Nicotine is an addictive substance that poses substantial health and societal challenges. Despite the known links between the medial habenula (MHb) and nicotine avoidance, the ionic mechanisms underlying MHb neuronal responses to nicotine remain unclear. Here, we report that MHb neurons use a long-lasting refractory period (LLRP) as an unconventional inhibitory mechanism to curb hyperexcitability. This process is initiated by nicotine-induced calcium influx through nicotinic acetylcholine receptors, which activates a calcium-activated chloride channel (CaCC). Owing to high intracellular chloride levels in MHb neurons, chloride efflux through CaCC, coupled with high-threshold voltage-gated calcium channels, sustains MHb depolarization near the chloride equilibrium potential of -30 millivolts, thereby enabling LLRP. Concurrently, calcium-activated BK potassium channels counteract this depolarization, promoting LLRP termination. Our findings reveal an atypical inhibitory mechanism, orchestrated by synergistic actions between calcium-permeable and calcium-activated channels. This discovery advances our understanding of neuronal excitability control and nicotine addiction.

Cell-surface exposure of phosphatidylserine (PS) is essential for phagocytic clearance and blood clotting. Although a calcium-activated phospholipid scramblase (CaPLSase) has long been proposed to mediate PS exposure in red blood cells (RBCs), its identity, activation mechanism, and role in RBC biology and disease remain elusive. Here, we demonstrate that TMEM16F, the long-sought-after RBC CaPLSase, is activated by calcium influx through the mechanosensitive channel PIEZO1 in RBCs. PIEZO1-TMEM16F functional coupling is enhanced in RBCs from individuals with hereditary xerocytosis (HX), an RBC disorder caused by PIEZO1 gain-of-function channelopathy. Enhanced PIEZO1-TMEM16F coupling leads to an increased propensity to expose PS, which may serve as a key risk factor for HX clinical manifestations including anemia, splenomegaly, and postsplenectomy thrombosis. Spider toxin GsMTx-4 and antigout medication benzbromarone inhibit PIEZO1, preventing force-induced echinocytosis, hemolysis, and PS exposure in HX RBCs. Our study thus reveals an activation mechanism of TMEM16F CaPLSase and its pathophysiological function in HX, providing insights into potential treatment.

ABSTRACT TMEM16F (also known as ANO6), a Ca2+-activated lipid scramblase (CaPLSase) that dynamically disrupts lipid asymmetry, plays a crucial role in various physiological and pathological processes, such as blood coagulation, neurodegeneration, cell–cell fusion and viral infection. However, the mechanisms through which it regulates these processes remain largely elusive. Using endothelial cell-mediated angiogenesis as a model, here we report a previously unknown intracellular signaling function of TMEM16F. We demonstrate that TMEM16F deficiency impairs developmental retinal angiogenesis in mice and disrupts angiogenic processes in vitro. Biochemical analyses indicate that the absence of TMEM16F enhances the plasma membrane association of activated Src kinase. This in turn increases VE-cadherin phosphorylation and downregulation, accompanied by suppressed angiogenesis. Our findings not only highlight the role of intracellular signaling by TMEM16F in endothelial cells but also open new avenues for exploring the regulatory mechanisms for membrane lipid asymmetry and their implications in disease pathogenesis.

Phosphatidylserine (PS) exposure on the cell surface is crucial for processes such as phagocytic clearance and blood clotting. Despite the early conceptual proposal about a calcium-activated phospholipid scramblase (CaPLSase) that facilitates PS exposure in red blood cells (RBCs), its molecular identity, activation process, and relevance in RBC health and disorders remain elusive. Here we demonstrate that TMEM16F, the long-sought-after RBC CaPLSase, is activated by calcium influx through the mechanosensitive channel PIEZO1 in RBCs. PIEZO1-TMEM16F functional coupling is enhanced in RBCs from individuals with hereditary xerocytosis (HX), a RBC disorder caused by PIEZO1 gain-of-function channelopathy. This increased coupling results in a higher propensity of PS exposure, potentially increasing risks related to HX such as anemia, splenomegaly and post-splenectomy thrombosis. We also discovered that spider toxin GsMTx-4 and anti-gout medication benzbromarone inhibit PIEZO1, preventing force-induced echinocytosis, hemolysis and PS exposure in HX RBCs. This discovery sheds light on how TMEM16F CaPLSase is activated and its role in HX, offering new therapeutic perspectives to treat this poorly understood blood disorder.

