A Novel Effect of PDLIM5 In α7 Nicotinic Acetylcholine Receptors Up-Regulation And Surface Expression

α7 neuronal nicotinic acetylcholine receptors (α7nAChRs) are expressed widely in the brain, where they contribute to a variety of behaviors including arousal and cognition, participate in a number of neurodegenerative disorders including Alzheimer’s and Parkinson’s disease, and is responsible for nicotine addiction. Although recent studies indicate that the PDZ-containing proteins comprising PSD-95 family co-localize with nicotinic acetylcholine receptors and mediate downstream signaling in the neurons, the mechanisms by which α7nAChRs are regulated are still less well understood. Here we show that the regulation of the α7nAChRs is controlled by PDLIM5 in the endogenous PDZ domain proteins family. We find that chronic exposure to 1 μM nicotine up-regulated both α7, β2-contained nAChRs and PDLIM5 in primary cultured hippocampal neurons, and the up-regulation of α7nAChRs and PDLIM5 is increased more on the cell membrane than the cytoplasm. Interestingly, the α7nAChRs and β2nAChRs display distinct patterns of expression, with α7 co-localized more with PDLIM5. Meanwhile, PDLIM5 interacts with native brain α7 but not β2 nAChRs in neurons. Moreover, knocking down of PDLIM5 in heterologous cells abolishes nicotine-induced up-regulation of α7nAChRs. In cultured hippocampal neurons, shRNA against PDLIM5 decreased both surface clustering of α7nAChRs and α7nAChRs mediated currents. Proteomics analysis shows PDLIM5 interacts with α7nAChRs through the PDZ domain and the interaction between PDLIM5 and α7nAChRs can be promoted by nicotine. Collectively, our data suggest a novel cellular role of PDLIM5 in regulating α7nAChRs, which may be relevant to plastic changes in the nervous system.

An Overview on the Effect of Neonicotinoid Insecticides on Mammalian Cholinergic Functions through the Activation of Neuronal Nicotinic Acetylcholine Receptors

Neonicotinoid insecticides are used worldwide and have been demonstrated as toxic to beneficial insects such as honeybees. Their effectiveness is predominantly attributed to their high affinity for insect neuronal nicotinic acetylcholine receptors (nAChRs). Mammalian neuronal nAChRs are of major importance because cholinergic synaptic transmission plays a key role in rapid neurotransmission, learning and memory processes, and neurodegenerative diseases. Because of the low agonist effects of neonicotinoid insecticides on mammalian neuronal nAChRs, it has been suggested that they are relatively safe for mammals, including humans. However, several lines of evidence have demonstrated that neonicotinoid insecticides can modulate cholinergic functions through neuronal nAChRs. Major studies on the influence of neonicotinoid insecticides on cholinergic functions have been conducted using nicotine low-affinity homomeric α7 and high-affinity heteromeric α4β2 receptors, as they are the most abundant in the nervous system. It has been found that the neonicotinoids thiamethoxam and clothianidin can activate the release of dopamine in rat striatum. In some contexts, such as neurodegenerative diseases, they can disturb the neuronal distribution or induce oxidative stress, leading to neurotoxicity. This review highlights recent studies on the mode of action of neonicotinoid insecticides on mammalian neuronal nAChRs and cholinergic functions.

In Silico Analysis of Ethanol Binding Activity in Neuronal Nicotinic Acetylcholine Receptors

Ethanol and nicotine are two common substances that are often linked to complications in alcoholic smokers. The high number of the co-consumptions in alcoholic smokers suggested a possible interaction between ethanol and nicotine in the central nervous system and a potential similar mechanism of action. Both ethanol and nicotine are shown to bind with neuronal nicotinic acetylcholine receptors (nAChRs), a ligand gated cation channel specifically targeted by the endogenous acetylcholine. Ethanol has a much less specific binding capability to modulate the receptors, however, emerging reports indicates that ethanol can interact with nAChRs both directly and indirectly. This study focuses on the analysis of ethanol binding sites with nAChRs using molecular docking techniques obtained from the Protein Data Bank. The obtained data showed a possible binding site for ethanol in nAChRs, however, upon validation, result is not substantial. Nevertheless, the obtained data should be useful for future reference for the basis of ethanol interactions with the human nAChRs proteins.

Acute Administration of Desformylflustrabromine Relieves Chemically Induced Pain in CD-1 Mice

Neuronal nicotinic acetylcholine receptors are cell membrane-bound ion channels that are widely distributed in the central nervous system. The α4β2 subtype of neuronal nicotinic acetylcholine receptor plays an important role in modulating the signaling pathways for pain. Previous studies have shown that agonists, partial agonists, and positive allosteric modulators for the α4β2 receptors are effective in relieving pain. Desformylflustrabromine is a compound that acts as an allosteric modulator of α4β2 receptors. The aim of this study was to assess the effects of desformylflustrabromine on chemically induced pain. For this purpose, the formalin-induced pain test and the acetic acid-induced writhing response test were carried out in CD-1 mice. Both tests represent chemical assays for nociception. The results show that desformylflustrabromine is effective in producing an analgesic effect in both tests used for assessing nociception. These results suggest that desformylflustrabromine has the potential to become a clinically used drug for pain relief.