Interaction of "readthrough" acetylcholinesterase with RACK1 and PKCbeta II correlates with intensified fear-induced conflict behavior

The roles of RACK1 in the pathogenesis of Alzheimer's disease

The receptor for activated C kinase 1 (RACK1) is a protein that plays a crucial role in various signaling pathways and is involved in the pathogenesis of Alzheimer's disease (AD), a prevalent neurodegenerative disease. RACK1 is highly expressed in neuronal cells of the central nervous system and regulates the pathogenesis of AD. Specifically, RACK1 is involved in regulation of the amyloid-β precursor protein processing through α- or β-secretase by binding to different protein kinase C isoforms. Additionally, RACK1 promotes synaptogenesis and synaptic plasticity by inhibiting N-methyl-D-aspartate receptors and activating gamma-aminobutyric acid A receptors, thereby preventing neuronal excitotoxicity. RACK1 also assembles inflammasomes that are involved in various neuroinflammatory pathways, such as nuclear factor-kappa B, tumor necrosis factor-alpha, and NOD-like receptor family pyrin domain-containing 3 pathways. The potential to design therapeutics that block amyloid-β accumulation and inflammation or precisely regulate synaptic plasticity represents an attractive therapeutic strategy, in which RACK1 is a potential target. In this review, we summarize the contribution of RACK1 to the pathogenesis of AD and its potential as a therapeutic target.

Cholinergic neurotransmission in the basolateral amygdala during cued fear extinction

Cholinergic neuromodulation plays an important role in numerous cognitive functions including regulating arousal and attention, as well as associative learning and extinction processes. Further, studies demonstrate that cholinergic inputs from the basal forebrain cholinergic system influence physiological responses in the basolateral amygdala (BLA) as well as fear extinction processes. Since rodent models display individual differences in conditioned fear and extinction responses, this study investigated if cholinergic transmission in the BLA during fear extinction could contribute to differences between extinction resistant and extinction competent phenotypes in outbred Long-Evans male rats. Experiment 1 used in vivo microdialysis to test the hypothesis that acetylcholine (ACH) efflux in the BLA would increase with presentation of an auditory conditioned stimulus (CS+) during extinction learning. Acetylcholine efflux was compared in rats exposed to the CS+, a CS- (the tone never paired with a footshock), or to a context shift alone (without CS+ tone presentation). Consistent with acetylcholine's role in attention and arousal, ACH efflux in the BLA was increased in all three groups (CS+, CS-, Shift Alone) by the initial context shift into the extinction learning chamber, but returned more rapidly to baseline levels in the Shift Alone group (no CS+). In contrast, in the group exposed to the CS+, ACH efflux in the BLA remained elevated during continued presentation of conditioned cues and returned to baseline more slowly, leading to an overall increase in ACH efflux compared with the Shift Alone group. Based on the very dense staining in the BLA for acetylcholinesterase (ACHE), Experiment 2 examined if individual differences in fear extinction were associated with differences in cholinesterase enzyme activity (CHE) in the BLA and/or plasma with a separate cohort of animals. Cholinesterase activity (post-testing) in both the BLA and plasma was higher in extinction competent rats versus rats resistant to extinction learning. There was also a significant negative correlation between BLA CHE activity and freezing during extinction learning. Taken together, our results support a role for ACH efflux in the BLA during cued fear extinction that may be modulated by individual differences in ACHE activity, and are associated with behavioral responses during fear extinction. These findings implicate individual differences in cholinergic regulation in the susceptibility to disorders with dysregulation of extinction learning, such post-traumatic stress disorder (PTSD) in humans.

Acetylcholinesterase inhibition ameliorates retinal neovascularization and glial activation in oxygen-induced retinopathy

AIM

To investigate whether inhibition of acetylcholinesterase (AChE) by donepezil ameliorate aberrant retinal neovascularization (RNV) and abnormal glial activation in oxygen-induced retinopathy (OIR).

METHODS

A mouse model of RNV was induced in postnatal day 7 (P7) mice by exposure to 75% oxygen. Donepezil was administrated to P12 mice by intraperitoneal injection. Expression and localization of AChE in mouse retinas were determined by immunofluorescence. RNV was evaluated by paraffin sectioning and hematoxylin and eosin (HE) staining. Activation of retinal Müller glial cells were examined by immunoblot of glial fibrillary acidic protein (GFAP). rMC-1, a retinal Müller cell line, was used for in vitro study. Expression of hypoxia-induced factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) were determined by Western-blot analysis, enzyme-linked immunosorbent assay (ELISA) or immunostaining.

RESULTS

Aberrant RNV and glial activation was observed after OIR. Of note, retinal AChE was mainly expressed by retinal Müller glial cells and markedly increased in OIR mice. Systemic administration of donepezil significantly reduced RNV and abnormal glial activation in mice with OIR. Moreover, ischemia-induced HIF-1α accumulation and VEGF upregulation in OIR mouse retinas and cultured rMC-1 were significantly inhibited by donepezil intervention.

CONCLUSION

AchE is implicated in RNV with OIR. Inhibition of AChE by donepeizl is likely to be a potential therapeutic approach for retinal neovascular diseases.

Cholinergic Stress Signals Accompany MicroRNA-Associated Stereotypic Behavior and Glutamatergic Neuromodulation in the Prefrontal Cortex

Stereotypic behavior (SB) is common in emotional stress-involved psychiatric disorders and is often attributed to glutamatergic impairments, but the underlying molecular mechanisms are unknown. Given the neuro-modulatory role of acetylcholine, we sought behavioral-transcriptomic links in SB using TgR transgenic mice with impaired cholinergic transmission due to over-expression of the stress-inducible soluble 'readthrough' acetylcholinesterase-R splice variant AChE-R. TgR mice showed impaired organization of behavior, performance errors in a serial maze test, escape-like locomotion, intensified reaction to pilocarpine and reduced rearing in unfamiliar situations. Small-RNA sequencing revealed 36 differentially expressed (DE) microRNAs in TgR mice hippocampi, 8 of which target more than 5 cholinergic transcripts. Moreover, compared to FVB/N mice, TgR prefrontal cortices displayed individually variable changes in over 400 DE mRNA transcripts, primarily acetylcholine and glutamate-related. Furthermore, TgR brains presented c-fos over-expression in motor behavior-regulating brain regions and immune-labeled AChE-R excess in the basal ganglia, limbic brain nuclei and the brain stem, indicating a link with the observed behavioral phenotypes. Our findings demonstrate association of stress-induced SB to previously unknown microRNA-mediated perturbations of cholinergic/glutamatergic networks and underscore new therapeutic strategies for correcting stereotypic behaviors.