Fear-related disorders (for example, phobias and anxiety) cause a substantial public health problem. To date, studies of the neural basis of fear have mostly focused on the amygdala. Here we identify a molecularly defined amygdala-independent tetra-synaptic pathway for olfaction-evoked innate fear and anxiety in male mice. This pathway starts with inputs from the olfactory bulb mitral and tufted cells to pyramidal neurons in the dorsal peduncular cortex that in turn connect to cholecystokinin-expressing ( Cck + ) neurons in the superior part of lateral parabrachial nucleus, which project to tachykinin 1-expressing ( Tac1 + ) neurons in the parasubthalamic nucleus. Notably, the identified pathway is specifically involved in odor-driven innate fear. Selective activation of this pathway induces innate fear, while its inhibition suppresses odor-driven innate fear. In addition, the pathway is both necessary and sufficient for stress-induced anxiety-like behaviors. These findings reveal a forebrain-to-hindbrain neural substrate for sensory-triggered fear and anxiety that bypasses the amygdala.

Advancing the mechanistic understanding of absence epilepsy is crucial for developing new therapeutics, especially for patients unresponsive to current treatments. Utilizing a recently developed mouse model of absence epilepsy carrying the BK gain-of-function channelopathy D434G, here we report that attenuating the burst firing of midline thalamus (MLT) neurons effectively prevents absence seizures. We found that enhanced BK channel activity in the BK-D434G MLT neurons promotes synchronized bursting during the ictal phase of absence seizures. Modulating MLT neurons through pharmacological reagents, optogenetic stimulation, or deep brain stimulation effectively attenuates burst firing, leading to reduced absence seizure frequency and increased vigilance. Additionally, enhancing vigilance by amphetamine, a stimulant medication, or physical perturbation also effectively suppresses MLT bursting and prevents absence seizures. These findings suggest that the MLT is a promising target for clinical interventions. Our diverse approaches offer valuable insights for developing next generation therapeutics to treat absence epilepsy.

Cell surface exposure of phosphatidylserine (PS), an anionic phospholipid that is usually confined to the inner leaflet of the plasma membrane, triggers a plethora of cellular responses. PS exposure in RBCs contributes to blood coagulation, promotes RBC aggregation and adhesion to endothelial cells, and accelerates the removal of aging RBCs from circulation. The existence of CaPLSase, a passive phospholipid transporter that catalyzes rapid PS exposure in response to intracellular Ca 2+ elevation, was first observed in RBCs in the 1990s. However, the molecular identity of RBC CaPLSase, its activation mechanism and its role in red cell disorders remain elusive. Here we demonstrate that TMEM16F, the long-sought-after RBC CaPLSase, is activated by calcium influx through the mechanosensitive channel PIEZO1 in RBCs. PIEZO1-TMEM16F functional coupling is enhanced in RBCs from individuals with hereditary xerocytosis (HX), a RBC disorder caused by PIEZO1 gain-of-function (GOF) channelopathy. Enhanced PIEZO1-TMEM16F coupling leads to an increased propensity to expose PS, which may contribute to HX clinical manifestations including anemia, splenomegaly and post-splenectomy thrombosis. Pharmacological inhibition of PIEZO1 prevents calcium-induced dehydration, hemolysis and PS exposure in HX RBCs. Our study reveals an activation mechanism of TMEM16F and its pathophysiological function in HX, providing insights into potential treatment.

