Background: STIM1-operated Orai1 channels mediate Ca 2ϩ entry for T cell activation, but the gating mechanism remains elusive. Results: The C and N termini of Orai1 have differential roles in STIM1-triggered channel activation. Conclusion:The binding between STIM1 and the Orai1 C terminus docks STIM1 onto the Orai1 N terminus, leading to channel activation. Significance: This stepwise gating mechanism contributes to ER-PM crosstalk for Ca 2ϩ entry, a fundamental process in cell biology.

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GDF15 (growth/differentiation factor 15), a novel member of the TGFβ (transforming growth factor β) superfamily, plays critical roles in the central and peripheral nervous systems, but the signal transduction pathways and receptor subtypes involved are not well understood. In the present paper, we report that GDF15 specifically increases the IK (delayed-rectifier outward K+ current) in rat CGNs (cerebellar granule neurons) in time- and concentration-dependent manners. The GDF15-induced amplification of the IK is mediated by the increased expression and reduced lysosome-dependent degradation of the Kv2.1 protein, the main α-subunit of the IK channel. Exposure of CGNs to GDF15 markedly induced the phosphorylation of ERK (extracellular-signal-regulated kinase), Akt and mTOR (mammalian target of rapamycin), but the GDF15-induced IK densities and increased expression of Kv2.1 were attenuated only by Akt and mTOR, and not ERK, inhibitors. Pharmacological inhibition of the Src-mediated phosphorylation of TGFβR2 (TGFβ receptor 2), not TGFβR1, abrogated the effect of GDF15 on IK amplification and Kv2.1 induction. Immunoprecipitation assays showed that GDF15 increased the tyrosine phosphorylation of TGFβRII in the CGN lysate. The results of the present study reveal a novel regulation of Kv2.1 by GDF15 mediated through the TGFβRII-activated Akt/mTOR pathway, which is a previously uncharacterized Smad-independent mechanism of GDF15 signalling.

Background: Histamine is a major inflammatory mediator. Results: H 1 receptor, STIM1, Orai1, and extracellular calcium are indispensable for histamine-induced intracellular calcium mobilization, NFAT nuclear translocation, and IL-8 production in HUVECs. Conclusion: STIM1 and Orai1 mediate histamine-evoked calcium entry and NFAT signaling in endothelial cells. Significance: STIM1 and Orai1 are essential for histamine-induced inflammatory signaling of endothelial cells.

N-methyl-D-aspartate receptors (NMDARs) are important for synaptic plasticity associated with many physiological functions and neurologic disorders. Protein kinase C (PKC) activation increases the phosphorylation and activity of NMDARs, and a2d-1 is a critical NMDAR-interacting protein and controls synaptic trafficking of NMDARs. In this study, we determined the relative roles of PKC and a2d-1 in the control of NMDAR activity. We found that a2d-1 coexpression significantly increased NMDAR activity in HEK293 cells transfected with GluN1/GluN2A or GluN1/GluN2B. PKC activation with phorbol 12-myristate 13-acetate (PMA) increased receptor activity only in cells coexpressing GluN1/GluN2A and a2d-1. Remarkably, PKC inhibition with Gӧ6983 abolished a2d-1-coexpression-induced potentiation of NMDAR activity in cells transfected with GluN1/ GluN2A or GluN1/GluN2B. Treatment with PMA increased the a2d-1-GluN1 interaction and promoted a2d-1 and GluN1 cell surface trafficking. PMA also significantly increased NMDAR activity of spinal dorsal horn neurons and the amount of a2d-1-bound GluN1 protein complexes in spinal cord synaptosomes in wild-type mice, but not in a2d-1 knockout mice. Furthermore, inhibiting a2d-1 with pregabalin or disrupting the a2d-1-NMDAR interaction with the a2d-1 C-terminus peptide abolished the potentiating effect of PMA on NMDAR activity. Additionally, using quantitative phosphoproteomics and mutagenesis analyses, we identified S929 on GluN2A and S1413 (S1415 in humans) on GluN2B as the phosphorylation sites responsible for NMDAR potentiation by PKC and a2d-1. Together, our findings demonstrate the interdependence of a2d-1 and PKC phosphorylation in regulating NMDAR trafficking and activity. The phosphorylation-dependent, dynamic a2d-1-NMDAR interaction constitutes an important molecular mechanism of synaptic plasticity.

Highlights d Nerve injury augments postsynaptic Ca 2+ -permeable AMPARs in the spinal cord via a2d-1 d a2d-1, but not a2d-2 or a2d-3, interacts directly with GluA1 and GluA2 via its C terminus d a2d-1 disrupts heteromeric, but not homomeric, assembly of GluA1 and GluA2 in the ER d Gabapentin restores assembly and synaptic expression of GluA1/GluA2 in neuropathic pain

Cholangiocarcinoma (CCA) is an aggressive and multifactorial malignancy of the biliary tract. The carcinogenesis of CCA is associated with genomic and epigenetic abnormalities, as well as environmental effects. However, early clinical diagnosis and reliable treatment strategies of CCA remain unsatisfactory. Multiple compartments of the tumor microenvironment significantly affect the progression of CCA. Tumor-associated macrophages (TAMs) are a type of plastic immune cells that are recruited and activated in the CCA microenvironment, especially at the tumor invasive front and perivascular sites. TAMs create a favorable environment that benefits CCA growth by closely interacting with CCA cells and other stromal cells via releasing multiple protumor factors. In addition, TAMs exert immunosuppressive and antichemotherapeutic effects, thus intensifying the malignancy. Targeting TAMs may provide an improved understanding of, and novel therapeutic approaches for, CCA. This review focuses on revealing the interplay between TAMs and CCA.

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