The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform

Jianliang Zhang - One of the best experts on this subject based on the ideXlab platform.

George A Gerencser - One of the best experts on this subject based on the ideXlab platform.

Jonathan V. Sweedler - One of the best experts on this subject based on the ideXlab platform.

  • synthesis accumulation and release of d aspartate in the Aplysia Californica cns
    Journal of Neurochemistry, 2010
    Co-Authors: Cory Scanlan, Stanislav S Rubakhin, Ting Shi, Nathan G Hatcher, Jonathan V. Sweedler
    Abstract:

    J. Neurochem. (2010) 115, 1234–1244. Abstract d-Aspartate (d-Asp) is an endogenous molecule that is often detected in CNS and endocrine tissues. Using capillary electrophoresis and a variety of radionuclide detection techniques, we examine the synthesis, release, and uptake/accumulation of d-Asp in the CNS of the marine mollusk Aplysia Californica. We observe the preferential synthesis and accumulation of d-Asp over l-aspartate (l-Asp) in neuron-containing ganglia compared to surrounding sheath tissues. Little conversion of d-Asp to l-Asp is detected. The Ca2+ ionophore ionomycin and elevated extracellular potassium stimulates release of d-Asp from the cerebral ganglia. Lastly, radioactive d-Asp in the extracellular media is efficiently taken up and accumulated by individual F-cluster neurons. These observations point to a role for d-Asp in cell-to-cell signaling with many characteristics similar to classical transmitters.

  • identification and characterization of homologues of vertebrate β thymosin in the marine mollusk Aplysia Californica
    Journal of Mass Spectrometry, 2006
    Co-Authors: Elena V Romanova, Wayne P. Kelley, Michael J Roth, Stanislav S Rubakhin, Jennifer A Jakubowski, Mark D Kirk, Neil L Kelleher, Jonathan V. Sweedler
    Abstract:

    The β-thymosins have been known as actin-sequestering proteins, but now are recognized as molecules with multiple and diverse intracellular and extracellular functions. Two closely related proteins, β-thymosinHis and β-thymosinGln, have been de novo sequenced by top-down mass spectrometry in the common neurobiology model, Aplysia Californica. As determined by nanoelectrospray quadrupole-enhanced Fourier-Transform mass spectrometry with collisionally activated and electron-capture dissociations, both of these Aplysia β-thymosins are acetylated and differ by a single residue in the central actin-binding domain. Profiling of individual cells and tissue by matrix-assisted laser desorption/ionization mass spectrometry reveals that these proteins are widely expressed in the Aplysia central nervous system, including in individual identified neurons, neuronal clusters, nerves and connective tissues. Newly identified β-thymosinHis and β-thymosinGln are also detected by mass spectrometry in hemolymph, and in releasates collected from whole ganglia. When applied exogenously, β-thymosin proteins, purified from nerve cell extract, support the anchoring of neurons, and increase neurite sprouting and total neurite outgrowth in culture. These positive effects on neurite regeneration in cell culture suggest that the β-thymosin proteins have an extracellular function in the central nervous system of Aplysia Californica. Copyright © 2006 John Wiley & Sons, Ltd.

  • Identification and characterization of homologues of vertebrate β‐thymosin in the marine mollusk Aplysia Californica
    Journal of mass spectrometry : JMS, 2006
    Co-Authors: Elena V Romanova, Wayne P. Kelley, Michael J Roth, Stanislav S Rubakhin, Jennifer A Jakubowski, Mark D Kirk, Neil L Kelleher, Jonathan V. Sweedler
    Abstract:

    The β-thymosins have been known as actin-sequestering proteins, but now are recognized as molecules with multiple and diverse intracellular and extracellular functions. Two closely related proteins, β-thymosinHis and β-thymosinGln, have been de novo sequenced by top-down mass spectrometry in the common neurobiology model, Aplysia Californica. As determined by nanoelectrospray quadrupole-enhanced Fourier-Transform mass spectrometry with collisionally activated and electron-capture dissociations, both of these Aplysia β-thymosins are acetylated and differ by a single residue in the central actin-binding domain. Profiling of individual cells and tissue by matrix-assisted laser desorption/ionization mass spectrometry reveals that these proteins are widely expressed in the Aplysia central nervous system, including in individual identified neurons, neuronal clusters, nerves and connective tissues. Newly identified β-thymosinHis and β-thymosinGln are also detected by mass spectrometry in hemolymph, and in releasates collected from whole ganglia. When applied exogenously, β-thymosin proteins, purified from nerve cell extract, support the anchoring of neurons, and increase neurite sprouting and total neurite outgrowth in culture. These positive effects on neurite regeneration in cell culture suggest that the β-thymosin proteins have an extracellular function in the central nervous system of Aplysia Californica. Copyright © 2006 John Wiley & Sons, Ltd.

