The Open Biochemistry Journal




ISSN: 1874-091X ― Volume 13, 2019

Calcium-Induced Conformational Transition of Trout Ependymins Monitored by Tryptophan Fluorescence



Bernhard Ganss1, 2, Werner Hoffmann*, 1, 3
1 Max-Planck-Institute for Psychiatry, Department of Neurochemistry, D-82152 Martinsried, Germany
2 CIHR Group in Matrix Dynamics, University of Toronto, Toronto, Ontario M5S 3E2, Canada
3 Institute of Molecular Biology and Medical Chemistry, Otto-von-Guericke-University, D-39120 Magdeburg, Germany

Abstract

Ependymins are secretory, calcium-binding sialoproteins which are the predominant constituents of the cerebrospinal fluid of many teleost fish. A bound form of these regeneration-responsive glycoproteins is associated with collagen fibrils of the extracellular matrix. Here, the tryptophan fluorescence of ependymins was monitored at various Ca2+ concentrations. Two distinct states were identified with a relatively sharp transition at about 1 mM Ca2+. In agreement with previous circular dichroism measurements, this strongly supports the hypothesis that a calcium-induced conformational change is important for the interaction of ependymins with components of the extracellular matrix. Such interactions with constituents of various basal laminae would also explain the important roles of piscine ependymins as well as invertebrate and mammalian ependymin-related proteins for cell adhesion processes and cell migration.

Keywords: Ependymins, MERP, calcium binding, extracellular matrix, tryptophan fluorescence, cell adhesion molecule, learning and memory.


Article Information


Identifiers and Pagination:

Year: 2009
Volume: 3
First Page: 14
Last Page: 17
Publisher Id: TOBIOCJ-3-14
DOI: 10.2174/1874091X00903010014

Article History:

Received Date: 20/11/2008
Revision Received Date: 05/12/2008
Acceptance Date: 20/1/2009
Electronic publication date: 24/2/2009
Collection year: 2009

Article Metrics:

CrossRef Citations:
0

Total Statistics:

Full-Text HTML Views: 920
Abstract HTML Views: 976
PDF Downloads: 207
Total Views/Downloads: 2103

Unique Statistics:

Full-Text HTML Views: 610
Abstract HTML Views: 647
PDF Downloads: 152
Total Views/Downloads: 1409
Geographical View

© Ganss and Hoffmann; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.


* Address correspondence to this author at the Institut für Molekularbiologie und Medizinische Chemie, Universitätsklinikum, Leipziger Str. 44, D-39120 Magdeburg, Germany; Tel: +49-(391)-67-15 895; Fax: +49-(391)-67-13 096; E-mail: werner.hoffmann@med.ovgu.de




INTRODUCTION

Ependymins are unique calcium-binding secretory proteins of the endomeninx of many teleost fish (for review, see [1Hoffmann, W; Schwarz, H Ependymins: meningeal derived extracellular matrix proteins at the blood brain barrier Int. Rev. Cytol, 1996, 165, 121-158.
[http://dx.doi.org/10.1016/S0074-7696(08)62221-4]
]). Here, fibroblast-like cells synthesize these glycoproteins together with a number of extracellular matrix (ECM) molecules [1Hoffmann, W; Schwarz, H Ependymins: meningeal derived extracellular matrix proteins at the blood brain barrier Int. Rev. Cytol, 1996, 165, 121-158.
[http://dx.doi.org/10.1016/S0074-7696(08)62221-4]
-4Schwarz, H; Müller-Schmid, A; Hoffmann, W Ultrastructural localization of ependymins in the endomeninx of the brain of the rainbow trout: possible association with collagen fibrils of the extracellular matrix Cell Tissue Res, 1993, 273, 417-425.
[http://dx.doi.org/10.1007/BF00333696]
]. Fish ependymins are highly divergent [5Müller-Schmid, A; Rinder, H; Lottspeich, F; Gertzen, E-M; Hoffmann, W Ependymins from the cerebrospinal fluid of salmonid fish: gene structure and molecular characterization Gene, 1992, 118, 189-196.-7Orti, G; Meyer, A Molecular evolution of ependymin and the phylogenetic resolution of early divergences among euteleost fishes Mol. Biol. Evol, 1996, 13, 556-573.
[http://dx.doi.org/10.1093/oxfordjournals.molbev.a025616] [PMID: 8882499]
]. The most conserved feature of piscine ependymins, other than the sequence F-E-E-G-V-x-Y-E/D-I/L-D between the two canonical N-glycosylation sites [6Müller-Schmid, A; Ganß, B; Gorr, T; Hoffmann, W Molecular analysis of ependymins from the cerebrospinal fluid of the orders Clupeiformes and Salmoniformes: no indication for the existence of an euteleost infradivision J. Mol. Evol, 1993, 36, 578-585.
[http://dx.doi.org/10.1007/BF00556362] [PMID: 8350351]
], is the presence of sialic acid residues in the N-linked sugar moiety [8Ganss, B; Hoffmann, W Calcium binding to sialic acids and its effect on the conformation of ependymins Eur. J. Biochem, 1993, 217, 275-280.
[http://dx.doi.org/10.1111/j.1432-1033.1993.tb18243.x] [PMID: 7693461]
]. As also shown for other extracellular proteins, e.g. fibrinogen [9Dang, CV; Shin, CK; Bell, WR; Nagaswami, C; Weisel, JW Fibrinogen sialic acid residues are low affinity calcium-binding sites that influence fibrin assembly J. Biol. Chem, 1989, 264, 15104-15108.
[PMID: 2549051]
], these acid structures are responsible for the calcium-binding capacity of ependymins [8Ganss, B; Hoffmann, W Calcium binding to sialic acids and its effect on the conformation of ependymins Eur. J. Biochem, 1993, 217, 275-280.
[http://dx.doi.org/10.1111/j.1432-1033.1993.tb18243.x] [PMID: 7693461]
].