Increased Active OMI/HTRA2 Serine Protease Displays a Positive Correlation with Cholinergic Alterations in the Alzheimer's Disease Brain

OMI/HTRA2 (high-temperature requirement serine protease A2) is a mitochondrial serine protease involved in several cellular processes, including autophagy, chaperone activity, and apoptosis. Few studies on the role of OMI/HTRA2 in Alzheimer's disease (AD) are available, but none on its relationship with the cholinergic system and neurotrophic factors as well as other AD-related proteins. In this study, immunohistochemical analyses revealed that AD patients had a higher cytosolic distribution of OMI/HTRA2 protein compared to controls. Quantitative analyses on brain extracts indicated a significant increase in the active form of OMI/HTRA2 in the AD brain. Activated OMI/HTRA2 protein positively correlated with stress-associated read-through acetylcholinesterase activity. In addition, α7 nicotinic acetylcholine receptor gene expression, a receptor also known to be localized on the outer membrane of mitochondria, showed a strong correlation with OMI/HTRA2 gene expression in three different brain regions. Interestingly, the activated OMI/HTRA2 levels also correlated with the activity of the acetylcholine-biosynthesizing enzyme, choline acetyltransferase (ChAT); with levels of the neurotrophic factors, NGF and BDNF; with levels of the soluble fragments of amyloid precursor protein (APP); and with gene expression of the microtubule-associated protein tau in the examined brain regions. Overall, the results demonstrate increased levels of the mitochondrial serine protease OMI/HTRA2, and a coherent pattern of association between the activated form of OMI/HTRA2 and several key proteins involved in AD pathology. In this paper, we propose a new hypothetical model to highlight the importance and needs of further investigation on the role of OMI/HTRA2 in the mitochondrial function and AD.

Expression of acetylcholinesterase 1 is associated with brood rearing status in the honey bee, Apis mellifera

Acetylcholinesterase 1 (AmAChE1) of the honey bee, Apis mellifera, has been suggested to have non-neuronal functions. A systematic expression profiling of AmAChE1 over a year-long cycle on a monthly basis revealed that AmAChE1 was predominantly expressed in both head and abdomen during the winter months and was moderately expressed during the rainy summer months. Interestingly, AmAChE1 expression was inhibited when bees were stimulated for brood rearing by placing overwintering beehives in strawberry greenhouses with a pollen diet, whereas it resumed when the beehives were moved back to the cold field, thereby suppressing brood rearing. In early spring, pollen diet supplementation accelerated the induction of brood-rearing activity and the inhibition of AmAChE1 expression. When active beehives were placed in a screen tent in late spring, thereby artificially suppressing brood-rearing activity, AmAChE1 was highly expressed. In contrast, AmAChE1 expression was inhibited when beehives were allowed to restore brood rearing by removing the screen, supporting the hypothesis that brood rearing status is a main factor in the regulation of AmAChE1 expression. Since brood rearing status is influenced by various stress factors, including temperature and diet shortage, our finding discreetly suggests that AmAChE1 is likely involved in the stress response or stress management.

Muscarinic M1 receptor partially modulates higher sensitivity to cadmium-induced cell death in primary basal forebrain cholinergic neurons: A cholinesterase variants dependent mechanism

Cadmium is a toxic compound reported to produce cognitive dysfunctions, though the mechanisms involved are unknown. In a previous work we described how cadmium blocks cholinergic transmission and induces greater cell death in primary cholinergic neurons from the basal forebrain. It also induces cell death in SN56 cholinergic neurons from the basal forebrain through M1R blockage, alterations in the expression of AChE variants and GSK-3β, and an increase in Aβ and total and phosphorylated Tau protein levels. It was observed that the silencing or blockage of M1R altered ChAT activity, GSK-3β, AChE splice variants gene expression, and Aβ and Tau protein formation. Furthermore, AChE-S variants were associated with the same actions modulated by M1R. Accordingly, we hypothesized that cholinergic transmission blockage and higher sensitivity to cadmium-induced cell death of primary basal forebrain cholinergic neurons is mediated by M1R blockage, which triggers this effect through alteration of the expression of AChE variants. To prove this hypothesis, we evaluated, in primary culture from the basal forebrain region, whether M1R silencing induces greater cell death in cholinergic neurons than cadmium does, and whether in SN56 cells M1R mediates the mechanisms described so as to play a part in the cadmium induction of cholinergic transmission blockage and cell death in this cell line through alteration of the expression of AChE variants. Our results prove that M1R silencing by cadmium partially mediates the greater cell death observed on basal forebrain cholinergic neurons. Moreover, all previously described mechanisms for blocking cholinergic transmission and inducing cell death on SN56 cells after cadmium exposure are partially mediated by M1R through the alteration of AChE expression. Thus, our results may explain cognitive dysfunctions observed in cadmium toxicity.

A novel missense variant in PRKCB segregates low-frequency hearing loss in an autosomal dominant family with Meniere's disease

Meniere's Disease (MD) is a complex disorder associated with an accumulation of endolymph in the membranous labyrinth in the inner ear. It is characterized by recurrent attacks of spontaneous vertigo associated with sensorineural hearing loss (SNHL) and tinnitus. The SNHL usually starts at low and medium frequencies with a variable progression to high frequencies. We identified a novel missense variant in the PRKCB gene in a Spanish family with MD segregating low-to-middle frequency SNHL. Confocal imaging showed strong PKCB II protein labelling in non-sensory cells, the tectal cells and inner border cells of the rat organ of Corti with a tonotopic expression gradient. The PKCB II signal was more pronounced in the apical turn of the cochlea when compared with the middle and basal turns. It was also much higher in cochlear tissue than in vestibular tissue. Taken together, our findings identify PRKCB gene as a novel candidate gene for familial MD and its expression gradient in supporting cells of the organ of Corti deserves attention, given the role of supporting cells in K⁺recycling within the endolymph, and its apical turn location may explain the onset of hearing loss at low frequencies in MD.

Deficit of RACK1 contributes to the spatial memory impairment via upregulating BECLIN1 to induce autophagy

AIMS

Deficiency of activated C kinase1 (RACK1) in the brain of aging animal and Alzheimer's disease was characterized by cognitive dementia and spatial memory impairment. However, the correlation between the RACK1 and spatial memory impairment and the mechanism involved in it remains unknown.

MAIN METHODS

Spatial memory impairment was performed in mice by lateral ventricle injection of Aβ25-35 (n=16, 10μl) and intraperitoneal injection of scopolamine (n=16, 10ml/kg). After the Morris water maze (MWM) which was performed to determine the ability of learning and memory in mice, expression of RACK1 was tested and the damage of hippocampus was confirmed by histopathology test. ShRACK1 was then used to decrease the level of RACK1 in hippocampus to test the ability of learning and memory and histopathology changes in hippocampus. To look into the mechanism of RACK1 on spatial memory impairment, we further measured the expression of autophagy proteins BECLIN1 and LC3-II/I in hippocampus of all mice.

