M Crispino

University of Naples Federico II, Napoli, Campania, Italy

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Publications (14)49.09 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Previous biochemical, autoradiographic, and ultrastructural data have shown that, in the synaptosomal fraction of the squid optic lobe, protein synthesis is largely due to the presynaptic terminals of the retinal photoreceptor neurons (Crispino et al. [1993a] Mol. Cell. Neurosci. 4:366-374; Crispino et al. [1993b] J. Neurochem. 61:1144-1146; Crispino et al. [1997] J. Neurosci. 17:7694-7702). We now report that this process is close to its maximum at the basal concentration of cytosolic Ca++, and is markedly inhibited when the concentration of this ion is either decreased or increased. This conclusion is supported by the results of experiments with: 1) compounds known to increase the level of cytosolic Ca++, such as A23187, ionomycin, thapsigargin, and caffeine; 2) compounds sequestering cytosolic calcium ions such as BAPTA-AM; and 3) agents that block the role of Ca++ as second messenger, such as TFP and W7, which inhibit calmodulin, and calphostin, which inhibits protein kinase C. We conclude that variations in the level of cytosolic Ca++ induced in presynaptic terminals by neuronal activity may contribute to the modulation of the local synthesis of protein.
    Journal of Neuroscience Research 04/1999; 55(6):776-81. · 2.97 Impact Factor
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    ABSTRACT: Putative protein synthesizing domains, called plaques, are characterized in the squid giant synapse and axon and in terminals of squid photoreceptor neurons. Plaques are oval-shaped formations of about 1 microm in size, which (1) generate signals that have spectroscopic electron energy loss characteristics of ribosomes, (2) exhibit ribonuclease-sensitive binding of YOYO-1, a fluorescent RNA/DNA dye, and (3) in part hybridize with a poly(dT) oligonucleotide. In the giant synapse plaques are abundant in the postsynaptic area, but are absent in the presynaptic terminal. In the cortical layer of the optic lobes, plaques are localized in the large carrot-shaped presynaptic terminals of photoreceptor neurons, where they are surrounded by synaptic vesicles and mitochondria. Biochemical and autoradiographic data have documented that the protein synthetic activity of squid optic lobe synaptosomes is largely due to the presynaptic terminals of the photoreceptor neurons. The identification of ribosomes and poly(A+)-mRNA in the plaques indicates that these structures are sites of local protein synthesis in synaptic domains.
    Journal of Cell Science 12/1998; 111 ( Pt 21):3157-66. · 5.88 Impact Factor
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    ABSTRACT: The presence and distribution of dystrophin was studied in selected areas of the chick embryo nervous system and in primary cultures. Dystrophin was examined at the protein level by immunocytochemistry and at the transcriptional level by a semiquantitative reverse transcriptase-polymerase chain reaction analysis. Immunofluorescence staining shows that dystrophin is present early during embryogenesis in dorsal root ganglia, spinal cord, and ciliary ganglia and colocalizes with neurofilament subunits. Cultured dorsal root ganglion, spinal cord, and ciliary ganglion neurons show immunoreactivity for dystrophin, both in cell bodies and along fibers. Dystrophin mRNA level in ciliary and dorsal root ganglia is higher than in spinal cord throughout development and shows a tissue-specific pattern of expression. In primary cultures of dorsal root ganglia and ciliary ganglia, dystrophin mRNA level increases with time in vitro. However, in spinal cord cultures, dystrophin mRNA drastically decreases with time in vitro, but it is significantly increased when embryonic muscle extract is added to the cultures. Our results show that dystrophin is present in neurons from different areas of embryonic chick nervous system and that its mRNA level is developmentally regulated both in vivo and in vitro.
    Journal of Neuroscience Research 02/1998; 51(1):109-18. · 2.97 Impact Factor
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    ABSTRACT: Previous data have suggested that the large nerve terminals present in the synaptosomal fraction from squid optic lobe are capable of protein synthesis (Crispino et al., 1993a,b). We have further examined this issue by comparing the translation products of synaptosomal and microsomal polysomes. Both preparations programmed an active process of translation, which was completely abolished by their previous treatment with EDTA. After immunoabsorption of the newly synthesized neurofilament (NF) proteins, the labeling ratio of the 60 and 70 kDa NF proteins was found to differ, in agreement with comparable differences obtained with intact synaptosomes. These observations indicate that the set of mRNAs translated by synaptosomes differs from that translated by nerve cell bodies. Hence, because NF proteins are neuron-specific, they support the view that the active synaptosomal polysomes are mostly localized in the large nerve terminals that represent the most abundant neuronal component of the fraction. This hypothesis was confirmed (1) by electron spectroscopic data demonstrating the presence of ribosomes and polysomes within the large nerve endings of the synaptosomal fraction, as well as in the carrot-like nerve endings of the retinal photoreceptors that constitute the only large terminals in the optic lobe, and (2) by light and high resolution autoradiography of synaptosomal samples incubated with [3H]leucine, showing that most labeled proteins are associated with the large nerve endings. This response was abolished by cycloheximide. Taken together, the data provide the first unequivocal demonstration that presynaptic nerve terminals are capable of protein synthesis.
