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Adherens junction-associated protein 1 (AJAP1) has been implicated in brain diseases; however, a pathogenic mechanism has not been identified. AJAP1 is widely expressed in neurons and binds to γ-aminobutyric acid type B receptors (GBRs), which inhibit neurotransmitter release at most synapses in the brain. Here, we show that AJAP1 is selectively expressed in dendrites and trans-synaptically recruits GBRs to presynaptic sites of neurons expressing AJAP1. We have identified several monoallelic AJAP1 variants in individuals with epilepsy and/or neurodevelopmental disorders. Specifically, we show that the variant p.(W183C) lacks binding to GBRs, resulting in the inability to recruit them. Ultrastructural analysis revealed significantly decreased presynaptic GBR levels in Ajap1-/- and Ajap1W183C/+ mice. Consequently, these mice exhibited reduced GBR-mediated presynaptic inhibition at excitatory and inhibitory synapses, along with impaired synaptic plasticity. Our study reveals that AJAP1 enables the postsynaptic neuron to regulate the level of presynaptic GBR-mediated inhibition, supporting the clinical relevance of loss-of-function AJAP1 variants.

In hypoxic and pseudohypoxic rodent models of pulmonary hypertension (PH), hypoxia-inducible factor (HIF) inhibition attenuates disease initiation. However, HIF activation alone, due to genetic alterations or use of inhibitors of prolyl hydroxylase domain (PHD) enzymes, has not been definitively shown to cause PH in humans, indicating the involvement of other mechanisms. Given the association between endothelial cell dysfunction and PH, the effects of pseudohypoxia and its underlying pathways were investigated in primary human lung endothelial cells. PHD2 silencing or inhibition, while activating HIF2α, induced apoptosis-resistance and IFN/STAT activation in endothelial cells, independent of HIF signaling. Mechanistically, PHD2 deficiency activated AKT and ERK, inhibited JNK, and reduced AIP1 (ASK1-interacting protein 1), all independent of HIF2α. Like PHD2, AIP1 silencing affected these same kinase pathways and produced a similar dysfunctional endothelial cell phenotype, which was partially reversed by AKT inhibition. Consistent with these in vitro findings, AIP1 protein levels in lung endothelial cells were decreased in Tie2-Cre/Phd2 knockout mice compared with wild-type controls. Lung vascular endothelial cells from patients with pulmonary arterial hypertension (PAH) showed IFN/STAT activation. Lung tissue from both SU5416/hypoxia PAH rats and patients with PAH all showed AKT activation and dysregulated AIP1 expression. In conclusion, PHD2 deficiency in lung vascular endothelial cells drives an apoptosis-resistant and inflammatory phenotype, mediated by AKT activation and AIP1 loss independent of HIF signaling. Targeting these pathways, including PHD2, AKT, and AIP1, holds the potential for developing new treatments for endothelial dysfunction in PH. NEW & NOTEWORTHY: HIF activation alone does not conclusively lead to human PH, suggesting that HIF-independent signaling may also contribute to hypoxia-induced PH. This study demonstrated that PHD2 silencing-induced pseudohypoxia in human lung endothelial cells suppresses apoptosis and activates STAT, effects that persist despite HIF2α inhibition or knockdown and are attributed to AKT and ERK activation, JNK inhibition, and AIP1 loss. These findings align with observations in lung endothelial cells and tissues from PAH rodent models and patients. [ABSTRACT FROM AUTHOR]

In order to eliminate the hazard effects of the leaching of fluorine in mold fluxes,this paper introduces a mold flux with high Al2O3 content. The effects of Al2O3 content on the concentration of F- ions and the pH value of leaching water were investigated,and the dependence of Al2O3 on the structure of mold fluxes was analyzed by X-ray photoelectron spectroscopy(XPS). When the mass fraction of Al2O3 is 4%,the concentration of F- ions in leaching water is about 22.8 to 35.4 mg·L-1,and the pH range is between 4.0 and 9.5. The F- concentration and the pH range initially reduces and then slightly rises again as the Al2O3 content increases from 4% to 34%. The XPS spectra show that the Al-F bond forms in the mold flux when the Al2O3 content increases. This can restrain the dissolution of fluorine in water. Controlling the content of Al2O3 between 16% and 34%,the F- concentration in leaching water is about 4.0 to 10.0 mg·L-1,and the pH range is between 6.5 and 7.5. This is helpful to reduce the hazard effects of the leaching of fluorine in mold fluxes.

