. Applying these agonists, we demonstrate that GPR30 couples to the canonical G q -phospholipase C pathway and is rapidly internalized upon continuous exposure to the agonists.