    Journal of Neuroscience 11/1997; 17(20):7694-702. · 6.91 Impact Factor
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    ABSTRACT: Previously, we reported the presence of a heterogeneous population of mRNAs in the squid giant axon. The construction of a cDNA library to this mRNA population has facilitated the identification of several of the constituent mRNAs which encode several cytoskeletal and motor proteins as well as enolase, a glycolytic enzyme. In this communication, we report the isolation of a novel mRNA species (pA6) from the axonal cDNA library. The pA6 mRNA is relatively small (550 nucleotides in length) and is expressed in both nervous tissue and skeletal muscle. The axonal localization of pA6 mRNA was unequivocally established by in situ hybridization histochemistry. The results of quantitative RT-PCR analysis indicate that there are 1.8 x 10(6) molecules of pA6 mRNA (approximately 0.45 pg) in the analyzed segment of the giant axon and suggest that the level of pA6 mRNA in the axonal domain of the giant fiber system might be equal to or greater than the level present in the parental cell soma. Sequence analysis of pA6 suggests that the mRNA encodes an integral membrane protein comprising 84 amino acids. The putative protein contains a single transmembrane domain located in the middle of the molecule and a phosphate-binding loop situated near the N terminus. The C-terminal region of the protein contains two potential phosphorylation sites. These four structural motifs manifest striking similarity to domains present in the ryanodine receptor, raising the possibility that pA6 represents a cephalopod intracellular calcium release channel protein.
    Journal of Neuroscience Research 08/1997; 49(2):144-53. · 2.97 Impact Factor
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    ABSTRACT: Previously, we reported that the squid giant axon contains a heterogeneous population of mRNAs that includes beta-actin, beta-tubulin, kinesin, neurofilament proteins, and enolase. To define the absolute levels and relative distribution of these mRNAs, we have used competitive reverse transcription-PCR to quantify the levels of five mRNAs present in the giant axon and giant fiber lobe (GFL), the location of the parental cell soma. In the GFL, the number of transcripts for these mRNAs varied over a fourfold range, with beta-tubulin being the most abundant mRNA species (1.25 x 10(9) molecules per GFL). Based on transcript number, the rank order of mRNA levels in the GFL was beta-tubulin > beta-actin > kinesin > enolase > microtubule-associated protein (MAP) H1. In contrast, kinesin mRNA was most abundant in the axon (4.1 x 10(7) molecules per axon) with individual mRNA levels varying 15-fold. The rank order of mRNA levels in the axon was kinesin > beta-tubulin > MAP H1 > beta-actin > enolase. The relative abundance of the mRNA species in the axon did not correlate with the size of the transcript, nor was it directly related to their corresponding levels in the GFL. Taken together, these findings confirm that significant amounts of mRNA are present in the giant axon and suggest that specific mRNAs are differentially transported into the axonal domain.
    Journal of Neurochemistry 12/1996; 67(5):1806-12. · 3.97 Impact Factor
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    Biological Bulletin 11/1996; 191(2):263. · 1.23 Impact Factor
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    Biological Bulletin 11/1994; 187(2):269. · 1.23 Impact Factor
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    ABSTRACT: Recently, we reported the construction of a cDNA library encoding a heterogeneous population of polyadenylated mRNAs present in the squid giant axon. The nucleic acid sequencing of several randomly selected clones led to the identification of cDNAs encoding beta-actin and beta-tubulin, two relatively abundant axonal mRNA species. To continue characterization of this unique mRNA population, the axonal cDNA library was screened with a cDNA probe encoding the carboxy terminus of the squid kinesin heavy chain. The sequencing of several positive clones unambiguously identified axonal kinesin cDNA clones. The axonal localization of kinesin mRNA was subsequently verified by in situ hybridization histochemistry. In addition, the presence of kinesin RNA sequences in the axoplasmic polyribosome fraction was demonstrated using PCR methodology. In contrast to these findings, mRNA encoding the squid sodium channel was not detected in axoplasmic RNA, although these sequences were relatively abundant in the giant fiber lobe. Taken together, these findings demonstrate that kinesin mRNA is a component of a select group of mRNAs present in the squid giant axon, and suggest that kinesin may be synthesized locally in this model invertebrate motor neuron.