S1. FXYD3 is required for the maintenance of the ER+ cancer stem cells. S2. A) Immunohistochemistry of FXYD3 in a tissue microarray (TMA) of human breast cancers showed representative examples of strong (score 4), moderate (score 3), weak (score 2), and negative (score 1) staining. Scale bar, 100 μm (upper), 20 μm (lower). B) Bioinformatics analysis of the public dataset (GEO: GSE75688) for the expression of FXYD3 based on the indicated stratifications (unpaired t test, *p<0.05, **p<0.01, ***p<0.001). ER+ breast cancer, N=85; triple-negative breast cancer (TNBC), N=166. C) Bioinformatics analysis of the public dataset (GEO: GSE4057) of FXYD3 expression in ER+ and ERï¡- breast cancer. P=0.0169; ER+ breast cancer patients, N=42; ER- breast cancer patients, N=56 (unpaired t-test, *p<0.05, **p< 0.01, ***p<0.001). D) GFP images and DPAI staining of spontaneous breast tumors in MMTV-PyMT mice injected with shNC or shFXYD3-containing lentivirus. Scale bar, 100 μm. E) Representative pictures and tumor volumes of spontaneous breast tumors in MMTV-PyMT mice injected with shNC or shFXYD3 lentivirus in mammary fat pad (unpaired t-test, **p<0.01). S3. FXYD3 potently promotes Src activation in non-genomic estrogen signaling.

Dynamic loss of lipid asymmetry through the activation of TMEM16 Ca2+-activated lipid scramblases (CaPLSases) has been increasingly recognized as an essential membrane event in a wide range of physiological and pathological processes, including blood coagulation, microparticle release, bone development, pain sensation, cell-cell fusion, and viral infection. Despite the recent implications of TMEM16F CaPLSase in vascular development and endothelial cell-mediated coagulation, its signaling role in endothelial biology remains to be established. Here, we show that endothelial TMEM16F regulates in vitro and in vivo angiogenesis through intracellular signaling. Developmental retinal angiogenesis is significantly impaired in TMEM16F deficient mice, as evidenced by fewer vascular loops and larger loop areas. Consistent with our in vivo observation, TMEM16F siRNA knockdown in human umbilical vein endothelial cells compromises angiogenesis in vitro. We further discovered that TMEM16F knockdown enhances VE-cadherin phosphorylation and reduces its expression. Moreover, TMEM16F knockdown also promotes Src kinase phosphorylation at tyrosine 416, which may be responsible for downregulating VE-cadherin expression. Our study thus uncovers a new biological function of TMEM16F in angiogenesis and provides a potential mechanism for how the CaPLSase regulates angiogenesis through intracellular signaling.

A growing number of gain-of-function (GOF) BK channelopathies have been identified in patients with epilepsy and movement disorders. Nevertheless, the underlying pathophysiology and corresponding therapeutics remain obscure. Here, we utilized a knock-in mouse model carrying human BK-D434G channelopathy to investigate the neuronal mechanism of BK GOF in the pathogenesis of epilepsy and dyskinesia. The BK-D434G mice manifest the clinical features of absence epilepsy and exhibit severe motor deficits and dyskinesia-like behaviors. The cortical pyramidal neurons and cerebellar Purkinje cells from the BK-D434G mice show hyperexcitability, which likely contributes to the pathogenesis of absence seizures and paroxysmal dyskinesia. A BK channel blocker, paxilline, potently suppresses BK-D434G–induced hyperexcitability and effectively mitigates absence seizures and locomotor deficits in mice. Our study thus uncovered a neuronal mechanism of BK GOF in absence epilepsy and dyskinesia. Our findings also suggest that BK inhibition is a promising therapeutic strategy for mitigating BK GOF-induced neurological disorders.

Pain is a source of substantial discomfort. Abnormal activity in both the zona incerta (ZI) and posterior complex of the thalamus (Po) are implicated in neuropathic pain, but their exact roles remain unclear. In particular, the precise cell types and molecular mechanisms of the ZI-Po circuit that regulate nociception are largely uncharacterized. Here, we found that parvalbumin (PV)-positive neuronal projections from the ventral ZI (ZIv) to the Po (ZIv-Po) are critical for promoting nocifensive behaviors, whereas selectively inhibiting ZIv-Po activity reduces nocifensive withdrawal responses. Furthermore, cannabinoid type 1 receptors (CB1Rs) are expressed specifically at ZIv-Po axon terminals in this circuit, and cannabinoids attenuate nocifensive responses through presynaptic inhibition. Selective inhibition of the ZIv-Po circuit or administration of cannabinoids into the Po are sufficient to ameliorate pathological pain. These findings identify the critical role of the ZIv-Po circuit and its modulation by endocannabinoids in controlling nocifensive behaviors.

