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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cyclic AMP (cAMP) system plays a critical role in olfactory learning in the fruit fly, Drosophila melanogaster, as evidenced by the following: [1] The dunce gene encodes a form of cAMP phosphodiesterase (PDE). Flies carrying mutations at this gene show reduced PDE activity, high cAMP levels, and deficits in olfactory learning and memory [2]. The rutabaga gene encodes one type of adenylyl cyclase (AC) similar in properties to the Type I AC characterized from vertebrate brain. This enzyme is activated by G-protein and Ca++ and has been postulated to be a molecular coincidence detector, capable of integrating information from two independent sources such as the conditioned stimulus (CS) and the unconditioned stimulus (US) delivered to animals during Pavlovian conditioning. Rutabaga mutant flies are deficient in AC activity and show behavioral defects similar to those exhibited by dunce mutants [3]. Flies carrying mutations in the gene (DC0) that encodes the catalytic subunit of protein kinase A (PKA), the major mediator of cAMP actions, show alterations in learning performance and a loss in PKA activity. All three genes are expressed preferentially in mushroom bodies, neuroanatomical sites that mediate olfactory learning. Interestingly, the PDE and the catalytic subunit of PKA are found primarily in axonal and dendritic compartments of the mushroom body cells, whereas the AC is found primarily in the axonal compartment. The reason for this differential compartmentalization is unclear, although the hypothetical role of AC as coincidence detector would predict that CS and US stimuli are integrated in the axonal compartment. These observations suggest that cAMP is a dominant second messenger utilized by mushroom body cells to modulate their physiology while the animal is learning and consolidating memory. However, many other types of molecules are likely involved in the physiological alterations that occur in these cells during learning, including cell surface proteins, transcription factors, and synaptic proteins.
Mol Cell Biochem
PMID:The cyclic AMP system and Drosophila learning. 856 40

Neuronal differentiation involves extensive rearrangement of the cytoskeleton, including the actin-based microfilament system, and establishment of molecular compartments within the neuron. The intracellular distribution of tropomyosin (Tm) mRNA in vivo and in vitro has been examined and correlated with protein targetting. The mRNAs encoding two Tm isoforms were found to be differentially localized in developing neurons. Tm-5 mRNA is localized to the axonal pole of differentiating embryonic rat neurons, in contrast to TmBr-2 mRNA distribution throughout the cell body. Tm-5 mRNA is transported into the axon of differentiating primary cultured neurons. This mRNA localization is developmentally regulated and correlates with the targeting of Tm-5 protein to growing axons. Tm-5 colocalizes with a subset of neuronal microfilaments associated with the initiation and maintenance of outgrowth. The segregation of Tm-5 is the earliest known marker of neuronal polarity and may play a role in the establishment of polarity.
Mol Cell Neurosci 1995 Oct
PMID:Intracellular localization of tropomyosin mRNA and protein is associated with development of neuronal polarity. 858 12

The cell-surface glycoprotein, CD9, has been implicated in hematopoietic and Schwann cell signaling in vitro. In vivo, Schwann cell CD9 expression follows a developmental time course that parallels that of myelin genes. Here we report that Schwann cell CD9 mRNA expression is regulated by axonal contact in culture and in vivo. Following adult rat sciatic nerve injury, CD9 mRNA expression in distal nerve sections is correlated with the presence of axons; CD9 is down-regulated when axons are degenerating and is reexpressed when axons are regenerating, but not if they are prevented from doing so by transection. CD9 regulation in cultured Schwann cells is also dependent on the presence of neurons such that dissociated Schwann cells down-regulate CD9 mRNA expression in culture, but in the presence of sensory neurons they continue to express CD9. Therefore, regulation of Schwann cell CD9 expression parallels that of myelin genes protein 0 and myelin basic protein in culture and in vivo. A signaling role for CD9 in nerve development and regeneration is proposed.
Mol Cell Neurosci 1995 Oct
PMID:Schwann cell CD9 expression is regulated by axons. 858 16

1. The morphology of neurons in the dentate gyrus of the adult human brain was analyzed with two variants of Golgi technique. 2. About 20 neuronal types and subtypes were observed in the dentate gyrus of the adult human, several of which has not previously been described in the human. The human dentate gyrus harbors 4 types of neurons in the molecular layer, 3 types within the granule cell layer, and at least 10 types in the hilus. 3. Compared to the granule neurons in the rat brain, human granule neurons show a much greater variability. Many of these human neurons have basal dendrites and/or axonal spines. Also, there are significant differences among these neurons regarding the density of their dendritic trees and dendritic spines. In contrast to the rat, human hilar neurons with complex spines have complex spines not only on their dendrites but also on their cell bodies. 4. This study opens the door for further morphological studies involving specific diseases such as Alzheimer's disease and epilepsy.
Cell Mol Neurobiol 1995 Apr
PMID:A golgi study of cell types in the dentate gyrus of the adult human brain. 859 Apr 52