An ependymin-related gene has been detected also in human where it is expressed mainly in brain, heart, and skeletal muscle. This gene was originally termed UCC1 because it is up-regulated in colon cancer [10Nimmrich, I; Erdmann, S; Melchers, U; Chtarbova, S; Finke, U; Hentsch, S; Hoffmann, I; Oertel, M; Hoffmann, W; Müller, O The novel ependymin related gene UCC1 is highly expressed in colorectal tumor cells Cancer Lett, 2001, 165, 71-79.
[http://dx.doi.org/10.1016/S0304-3835(01)00390-1]
]. Nowadays, this gene and its various mammalian homologs are named MERPs [11Apostolopoulos, J; Sparrow, RL; McLeod, JL; Collier, FM; Darcy, PK; Slater, HR; Ngu, C; Gregorio-King, CC; Kirkland, MA Identification and characterization of a novel family of mammalian ependymin-related proteins (MERPs) in hematopoietic, nonhematopoietic, and malignant tissues DNA Cell Biol, 2001, 20, 625-635.]. Ependymin-related genes are also present in invertebrate deuterostomes such as sea cucumbers [12Suárez-Castillo, EC; Medina-Ortíz, WE; Roig-López, JL; García-Arrarás, JE Ependymin a gene involved in regeneration and neuroplasticity in vertebrates, is overexpressed during regeneration in the echinoderm Holothuria glaberrima Gene, 2004, 334, 133-143.] as well as protostomes [13Suárez-Castillo, EC; García-Arrarás, JE Molecular evolution of the ependymin protein family: a necessary update BMC Evol. Biol, 2007, 7, 23-42.
[http://dx.doi.org/10.1186/1471-2148-7-23] [PMID: 17302986] [PMCID: PMC1805737]
]. Generally, there is only little amino acid sequence similarity between these ependymin-related proteins. Strictly conserved are four cysteine residues, a tryptophan residue and a few other positions. Furthermore, all ependymin-related proteins contain at least one N-glycosylation site.

Originally, piscine ependymins were detected when studying neuroplasticity in the goldfish (for review see [14Shashoua, VE The role of brain extracellular proteins in neuroplasticity and learning Cell Mol. Neurobiol, 1985, 5, 183-207.
[http://dx.doi.org/10.1007/BF00711092] [PMID: 4028066]
]).