KEY FINDINGS

Both the Aβ25-35, scopolamine impaired the spatial memory in mice (for escape latency, P=0.0004, P<0.0001) and severely damaged hippocampal DG neurons (P=0.012, P=0.014). The expression of RACK1 was significantly decreased which was concomitant with elevated BECLIN1 and LC3-II/I (P<0.001). Suppression of RACK1 by ShRACK1 plasmid (shGnb2l1) significantly impaired the spatial memory in mice, damaged hippocampal DG neurons (P=0.013), and increased the proteins of BECLIN1 and LC3-II/I (P<0.005).

SIGNIFICANCE

It demonstrated that the deficit of RACK1 in hippocampus impairs the ability of learning and memory in mice via up regulating autophagy.

RACK1 affects glioma cell growth and differentiation through the CNTN2-mediated RTK/Ras/MAPK pathway

Receptor for activated C kinase 1 (RACK1) and contactin-2 (CNTN2) are known to be abnormally expressed in gliomas; however, the association between RACK1 and CNTN2, and the effects of RACK1 and CNTN2 on glioma cell differentiation and the related molecular mechanisms remain largely unknown. The present study aimed to investigate the interaction between RACK1 and CNTN2, and to examine whether RACK1/CNTN2/receptor tyrosine kinase (RTK)/Ras/mitogen-activated protein kinase (MAPK) axis plays a role in glioma growth and differentiation. The results from western blot analysis revealed that the protein expression levels of RACK1 and CNTN2 were higher in high‑grade glioma tissues and cells, and lower in low-grade glioma tissues and cells. A co-immunoprecipitation assay demonstrated that RACK1 interacts with CNTN2, and RACK1 upregulated the expression of CNTN2. Gain-of‑function and loss-of‑function experiments indicated that both RACK1 and CNTN2 promoted glioma cell proliferation, inhibited glioma cell differentiation and activated the RTK/Ras/MAPK pathway. However, the effects of RACK1 on glioma cell proliferation, differentiation and the activation of the RTK/Ras/MAPK signaling pathway were abolished by the knockdown of CNTN2 using siRNA. In Therefore, the findings of this study firstly demonstrate that RACK1 interacts with CNTN2, and that the effects of RACK1 on glioma cell growth and differentiation are mediated by CNTN2. The RACK1/CNTN2/RTK/Ras/MAPK axis exists in glioma cells, and it may be a potential therapeutic target in gliomas.

Mutation and duplication of arthropod acetylcholinesterase: Implications for pesticide resistance and tolerance

A series of common/shared point mutations in acetylcholinesterase (AChE) confers resistance to organophosphorus and carbamate insecticides in most arthropod pests. However, the mutations associated with reduced sensitivity to insecticides usually results in the reduction of catalytic efficiency and leads to a fitness disadvantage. To compensate for the reduced catalytic activity, overexpression of neuronal AChE appears to be necessary, which is achieved by a relatively recent duplication of the AChE gene (ace) as observed in the two-spotted spider mite and other insects. Unlike the cases with overexpression of neuronal AChE, the extensive generation of soluble AChE is observed in some insects either from a distinct non-neuronal ace locus or from a single ace locus via alternative splicing. The production of soluble AChE in the fruit fly is induced by chemical stress. Soluble AChE acts as a potential bioscavenger and provides tolerance to xenobiotics, suggesting its role in chemical adaptation during evolution.

Role of acetylcholinesterase in lung cancer

Acetylcholinesterase (AChE) plays a key role in catalytic hydrolysis of cholinergic neurotransmitters. Intensive research has proven the involvement of this protein in novel functions, such as cell adhesion, differentiation, and proliferation. In addition, several recent studies have indicated that acetylcholinesterase is potentially a marker and regulator of apoptosis. Importantly, AChE is also a promising tumor suppressor. In this review, we briefly summarize the involvement of AChE in apoptosis and cancer, focusing on the role of AChE in lung cancer, as well as the therapeutic consideration of AChE for cancer therapy.

Induction of soluble AChE expression via alternative splicing by chemical stress in Drosophila melanogaster

Various molecular forms of acetylcholinesterase (AChE) have been characterized in insects. Post-translational modification is known to be a major mechanism for the molecular diversity of insect AChE. However, multiple forms of Drosophila melanogaster AChE (DmAChE) were recently suggested to be generated via alternative splicing (Kim and Lee, 2013). To confirm alternative splicing as the mechanism for generating the soluble form of DmAChE, we generated a transgenic fly strain carrying the cDNA of DmAChE gene (Dm_ace) that predominantly expressed a single transcript variant encoding the membrane-anchored dimer. 3' RACE (rapid amplification of cDNA ends) and western blotting were performed to compare Dm_ace transcript variants and DmAChE forms between wild-type and transgenic strains. Various Dm_ace transcripts and DmAChE molecular forms were observed in wild-type flies, whereas the transgenic fly predominantly expressed Dm_ace transcript variant encoding the membrane-anchored dimer. This supports alternative splicing as the major determinant in the generation of multiple forms of DmAChE. In addition, treatment with DDVP as a chemical stress induced the expression of the Dm_ace splice variant without the glycosylphosphatidylinositol anchor site in a dose-dependent manner and, accordingly, the soluble form of DmAChE in wild-type flies. In contrast, little soluble DmAChE was expressed in the transgenic fly upon exposure to DDVP. DDVP bioassays revealed that transgenic flies, which were unable to express a sufficient amount of soluble monomeric DmAChE, were more sensitive to DDVP compared to wild-type flies, suggesting that the soluble monomer may exert non-neuronal functions, such as chemical defense against xenobiotics.

AChE and RACK1 promote the anti-inflammatory properties of fluoxetine

Selective serotonin reuptake inhibitors (SSRIs) show anti-inflammatory effects, suggesting a possible interaction with both Toll-like-receptor 4 (TLR4) responses and cholinergic signaling through as yet unclear molecular mechanism(s). Our results of structural modeling support the concept that the antidepressant fluoxetine physically interacts with the TLR4-myeloid differentiation factor-2 complex at the same site as bacterial lipopolysaccharide (LPS). We also demonstrate reduced LPS-induced pro-inflammatory interleukin-6 and tumor necrosis factor alpha in human peripheral blood mononuclear cells preincubated with fluoxetine. Furthermore, we show that fluoxetine intercepts the LPS-induced decreases in intracellular acetylcholinesterase (AChE-S) and that AChE-S interacts with the nuclear factor kappa B (NFκB)-activating intracellular receptor for activated C kinase 1 (RACK1). This interaction may prevent NFκB activation by residual RACK1 and its interacting protein kinase PKCβII. Our findings attribute the anti-inflammatory properties of SSRI to surface membrane interference with leukocyte TLR4 activation accompanied by intracellular limitation of pathogen-inducible changes in AChE-S, RACK1, and PKCβII.