Cytoplasmic dynein is the microtubule minus-end-directed motor for the retrograde axonal transport of membranous organelles. Because of its similarity to the intermediate chains of flagellar dynein, the 74-kDa intermediate chain (IC74) subunit of dynein is thought to be involved in binding dynein to its membranous organelle cargo. Previously, we identified six isoforms of the IC74 cytoplasmic dynein subunit in the brain. We further demonstrated that cultured glia and neurons expressed different dynein IC74 isoforms and phospho-isoforms. Two isoforms were observed when dynein from glia was analyzed. When dynein from cultured neurons was analyzed, six IC74 isoforms were observed, although the relative amounts of the dynein isoforms from cultured neurons differed from those found in dynein from brain. To better understand the role of the neuronal IC74 isoforms and identify neuron-specific IC74 dynein subunits, the expression of the IC74 protein isoforms and mRNAs of various tissues were compared. As a result of this comparison, the identity of each of the isoform spots observed on two-dimensional gels was correlated with the products of each of the IC74 mRNAs. We also found that between the fifteenth day of gestation (E15) and the fifth day after birth (P5), the relative expression of the IC74 protein isoforms changes, demonstrating that the expression of IC74 isoforms is developmentally regulated in brain. During this time period, there is relatively little change in the abundance of the various IC74 mRNAs. The E15 to P5 time period is one of rapid process extension and initial pattern formation in the rat brain. This result indicates that the changes in neuronal IC74 isoforms coincide with neuronal differentiation, in particular the extension of processes. This suggests a role for the neuronal IC74 isoforms in the establishment or regulation of retrograde axonal transport.
Mol Biol Cell 1996 Feb
PMID:Identification and developmental regulation of a neuron-specific subunit of cytoplasmic dynein. 868 62

1. Expression of the apamin-sensitive K+ channel (SK+) in rat skeletal muscle is neurally regulated. The regulatory effect of the nerve over the expression of some muscle ion channels has been attributed to the electrical activity triggered by the nerve and/or to a trophic effect of some molecules transported from the soma to the axonal endings. 2. SK+ channels apparently are involved in myotonic dystrophy (MD), therefore understanding the factors that regulate their expression may ultimately have important clinical relevance. 3. To establish if axoplasmic transport is involved in this process, we used two experimental approaches in adult rats: (a) Both sciatic nerves were severed, leaving a short or a long nerve stump attached to the anterior tibialis (AT). (b) Colchicine or vinblastine (VBL), two axonal transport blockers of different potencies, was applied on one leg to the sciatic nerve. To determine whether electrical activity affects the expression of SK+ channels, denervated AT were directly stimulated. The corresponding contralateral muscles were used as controls.
Cell Mol Neurobiol 1996 Feb
PMID:Neural control of the expression of a Ca(2+)-activated K+ channel involved in the induction of myotonic-like characteristics. 871 58

Myelin-associated glycoprotein (MAG) is a potent inhibitor of axonal regeneration from both cerebellar neurons and adult dorsal root ganglion (DRG) neurons. In contrast, MAG promotes axonal growth from newborn DRG neurons. Here, we show that the switch in response to MAG from promotion to inhibition of neurite outgrowth by DRg neurons occurs sharply at Postnatal Day 3. To date, of all the neurons tested a postnatal switch in response is only observed for DRG neurons; MAG inhibits axonal growth from retinal, superior cervical ganglion, spinal, and hippocampal neurons of all postnatal ages. Furthermore, MAG binds to neurons from which it promotes and from which it inhibits outgrowth, in a sialic-acid-dependent manner. Now we show this binding is also trypsin-sensitive. Hence, the interaction is via a sialoglycoprotein. Binding of MAG to all the neurons tested here was also sialic-acid-dependent. Importantly, both inhibition and promotion of neurite outgrowth by MAG are reduced, or abolished completely, either by desialyation of the neurons prior to the outgrowth assay or by including small sialic-acid-bearing sugars in the cultures. These results suggest that MAG is likely to contribute to the lack of regeneration observed throughout the nervous system. Also, it is likely that MAG is exerting its effect, either directly or indirectly, on both promotion and inhibition of neurite outgrowth via a neuronal sialoglycoprotein.
Mol Cell Neurosci 1996 Feb
PMID:Myelin-associated glycoprotein inhibits axonal regeneration from a variety of neurons via interaction with a sialoglycoprotein. 873 78

