The molecular mechanisms that regulate survival of embryonic neural precursors are still relatively ill-defined. Here, we have asked whether the p53 family member p63 plays any role during this developmental window, focusing on the embryonic cerebral cortex. We show that genetic knockdown of p63 either in culture or in the embryonic telencephalon causes apoptosis of cortical precursors and newly born cortical neurons, and that this can be rescued by expression of ΔNp63, but not TAp63 isoforms. This cortical precursor apoptosis is the consequence of deregulated p53 activity, since both basal precursor apoptosis and that induced by loss of p63 are rescued by coincident genetic silencing of p53. Finally, we demonstrate that the third p53 family member, ΔNp73, does not regulate survival of cortical precursor cells, but that it collaborates with ΔNp63 to ensure the survival of newly born cortical neurons. Thus, the balance of ΔNp63 versus p53 determines the life versus death of embryonic cortical precursors, a ...

The transduction current in several different types of sensory neurons arises from the activity of cyclic nucleotide-gated (CNG) ion channels. The channels in these sensory neurons vary in structure and function, yet each one demonstrates calcium-dependent modulation of ligand sensitivity mediated by the interaction of the channel with a soluble modulator protein. In cone photoreceptors, the molecular identity of the modulator protein was previously unknown. We report the discovery and characterization of CNG-modulin, a novel 301 aa protein that interacts with the N terminus of the β subunit of the cGMP-gated channel and modulates the cGMP sensitivity of the channels in cone photoreceptors of striped bass ( Morone saxatilis ). Immunohistochemistry and single-cell PCR demonstrate that CNG-modulin is expressed in cone but not rod photoreceptors. Adding purified recombinant CNG-modulin to cone membrane patches containing the native CNG channels shifts the midpoint of cGMP dependence from ∼91 μm in the absence...

Cav1 (L-type) channels and calmodulin-dependent protein kinase II (CaMKII) are key regulators of Ca2+ signaling in neurons. CaMKII directly potentiates the activity of Cav1.2 and Cav1.3 channels, but the underlying molecular mechanisms are incompletely understood. Here, we report that the CaMKII-associated protein densin is required for Ca2+-dependent facilitation of Cav1.3 channels. While neither CaMKII nor densin independently affects Cav1.3 properties in transfected HEK293T cells, the two together augment Cav1.3 Ca2+ currents during repetitive, but not sustained, depolarizing stimuli. Facilitation requires Ca2+, CaMKII activation, and its association with densin, as well as densin binding to the Cav1.3 α1 subunit C-terminal domain. Cav1.3 channels and densin are targeted to dendritic spines in neurons and form a complex with CaMKII in the brain. Our results demonstrate a novel mechanism for Ca2+-dependent facilitation that may intensify postsynaptic Ca2+ signals during high-frequency stimulation.

Relapse to drug use can be initiated by drug-associated cues. The intensity of cue-induced relapse is correlated with the induction of transient synaptic potentiation (t-SP) at glutamatergic synapses on medium spiny neurons (MSNs) in the nucleus accumbens core (NAcore) and requires spillover of glutamate from prefrontal cortical afferents. We used a rodent self-administration/reinstatement model of relapse to show that cue-induced t-SP and reinstated cocaine seeking result from glutamate spillover, initiating a metabotropic glutamate receptor 5 (mGluR5)-dependent increase in nitric oxide (NO) production. Pharmacological stimulation of mGluR5 in NAcore recapitulated cue-induced reinstatement in the absence of drug-associated cues. Using NO-sensitive electrodes, mGluR5 activation by glutamate was shown to stimulate NO production that depended on activation of neuronal nitric oxide synthase (nNOS). nNOS is expressed in ∼1% of NAcore neurons. Using a transgene strategy to express and stimulate designer recepto...

G-protein-gated inwardly rectifying potassium (GIRK) channels, which help control neuronal excitability, are important for the response to drugs of abuse. Here, we describe a novel pathway for morphine-dependent enhancement of GIRK channel signaling in hippocampal neurons. Morphine treatment for ∼20 h increased the colocalization of GIRK2 with PSD95, a dendritic spine marker. Western blot analysis and quantitative immunoelectron microscopy revealed an increase in GIRK2 protein and targeting to dendritic spines. In vivo administration of morphine also produced an upregulation of GIRK2 protein in the hippocampus. The mechanism engaged by morphine required elevated intracellular Ca2+ and was insensitive to pertussis toxin, implicating opioid receptors that may couple to Gq G-proteins. Met-enkephalin, but not the μ-selective (DAMGO) and δ-selective (DPDPE) opioid receptor agonists, mimicked the effect of morphine, suggesting involvement of a heterodimeric opioid receptor complex. Peptide (KN-93) inhibition of ...