    Journal of Neurochemistry 08/1994; 63(1):13-8. · 3.97 Impact Factor
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    ABSTRACT: It is generally believed that the proteins of the nerve endings are synthesized on perikaryal polysomes and are eventually delivered to the presynaptic domain by axoplasmic flow. At variance with this view, we have reported previously that a synaptosomal fraction from squid brain actively synthesizes proteins whose electrophoretic profile differs substantially from that of the proteins made in nerve cell bodies, axons, or glial cells, i.e., by the possible contaminants of the synaptosomal fraction. Using western analyses and immunoabsorption methods, we report now that (a) the translation products of the squid synaptosomal fraction include neurofilament (NF) proteins and (b) the electrophoretic pattern of the synaptosomal newly synthesized NF proteins is drastically different from that of the NF proteins synthesized by nerve cell bodies. The latter results exclude the possibility that NF proteins synthesized by the synaptosomal fraction originate in fragments of nerve cell bodies possibly contaminating the synaptosomal fraction. They rather indicate that in squid brain, nerve terminals synthesize NF proteins.
    Journal of Neurochemistry 10/1993; 61(3):1144-6. · 3.97 Impact Factor
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    ABSTRACT: A synaptosomal fraction from squid brain containing a large proportion of well-presarved nerve terminals displays a high rate of [(35)S]methionine incorporation into protein. The reaction is dependent on time and protein concentration, is strongly inhibited by hypo-osmotic shock and cycloheximide, and is not affected by RNase. Chloramphenicol, an inhibitor of mitochondrial protein synthesis, partially inhibits the reaction. The ionic composition of the incubation medium markedly modulates the rate of [(35)S]methionine incorporation. Na(+) and K(+) ions are required for maximal activity, while complete inhibition is achieved by addition of the calcium ionophore A23187 and, to a substantial extent, by tetraethylammonium, ouabain, and high concentrations K(+). A thermostable inhibitor of synaptosomal protein synthesis is also present in the soluble fraction of squid brain. Using sucrose density gradient sedimentation procedures, cytoplasmic polysomes associated with nascent radiolabeled peptide chains have been identified in the synaptosomal preparation. Newly synthesized synaptosomal proteins are largely associated with a readily sedimented particulate fraction and may be resolved by gel electrophoresis into more than 30 discrete bands ranging in size from about 14 to 200 kDa. The electrophoretic pattern of the newly synthesized synaptosomal proteins is significantly different from the corresponding patterns displayed by the giant axon's axoplasm and by glial and nerve cell bodies (in the stellate nerve and ganglion, respectively). On the whole, these observations suggest that the nerve endings from squid brain are capable of protein synthesis.
    Molecular and Cellular Neuroscience 08/1993; 4(4):366-74. · 3.84 Impact Factor
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    ABSTRACT: Previously, we have reported that the squid giant axon contains a heterogeneous population of polyadenylated mRNAs, as well as biologically active polyribosomes. To define the composition of this unique mRNA population, cDNA libraries were constructed to RNA obtained from the axoplasm of the squid giant axon and the parental cell bodies located in the giant fiber lobe. Here, we report that the giant axon contains mRNAs encoding beta-actin and beta-tubulin. The axonal location of these mRNA species was confirmed by in situ hybridization histochemistry, and their presence in the axoplasmic polyribosome fraction was demonstrated by polymerase chain reaction methodology. Taken together, these findings establish the identity of two relatively abundant members of the axonal mRNA population and suggest that key elements of the cytoskeleton are synthesized de novo in the squid giant axon.
    Molecular and Cellular Neuroscience 04/1992; 3(2):133-44. · 3.84 Impact Factor
  • Neurochemistry International 21:A4. · 2.66 Impact Factor
  • Neurochemistry International 21:A3. · 2.66 Impact Factor

Publication Stats

257 Citations
49.09 Total Impact Points

Institutions

  • 1992–1999
    • University of Naples Federico II
      • Department of Biology
      Napoli, Campania, Italy
  • 1998
    • Universität Ulm
      • Workgroup of Electron Microscopy
      Ulm, Baden-Wuerttemberg, Germany
  • 1997
    • University of Pittsburgh
      • Department of Psychiatry
      Pittsburgh, PA, United States