Also interference of anti-sense ependymin-mRNA with memory consolidation has been reported [15Schmidt, R; Brysch, W; Rother, S; Schlingensiepen, K-H Inhibition of memory consolidation after active avoidance conditioning by antisense intervention with ependymin gene expression J. Neurochem, 1995, 65, 1465-1471.
[http://dx.doi.org/10.1046/j.1471-4159.1995.65041465.x] [PMID: 7561839]
]. However, ependymins are also attracting increasing interest because they share several characteristics with glycoproteins involved in cell contact phenomena [1Hoffmann, W; Schwarz, H Ependymins: meningeal derived extracellular matrix proteins at the blood brain barrier Int. Rev. Cytol, 1996, 165, 121-158.
[http://dx.doi.org/10.1016/S0074-7696(08)62221-4]
]. For example, in the goldfish, infusion of ependymin antibodies blocks the sharpening of the regenerating retinotectal projection [16Schmidt, JT; Shashoua, VE Antibodies to ependymin block the sharpening of the regenerating retinotectal projection in goldfish Brain Res, 1988, 446, 269-284.
[http://dx.doi.org/10.1016/0006-8993(88)90886-4]
], and increased synthesis of ependymins in the optic nerve has been reported during its regeneration [17Thormodsson, FR; Antonian, E; Grafstein, B Extracellular proteins of goldfish optic tectum labeled by intraocular injection of 3H proline Exp. Neurol, 1992, 117, 260-268.
[http://dx.doi.org/10.1016/0014-4886(92)90135-D]
]. Generally, an anti-adhesive potential of ependymins would be in agreement with their synthesis in the endomeninx, where they could be responsible for a diffuse projection of posthatching retinal axons [1Hoffmann, W; Schwarz, H Ependymins: meningeal derived extracellular matrix proteins at the blood brain barrier Int. Rev. Cytol, 1996, 165, 121-158.
[http://dx.doi.org/10.1016/S0074-7696(08)62221-4]
].

Soluble ependymins are the major protein constituents of the cerebrospinal fluid (CSF) of many teleost fish [5Müller-Schmid, A; Rinder, H; Lottspeich, F; Gertzen, E-M; Hoffmann, W Ependymins from the cerebrospinal fluid of salmonid fish: gene structure and molecular characterization Gene, 1992, 118, 189-196., 6Müller-Schmid, A; Ganß, B; Gorr, T; Hoffmann, W Molecular analysis of ependymins from the cerebrospinal fluid of the orders Clupeiformes and Salmoniformes: no indication for the existence of an euteleost infradivision J. Mol. Evol, 1993, 36, 578-585.
[http://dx.doi.org/10.1007/BF00556362] [PMID: 8350351]
, 18Königstorfer, A; Sterrer, S; Hoffmann, W Biosynthesis of ependymins from goldfish brain J. Biol. Chem, 1989, 264, 13689-13692.
[PMID: 2760037]
, 19Hoffmann, W Goldfish ependymins: cerebrospinal fluid proteins of meningeal origin Prog. Brain Res, 1992, 91, 13-17.
[http://dx.doi.org/10.1016/S0079-6123(08)62310-9]
]. Here they bind approximately 66% of the soluble Ca2+ (for example, trout CSF contains about 2.7 mM soluble Ca2+) [8Ganss, B; Hoffmann, W Calcium binding to sialic acids and its effect on the conformation of ependymins Eur. J. Biochem, 1993, 217, 275-280.
[http://dx.doi.org/10.1111/j.1432-1033.1993.tb18243.x] [PMID: 7693461]
]. Interestingly, the expression of ependymins is strongly cold-induced [20Tang, S-J; Sun, K-H; Sun, G-H; Lin, G; Lin, W-W; Chuang, M-J Cold-induced ependymin expression in zebrafish and carp brain: implications for cold acclimation FEBS Lett, 1999, 459, 95-99.
[http://dx.doi.org/10.1016/S0014-5793(99)01229-6]
]. A bound form of these glycoproteins is associated with the brain ECM, collagen fibrils being the predominant targets [4Schwarz, H; Müller-Schmid, A; Hoffmann, W Ultrastructural localization of ependymins in the endomeninx of the brain of the rainbow trout: possible association with collagen fibrils of the extracellular matrix Cell Tissue Res, 1993, 273, 417-425.
[http://dx.doi.org/10.1007/BF00333696]
]. Thus far, the precise mode of interaction is not known. However, the calcium-binding capacity of ependymins [8Ganss, B; Hoffmann, W Calcium binding to sialic acids and its effect on the conformation of ependymins Eur. J. Biochem, 1993, 217, 275-280.
[http://dx.doi.org/10.1111/j.1432-1033.1993.tb18243.x] [PMID: 7693461]
] may be important for this association because self-assembly of the extracellular matrix is known to be Ca2+-dependent [21Yurchenco, PD; Schittny, JC Molecular architecture of basement membranes FASEB J, 1990, 4, 1577-1590.
[PMID: 2180767]
]. Circular dichroism (CD) measurements have revealed that binding of Ca2+ effects the conformation of trout ependymins by changing their tertiary but not their secondary structure [8Ganss, B; Hoffmann, W Calcium binding to sialic acids and its effect on the conformation of ependymins Eur. J. Biochem, 1993, 217, 275-280.
[http://dx.doi.org/10.1111/j.1432-1033.1993.tb18243.x] [PMID: 7693461]
]. The drastic change of the predominant signal at 288 nm is a strong indication that the single tryptophan residue at position 120 [5Müller-Schmid, A; Rinder, H; Lottspeich, F; Gertzen, E-M; Hoffmann, W Ependymins from the cerebrospinal fluid of salmonid fish: gene structure and molecular characterization Gene, 1992, 118, 189-196.] is affected by this transition [8Ganss, B; Hoffmann, W Calcium binding to sialic acids and its effect on the conformation of ependymins Eur. J. Biochem, 1993, 217, 275-280.
[http://dx.doi.org/10.1111/j.1432-1033.1993.tb18243.x] [PMID: 7693461]
]. However, the CD measurements covered only the range up to 2 mM Ca2+ and a clear statement concerning the transition point was not possible with this method.