Cytosolic phospholipase [A.sub.2[[alpha] (cPL[A.sub.2][alpha]) activation is a regulatory step in the control of arachidonic acid (AA) liberation for eicosanoid formation. Sphingosine 1-phosphate (SIP) is a bioactive lipid mediator involved in the regulation of many important proinflammatory processes and has been found in the airways of asthmatic subjects. We investigated the mechanism of SIP-induced AA release and determined the involvement of cPL[A.sub.2][alpha] in these events in A549 human lung epithelial cells. S1P induced AA release rapidly within 5 min in a dose- and time-dependent manner. SIPinduced AA release was inhibited by the cPL[A.sub.2][alpha] inhibitors methyl arachidonyl fluorophosphonate (MAFP) and pyrrolidine derivative, by small interfering RNA-mediated downregulation of cPL[A.sub.2][alpha], and by inhibition of SIP-induced calcium flux, suggesting a significant role of cPL[A.sub.2][alpha] in S1P-mediated AA release. Knockdown of the S1P3 receptor, the major S1P receptor expressed on A549 cells, inhibited SIP-induced calcium flux and AA release. The S l P-induced calcium flux and AA release was associated with sphingosine kinase 1 (Sphkl) expression and activity. Furthermore, Rho-associated kinase, downstream of S IP3, was crucial for S IP-induced cPL[A.sub.2][alpha] activation. Our data suggest that S1P acting through S1P3, calcium flux, and Rho kinase activates cPL[A.sub.2][alpha] and releases AA in lung epithelial cells. An understanding of SiP-induced cPL[A.sub.2][alpha] activation mechanisms in epithelial cells may provide potential targets to control inflammatory processes in the lung. eicosanoid; calcium flux; airway inflammation

Hepatocyte growth factor activator inhibitor-1 (HAI-1) was initially identified as cognate inhibitor of matriptase, a membrane-bound serine protease. Paradoxically, HAI-1 is also required for matriptase activation, a process that requires sphingosine 1-phosphate (S1P)-mediated translocation of the protease to cell-cell junctions in human mammary epithelial cells. In the present study, we further explored how HAI-1 regulates this protease. First, we observed that after S1P treatment HAI-1 was cotranslocated with matriptase to cell-cell junctions and that the cellular ratio of HAI-1 to matriptase was maintained during this process. However, when this ratio was changed by cell treatment with HAI-1 small interfering RNA or anti-HAI-1 MAb M 19, spontaneous activation of matriptase occurred in the absence of SiP-induced translocation; S1P-induced matriptase activation was also enhanced. These results support a role for HAI-1 in protection of cell from uncontrolled matriptase activation. We next expressed matriptase, either alone or with HAI-1 in breast cancer cells that do not endogenously express either protein. A defect in matriptase trafficking to the cell surface occurred if wild-type matriptase was expressed in the absence of HAI-1; this defect appeared to result from matriptase toxicity to cells. Coexpression with matriptase of wild-type HAI-1, but not HAI-1 mutants altered in its Kunitz domain 1, corrected the trafficking defect. In contrast, catalytically defective matriptase mutants were normal in their trafficking in the absence of HAI-1. These results are also consistent with a role for HAI-1 to prevent inappropriate matriptase proteolytic activity during its protein synthesis and trafficking. Taken together, these results support multiple roles for HAI-1 to regulate matriptase, including its proper expression, intracellular trafficking, activation, and inhibition. protease-activated receptor-2; hepatocyte growth factor; urokinase; sphingosine 1-phosphate; Kunitz domain