Single cell transcriptome analysis identified a unique neutrophil type associated with Alzheimer's disease.

BACKGROUND: Neutrophils play an essential role in Alzheimer's disease (AD) pathology. However, the extent of their heterogeneity remains poorly explored, particularly in the context of developing novel therapies targeting these cells. RESULTS: We investigate the population structure of neutrophils purified from peripheral blood samples of AD mice. Utilizing single cell RNA sequencing, we comprehensively map neutrophil populations into six distinct clusters and find that the Neu-5 subset is specially enriched in AD mice. This subset exhibits fewer specific granules and a lower mature score. Gene ontology (GO) analysis reveals that genes involved in cytokine-mediated signaling are downregulated in the Neu-5 cluster. Furthermore, we identify the Ccrl2 gene is specifically upregulated in this subgroup, which is confirmed by flow cytometry in AD mice. Finally, immunohistochemical staining indicates that CCRL2 protein is increased in the brains of AD mice. CONCLUSIONS: We identify a unique CCRL2 positive neutrophil cluster, that is specifically enriched in the peripheral blood of AD mice.

Retrieval-extinction of drug memory requires AMPA receptor trafficking.

Disruption of drug-associated memory reduces relapse. Transient memory retrieval facilitates the upcoming extinction of addiction memory, while the neural basis for this beneficial outcome remains unelucidated. Here, we report that AMPA receptor trafficking acts as the central component for retrieval-extinction-based drug memory intervention. Drug memory retrieval transiently reduces AMPA receptor-mediated synaptic transmission in prefrontal cortical neurons (lasting for 2 to 4 hours) through rapid removal of calcium-permeable AMPA receptors from the synapse, which returned to basal state level after 6 hours. The receptor trafficking is orchestrated by dopamine D1 but not D2 receptor signaling. Blocking AMPA receptor trafficking abolishes retrieval-extinction-mediated addiction memory degradation. These results reveal the molecular mechanism underlying the efficacy of transient memory retrieval on helping to erase addiction memory and support targeting the prefrontal cortex to reduce relapse (e.g., with noninvasive brain stimulation).

Adaptor protein APPL1 links neuronal activity to chromatin remodeling in cultured hippocampal neurons.

Local signaling events at synapses or axon terminals are communicated to the nucleus to elicit transcriptional responses, and thereby translate information about the external environment into internal neuronal representations. This retrograde signaling is critical to dendritic growth, synapse development, and neuronal plasticity. Here, we demonstrate that neuronal activity induces retrograde translocation and nuclear accumulation of endosomal adaptor APPL1. Disrupting the interaction of APPL1 with Importin α1 abolishes nuclear accumulation of APPL1, which in turn decreases the levels of histone acetylation. We further demonstrate that retrograde translocation of APPL1 is required for the regulation of gene transcription and then maintenance of hippocampal late-phase long-term potentiation. Thus, these results illustrate an APPL1-mediated pathway that contributes to the modulation of synaptic plasticity via coupling neuronal activity with chromatin remodeling.

The multiple roles of deubiquitinases in liver cancer.

Primary liver cancer ranks the second leading cause of death associated with cancer in the world and therefore a major public health challenge. The mortality rates of liver cancer has been increasing during the past decades with the reality that the alternative therapeutic drugs are not available. Although growing numbers of proteins involved in liver cancer progression have been identified, many of these are not suitable drug targets, which hinders the development of new drugs to cure liver cancer. It is in urgent demand that novel therapeutic approaches should be explored. Deubiquitinases (DUBs), specifically removing ubiquitin chains from the target protein, have showed vital roles for protein homeostasis and quality control by rigidly regulating the balance between ubiquitination and deubiquitination in normal physiology. Recent studies have revealed deregulation or dysfunction of DUBs always associates with cancer and other diseases. Targeting certain DUBs, leading to degradation or loss function of the key oncoproteins, including undruggable ones, seems to provide a potential therapy for cancer patients. In liver cancer, numberous of DUBs are demonstrated to participate in hepatocarcinogenesis, metastasis and so on. Depending on the substrates, some DUBs may suppress liver cancers while others promote. In this review, we primarily summarize the roles of DUBs in liver tumors, and illustrate opportunities for the application of targeting DUBs for cancer therapy.

The anterior insular cortex unilaterally controls feeding in response to aversive visceral stimuli in mice.

Reduced food intake is common to many pathological conditions, such as infection and toxin exposure. However, cortical circuits that mediate feeding responses to these threats are less investigated. The anterior insular cortex (aIC) is a core region that integrates interoceptive states and emotional awareness and consequently guides behavioral responses. Here, we demonstrate that the right-side aIC CamKII+ (aICCamKII) neurons in mice are activated by aversive visceral signals. Hyperactivation of the right-side aICCamKII neurons attenuates food consumption, while inhibition of these neurons increases feeding and reverses aversive stimuli-induced anorexia and weight loss. Similar manipulation at the left-side aIC does not cause significant behavioral changes. Furthermore, virus tracing reveals that aICCamKII neurons project directly to the vGluT2+ neurons in the lateral hypothalamus (LH), and the right-side aICCamKII-to-LH pathway mediates feeding suppression. Our studies uncover a circuit from the cortex to the hypothalamus that senses aversive visceral signals and controls feeding behavior.