We have identified a novel family of synaptic adhesion-like molecules (SALMs). The family members, SALM1–SALM4, have a single transmembrane (TM) domain and contain extracellular leucine-rich repeats, an Ig C2 type domain, a fibronectin type III domain, and an intracellular postsynaptic density-95 (PSD-95)/Discs large/zona occludens-1 (PDZ) binding domain, which is present on all members except SALM4. SALM1 interacts with PSD-95, synapse-associated protein 102 (SAP102), and SAP97 based on coimmunoprecipitation of detergent-solubilized brain. Distribution studies show that SALM1 is present in synaptic membrane and postsynaptic density fractions but is also distributed in axons and dendrites. Transfection of hippocampal neurons for 4 d in vitro (DIV) with SALM1 more than doubles the dendritic lengths of neurons after 48 h, whereas transfection of neurons 14 DIV has no significant effect on neurite outgrowth. Overexpression of SALM1 in 14 DIV neurons recruits NMDA receptors (NR) and PSD-95 to dendritic puncta....

Extended access to cocaine produces an increase in cocaine self-administration in rats that mimics aspects of compulsive drug intake in human addicts. Although emerging evidence implicates the endogenous cannabinoid system in aspects of opioid and ethanol addiction, a role of the endocannabinoid system in cocaine addiction remains widely inconclusive. Here, we investigate the effects of systemic and intra-accumbal administration of the CB1 antagonist SR141716A (Rimonabant) on cocaine self-administration (0.5 mg/kg/infusion) under a progressive ratio (PR) schedule in rats with extended [long access (LgA); 6 h/d] or limited [short access (ShA); 1 h/d] access to cocaine. LgA rats, but not ShA rats, showed an increase in cocaine intake as previously reported, and responding for cocaine by LgA rats was higher than in ShA rats under a PR schedule. Systemic SR141716A induced a dramatic dose-dependent decrease in the breakpoint for cocaine by LgA rats, whereas only the highest dose of the antagonist had a signific...

The striatum is essential for many aspects of mammalian behavior, including motivation and movement, and is dysfunctional in motor disorders such as Parkinson's disease. The vesicular glutamate transporter 3 (VGLUT3) is expressed by striatal cholinergic interneurons (CINs) and is thus well positioned to regulate dopamine (DA) signaling and locomotor activity, a canonical measure of basal ganglia output. We now report that VGLUT3 knock-out (KO) mice show circadian-dependent hyperlocomotor activity that is restricted to the waking cycle and is due to an increase in striatal DA synthesis, packaging, and release. Using a conditional VGLUT3 KO mouse, we show that deletion of the transporter from CINs, surprisingly, does not alter evoked DA release in the dorsal striatum or baseline locomotor activity. The mice do, however, display changes in rearing behavior and sensorimotor gating. Elevation of DA release in the global KO raised the possibility that motor deficits in a Parkinson's disease model would be reduce...

Brain-derived neurotrophic factor (BDNF) is an important mediator of long-term synaptic potentiation (LTP) in the hippocampus. The local effects of BDNF depend on the activation of translation activity, which requires the delivery of transcripts to the synapse. In this work, we found that neuronal activity regulates the dendritic localization of the RNA-binding protein heterogeneous nuclear ribonucleoprotein K (hnRNP K) in cultured rat hippocampal neurons by stimulating BDNF-Trk signaling. Microarray experiments identified a large number of transcripts that are coimmunoprecipitated with hnRNP K, and about 60% of these transcripts are dissociated from the protein upon stimulation of rat hippocampal neurons with BDNF. In vivo studies also showed a role for TrkB signaling in the dissociation of transcripts from hnRNP K upon high-frequency stimulation (HFS) of medial perforant path-granule cell synapses of male rat dentate gyrus (DG). Furthermore, treatment of rat hippocampal synaptoneurosomes with BDNF decrea...

Cyclin-dependent kinase 5 (Cdk5) is a critical regulator of neuronal migration in the developing CNS, and recent studies have revealed a role for Cdk5 in synaptogenesis and regulation of synaptic transmission. Deregulation of Cdk5 has been linked to the pathology of neurodegenerative diseases such as Alzheimer's disease. Activation of Cdk5 requires its association with a regulatory subunit, and two Cdk5 activators, p35 and p39, have been identified. To gain further insight into the functions of Cdk5, we identified proteins that interact with p39 in a yeast two-hybrid screen. In this study we report that α-actinin-1 and the α-subunit of Ca2+/calmodulin-dependent protein kinase II (CaMKIIα), two proteins localized at the postsynaptic density, interact with Cdk5 via their association with p35 and p39. CaMKIIα and α-actinin-1 bind to distinct regions of p35 and p39 and also can interact with each other. The association of CaMKIIα and α-actinin-1 to the Cdk5 activators, as well as to each other, is stimulated b...