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Sympathetic neurons in culture die by apoptosis when deprived of nerve growth factor (NGF). We used this model of programmed cell death to study the mechanisms that mediate neuronal apoptosis. Cultured sympathetic neurons were injected with copper/zinc superoxide dismutase protein (SOD) or with an expression vector containing an SOD cDNA. In both cases apoptosis was delayed when the neurons were deprived...
A major difference between short- and long-term memory is that long-term memory is dependent on new protein synthesis. Long-term memory can be further subdivided into a transient, initial phase that is readily susceptible to disruption and a later, more stable and persistent stage. To analyze this transition on the cellular level, we have examined the steps whereby short-term facilitation is converted...
Guidepost cells are known to alter the behavior of growth cones in vivo, yet the nature of communication and the type of signals employed are largely undefined. The present study demonstrates that model guideposts, composed of a single molecular species, are sufficient to change the navigation and the behavior of advancing growth cones well beyond the time of contact. Laminin on model guideposts caused...
The amyloid deposits of Alzheimer's disease contain, in addition to the β protein (Aβ), lesser amounts of other proteins including the protease inhibitor α1-antichymotrypsin (ACT). We have recently shown that ACT acts as a pathological chaperone, binding to the β protein and strongly promoting its polymerization into amyloid filaments in vitro. The data of this paper show that ACT synthesis is induced...
Transcription control regions of eukaryotic genes contain multiple sequence elements proposed to function independently to regulate transcription. We developed transgenic mice carrying fos-IacZ fusion genes with clustered point mutations in each of several distinct regulatory sequences: the sis-inducible element, the serum response element, the fos AP-1 site, and the calcium/cAMP response element...
Tetanus toxin cleaves the synaptic vesicle protein synaptobrevin, and the ensuing loss of neurotransmitter exocytosis has implicated synaptobrevin in this process. To further the study of synaptic function in a genetically tractable organism and to generate a tool to disable neuronal communication for behavioural studies, we have expressed a gene encoding tetanus toxin light chain in Drosophila. Toxin...
We investigated the transmembrane topology of the GluR3 subunit that was translated in rabbit reticulocytes supplemented with microsomal membranes. A prolactin reporter epitope was fused to GluR3 at six locations, bracketing each of the proposed transmembrane domains. The sidedness of the epitope in the microsomal membrane was then assessed by proteinase K sensitivity. The N terminus and the entire...
The mammalian rod synapse transmits a binary signal (one photon or none) using tonic, rapid exocytosis. We constructed a quantitative, physical model of the synapse. Presynaptically, a single, linear active zone provides docking sites for ~130 vesicles, and a ''ribbon'' anchored to the active zone provides a depot for ~640 vesicles. Postsynaptically, 4 processes invaginate the terminal: 2 (known to...
Motor axons preferentially reinnervate original synaptic sites on denervated muscle fibers. We have shown that components of synaptic basal lamina direct this selectivity, and we identified a protein, s-laminin, that is concentrated in synaptic basal lamina. Here, we report that a recombinant s-laminin fragment inhibits neurite outgrowth promoted by laminin. A tripeptide sequence in this fragment,...
Through specific intersubunit contacts, the four subunits of the nicotinic acetylcholine receptor assemble into an α2βγδ pentamer. The specificity of subunit association leads to formation of proper ligand binding sites and to transport of assembled pentamers to the cell surface. To identify determinants of subunit association, we constructed chimeric subunits, transfected them into HEK 293 cells,...
Experiments in which several high and/or low frequency stimulation patterns were applied to different groups of afferents in CA1 hippocampal slices revealed the existence of heterosynaptic interactions between UP and LTD. Specifically, we report that repeated induction of LTD on one input was associated with a heterosynaptic reversal of the UP previously induced on a separate pathway. Reapplication...
The role of glia in suppressing neuronal cell death was investigated in the visual system of the Drosophila mutant, reversed polarity (repo). The repo locus encodes a glial-specific homeodomain protein expressed in the optic lobes. Here, we show that survival of the laminar neurons in the optic lobe depends on repo expression in the laminar glia, indicating that the laminar glia supply factors required...
Neurexins, a family of cell surface proteins specific to brain, are transcribed from two promoters in three genes, resulting in three α- and three β-neurexins. In situ hybridization revealed differential but overlapping distributions of neurexin isoforms in different classes of neurons. PCRs demonstrated that a-neurexins are alternatively spliced at five canonical positions, and β-neurexins at two...
Neuropeptide-mediated transmission was analyzed at Drosophila larval body-wall neuromuscular junctions. Focal application of vertebrate pituitary adenylyl cyclase-activating polypeptide (PACAP38) to the neuromuscular junction region triggered two temporally distinct muscle responses: an immediate depolarization followed by a large enhancement of K+ current. This late enhancement occurred many minutes...
Replication of prions is dependent on the presence of the host protein PrPc. During the course of disease, PrPc is converted into an abnormal isoform, PrPsc, which accumulates in the brain. Attempts to identify the cell type(s) in which prion replication and PrP conversion occur have reached conflicting results. Although PrP mRNA is present in high amounts in neurons throughout the life of the animal,...
Cerebral deposition of β-amyloid protein is a pathological feature central to Alzheimer's disease. Production of β-amyloid by proteolytic processing of the β-amyloid precursor protein (βAPP) is a critical initial step in β-amyloidogenesis. We use an inhibitor of βAPP processing to block β-amyloid peptide formation. Application of the inhibitor to cultured cells results in an accumulation of proteolytic...
In Alzheimer's disease brains, more than 90% of pyramidal neurons in lamina V and 70% in lamina III displayed 2- to 5-fold elevated levels of cathepsin D (Cat D) mRNA by in situ hybridization compared with neurologically normal controls. Most of these cells appeared histologically normal. The less vulnerable nonpyramidal neuron population in lamina IV had relatively normal message levels. Neuronal...
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