Domain-selective and sex-dependent regulation of learning and memory in mice by GIRK channel activity in CA1 pyramidal neurons of the dorsal hippocampus.

G protein-gated inwardly rectifying K+ (GIRK) channels mediate the postsynaptic inhibitory effect of many neurotransmitters in the hippocampus and are implicated in neurological disorders characterized by cognitive deficits. Here, we show that enhancement or suppression of GIRK channel activity in dorsal CA1 pyramidal neurons disrupted novel object recognition in mice, without impacting open field activity or avoidance behavior. Contextual fear learning was also unaffected, but extinction of contextual fear was disrupted by suppression of GIRK channel activity in male mice. Thus, the strength of GIRK channel activity in dorsal CA1 pyramidal neurons regulates select cognitive task performance in mice.

Bidirectional influence of limbic GIRK channel activation on innate avoidance behavior.

Systemic administration of ML297, a selective activator of G protein-gated inwardly rectifying K+ (GIRK) channels, decreases innate avoidance behavior in male C57BL/6J mice. The cellular mechanisms mediating the ML297-induced suppression of avoidance behavior are unknown. Here, we show that systemic ML297 administration suppresses elevated plus maze (EPM)-induced neuronal activation in the ventral hippocampus (vHPC) and basolateral amygdala (BLA), and that ML297 activates GIRK1-containing GIRK channels in these limbic structures. While intracranial infusion of ML297 into the vHPC suppressed avoidance behavior in the EPM test, mirroring the effect of systemic ML297, intra-BLA administration of ML297 provoked the opposite effect. Using neuron-specific viral genetic and chemogenetic approaches, we found that the combined inhibition of excitatory neurons in CA3 and dentate gyrus (DG) sub-regions of the vHPC was sufficient to decrease innate avoidance behavior in the EPM, open-field, and light-dark tests in male C57BL/6J mice, while performance in the marble-burying test was not impacted. Furthermore, genetic ablation of GIRK channels in CA3/DG excitatory neurons precluded the suppression of avoidance behavior evoked by systemic ML297 in the EPM test. Thus, acute inhibition of excitatory neurons in the ventral CA3 and DG sub-regions of the vHPC is necessary for the apparent anxiolytic efficacy of systemic ML297 and is sufficient to decrease innate avoidance behavior in male C57BL/6J mice.SIGNIFICANT STATEMENTWe interrogated the cellular mechanisms underlying the apparent anxiolytic efficacy of ML297, a selective activator of GIRK channels and promising lead compound. Intracranial infusion of ML297 into the vHPC and BLA complex exerted opposing influence on innate avoidance behavior in male C57BL/6J mice, the former recapitulating the suppression of avoidance behavior evoked by systemic ML297. Using viral genetic and chemogenetic approaches, we showed that combined inhibition of excitatory neurons in CA3 and dentate gyrus sub-regions of the ventral hippocampus is sufficient to decrease innate avoidance behavior in male mice and mediates the decrease in avoidance behavior evoked by systemic ML297. These findings establish a foundation for future investigations into the therapeutic potential of GIRK channel modulation in anxiety disorders.

Neuronal G protein-gated K+ channels.

G protein-gated inwardly rectifying K+ (GIRK/Kir3) channels exert a critical inhibitory influence on neurons. Neuronal GIRK channels mediate the G protein-dependent, direct/postsynaptic inhibitory effect of many neurotransmitters including γ-aminobutyric acid (GABA), serotonin, dopamine, adenosine, somatostatin, and enkephalin. In addition to their complex regulation by G proteins, neuronal GIRK channel activity is sensitive to phosphatidylinositol 4,5-bisphosphate (PIP2), phosphorylation, regulator of G protein signaling (RGS) proteins, intracellular Na+ and Ca2+, and cholesterol. The application of genetic and viral manipulations in rodent models, together with recent progress in the development of GIRK channel modulators, has increased our understanding of the physiological and behavioral impact of neuronal GIRK channels. Work in rodent models has also revealed that neuronal GIRK channel activity is modified, transiently or persistently, by various stimuli including exposure drugs of abuse, changes in neuronal activity patterns, and aversive experience. A growing body of preclinical and clinical evidence suggests that dysregulation of GIRK channel activity contributes to neurological diseases and disorders. The primary goals of this review are to highlight fundamental principles of neuronal GIRK channel biology, mechanisms of GIRK channel regulation and plasticity, the nascent landscape of GIRK channel pharmacology, and the potential relevance of GIRK channels to the pathophysiology and treatment of neurological diseases and disorders.