Here, we report on extended studies where the tryptophan fluorescence of ependymins from the rainbow trout has been monitored at various Ca2+ concentrations. Ependymins from this quasi-tetraploid species are encoded by two homologous genes. Both gene products contain a single tryptophan residue [5Müller-Schmid, A; Rinder, H; Lottspeich, F; Gertzen, E-M; Hoffmann, W Ependymins from the cerebrospinal fluid of salmonid fish: gene structure and molecular characterization Gene, 1992, 118, 189-196.] which is strictly conserved in ependymin sequences of all species analyzed thus far [6Müller-Schmid, A; Ganß, B; Gorr, T; Hoffmann, W Molecular analysis of ependymins from the cerebrospinal fluid of the orders Clupeiformes and Salmoniformes: no indication for the existence of an euteleost infradivision J. Mol. Evol, 1993, 36, 578-585.
[http://dx.doi.org/10.1007/BF00556362] [PMID: 8350351]
, 7Orti, G; Meyer, A Molecular evolution of ependymin and the phylogenetic resolution of early divergences among euteleost fishes Mol. Biol. Evol, 1996, 13, 556-573.
[http://dx.doi.org/10.1093/oxfordjournals.molbev.a025616] [PMID: 8882499]
].

MATERIALS AND METHODS

Ependymins (Mr on SDS polyacrylamide gel electrophoresis: ≈ 37k) were purified from the CSF of rainbow trouts (Oncorhynchus mykiss) via a two step FPLC procedure using ion exchange and hydrophobic interaction chromatography as described previously [8Ganss, B; Hoffmann, W Calcium binding to sialic acids and its effect on the conformation of ependymins Eur. J. Biochem, 1993, 217, 275-280.
[http://dx.doi.org/10.1111/j.1432-1033.1993.tb18243.x] [PMID: 7693461]
]. Purified ependymins consisted of three glycoforms termed A, B, and C [5Müller-Schmid, A; Rinder, H; Lottspeich, F; Gertzen, E-M; Hoffmann, W Ependymins from the cerebrospinal fluid of salmonid fish: gene structure and molecular characterization Gene, 1992, 118, 189-196.] where form A contributed to more than 95% and form C was detectable only in traces (data not shown).

Specific monitoring of the tryptophan fluorescence after excitation at 295 nm has been established as a method for the detection of conformational changes of proteins [22Lakowicz, JR Principles of Fluorescence Spectroscopy; Plenum Press, New York: London, 1983.
[http://dx.doi.org/10.1007/978-1-4615-7658-7]
, 23Hutnik, CML; MacManus, JP; Banville, D; Szabo, AG Comparison of metal ion-induced conformational changes in parvalbumin and oncomodulin as probed by the intrinsic fluorescence of tryptophan 102 J. Biol. Chem, 1990, 265, 11456-11464.
[PMID: 2365679]
]. Thus, 180 μg FPL-purified trout ependymins were dissolved per ml of 14 mM NaCl, 10 mM Tris/pH 7.4, 10 mM CaCl2 and a fluorescence spectrum was recorded with a RF-5000 spectrofluorometer (Shimadzu Deutschland GmbH, Duisburg, Germany) at 20°C using thermostat-controlled quartz cells (Hellma, Mühlheim, Germany) of 1-cm path length. Additionally, the fluorescence spectrum was recorded after complete complexation of Ca2+ by EDTA/pH 7.5. A maximum was observed for both Ca2+ concentrations at 335 nm. Then, FPLC-purified trout ependymins were dissolved in 14 mM NaCl, 10 mM Tris/pH 7.4, 10 mM CaCl2. Different Ca2+ concentrations were titrated with various amounts of EDTA/pH 7.5. After excitation at 295 nm, the tryptophan fluorescence of each concentration point was measured at 335 nm. The fluorescence at each concentration point was measured three times (after equilibration for 7 sec). Each relative fluorescence measured was corrected for its actual ependymin concentration. Two independent experimental series were carried out with trout ependymins.