Cholinesterases as biomarkers for parasympathetic dysfunction and inflammation-related disease

Accumulating evidence suggests parasympathetic dysfunction and elevated inflammation as underlying processes in multiple peripheral and neurological diseases. Acetylcholine, the main parasympathetic neurotransmitter and inflammation regulator, is hydrolyzed by the two closely homologous enzymes, acetylcholinesterase and butyrylcholinesterase (AChE and BChE, respectively), which are also expressed in the serum. Here, we consider the potential value of both enzymes as possible biomarkers in diseases associated with parasympathetic malfunctioning. We cover the modulations of cholinesterase activities in inflammation-related events as well as by cholinesterase-targeted microRNAs. We further discuss epigenetic control over cholinesterase gene expression and the impact of single-nucleotide polymorphisms on the corresponding physiological and pathological processes. In particular, we focus on measurements of circulation cholinesterases as a readily quantifiable readout for changes in the sympathetic/parasympathetic balance and the implications of changes in this readout in health and disease. Taken together, this cumulative know-how calls for expanding the use of cholinesterase activity measurements for both basic research and as a clinical assessment tool.

AhR-mediated effects of dioxin on neuronal acetylcholinesterase expression in vitro

BACKGROUND

Deficits in cognitive functioning have been reported in humans exposed to dioxins and dioxin-like compounds. Evidence suggests that dioxins induce cholinergic dysfunction mediated by hypothyroidism. However, little is known about direct effects of dioxins on the cholinergic system.

OBJECTIVES

We investigated the action of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on acetylcholinesterase (AChE), a key enzyme in cholinergic neurotransmission.

METHODS

We used SK-N-SH human-derived neuronal cells to evaluate the effect of dioxin exposure on AChE.

RESULTS

We consistently found a significant decrease in enzymatic activity of AChE in cultured neurons treated with TCDD. We also found that, unlike organophosphate pesticides that directly act on the catalytic center of AChE, the suppressive effect of dioxin was through transcriptional regulation. The addition of CH223191, an inhibitor of the aryl hydrocarbon receptor (AhR)-dependent pathway, counteracted the TCDD-induced suppression of AChE, suggesting involvement of the AhR-dependent pathway. The existence of putative dioxin-responsive element (DRE) consensus sequences in the human ACHE promoter region further supported this hypothesis. Consistent with the absence of DRE elements in mouse or rat ACHE promoter regions, suppression of AChE by TCDD did not occur in rat neuronal cells, indicating a potential species-specific effect.

CONCLUSIONS

In SK-N-SH cells, dioxin suppressed the activity of neuronal AChE via AhR-mediated transcriptional down-regulation. This is the first study to report direct interference by dioxin with the cholinergic neurotransmission system.

Chronic dietary exposure to chlorpyrifos causes behavioral impairments, low activity of brain membrane-bound acetylcholinesterase, and increased brain acetylcholinesterase-R mRNA

Chlorpyrifos (CPF) is an organophosphate (OP) insecticide that is metabolically activated to the highly toxic chlorpyrifos oxon. Dietary exposure is the main route of intoxication for non-occupational exposures. However, only limited behavioral effects of chronic dietary exposure have been investigated. Therefore, male Wistar rats were fed a dose of 5mg/kg/day of CPF for thirty-one weeks. Animals were evaluated in spatial learning and impulsivity tasks after 21 weeks of CPF dietary exposure and one week after exposure ended, respectively. In addition, the degree of inhibition of brain acetylcholinesterase (AChE) was evaluated for both the soluble and particulate forms of the enzyme, as well as AChE gene expression. Also, brain acylpeptide hydrolase (APH) was investigated as an alternative target for OP-mediated effects. All variables were evaluated at various time points in response to CPF diet and after exposure ended. Results from behavioral procedures suggest cognitive and emotional disorders. Moreover, low levels of activity representing membrane-bound oligomeric forms (tetramers) were also observed. In addition, increased brain AChE-R mRNA levels were detected after four weeks of CPF dietary exposure. However, no changes in levels of brain APH were observed among groups. In conclusion, our data point to a relationship between cognitive impairments and changes in AChE forms, specifically to a high inhibition of the particulate form and a modification of alternative splicing of mRNA during CPF dietary exposure.

RACK1 is involved in endothelial barrier regulation via its two novel interacting partners

Background

RACK1, receptor for activated protein kinase C, serves as an anchor in multiple signaling pathways. TIMAP, TGF-β inhibited membrane-associated protein, is most abundant in endothelial cells with a regulatory effect on the endothelial barrier function. The interaction of TIMAP with protein phosphatase 1 (PP1cδ) was characterized, yet little is known about its further partners.

Results

We identified two novel interacting partners of RACK1, namely, TGF-β inhibited membrane-associated protein, TIMAP, and farnesyl transferase. TIMAP is most abundant in endothelial cells where it is involved in the regulation of the barrier function. WD1-4 repeats of RACK1 were identified as critical regions of the interaction both with TIMAP and farnesyl transferase. Phosphorylation of TIMAP by activation of the cAMP/PKA pathway reduced the amount of TIMAP-RACK1 complex and enhanced translocation of TIMAP to the cell membrane in vascular endothelial cells. However, both membrane localization of TIMAP and transendothelial resistance were attenuated after RACK1 depletion. Farnesyl transferase, the enzyme responsible for prenylation and consequent membrane localization of TIMAP, is present in the RACK1-TIMAP complex in control cells, but it does not co-immunoprecipitate with TIMAP after RACK1 depletion.

Conclusions

Transient parallel linkage of TIMAP and farnesyl transferase to RACK1 could ensure prenylation and transport of TIMAP to the plasma membrane where it may attend in maintaining the endothelial barrier as a phosphatase regulator.

Environmental enrichment upregulates micro-RNA-183 and alters acetylcholinesterase splice variants to reduce anxiety-like behavior in the little Indian field mouse (Mus booduga)

Environmental enrichment (EE) has an influential role in reducing behavioral reactivity to stress. We previously observed that EE reduces the anxiety-like behavior in the field mouse Mus booduga accompanied by a reduction in the expression of molecules involved in the stress pathway. In this study, we demonstrate the effect of different housing condition on regulation of micro-RNA-183-SC35-mediated splicing of acetylcholinesterase (AChE). Adult male M. booduga were captured from an agricultural field and housed under nonenriched standard conditions (SC) for 7 days and considered as directly from the wild (DW). On day 8, individuals were randomly assigned to three groups; DW, SC, and EE. The DW group's anxiety-like behavior was assessed in the elevated plus maze (EPM) and open field test (OFT). The SC and EE groups were transferred to their respective conditions and housed for another 30 days. The mice housed in EE showed less anxiety-like behavior on EPM and in OFT compared with DW and SC mice. Interestingly, miR-183 expression was increased following exposure to EPM in EE mice but not in SC mice. Subsequently, the upregulated miR-183 expression suppresses the SC35 expression and shifting of splicing from AChE-S (synaptic) to AChE-R (read-through) form, whereas standard housing condition downregulate miR-183 and induces the splicing of AChE. The upregulated AChE-R form possibly terminates ACh transmission, which is reflected in the level of anxiety-like behavior. Overall, the present study suggests that EE effectively regulates the miR-183 pathway to reduce anxiety-like behavior.