  • A novel prohormone processing site in Aplysia Californica: the Leu-Leu rule.
    Journal of neurochemistry, 2002
    Co-Authors: Amanda B. Hummon, He Qing Huang, Wayne P. Kelley, Jonathan V. Sweedler
    Abstract:

    Neuropeptides are a complex set of signaling molecules produced through enzymatic cleavages from longer prohormone sequences. The most common cleavage sites in prohormones are basic amino acid residues; however, processing is observed at non-basic sites. Cleavage at Leu-Leu sequences has been observed in three Aplysia Californica prohormones. To further investigate this unusual event, native and non-native synthetic peptides containing Leu-Leu residues are incubated with homogenates of Aplysia Californica ganglia and the resulting products monitored with MALDI MS. Cleavage near and between Leu-Leu residues is observed in the abdominal and buccal ganglia homogenates, confirming the presence of an unidentified peptidase. In addition, fractions from an HPLC separation of buccal ganglia homogenates also produce cleavages at Leu-Leu residues. Products resulting from cleavage at Leu-Leu sites are observed and are produced in larger amounts in acidic and neutral pH ranges, and cleavage is inhibited by the addition of EDTA, suggesting a metal is required for activity.

  • Insulin Prohormone Processing, Distribution, and Relation to Metabolism in Aplysia Californica
    The Journal of neuroscience : the official journal of the Society for Neuroscience, 1999
    Co-Authors: Philip D. Floyd, Jonathan V. Sweedler, Irving Kupfermann, Stanislav S Rubakhin, Charles C. Horn, Vera Alexeeva, Timothy A. Ellis, N. C. Dembrow, Klaudiusz R. Weiss
    Abstract:

    The first Aplysia Californica insulin gene is characterized and its proteolytic processing from prohormone to final peptides elucidated using a combination of biochemical and mass spectrometric methods. Aplysia insulin (AI) is one of the largest insulins found, with a molecular weight of 9146 Da, and an extended A chain compared with other invertebrate and vertebrate insulins. The AI prohormone produces a series of C peptides and also a unique N-terminally acetylated D peptide. AI-producing cells are restricted to the central region of the cerebral ganglia mostly within the F and C clusters, and AI is transported to neurohemal release sites located on the upper labial and anterior tentacular nerves. The expression of AI mRNA decreases when the animal is deprived of food, and injections of AI reduce hemolymph glucose levels, suggesting that the function of insulin-regulating metabolism has been conserved.

Juan Carlos Lacal - One of the best experts on this subject based on the ideXlab platform.

  • tumorigenic activity of rho genes from Aplysia Californica
    Oncogene, 1993
    Co-Authors: Rosario Perona, Rafael P. Ballestero, Pilar Esteve, Benilde Jiménez, Ramon S Y Cajal, Juan Carlos Lacal
    Abstract:

    rho genes have been found in both lower and higher eucaryotes. They code for proteins of 21 kDa, highly conserved in evolution, which belong to the superfamily of ras GTPases. Among the members of this superfamily there are proteins with a regulatory function, such as ras, and proteins involved in vesicular trafficking, such as the family of rab proteins. We have investigated the putative role of rho proteins from Aplysia Californica as transforming GTPases utilizing the wild-type and a Val-14 mutant, equivalent to the oncogenic Val-12 mutation of ras genes found in animal and human tumors. Over-expression of either rho gene was sufficient to confer anchorage- and serum-independent growth. Moreover, when introduced into nude mice, selected clones generated from either gene were able to induce tumors, although those carrying the mutated version were more efficient. Pathological analysis indicated that generated tumors corresponded to well-differentiated fibrosarcomas with distinct and intersecting bundles and spindle cells. By contrast, ras-induced tumors were poorly differentiated fibrosarcomas. Thus, our results indicate that under appropriate conditions rho genes function as oncogenes and may have a role in the regulation of proliferation in fibroblast cells.

  • Biological Function of Aplysia Californica rho Gene
    The Superfamily of ras-Related Genes, 1991
    Co-Authors: Rafael P. Ballestero, Pilar Esteve, Rosario Perona, Benilde Jiménez, Juan Carlos Lacal
    Abstract:

    rho genes are a family of genes which are structurally related to the oncogenic ras family. The primary structure of rho genes has been elucidated for the marine snail Aplysia Californica, two S. cerevisiae genes, and three human versions, rho A, B and C. They all codify for proteins of an approximate M.W. of 21 kDa (rho-p21) which show 35% homology to the ras proteins. It has been observed that rho proteins are ADP-ribosylated by the botulinum toxin C3 exoenzyme, suggesting that rho proteins could be involved in regulating neuronal function. However very little is known about their actual biological functions. While the human rho A and rho C products have been related to cytoeskeleton organization, the rho A product has a weak transforming activity. We have investigated the biological properties of the Aplysia Californica rho-p21 protein when introduced into an heterologous system, and found that it does not induce foci in a regular NIH-3T3 transfection assay. However, the morphology of the cells was slightly altered and cells grew to higher cell densities. Moreover, transforming activity was detected when isolated cell lines were inoculated into nude mice. To further investigate the potential transforming activity of the Aplysia gene, we have also generated a Gly→Val mutation at position 14, equivalent to the activating mutation found in oncogenic ras genes. No apparent increase in the transforming activity was observed, indicating that the effects on growth behaviour are probably not the primary function of rho proteins.

Randy Levin - One of the best experts on this subject based on the ideXlab platform.