RESULTS AND DISCUSSION

When ependymins at various Ca2+ concentrations were excited at 295 nm, the corrected steady-state emission spectra originating from the single tryptophan residue were comparable in shape, as well as in the wavelength position of the maximum fluorescence intensity (λmax = 335-340 nm) (Fig. 1). In contrast, the relative intensities at λmax varied at different Ca2+ concentrations.

Fig. (1)

Fluorescence spectrum of FPLC-purified ependymins from the rainbow trout. Shown is the relative emission fluorescence of trout ependymins (180 µg/ml) between 300 and 420 nm (Frel, in arbitrary units; excitation at 295 nm) at 10 mM Ca2+ and after complexation with EDTA.



Fig. (2) outlines the result of a typical experiment measuring the fluorescence at 335 nm as a function of the Ca2+ concentration. Generally, two states of ependymins are observed. There is a relatively sharp transition from the apo(Ca2+-free)-proteins to the holo(Ca2+-loaded)-proteins at about 1.0 mM Ca2+. Interestingly, this is very close to the free Ca2+ concentration in the trout CSF (which is about 0.9 mM) and below the total Ca2+ concentration of trout CSF (which is about 2.7 mM) [8Ganss, B; Hoffmann, W Calcium binding to sialic acids and its effect on the conformation of ependymins Eur. J. Biochem, 1993, 217, 275-280.
[http://dx.doi.org/10.1111/j.1432-1033.1993.tb18243.x] [PMID: 7693461]
].

Fig. (2)

Tryptophan fluorescence of FPLC-purified ependymins from the rainbow trout. Shown is the relative emission fluorescence of trout ependymins (191 µg/ml) at 335 nm (Frel, in arbitrary units; excitation at 295 nm) as a function of the Ca2+ concentration. Each point represents the mean of three measurements.



Thus, the holo-state can be considered as the native state of ependymins. Here, similarly to osteonectin/SPARC/BM-40 [24Engel, J; Taylor, W; Paulsson, M; Sage, H; Hogan, B Calcium binding domains and calcium induced conformational transition of SPARC/BM-40/osteonectin, an extracellular glycoprotein expressed in mineralized and nonmineralized tissues Biochemistry, 1987, 26, 6958-6965.
[http://dx.doi.org/10.1021/bi00396a015] [PMID: 3427055]
-26Maurer, P; Mayer, U; Bruch, M; Jenö, P; Mann, K; Landwehr, R; Engel, J; Timpl, R High-affinity and low affinity calcium binding and stability of the multidomain extracellular 40-kDa basement membrane glycoprotein (BM-40/SPARC/osteonectin) Eur. J. Biochem, 1992, 205, 233-240.
[http://dx.doi.org/10.1111/j.1432-1033.1992.tb16773.x] [PMID: 1555584]
], osteopontin, bone sialoprotein and BAG-75 [27Chen, Y; Bal, BS; Gorski, JP Calcium and collagen binding properties of osteopontin, bone sialoprotein, and bone acidic glyco-protein-75 from bone J. Biol. Chem, 1992, 267, 24871-24878.
[PMID: 1447223]
], Ca2+ may trigger maintenance of a native structure which is essential for interaction with the ECM. Also aggregation of ependymins to naturally occurring multimers with Mr of about 200k [28Thormodsson, FR; Parker, TS; Grafstein, B Immunochemical studies of extracellular glycoproteins (X-GPs) of goldfish brain Exp. Neurol, 1992, 118, 275-283.
[http://dx.doi.org/10.1016/0014-4886(92)90184-R]
] may require Ca2+. This processes is particularly reminiscent of the aggregation of fibrinogen at physiological millimolar Ca2+ concentrations, where sialic acid residues represent the low affinity calcium-binding sites [9Dang, CV; Shin, CK; Bell, WR; Nagaswami, C; Weisel, JW Fibrinogen sialic acid residues are low affinity calcium-binding sites that influence fibrin assembly J. Biol. Chem, 1989, 264, 15104-15108.
[PMID: 2549051]
].