Readthrough acetylcholinesterase is increased in human liver cirrhosis

Background & Aims

There have been many studies on plasma butyrylcholinesterase in liver dysfunction. However, no data is available about acetylcholinesterase in human cirrhosis, although profound changes have been described in cirrhotic rat models.

Methods

Human serum and liver acetylcholinesterase and its molecular forms were determined enzymatically, after butyrylcholinesterase immunodepletion. The distinct species of acetylcholinesterase, with a distinct C-terminus, were determined by western blotting, and the level of liver transcripts by real-time PCR. Liver acetylcholinesterase was also evaluated by immunocytochemistry.

Results

In patients with liver cirrhosis, the activity of plasma acetylcholinesterase (rich in light species), appeared to be apparently unaffected. However, the levels of the soluble readthrough (R) acetylcholinesterase form, an acetylcholinesterase species usually associated with stress and pathology, was increased compared to controls. Human liver acetylcholinesterase activity levels were also unchanged, but protein levels of the acetylcholinesterase-R and other acetylcholinesterase subunit species were increased in the cirrhotic liver. This increase in acetylcholinesterase protein expression in the cirrhotic liver was confirmed by PCR analysis. Immunohistological examination confirmed that acetylcholinesterase immunoreactivity is increased in parenchymal cells of the cirrhotic liver.

Conclusions

We demonstrate significant changes in acetylcholinesterase at the protein and mRNA levels in liver cirrhosis, with no difference in enzymatic activity. The altered expression of acetylcholinesterase protein may reflect changes in its pathophysiological role.

Mouse acetylcholinesterase enhances neurite outgrowth of rat R28 cells through interaction with laminin-1

The enzyme acetylcholinesterase (AChE) terminates synaptic transmission at cholinergic synapses by hydrolyzing the neurotransmitter acetylcholine, but can also exert 'non-classical', morpho-regulatory effects on developing neurons such as stimulation of neurite outgrowth. Here, we investigated the role of AChE binding to laminin-1 on the regulation of neurite outgrowth by using cell culture, immunocytochemistry, and molecular biological approaches. To explore the role of AChE, we examined fiber growth of cells overexpressing different forms of AChE, and/or during their growth on laminin-1. A significant increase of neuritic growth as compared with controls was observed for neurons over-expressing AChE. Accordingly, addition of globular AChE to the medium increased total length of neurites. Co-transfection with PRIMA, a membrane anchor of AChE, led to an increase in fiber length similar to AChE overexpressing cells. Transfection with an AChE mutant that leads to the retention of AChE within cells had no stimulatory effect on neurite length. Noticeably, the longest neurites were produced by neurons overexpressing AChE and growing on laminin-1, suggesting that the AChE/laminin interaction is involved in regulating neurite outgrowth. Our findings demonstrate that binding of AChE to laminin-1 alters AChE activity and leads to increased neurite growth in culture. A possible mechanism of the AChE effect on neurite outgrowth is proposed due to the interaction of AChE with laminin-1.

RACK1, A multifaceted scaffolding protein: Structure and function

The Receptor for Activated C Kinase 1 (RACK1) is a member of the tryptophan-aspartate repeat (WD-repeat) family of proteins and shares significant homology to the β subunit of G-proteins (Gβ). RACK1 adopts a seven-bladed β-propeller structure which facilitates protein binding. RACK1 has a significant role to play in shuttling proteins around the cell, anchoring proteins at particular locations and in stabilising protein activity. It interacts with the ribosomal machinery, with several cell surface receptors and with proteins in the nucleus. As a result, RACK1 is a key mediator of various pathways and contributes to numerous aspects of cellular function. Here, we discuss RACK1 gene and structure and its role in specific signaling pathways, and address how posttranslational modifications facilitate subcellular location and translocation of RACK1. This review condenses several recent studies suggesting a role for RACK1 in physiological processes such as development, cell migration, central nervous system (CN) function and circadian rhythm as well as reviewing the role of RACK1 in disease.

ATP induces synaptic gene expressions in cortical neurons: transduction and transcription control via P2Y1 receptors

Studies in vertebrate neuromuscular synapses have revealed previously that ATP, via P2Y receptors, plays a critical role in regulating postsynaptic gene expressions. An equivalent regulatory role of ATP and its P2Y receptors would not necessarily be expected for the very different situation of the brain synapses, but we provide evidence here for a brain version of that role. In cultured cortical neurons, the expression of P2Y(1) receptors increased sharply during neuronal differentiation. Those receptors were found mainly colocalized with the postsynaptic scaffold postsynaptic density protein 95 (PSD-95). This arises through a direct interaction of a PDZ domain of PSD-95 with the C-terminal PDZ-binding motif, D-T-S-L of the P2Y(1) receptor, confirmed by the full suppression of the colocalization upon mutation of two amino acids therein. This interaction is effective in recruiting PSD-95 to the membrane. Specific activation of P2Y(1) (G-protein-coupled) receptors induced the elevation of intracellular Ca(2+) and activation of a mitogen-activated protein kinase/Raf-1 signaling cascade. This led to distinct up-regulation of the genes encoding acetylcholinesterase (AChE(T) variant), choline acetyltransferase, and the N-methyl-d-aspartate receptor subunit NR2A. This was confirmed, in the example of AChE, to arise from P2Y(1)-dependent stimulation of a human ACHE gene promoter. That involved activation of the transcription factor Elk-1; mutagenesis of the ACHE promoter revealed that Elk-1 binding at its specific responsive elements in that promoter was induced by P2Y(1) receptor activation. The combined findings reveal that ATP, via its P2Y(1) receptor, can act trophically in brain neurons to regulate the gene expression of direct effectors of synaptic transmission.

Rosmarinus officinalis polyphenols activate cholinergic activities in PC12 cells through phosphorylation of ERK1/2

AIM OF THE STUDY

This paper aimed to elucidate the traditional use of Rosmarinus officinalis through the investigation of cholinergic activities and neuronal differentiation in rat pheochromocytoma PC12 cells. These effects were examined in relation to the plant's habitat, the extraction procedure, and the major active compounds of R. officinalis.

MATERIALS AND METHODS

Cell viability, cell differentiation, acetylcholinesterase (AChE) activity, total choline, acetylcholine (ACh) and extracellular signal-regulated kinases (ERK1/2) were determined in PC12 cells treated with extracts and HPLC-identified polyphenols of R. officinalis originated from Tunisian semi-arid and subhumid area in comparison with nerve growth factor (NGF).