The precise circuit of the substantia nigra pars reticulata (SNr) involved in temporal lobe epilepsy (TLE) is still unclear. Here we found that optogenetic or chemogenetic activation of SNr parvalbumin + (PV) GABAergic neurons amplifies seizure activities in kindling- and kainic acid-induced TLE models, whereas selective inhibition of these neurons alleviates seizure activities. The severity of seizures is bidirectionally regulated by optogenetic manipulation of SNr PV fibers projecting to the parafascicular nucleus (PF). Electrophysiology combined with rabies virus-assisted circuit mapping shows that SNr PV neurons directly project to and functionally inhibit posterior PF GABAergic neurons. Activity of these neurons also regulates seizure activity. Collectively, our results reveal that a long-range SNr-PF disinhibitory circuit participates in regulating seizure in TLE and inactivation of this circuit can alleviate severity of epileptic seizures. These findings provide a better understanding of pathological changes from a circuit perspective and suggest a possibility to precisely control epilepsy.

Abstract The presence of cancer stem cells (CSC), which possess the ability of self-renewal and cancer initiation, is correlated with poor prognosis and drug resistance of breast cancer patients. But the molecular regulatory networks for maintenance of CSC function still remain unclear. Here, we identified that an estrogen-inducible gene FXYD3, whose expression is significantly upregulated in ER+ breast CSCs, is a critical player for regulating ER+ breast CSC function. FXYD3 amplification is crucial in mediating tamoxifen resistance in ER+ breast cancer cells. Interestingly, we also find that stem cell–related transcription factor SOX9 directly promotes FXYD3 expression, and FXYD3 is indispensable for SOX9 nucleus localization, thus forming a positive regulatory feedback loop for FXYD3 amplification and function. In terms of mechanism, FXYD3 interacts with Src and ERα to form an activated complex and triggers Src to transduce nongenomic estrogen signaling for facilitating ER+ breast CSCs. Collectively, these results establish a critical role for SOX9/FXYD3/Src axis in boosting nongenomic estrogen signaling and SOX9 nucleus entry, which is required for maintenance of ER+ breast CSCs and endocrine resistance. Targeting FXYD3-mediated pathway might be a promising therapeutic strategy for hormone therapy–refractory ER+ breast cancer. Implications: SOX9/FXYD3/Src axis is critical for promoting CSC function and tamoxifen resistance in ER+ breast cancer.

Flight, an active fear response to imminent threat, is dependent on the rapid risk assessment of sensory information processed by the cortex. The thalamic reticular nucleus (TRN) filters information between the cortex and the thalamus, but whether it participates in the regulation of flight behavior remains largely unknown. Here, we report that activation of parvalbumin-expressing neurons in the limbic TRN, but not those in the sensory TRN, mediates flight. Glutamatergic inputs from the cingulate cortex (Cg) selectively activate the limbic TRN, which in turn inhibits the intermediodorsal thalamic nucleus (IMD). Activation of this Cg→limbic TRN→IMD circuit results in inhibition of the IMD and produces flight behavior. Conversely, removal of inhibition onto the IMD results in more freezing and less flight, suggesting that the IMD may function as a pro-freeze center. Overall, these findings reveal a novel corticothalamic circuit through the TRN that controls the flight response.

Both the ventral tegmental area (VTA) and dorsal raphe nucleus (DRN) are involved in affective control and reward-related behaviors. Moreover, the neuronal activities of the VTA and DRN are modulated by opioids. However, the precise circuits from the VTA to DRN and how opioids modulate these circuits remain unknown. Here, we found that neurons projecting from the VTA to DRN are primarily GABAergic. Rostral VTA (rVTA) GABAergic neurons preferentially innervate DRN GABAergic neurons, thus disinhibiting DRN serotonergic neurons. Optogenetic activation of this circuit induces aversion. In contrast, caudal VTA (cVTA) GABAergic neurons mainly target DRN serotonergic neurons, and activation of this circuit promotes reward. Importantly, μ-opioid receptors (MOPs) are selectively expressed at rVTA→DRN GABAergic synapses, and morphine depresses the synaptic transmission. Chronically elevating the activity of the rVTA→DRN pathway specifically interrupts morphine-induced conditioned place preference. This opioid-modulated inhibitory circuit may yield insights into morphine reward and dependence pathogenesis.