Whether the apo-state of ependymins is of any biological importance is not known thus far. As far as it is known it is always the Ca2+-bound state of a Ca2+-binding protein which is active [29Maurer, P; Hohenester, E Structural and functional aspects of calcium binding in extracellular matrix proteins Matrix Biol, 1997, 15, 569-580.
[http://dx.doi.org/10.1016/S0945-053X(97)90033-0]
]. Interestingly, there are multiple reports on severe fluctuations in the extracellular Ca2+ concentration of the brain [30Nicholson, C Modulation of extracellular calcium and its functional implications Fed. Proc, 1980, 39, 1519-1523.
[PMID: 6244979]
-34Pumain, R; Kurcewicz, I; Louvel, J Ionic changes induced by excitatory amino acids in the rat cerebral cortex Can. J. Physiol. Pharmacol, 1987, 65, 1067-1077.
[http://dx.doi.org/10.1139/y87-168] [PMID: 3040202]
]. They could locally be sufficient in order to affect ependymins. The precise nature of the apo-state has not been clarified currently. However, in contrast to a previous report [35Shashoua, VE Monomeric and polymeric forms of ependymin: a brain extracellular glycoprotein implicated in memory consolidation processes Neurochem. Res, 1988, 13, 649-655.
[http://dx.doi.org/10.1007/BF00973283] [PMID: 3412554]
], we have not succeeded in the precipitation of ependymins into insoluble aggregates solely by depletion of Ca2+. Consequently, we exclude that the apo-state represents an insoluble form of ependymins.

Taken together, the Ca2+-binding capacity of cold-induced ependymins would be in line with their postulated function for Ca2+ homeostasis in fish brain [20Tang, S-J; Sun, K-H; Sun, G-H; Lin, G; Lin, W-W; Chuang, M-J Cold-induced ependymin expression in zebrafish and carp brain: implications for cold acclimation FEBS Lett, 1999, 459, 95-99.
[http://dx.doi.org/10.1016/S0014-5793(99)01229-6]
]. Furthermore, the results presented here extend our previous CD measurements which showed a Ca2+ dependent gradual change in the tertiary structure of trout ependymins with only a slight discontinuity at about 1 mM Ca2+ [8Ganss, B; Hoffmann, W Calcium binding to sialic acids and its effect on the conformation of ependymins Eur. J. Biochem, 1993, 217, 275-280.
[http://dx.doi.org/10.1111/j.1432-1033.1993.tb18243.x] [PMID: 7693461]
]. Interestingly, both this discontinuity and the sharp conformational transition observed by monitoring the tryptophan fluorescence occur at the same Ca2+ concentration. Thus, both studies indicate a Ca2+ dependent conformational change of ependymins. However, the tryptophan measurements reported here defined the transition point more clearly. These results also support our hypothesis that this conformational transition is essential for association of ependymins with ECM proteins presumably of collagen fibrils [8Ganss, B; Hoffmann, W Calcium binding to sialic acids and its effect on the conformation of ependymins Eur. J. Biochem, 1993, 217, 275-280.
[http://dx.doi.org/10.1111/j.1432-1033.1993.tb18243.x] [PMID: 7693461]
]. Thus, defining precisely the molecular mode of this interaction might be a crucial step for understanding the molecular function of piscine ependymins in the future.

