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Background and purpose Pyrazole derivatives have recently been suggested as selective blockers of transient receptor potential cation ( TRPC) channels but their ability to distinguish between the TRPC and Orai pore complexes is ill-defined. This study was designed to characterize a series of pyrazole derivatives in terms of TRPC/ Orai selectivity and to delineate consequences of selective suppression of these pathways for mast cell activation. Experimental approach Pyrazoles were generated by microwave-assisted synthesis and tested for effects on Ca2+ entry by Fura-2 imaging and membrane currents by patch-clamp recording. Experiments were performed in HEK293 cells overexpressing TRPC3 and in RBL-2 H3 mast cells, which express classical store-operated Ca2+ entry mediated by Orai channels. The consequences of inhibitory effects on Ca2+ signalling in RBL-2 H3 cells were investigated at the level of both degranulation and nuclear factor of activated T-cells activation. Key Results Pyr3, a previously suggested selective inhibitor of TRPC3, inhibited Orai1- and TRPC3-mediated Ca2+ entry and currents as well as mast cell activation with similar potency. By contrast, Pyr6 exhibited a 37-fold higher potency to inhibit Orai1-mediated Ca2+ entry as compared with TRPC3-mediated Ca2+ entry and potently suppressed mast cell activation. The novel pyrazole Pyr10 displayed substantial selectivity for TRPC3-mediated responses (18-fold) and the selective block of TRPC3 channels by Pyr10 barely affected mast cell activation. Conclusions and Implications The pyrazole derivatives Pyr6 and Pyr10 are able to distinguish between TRPC and Orai-mediated Ca2+ entry and may serve as useful tools for the analysis of cellular functions of the underlying Ca2+ channels. [ABSTRACT FROM AUTHOR]

Store-operated Ca2+ influx, suggested to be mediated via store-operated cation channel (SOC), is present in all cells. The molecular basis of SOC, and possible heterogeneity of these channels, are still a matter of controversy. Here we have compared the properties of SOC currents (ISOC) in human submandibular glands cells (HSG) and human parotid gland cells (HSY) withICRAC (Ca2+ release-activated Ca2+ current) in RBL cells. Internal Ca2+ store-depletion with IP3 or thapsigargin activated cation channels in all three cell types. 1 µM Gd3+ blocked channel activity in all cells. Washout of Gd3+ induced partial recovery in HSY and HSG but not RBL cells. 2-APB reversibly inhibited the channels in all cells.I CRACin RBL cells displayed strong inward rectification withErev(Ca)?=?>+90 mV andErev (Na)?=?+60 mV.ISOC in HSG cells showed weaker rectification withErev(Ca)?=?+25 mV andErev(Na)?=?+10 mV. HSY cells displayed a linear current withErev?=?+5 mV, which was similar in Ca2+- or Na+-containing medium.pCa/pNa was>500, 40, and 4.6 whilepCs /pNa was 0.1,1, and 1.3, for RBL, HSG, and HSY cells, respectively. Evidence for anomalous mole fraction behavior of Ca2+/Na+ permeation was obtained with RBL and HSG cells but not HSY cells. Additionally, channel inactivation with Ca2+ + Na+ or Na+ in the bath was different in the three cell types. In aggregate, these data demonstrate that distinct store-dependent cation currents are stimulated in RBL, HSG, and HSY cells. Importantly, these data suggest a molecular heterogeneity, and possibly cell-specific differences in the function, of these channels. [ABSTRACT FROM AUTHOR]

The non-selective cation channel TRPC1 is highly expressed in the brain. Recent research shows that neuronal TRPC1 forms heteromeric complexes with TRPC4 and TRPC5, with a small portion existing as homotetramers, primarily in the ER. Given that most studies have focused on the role of heteromeric TRPC1/4/5 complexes, it is crucial to investigate the specific role of homomeric TRPC1 in maintaining brain homeostasis. This review highlights recent findings on TRPC1 in the brain, with a focus on the hippocampus, and compiles the latest data on modulators and their binding sites within the TRPC1/4/5 subfamily to stimulate new research on more selective TRPC1 ligands., Competing Interests: Declaration of competing interest There are no conflicts to declare., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The transient receptor potential canonical type 3 (TRPC3) channel plays a pivotal role in regulating neuronal excitability in the brain via its constitutive activity. The channel is intricately regulated by lipids and has previously been demonstrated to be positively modulated by PIP 2 . Using molecular dynamics simulations and patch clamp techniques, we reveal that PIP 2 predominantly interacts with TRPC3 at the L3 lipid binding site, located at the intersection of pre-S1 and S1 helices. We demonstrate that PIP 2 sensing involves a multistep mechanism that propagates from L3 to the pore domain via a salt bridge between the TRP helix and S4-S5 linker. Notably, we find that both stimulated and constitutive TRPC3 activity require PIP 2 . These structural insights into the function of TRPC3 are invaluable for understanding the role of the TRPC subfamily in health and disease, in particular for cardiovascular diseases, in which TRPC3 channels play a major role., (© 2024. The Author(s).)