Viruses can escape from host recognition by degradation of RIG-I or interference with the RIG-I signalling to establish persistent infections. However, the mechanisms by which host cells stabilize RIG-I protein for avoiding its degradation are largely unknown. We report here that, upon virus infection, the E3 ubiquitin ligase FBXW7 translocates from the nucleus into the cytoplasm and stabilizes RIG-I. FBXW7 interacts with SHP2 and mediates the degradation and ubiquitination of SHP2, thus disrupting the SHP2/c-Cbl complex, which mediates RIG-I degradation. When infected with VSV or influenza A virus, FBXW7 conditional knockout mice (Lysm_FBXW7f/f) show impaired antiviral immunity. FBXW7-deficient macrophages have decreased RIG-I protein levels and type-I interferon signalling. Furthermore, PBMCs from RSV-infected children have reduced FBXW7 mRNA levels. Our results identify FBXW7 as an important interacting partner for RIG-I. These findings provide insights into the function of FBXW7 in antiviral immunity and its related clinical significance.

Cholinergic projections from the basal forebrain and brainstem are thought to play important roles in rapid eye movement (REM) sleep and arousal. Using transgenic mice in which channelrhdopsin-2 is selectively expressed in cholinergic neurons, we show that optical stimulation of cholinergic inputs to the thalamic reticular nucleus (TRN) activates local GABAergic neurons to promote sleep and protect non-rapid eye movement (NREM) sleep. It does not affect REM sleep. Instead, direct activation of cholinergic input to the TRN shortens the time to sleep onset and generates spindle oscillations that correlate with NREM sleep. It does so by evoking excitatory postsynaptic currents via α7-containing nicotinic acetylcholine receptors and inducing bursts of action potentials in local GABAergic neurons. These findings stand in sharp contrast to previous reports of cholinergic activity driving arousal. Our results provide new insight into the mechanisms controlling sleep.

Follistatin (FST), a local regulator of gonadal functions is a powerful inhibitor of follicle stimulating hormone (FSH) secretion. In the present study, the expression of FST was partially silenced at both transcriptional and translational levels by RNAi-Ready pSIREN-RetroQ-ZsGreen Vector mediated recombinant pshRNA vectors in bovine granulosa cells (bGCs). The results showed that transfection with FST-1 and FST-2 vectors significantly down-regulated mRNA and protein expressions of follistatin by 51% (P = 0.0093) and 72% (P = 0.0078) respectively. After down-regulation of FST in bGCs, cell cycle was arrested at S-phase (9.2 ± 0.6 vs 12.5 ± 0.2, P = 0.0055), and apoptosis was significantly (21.3 ± 2.7 vs 13.9 ± 2.5, P = 0.0051) increased. These findings were further verified by down-regulation of protein level of B-cell leukemia/lymphoma 2 (Bcl2, P = 0.0423), and up-regulation of caspase-3 (P = 0.0362), p21 (P = 0.0067) and mRNA levels of Bcl2-associated X protein (Bax, P = 0.041). Knockdown of FST in bGCs significantly increased activin A concentration in culture medium, while level of estradiol (E2) was suppressed without affecting progesterone production. In addition, mRNA levels of all activin receptor subtypes [activin receptor types I (ACRI) and II (ACRIIA and ACRIIB)] and inhibin α-subunit were augmented (P < 0.05) without altering both inhibin β-subunits. These findings suggest that follistatin may participate in caspase3-dependent apoptosis through Bcl2/Bax gene family in bovine GCs, whereas, activin and its receptors are associated with its regulation. Activin-induced up-regulation of inhibin-α subunit in bGCs seems to be involved in the regulation of steroidogenesis.

•Bovine granulosa cells (GCs) express somatostatin receptor 2 (SSTR2) which appears to be directly modulated by FSH.•Disruption of SSTR2 by RNAi constitutively attenuates GCs apoptosis and increases basal progesterone production.•SSTR2 may counteract FSH-induced progesterone production and inhibition of bovine GCs apoptosis.