Leukemia inhibitory factor (LIF) plays an important role in regulating neuropeptide expression in sympathetic and sensory neurons after axonal transection. By 2 h after axotomy, LIF mRNA increased in nonneuronal cells in sympathetic ganglia and peripheral nerve. In addition, within 1 h of explanting sympathetic ganglia or segments of sympathetic nerve trunks, a protein factor(s) that was able to induce LIF mRNA both in sympathetic cultures and in intact ganglia in vivo was released. This factor(s) appeared to be present in sympathetic ganglia and their nerve trunks under normal conditions and to be activated and/or released after axonal injury. Since the factor(s) has a molecular weight(s) greater than 66 kDa, and no other proteins of such high molecular weight have been previously identified with LIF-inducing activity, it appears to be a novel inducer of LIF.
Mol Cell Neurosci 1996 Feb
PMID:Signals triggering the induction of leukemia inhibitory factor in sympathetic superior cervical ganglia and their nerve trunks after axonal injury. 873 83

The presence in hippocampus of a basic helix-loop-helix (bHLH) family of transcription factors (TFs) specifically binding in an electrophoretic mobility shift assay (EMSA) to the E-box recognition element was established by selective blockade of binding both by cold competition and by an antibody to MyoD1, an E-box TF. Protein source was from a micro-dissected preparation enriched in hippocampal granule cells. Specific E-box binding of hippocampal transcription factors was significantly reduced in kainate acid (KA) treated animals. This was observed at 24 and 72 h, but not before (3, 6 h) or after (96 h). This is the first report to our knowledge to study functional regulation of E-box binding protein in adult hippocampus. To determine the generality of this E-box regulatory event, we studied four other situations, in addition to kainate treatment, where axonal growth is known or has been suggested to increase: NGF treatment of PC12 cells, unilateral hilar lesions, long-term potentiation after 1 h, and postnatal rat hippocampal development. In all four cases, decreased E-box binding was observed. The recent link of F1/GAP-43 mRNA induction in hippocampal granule cells by KA to growth of their axons, the mossy fibers in the adult rat, suggests a potential role for the F1/GAP-43 5' flanking promoter region in regulating neurite outgrowth. Since in all cases decreased E-box binding preceded increased F1/GAP-43 mRNA expression, it is suggested that E-box binding to the F1/GAP-43 promoter in hippocampal granule cells could negatively regulate F1/GAP-43 gene expression. Indeed, analysis of recognition elements on the F1/GAP-43 gene revealed an arrangement, previously described in other genes, of multiple adjacent E-box elements. E-box binding of bHLH transcription factors is likely to occur on several different genes in addition to F1/GAP-43. It is, therefore, attractive to think that E-box binding is regulated by in vivo activation of the adult brain and that this gene regulatory event participates in the orchestration of molecular and cellular responses underlying axonal growth.
Brain Res Mol Brain Res 1996 May
PMID:Prolonged alteration in E-box binding after a single systemic kainate injection: potential relation to F1/GAP-43 gene expression. 873 64

Synaptosomal-associated protein of 25 kDa (SNAP-25) is involved in the molecular regulation of neurotransmitter release. SNAP-25 exists in two isoforms, which arise from alternative splicing of exon 5. In situ hybridization was used to examine whether SNAP-25 isoform mRNA expression may be altered by experimental manipulations. The effect of unilateral nerve injury on SNAP-25 mRNA levels was studied in motoneurons of the rat lumbar spinal cord. In all animals, SNAP-25a RNA transcripts were demonstrated in the nucleus of motoneurons, whereas SNAP-25b mRNA was present mainly in the cytoplasm. Cloning of the rat Snap gene intron spacing the alternative exon 5a and 5b sequences and generation of an intron-specific oligonucleotide probe used for in situ hybridization did not point to the presence of unspliced variants of SNAP-25b mRNA. After unilateral sciatic nerve transection (axotomy), SNAP-25a and SNAP-25b expression decreased in axotomized motoneurons compared with corresponding motoneurons on the unlesioned side. A significant decrease was demonstrated 2 days after axotomy, which reached a maximum after 7 days (62% for SNAP-25a and 67% for SNAP-25b), while levels had slightly recovered by 14 and 28 days. Ventral root avulsion also induced a decrease in levels of SNAP-25 RNA transcripts, suggesting that the axonal injury in itself was responsible for the down-regulation of Snap gene expression. This study shows that, in spinal motoneurons, SNAP-25a and SNAP-25b RNA transcripts have different subcellular localization and that levels of SNAP-25 RNA transcripts are down-regulated after axonal injury.
Brain Res Mol Brain Res 1996 Apr
PMID:Differential subcellular localization of SNAP-25a and SNAP-25b RNA transcripts in spinal motoneurons and plasticity in expression after nerve injury. 873 35


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