RESULTS

R. officinalis extracts potentiated cell differentiation and significantly enhanced AChE activity in PC12 cells. The highest AChE activity was induced by semi-arid hydro-ethanolic extract (137% of control). Among HPLC-identified and screened polyphenols, carnosic acid (CA) and rosmarinic acid (RA) significantly induced cell differentiation, increased ACh level, and enhanced AChE activity in PC12 cells. U0126, inhibitor of ERK1/2, significantly reduced CA and RA effects on cell differentiation and AChE activity.

CONCLUSIONS

R. officinalis' CA and RA exhibited neurotrophic effects in PC12 cells through cell differentiation induction and cholinergic activities enhancement. These effects could be regulated by mitogen-activated protein kinase (MAPK), ERK1/2 signaling pathway.

Strain and regional dependence of alternate splicing of acetylcholinesterase in the murine brain following stress or treatment with diisopropylfluorophosphate

Induction of the rare readthrough variant of acetylcholinesterase (AChE-R) by an acetylcholinesterase (AChE) inhibitor or by stress was tested in four mouse strains that differ in their behavioural profiles on tests of anxiety and depression. BALB/C, C57Bl/6, C3H/He and CD-1 mouse strains were tested in the elevated plus maze in two sessions, separated by 48h. All strains, except CD-1, showed the expected reduction in open arm exploration on the second session. BALB/C and C3H mice spent a greater proportion of the time in the open arms on the first exposure, but spent more time immobile in the maze compared to the CD1 and C57 strains. Immobility was attenuated upon the second exposure in all strains, except the BALB/C mice. Real-time PCR was used to investigate regional and strain differences in induction of AChE-R mRNA following four daily injections of diisopropylfluorophosphate (DFP) (.1mg/kg). AChE-R induction was found in the frontal cortex, but not in amygdala, hippocampus or striatum of CD-1 mice. Nor was there AChE-R induction in the brains of the inbred strains. Four daily sessions of swim stress were used to investigate stress-induced induction of AChE-R. BALB/C mice showed significantly more immobility in the forced swim test (FST) compared to the other strains. FST did not induce AChE-R mRNA in any brain region tested; however, AChE-R mRNA expression in the frontal cortex was negatively correlated with immobility in the FST.

Drastic decrease in dopamine receptor levels in the striatum of acetylcholinesterase knock-out mouse

BACKGROUND

The acetylcholinesterase knock-out mouse lives to adulthood despite 60-fold elevated acetylcholine concentrations in the brain that are lethal to wild-type animals. Part of its mechanism of survival is a 50% decrease in muscarinic and nicotinic receptors and a 50% decrease in adrenoceptor levels.

HYPOTHESIS

The hypothesis was tested that the dopaminergic neuronal system had also adapted.

METHODS

Radioligand binding assays measured dopamine receptor level and binding affinity in the striatum. Immunohistochemistry of brain sections with specific antibodies visualized dopamine transporter. Effects on the intracellular compartment were measured as cAMP content, PI-phospholipase C activity.

RESULTS

Dopamine receptor levels were decreased 28-fold for the D(1)-like, and more than 37-fold for the D(2)-like receptors, though binding affinity was normal. Despite these huge changes in receptor levels, dopamine transporter levels were not affected. The intracellular compartment had normal levels of cAMP and PI-phospholipase C activity.

CONCLUSION

Survival of the acetylcholinesterase knock-out mouse could be linked to adaptation of many neuronal systems during development including the cholinergic, adrenergic and dopaminergic. These adaptations balance the overstimulation of cholinergic receptors caused by high acetylcholine concentrations and thus maintain homeostasis inside the cell, allowing the animal to live.

Expression of receptor for activated C kinase 1 in healing skin and mucosal wounds

Postnatal (adult) mammalian wound healing results in the formation of scar, whereas fetal mammals are able to effect wound repair without scar. We have investigated the expression pattern of the receptor of activated C kinase 1 (RACK1), a pleiotropic G-protein-like molecule, in healing skin and mucosal wounds in a rabbit model after obtaining a full-length clone of the rabbit RACK1 cDNA. In both adult skin and mucosal wounds, RACK1 mRNA expression is decreased relative to unwounded controls. In contrast, in fetal skin wounds RACK1 expression is unaltered from fetal control. Fibroblasts derived from adult skin tissue express more RACK1 message than fetal skin fibroblasts. These observations suggest that RACK1 may play an important role in distinguishing scarless fetal wound healing from its scirrhous counterpart in adults.

RanBPM is an acetylcholinesterase-interacting protein that translocates into the nucleus during apoptosis

Acetylcholinesterase (AChE) expression may be induced during apoptosis in various cell types. Here, we used the C-terminal of AChE to screen the human fetal brain library and found that it interacted with Ran-binding protein in the microtubule-organizing center (RanBPM). This interaction was further confirmed by coimmunoprecipitation analysis. In HEK293T cells, RanBPM and AChE were heterogeneously expressed in the cisplatin-untreated cytoplasmic extracts and in the cisplatin-treated cytoplasmic or nuclear extracts. Our previous studies performed using morphologic methods have shown that AChE translocates from the cytoplasm to the nucleus during apoptosis. Taken together, these results suggest that RanBPM is an AChE-interacting protein that is translocated from the cytoplasm into the nucleus during apoptosis, similar to the translocation observed in case of AChE.

The aryl acylamidase activity is much more sensitive to Alzheimer drugs than the esterase activity of acetylcholinesterase in chicken embryonic brain

The appearance of cholinergic trait often precedes synaptogenesis, indicating the involvement of cholinesterase proteins in nervous system development, particularly so acetylcholinesterase (AChE). In addition to AChE's acclaimed esterase activity, its lesser known non-cholinergic functions have gained much attention, because of AChE protein expression in areas other than cholinergic innervations; one such function could be exerted by its associated aryl acylamidase (AAA) activity. In this study, an attempt has been made in profiling esterase and AAA activities of AChE at different developmental stages of the chick embryo, e.g. at embryonic day 6 (E6), E9, E12, E15 and E18. AAA activity showed a correlated expression with esterase activity at all stages, but the relative ratios of AAA to esterase activity were higher at younger stages. The inhibition of AAA activity was shown to be more sensitive towards Huperzine, Donepezil whereas inhibition of esterase activity was sensitive to Tacrine and DFP. Remarkably, the major Alzheimer drugs- Huperzine and Donepezil, much more strongly inhibited AAA activity of AChE at younger developmental stages whose IC50 values are 0.01 muM and 0.1 muM respectively. In the case of BW284c51, inhibition was more pronounced at older stages and IC50 value was 0.1 muM. Since in Alzheimer's disease (AD), embryonic forms of AChE have been reported to reappear, a possible role of AAA activity in the pathogenesis of AD should be considered.