Furthermore, the Ca2+-triggered conformational changes observed for piscine ependymins could also have some relevance for invertebrate and mammalian ependymin-related proteins. Generally, Ca2+-dependent interactions of ependymins/ependymin-related proteins and ECM proteins such as collagens would be perfectly designed to regulate cell adhesion and cell migration particularly on various basal laminae. This would explain why these enigmatic proteins play important roles for a variety of physiological and pathological processes such as neuronal regeneration and plasticity in fish (for review, see [1Hoffmann, W; Schwarz, H Ependymins: meningeal derived extracellular matrix proteins at the blood brain barrier Int. Rev. Cytol, 1996, 165, 121-158.
[http://dx.doi.org/10.1016/S0074-7696(08)62221-4]
]), intestinal regeneration in sea cucumbers [12Suárez-Castillo, EC; Medina-Ortíz, WE; Roig-López, JL; García-Arrarás, JE Ependymin a gene involved in regeneration and neuroplasticity in vertebrates, is overexpressed during regeneration in the echinoderm Holothuria glaberrima Gene, 2004, 334, 133-143.], tumorigenesis of the human colon [10Nimmrich, I; Erdmann, S; Melchers, U; Chtarbova, S; Finke, U; Hentsch, S; Hoffmann, I; Oertel, M; Hoffmann, W; Müller, O The novel ependymin related gene UCC1 is highly expressed in colorectal tumor cells Cancer Lett, 2001, 165, 71-79.
[http://dx.doi.org/10.1016/S0304-3835(01)00390-1]
], and remodeling of the respiratory mucosa in a murine asthma model [36Kouznetsova, I; Chwieralski, CE; Bälder, R; Hinz, M; Braun, A; Krug, N; Hoffmann, W Induced trefoil factor family 1 expression by trans-differentiating Clara cells in a murine asthma model Am. J. Respir. Cell Mol. Biol, 2007, 36, 286-295.
[http://dx.doi.org/10.1165/rcmb.2006-0008OC] [PMID: 16990615]
].

ACKNOWLEDGEMENTS

We thank Dr. J. Stadlmüller and E. Weiher (Genzentrum, Munich) for their advice during the tryptophan fluorescence measurements and Dr. C. Falkner (Institut für Klinische Chemie, Munich) for her atomic absorption measurements.