Reduced synaptic function of Kainate receptors in the insular cortex of Fmr1 Knock-out mice.

Fragile X syndrome is caused by the loss of fragile X mental retardation protein (FMRP). Kainate receptor (KAR) is a subfamily of ionotropic glutamate receptors (iGluR) that acts mainly as a neuromodulator of synaptic transmission and neuronal excitability. However, little is known about the changes of synaptic KAR in the cortical area of Fmr1 KO mice. In this study, we performed whole-cell patch-clamp recordings from layer II/III pyramidal neurons in the insular cortex of Fmr1 KO mice. We found that KARs mediated currents were reduced in Fmr1 KO mice. KARs were mainly located in the synaptosomal fraction of the insular cortex. The abundance of KAR subunit GluK1 and GluK2/3 in the synaptosome was reduced in Fmr1 KO mice, whereas the total expressions of these KARs subunits were not changed. Finally, lack of FMRP impairs subsequent internalization of surface GluK2 after KAR activation, while having no effect on the surface GluK2 expression. Our studies provide evidence indicating that loss of FMRP leads to the abnormal function and localization of KARs. This finding implies a new molecular mechanism for Fragile X syndrome.

Postsynaptic RIM1 modulates synaptic function by facilitating membrane delivery of recycling NMDARs in hippocampal neurons.

NMDA receptors (NMDARs) are crucial for excitatory synaptic transmission and synaptic plasticity. The number and subunit composition of synaptic NMDARs are tightly controlled by neuronal activity and sensory experience, but the molecular mechanism mediating NMDAR trafficking remains poorly understood. Here, we report that RIM1, with a well-established role in presynaptic vesicle release, also localizes postsynaptically in the mouse hippocampus. Postsynaptic RIM1 in hippocampal CA1 region is required for basal NMDAR-, but not AMPA receptor (AMPAR)-, mediated synaptic responses, and contributes to synaptic plasticity and hippocampus-dependent memory. Moreover, RIM1 levels in hippocampal neurons influence both the constitutive and regulated NMDAR trafficking, without affecting constitutive AMPAR trafficking. We further demonstrate that RIM1 binds to Rab11 via its N terminus, and knockdown of RIM1 impairs membrane insertion of Rab11-positive recycling endosomes containing NMDARs. Together, these results identify a RIM1-dependent mechanism critical for modulating synaptic function by facilitating membrane delivery of recycling NMDARs.

Cysteine residues 87 and 320 in the amino terminal domain of NMDA receptor GluN2A govern its homodimerization but do not influence GluN2A/GluN1 heteromeric assembly.

N-Methyl-D-aspartate receptors (NMDARs) play a central role in various physiological and pathological processes in the central nervous system. And they are commonly composed of four subunits, two GluN1 subunits and two GluN2 or GluN3 subunits. The different subunit compositions make NMDARs a heterogeneous population with distinct electrophysiological and pharmacological properties and thus with different abilities to conduct neuronal activities. The subunit composition, assembly process, and final structure of assembled NMDARs have been studied for years but no consensus has been achieved. In this study, we investigated the role of the amino terminal domain (ATD) of GluN2A in regulating NMDAR assembly. The ATD of GluN2A was first expressed in heterogeneous cells and the homodimer formation was investigated by fluorescent resonance energy transfer and non-reducing SDSPAGE electrophoresis. Each of the three cysteine residues located in the ATD was mutated into alanine, and the homodimerization of the ATD or GluN2A, as well as the heteromeric assembly of NMDARs was assessed by non-reducing SDSPAGE electrophoresis, co-immunoprecipitation and immunocytochemistry. We found that two cysteine residues, C87 and C320, in the ATD of the GluN2A subunit were required for the formation of disulfide bonds and GluN2A ATD homodimers. Furthermore, the disruption of GluN2A ATD domain dimerization had no influence on the assembly and surface expression of NMDARs. These results suggest that the two ATD domains of GluN2A are structurally adjacent in fully-assembled NMDARs. However, unlike GluN1, the homomerization of the ATD domain of GluN2A is not required for the assembly of NMDARs, implying that GluN2A and GluN1 play unequal roles in NMDAR assembly.

Nischarin is differentially expressed in rat brain and regulates neuronal migration.

Nischarin is a protein known to inhibit breast cancer cell motility by regulating the signaling of the Rho GTPase family. However, little is known about its location and function in the nervous system. The aim of the present study was to investigate the regional and cellular expression and functions of Nischarin in the adult rodent brain. As assessed by real-time PCR, Western blot analysis and immunostaining, we found that Nischarin was widely distributed throughout the brain, with a higher expression in the cerebral cortex and hippocampus. Double-labeling showed that Nischarin was expressed in neurons and was mainly located in the perinuclear region and F-actin-rich protrusions. The expression pattern of Nischarin in the brain was thought to be closely associated with its function. This was verified by our findings from cell migration assays that Nischarin regulated neuronal migration. These results provide a preliminary survey of the distribution of Nischarin in different regions and cell types in the rat brain. This might help to elucidate its physiological roles, and to evaluate its potential clinical implications.