Involvement of the PRKCB1 gene in autistic disorder: significant genetic association and reduced neocortical gene expression

Protein kinase C enzymes play an important role in signal transduction, regulation of gene expression and control of cell division and differentiation. The fsI and betaII isoenzymes result from the alternative splicing of the PKCbeta gene (PRKCB1), previously found to be associated with autism. We performed a family-based association study in 229 simplex and 5 multiplex families, and a postmortem study of PRKCB1 gene expression in temporocortical gray matter (BA41/42) of 11 autistic patients and controls. PRKCB1 gene haplotypes are significantly associated with autism (P<0.05) and have the autistic endophenotype of enhanced oligopeptiduria (P<0.05). Temporocortical PRKCB1 gene expression was reduced on average by 35 and 31% for the PRKCB1-1 and PRKCB1-2 isoforms (P<0.01 and <0.05, respectively) according to qPCR. Protein amounts measured for the PKCbetaII isoform were similarly decreased by 35% (P=0.05). Decreased gene expression characterized patients carrying the 'normal' PRKCB1 alleles, whereas patients homozygous for the autism-associated alleles displayed mRNA levels comparable to those of controls. Whole genome expression analysis unveiled a partial disruption in the coordinated expression of PKCbeta-driven genes, including several cytokines. These results confirm the association between autism and PRKCB1 gene variants, point toward PKCbeta roles in altered epithelial permeability, demonstrate a significant downregulation of brain PRKCB1 gene expression in autism and suggest that it could represent a compensatory adjustment aimed at limiting an ongoing dysreactive immune process. Altogether, these data underscore potential PKCbeta roles in autism pathogenesis and spur interest in the identification and functional characterization of PRKCB1 gene variants conferring autism vulnerability.

Rationally designed peptide regulators of protein kinase C

Protein-protein interactions sequester enzymes close to their substrates. Protein kinase C (PKC) is one example of a ubiquitous signaling molecule with effects that are dependent upon localization. Short peptides derived from interaction sites between each PKC isozyme and its receptor for activated C kinase act as highly specific inhibitors and have become available as selective drugs in basic research and animal models of human diseases, such as myocardial infarction and hyperglycemia. Whereas the earlier inhibitory peptides are highly specific, we believe that peptides targeting additional interactions between PKC and selective substrates will generate even more selective tools that regulate different functions of individual isozymes. Here, we discuss the methodologies and applications for identifying selective regulators of PKC.

The physiological basis of intracrine stem cell regulation

Intracrine peptides and proteins participate in the regulation of adult and pleuripotential embryonic-like stem cells. Included among these factors are VEGF, dynorphin, the readthrough form of acetylcholinesterase, Oct3/4, Pdx-1, Pax-6, and high-mobility group protein B1, among others. In some cases, the establishment of intracrine feedback loops can be shown to be relevant to this regulation, consistent with previously proposed principles of intracrine action. Here the role of intracrines in stem cell regulation is reviewed, with particular attention to the intracrine regulation of cardiac stem cells. The reprogramming of cells to restore the pleuripotent phenotype and the possible role of stem/progenitor cells in neoplasia are also discussed.

Alternate AChE-R variants facilitate cellular metabolic activity and resistance to genotoxic stress through enolase and RACK1 interactions

Tumorogenic transformation is a multifaceted cellular process involving combinatorial protein-protein interactions that modulate different cellular functions. Here, we report apparent involvement in two independent tumorogenic processes by distinct partner protein interactions of the stress-induced acetylcholinesterase AChE-R and N-AChE-R variants. Human testicular tumors showed elevated levels of N-terminally extended N-AChE-R compared with healthy tissue, indicating alternate promoter usage in the transformed cells. Two-hybrid screens demonstrate that the C-terminus common to both N-AChE-R and AChE-R interacts either with the glycolytic enzyme enolase or with the scaffold protein RACK1. In vitro, the AChE-R C-terminal peptide ARP elevated enolase's activity by 12%, suggesting physiological relevance for this interaction. Correspondingly, CHO cells expressing either human AChE-R or N-AChE-R but not AChE-S showed a 25% increase in cellular ATP levels, indicating metabolic significance for this upregulation of enolase activity. ATP levels could be reduced by AChE-targeted siRNA in CHO cells expressing AChE-R but not AChE-S, attributing this elevation to the AChE-R C-terminus. Additionally, transfected CHO cells expressing AChE-R but not N-AChE-R showed resistance to up to 60 microM of the common chemotherapeutic agent, cis-platinum, indicating AChE-R involvement in another molecular pathway. cis-Platinum elevates the expression of the apoptosis-regulator p53-like protein, p73, which is inactivated by interaction with the scaffold protein RACK1. In co-transfected cells, AChE-R competed with endogenous RACK1 for p73 interaction. Moreover, AChE-R-transfected CHO cells presented higher levels than control cells of the pro-apoptotic TAp73 as well as the anti-apoptotic dominant negative DeltaNp73 protein, leading to an overall decrease in the proportion of pro-apoptotic p73. Together, these findings are compatible with the hypothesis that in cancer cells, both AChE-R and N-AChE-R elevate cellular ATP levels and that AChE-R modifies p73 gene expression by facilitating two independent cellular pathways, thus conferring both a selective metabolic advantage and a genotoxic resistance.

Acetylcholinesterase readthrough peptide shares sequence similarity to the 28-53 peptide sequence of the acetylcholinesterase adhesion-mediating site and competes for ligand binding in vitro

It has been reported that unlike the more commonly expressed splice variants, the embryonic and stress-associated readthrough form of acetylcholinesterase (AChE-R) is unable to promote cell adhesion and neurite outgrowth. We investigated the possibility that the unique AChE-R C-terminal peptide (ARP) might be responsible for this difference, either by binding to AChE itself and inactivating the adhesion-mediating site or by competing with AChE for ligand binding. Synthetic peptides representing the ARP, a scrambled version of the ARP, and sequences of the previously identified adhesion-mediating site on AChE were used in in vitro binding and neuroblastoma cell-spreading assays. It was observed that the ARP was able to bind to laminin-1, identified previously as an in vitro AChE ligand and, to a lesser extent, to collagen IV and to AChE itself. ARP-AChE binding was, however, of very low affinity and was not significantly affected by peripheral site inhibitors, suggesting that inactivation of the AChE adhesion site is not the reason for AChE-R's antiadhesive character. On the other hand, the ARP competed with AChE and the adhesion site peptides for binding to laminin in vitro, and the ARP was observed to inhibit cell spreading in neuroblastoma cells grown on laminin. Monoclonal antibodies recognizing the known AChE adhesion site reacted with the ARP, suggesting structural similarities. These were borne out by an examination of sequence alignments of the ARP and the 28-53 AChE sequence. The ARP contains part of the PPxxxxRFxPPEP motif seen in AChEs and cholinesterase-domain proteins, and both it and the 37-53 sequence bear some resemblance to collagen and collagen-like proteins. It therefore appears likely that the ARP's structural similarity to the AChE adhesion-mediating site is the basis for the observed competition for ligand binding and might account for the antiadhesive characteristics of AChE-R.

