Nicotine-induced Ca2+-myristoyl switch of neuronal Ca 2+ sensor VILIP-1 in hippocampal neurons: A possible crosstalk mechanism for nicotinic receptors
ABSTRACT Visinin-like protein (VILIP-1) belongs to the neuronal Ca2+ sensor family of EF-hand Ca2+-binding proteins that regulate a variety of Ca2+-dependent signal transduction processes in neurons. It is an interaction partner of alpha4beta2 nicotinic acetylcholine receptor (nAChR) and increases surface expression level and agonist sensitivity of the receptor in oocytes. Nicotine stimulation of nicotinic receptors has been reported to lead to an increase in intracellular Ca2+ concentration by Ca2+-permeable nAChRs, which in turn might lead to activation of VILIP-1, by a mechanism described as the Ca2+-myristoyl switch. It has been postulated that this will lead to co-localization of the proteins at cell membranes, where VILIP-1 can influence functional activity of alpha4-containing nAChRs. In order to test this hypothesis we have investigated whether a nicotine-induced and reversible Ca2+-myristoyl switch of VILIP-1 exists in primary hippocampal neurons and whether pharmacological agents, such as antagonist specific for distinct nAChRs, can interfere with the Ca2+-dependent membrane localization of VILIP-1. Here we report, that only alpha7- but not alpha4-containing nAChRs are able to elicit a Ca2+-dependent and reversible membrane-translocation of VILIP-1 in interneurons as revealed by employing the specific receptor antagonists dihydro-beta-erythroidine and methylallylaconitine. The nAChRs are associated with processes of synaptic plasticity in hippocampal neurons and they have been implicated in the pathology of CNS disorders, including Alzheimer's disease and schizophrenia. VILIP-1 might provide a novel functional crosstalk between alpha4- and alpha7-containing nAChRs.
- SourceAvailable from: Burt Sharp
[Show abstract] [Hide abstract]
- "Vsnl1 interacts directly with the alpha4 subunit of the most abundant brain nicotinic cholinergic receptor (nAChR), alpha4beta2, increasing the surface expression of functional receptors, depending on Ca 2+ concentration (Zhao et al., 2009b). In contrast, alpha7- containing nAChRs elicit a calcium-dependent membrane localization of Vsnl1 (Zhao et al., 2009a). The inward Ca 2+ current induced by nicotinic stimulation of alpha7 nAChRs (Berg et al., 2006) may drive the activation and membrane localization of Vsnl1 that is associated with upregulation of alpha4beta2 nAChRs. "
ABSTRACT: Inbred Lewis and Fisher 344 rat strains differ greatly in drug self-administration; Lewis rats operantly self-administer drugs of abuse including nicotine, whereas Fisher self-administer poorly. As shown herein, operant food self-administration is similar. On the basis of their pivotal role in drug reward, we hypothesized that differences in basal gene expression in GABAergic neurons projecting from nucleus accumbens (NAcc) to ventral pallidum (VP) play a role in vulnerability to drug-taking behavior. The transcriptomes of NAcc shell-VP GABAergic neurons from these two strains were analyzed in adolescents, using a multidisciplinary approach that combined stereotaxic ionotophoretic brain microinjections, laser-capture microdissection (LCM) and microarray measurement of transcripts. Laser-capture microdissection enriched the gene transcripts detected in gamma-aminobutyric acid (GABA) neurons compared to the residual NAcc tissue: a ratio of neuron/residual >1 and false discovery rate (FDR) <5% yielded 6623 transcripts, whereas a ratio of >3 yielded 3514. Strain-dependent differences in gene expression within GABA neurons were identified; 322 vs. 60 transcripts showed 1.5-fold vs. 2-fold differences in expression (FDR < 5%). Classification by gene ontology showed that these 322 transcripts were widely distributed, without categorical enrichment. This is most consistent with a global change in GABA neuron function. Literature mining by Chilibot found 38 genes related to synaptic plasticity, signaling and gene transcription, all of which determine drug abuse; 33 genes have no known association with addiction or nicotine. In Lewis rats, upregulation of Mint-1, Cask, CamkII , Ncam1, Vsnl1, Hpcal1 and Car8 indicates that these transcripts likely contribute to altered signaling and synaptic function in NAcc GABA projection neurons to VP.Genes Brain and Behavior 07/2011; 10(7):778-88. DOI:10.1111/j.1601-183X.2011.00716.x · 3.51 Impact Factor
[Show abstract] [Hide abstract]
- "We observed intense punctate labeling on both the soma and neurites of a subpopulation of neurons (Fig. 8a and b). Based on the labeling pattern found here and previous identification of hippocampal neuron subtypes that express functional α7 nAChRs (Buhler & Dunwiddie 2002, Szabo et al. 2008, Zhao et al. 2009), we predict that these cells are interneurons. Preincubating the cultured neurons with 10 μM α-BgTx reduced the intensity of the labeling to a level indistinguishable from background (Fig. 8c). "
ABSTRACT: The alpha7* (*denotes the possible presence of additional subunits) nicotinic acetylcholine receptor (nAChR) subtype is widely expressed in the vertebrate nervous system and implicated in neuropsychiatric disorders that compromise thought and cognition. In this report, we demonstrate that the recently developed fluorescent ligand Cy3-ArIB[V11L;V16A] labels alpha7 nAChRs in cultured hippocampal neurons. However, photobleaching of this ligand during long image acquisition times prompted us to develop a new derivative. In photostability studies, this new ligand, Alexa Fluor 546-ArIB[V11L;V16A], was significantly more resistant to bleaching than the Cy3 derivative. The classic alpha7 ligand alpha-bungarotoxin binds to alpha1* and alpha9* nAChRs. In contrast, Alexa Fluor 546-ArIB[V11L;V16A] potently (IC(50) 1.8 nM) and selectively blocked alpha7 nAChRs but not alpha1* or alpha9* nAChRs expressed in Xenopus oocytes. Selectivity was further confirmed by competition binding studies of native nAChRs in rat brain membranes. The fluorescence properties of Alexa Fluor 546-ArIB[V11L;V16A] were assessed using human embryonic kidney-293 cells stably transfected with nAChRs; labeling was observed on cells expressing alpha7 but not cells expressing alpha3beta2, alpha3beta4, or alpha4beta2 nAChRs. Further imaging studies demonstrate that Alexa Fluor 546-ArIB[V11L;V16A] labels hippocampal neurons from wild-type mice but not from nAChR alpha7 subunit-null mice. Thus, Alexa Fluor 546-ArIB[V11L;V16A] represents a potent and selective ligand for imaging alpha7 nAChRs.Journal of Neurochemistry 08/2010; 114(4):994-1006. DOI:10.1111/j.1471-4159.2010.06819.x · 4.24 Impact Factor
Biochemical Pharmacology 10/2009; 78(7):903-903. DOI:10.1016/j.bcp.2009.06.039 · 4.65 Impact Factor
- "We observed intense punctate labeling on both the soma and neurites of a subpopulation of neurons (Fig. 8a and b). Based on the labeling pattern found here and previous identification of hippocampal neuron subtypes that express functional a7 nAChRs (Buhler and Dunwiddie 2002; Szabo et al. 2008; Zhao et al. 2009), we predict that these cells are interneurons . Pre-incubating the cultured neurons with 10 lM a- BgTx reduced the intensity of the labeling to a level indistinguishable from background (Fig. 8c). "