Amyloid-ß oligomers trigger sex-dependent inhibition of GIRK channel activity in hippocampal neurons in mice.

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by amyloid plaques and cognitive decline, the latter of which is thought to be driven by soluble oligomeric amyloid-ß (oAß). The dysregulation of G protein-gated inwardly rectifying K+ (GIRK; also known as Kir3) channels has been implicated in rodent models of AD. Here, seeking mechanistic insights, we uncovered a sex-dependent facet of GIRK-dependent signaling in AD-related amyloid pathophysiology. Synthetic oAß1-42 suppressed GIRK-dependent signaling in hippocampal neurons from male mice, but not from female mice. This effect required cellular prion protein, the receptor mGluR5, and production of arachidonic acid by the phospholipase PLA2. Although oAß suppressed GIRK channel activity only in male hippocampal neurons, intrahippocampal infusion of oAß or genetic suppression of GIRK channel activity in hippocampal pyramidal neurons impaired performance on a memory test in both male and female mice. Moreover, genetic enhancement of GIRK channel activity in hippocampal pyramidal neurons blocked oAß-induced cognitive impairment in both male and female mice. In APP/PS1 AD model mice, GIRK-dependent signaling was diminished in hippocampal CA1 pyramidal neurons from only male mice before cognitive deficit was detected. However, enhancing GIRK channel activity rescued cognitive deficits in older APP/PS1 mice of both sexes. Thus, whereas diminished GIRK channel activity contributes to cognitive deficits in male mice with increased oAß burden, enhancing its activity may have therapeutic potential for both sexes.

Brain-neuron targeted nanoparticles for peptide synergy therapy at dual-target of Alzheimer's disease.

Since the complex interactions of multiple mechanisms involved in Alzheimer's disease (AD) preclude the monotherapeutic approaches from clinical application, combination therapy has become an attractive strategy for AD treatment. However, to be emphasized, the realization of the edges of combination therapy greatly depends on the reasonable choice of targets and the rational design of combination scheme. Acknowledgedly, amyloid plaques and hyperphosphorylated tau (p-tau) are two main hallmarks in AD with close pathological correlations, implying the hopeful prospect of combined intervention in them for AD treatment. Herein, we developed the nano-combination system, neuron-targeting PEG-PLA nanoparticles (CT-NP) loading two peptide drugs H102, a ß-sheet breaker acting on Aß, and NAP, a microtubule stabilizer acting on p-tau. Compared with free peptide combination, nano-combination system partly aligned the in vivo behaviors of combined peptides and enhanced peptide accumulation in lesion neurons by the guidance of targeting peptide CGN and Tet1, facilitating the therapeutic performance of peptide combination. Further, to maximize the therapeutic potential of nano-combination system, the combination ratio and mode were screened by the quantitative evaluation with combination index and U test, respectively, in vitro and in vivo. The results showed that the separated-loading CT-NP at the combination molar ratio of 2:1 (H102:NAP), CT-NP/H102 + CT-NP/NAP(2:1), generated the strongest synergistic therapeutic effects on Aß, p-tau and their linkage, and effectually prevented neuroinflammation, reversed the neuronal damage and restored cognitive performance in 3 × Tg-AD transgenic mice. Our studies provide critical data on the effectiveness of nano-combination therapy simultaneously intervening in Aß and p-tau, confirming the promising application of nano-combination strategy in AD treatment.

Wnt signaling pathway in cancer immunotherapy.

Wnt/ß-catenin signaling is a highly conserved pathway that regulates cell proliferation, differentiation, apoptosis, stem cell self-renewal, tissue homeostasis, and wound healing. Dysregulation of the Wnt pathway is intricately involved in almost all stages of tumorigenesis in various cancers. Through direct and/or indirect effects on effector T cells, T-regulatory cells, T-helper cells, dendritic cells, and other cytokine-expressing immune cells, abnormal activation of Wnt/ß-catenin signaling benefits immune exclusion and hinders T-cell-mediated antitumor immune responses. Activation of Wnt signaling results in increased resistance to immunotherapies. In this review, we summarize the process by which Wnt signaling affects cancer and immune surveillance, and the potential for targeting the Wnt-signaling pathway via cancer immunotherapy.