Acetylcholinesterase in cell adhesion, neurite growth and network formation

The expression of acetylcholinesterase is not restricted to cholinergically innervated tissues and relates to both neurotransmission and multiple biological aspects, including neural development, stress response and neurodegenerative diseases. Therefore, the classical function of acetylcholinesterase has to be distinguished from its non-classical, e.g. enzymatic from non-enzymatic, functions. Here, the roles of acetylcholinesterase in cell adhesion, promoting neurite outgrowth and neural network formation are reviewed briefly, together with potential mechanisms to support these functions. Part of these functions may depend on the structural properties of acetylcholinesterase, for example, protein-protein interactions. Recent findings have revealed that laminin-1 is an interaction partner for acetylcholinesterase. The binding of acetylcholinesterase to this extracellular matrix component may allow cell-to-cell recognition, and also cell signalling via membrane receptors. Studies using monolayer and 3D spheroid retinal cultures, as well as the acetylcholinesterase-knockout mouse, have been instrumental in elaborating the non-classical functions of acetylcholinesterase.

Acetylcholinesterase and apoptosis. A novel perspective for an old enzyme

Acetylcholinesterase is indispensable for terminating acetylcholine-mediated neurotransmission at cholinergic synapses. In addition, there is evidence to suggest that acetylcholinesterase contributes to various physiological processes through its involvement in the regulation of cell proliferation, differentiation and survival. The effects of acetylcholinesterase depend on the cell type and cell-differentiation state, the modulation of expression levels, cellular distribution and binding with its protein partners. This minireview highlights recent progress that has advanced our understanding of the role of acetylcholinesterase in the process of cell proliferation and apoptosis.

Acetylcholinesterase-R increases germ cell apoptosis but enhances sperm motility

Changes in protein subdomains through alternative splicing often modify protein-protein interactions, altering biological processes. A relevant example is that of the stress-induced up-regulation of the acetylcholinesterase (AChE-R) splice variant, a common response in various tissues. In germ cells of male transgenic TgR mice, AChE-R excess associates with reduced sperm differentiation and sperm counts. To explore the mechanism(s) by which AChE-R up-regulation affects spermatogenesis, we identified AChE-R's protein partners through a yeast two-hybrid screen. In meiotic spermatocytes from TgR mice, we detected AChE-R interaction with the scaffold protein RACK1 and elevated apoptosis. This correlated with reduced scavenging by RACK1 of the pro-apoptotic TAp73, an outcome compatible with the increased apoptosis. In contrast, at later stages in sperm development, AChE-R's interaction with the glycolytic enzyme enolase-α elevates enolase activity. In transfected cells, enforced AChE-R excess increased glucose uptake and adenosine tri-phosphate (ATP) levels. Correspondingly, TgR sperm cells display elevated ATP levels, mitochondrial hyperactivity and increased motility. In human donors' sperm, we found direct association of sperm motility with AChE-R expression. Interchanging interactions with RACK1 and enolase-α may hence enable AChE-R to affect both sperm differentiation and function by participating in independent cellular pathways.

The role of the read through variant of acetylcholinesterase in anxiogenic effects of predator stress in mice

This study examined the role of the read through variant of acetylcholinesterase (AChE-R) in lasting changes in murine affective behavior produced by a brief predator stress. AChE-R is elevated by stress in limbic cholinergic circuits implicated in anxiogenic effects of predator stress. The expression of AChE-R was blocked with a systemically administered central acting antisense oligonucleotide for AChE-R (EN101). EN101 was injected at multiple points prior to and after a predator stress in male C57 mice. Seven days after the last injection, behavior was tested. Predator stress caused a significant increase in startle amplitude, which EN101 blocked. This effect was specific to EN101, as the negative control inactive form of EN101, INVEN101 was without effect on stress effects on startle. Neither EN101 nor INVEN101 altered the anxiogenic effects of predator stress on behavior in the elevated plus maze, and both drugs partially reduced stress suppression of time active in the hole board. In the light dark box test, INVEN101 exhibited a weak block of stress effects on behavior for reasons which are unclear. Taken together, findings support the view that multiple neural systems are responsible for the different changes in behavior produced by predator stress. Present findings also suggest a role for AChE-R in specific anxiogenic (hyperarousal) effects following predator stress. Since AChE-R manipulations took place starting 23 h prior to predator stress and continued 48 h after predator stress, further research is necessary to determine the role of AChE-R in initiation and/or consolidation of hyperarousal effects of predator stress.

IP3 receptor/Ca2+ channel: from discovery to new signaling concepts

Inositol 1,4,5-trisphosphate (IP(3)) is a second messenger that induces the release of Ca(2+) from the endoplasmic reticulum (ER). The IP(3) receptor (IP(3)R) was discovered as a developmentally regulated glyco-phosphoprotein, P400, that was missing in strains of mutant mice. IP(3)R can allosterically and dynamically change its form in a reversible manner. The crystal structures of the IP(3)-binding core and N-terminal suppressor sequence of IP(3)R have been identified. An IP(3) indicator (known as IP(3)R-based IP(3) sensor) was developed from the IP(3)-binding core. The IP(3)-binding core's affinity to IP(3) is very similar among the three isoforms of IP(3)R; instead, the N-terminal IP(3) binding suppressor region is responsible for isoform-specific IP(3)-binding affinity tuning. Various pathways for the trafficking of IP(3)R have been identified; for example, the ER forms a meshwork upon which IP(3)R moves by lateral diffusion, and vesicular ER subcompartments containing IP(3)R move rapidly along microtubles using a kinesin motor. Furthermore, IP(3)R mRNA within mRNA granules also moves along microtubules. IP(3)Rs are involved in exocrine secretion. ERp44 works as a redox sensor in the ER and regulates IP(3)R1 activity. IP(3) has been found to release Ca(2+), but it also releases IRBIT (IP(3)R-binding protein released with IP(3)). IRBIT is a pseudo-ligand for IP(3) that regulates the frequency and amplitude of Ca(2+) oscillations through IP(3)R. IRBIT binds to pancreas-type Na, bicarbonate co-transporter 1, which is important for acid-base balance. The presence of many kinds of binding partners, like homer, protein 4.1N, huntingtin-associated protein-1A, protein phosphatases (PPI and PP2A), RACK1, ankyrin, chromogranin, carbonic anhydrase-related protein, IRBIT, Na,K-ATPase, and ERp44, suggest that IP(3)Rs form a macro signal complex and function as a center for signaling cascades. The structure of IP(3)R1, as revealed by cryoelectron microscopy, fits closely with these molecules.