REFERENCES

[1] Hoffmann, W; Schwarz, H Ependymins: meningeal derived extracellular matrix proteins at the blood brain barrier Int. Rev. Cytol, 1996, 165, 121-158.
[http://dx.doi.org/10.1016/S0074-7696(08)62221-4]
[2] Königstorfer, A; Sterrer, S; Hoffmann, W Ependymins are expressed in the meninx of goldfish brain Cell Tissue Res, 1990, 261, 59-64.
[http://dx.doi.org/10.1007/BF00329438]
[3] Rinder, H; Bayer, TA; Gertzen, E-M; Hoffmann, W Molecular analysis of the ependymin gene and functional test of ist promoter region by transient expression in brachydanio rerio DNA Cell Biol, 1992, 11, 425-432.
[http://dx.doi.org/10.1089/dna.1992.11.425]
[4] Schwarz, H; Müller-Schmid, A; Hoffmann, W Ultrastructural localization of ependymins in the endomeninx of the brain of the rainbow trout: possible association with collagen fibrils of the extracellular matrix Cell Tissue Res, 1993, 273, 417-425.
[http://dx.doi.org/10.1007/BF00333696]
[5] Müller-Schmid, A; Rinder, H; Lottspeich, F; Gertzen, E-M; Hoffmann, W Ependymins from the cerebrospinal fluid of salmonid fish: gene structure and molecular characterization Gene, 1992, 118, 189-196.
[6] Müller-Schmid, A; Ganß, B; Gorr, T; Hoffmann, W Molecular analysis of ependymins from the cerebrospinal fluid of the orders Clupeiformes and Salmoniformes: no indication for the existence of an euteleost infradivision J. Mol. Evol, 1993, 36, 578-585.
[http://dx.doi.org/10.1007/BF00556362] [PMID: 8350351]
[7] Orti, G; Meyer, A Molecular evolution of ependymin and the phylogenetic resolution of early divergences among euteleost fishes Mol. Biol. Evol, 1996, 13, 556-573.
[http://dx.doi.org/10.1093/oxfordjournals.molbev.a025616] [PMID: 8882499]
[8] Ganss, B; Hoffmann, W Calcium binding to sialic acids and its effect on the conformation of ependymins Eur. J. Biochem, 1993, 217, 275-280.
[http://dx.doi.org/10.1111/j.1432-1033.1993.tb18243.x] [PMID: 7693461]
[9] Dang, CV; Shin, CK; Bell, WR; Nagaswami, C; Weisel, JW Fibrinogen sialic acid residues are low affinity calcium-binding sites that influence fibrin assembly J. Biol. Chem, 1989, 264, 15104-15108.
[PMID: 2549051]
[10] Nimmrich, I; Erdmann, S; Melchers, U; Chtarbova, S; Finke, U; Hentsch, S; Hoffmann, I; Oertel, M; Hoffmann, W; Müller, O The novel ependymin related gene UCC1 is highly expressed in colorectal tumor cells Cancer Lett, 2001, 165, 71-79.
[http://dx.doi.org/10.1016/S0304-3835(01)00390-1]
[11] Apostolopoulos, J; Sparrow, RL; McLeod, JL; Collier, FM; Darcy, PK; Slater, HR; Ngu, C; Gregorio-King, CC; Kirkland, MA Identification and characterization of a novel family of mammalian ependymin-related proteins (MERPs) in hematopoietic, nonhematopoietic, and malignant tissues DNA Cell Biol, 2001, 20, 625-635.
[12] Suárez-Castillo, EC; Medina-Ortíz, WE; Roig-López, JL; García-Arrarás, JE Ependymin a gene involved in regeneration and neuroplasticity in vertebrates, is overexpressed during regeneration in the echinoderm Holothuria glaberrima Gene, 2004, 334, 133-143.
[13] Suárez-Castillo, EC; García-Arrarás, JE Molecular evolution of the ependymin protein family: a necessary update BMC Evol. Biol, 2007, 7, 23-42.
[http://dx.doi.org/10.1186/1471-2148-7-23] [PMID: 17302986] [PMCID: PMC1805737]
[14] Shashoua, VE The role of brain extracellular proteins in neuroplasticity and learning Cell Mol. Neurobiol, 1985, 5, 183-207.
[http://dx.doi.org/10.1007/BF00711092] [PMID: 4028066]
[15] Schmidt, R; Brysch, W; Rother, S; Schlingensiepen, K-H Inhibition of memory consolidation after active avoidance conditioning by antisense intervention with ependymin gene expression J. Neurochem, 1995, 65, 1465-1471.
[http://dx.doi.org/10.1046/j.1471-4159.1995.65041465.x] [PMID: 7561839]
[16] Schmidt, JT; Shashoua, VE Antibodies to ependymin block the sharpening of the regenerating retinotectal projection in goldfish Brain Res, 1988, 446, 269-284.
[http://dx.doi.org/10.1016/0006-8993(88)90886-4]
[17] Thormodsson, FR; Antonian, E; Grafstein, B Extracellular proteins of goldfish optic tectum labeled by intraocular injection of 3H proline Exp. Neurol, 1992, 117, 260-268.
[http://dx.doi.org/10.1016/0014-4886(92)90135-D]
[18] Königstorfer, A; Sterrer, S; Hoffmann, W Biosynthesis of ependymins from goldfish brain J. Biol. Chem, 1989, 264, 13689-13692.
[PMID: 2760037]
[19] Hoffmann, W Goldfish ependymins: cerebrospinal fluid proteins of meningeal origin Prog. Brain Res, 1992, 91, 13-17.
[http://dx.doi.org/10.1016/S0079-6123(08)62310-9]
[20] Tang, S-J; Sun, K-H; Sun, G-H; Lin, G; Lin, W-W; Chuang, M-J Cold-induced ependymin expression in zebrafish and carp brain: implications for cold acclimation FEBS Lett, 1999, 459, 95-99.
[http://dx.doi.org/10.1016/S0014-5793(99)01229-6]
[21] Yurchenco, PD; Schittny, JC Molecular architecture of basement membranes FASEB J, 1990, 4, 1577-1590.
[PMID: 2180767]
[22] Lakowicz, JR Principles of Fluorescence Spectroscopy; Plenum Press, New York: London, 1983.
[http://dx.doi.org/10.1007/978-1-4615-7658-7]
[23] Hutnik, CML; MacManus, JP; Banville, D; Szabo, AG Comparison of metal ion-induced conformational changes in parvalbumin and oncomodulin as probed by the intrinsic fluorescence of tryptophan 102 J. Biol. Chem, 1990, 265, 11456-11464.
[PMID: 2365679]
[24] Engel, J; Taylor, W; Paulsson, M; Sage, H; Hogan, B Calcium binding domains and calcium induced conformational transition of SPARC/BM-40/osteonectin, an extracellular glycoprotein expressed in mineralized and nonmineralized tissues Biochemistry, 1987, 26, 6958-6965.
[http://dx.doi.org/10.1021/bi00396a015] [PMID: 3427055]
[25] Sage, H; Vernon, RB; Funk, SE; Everitt, EA; Angello, J SPARC, a secreted protein associated with cellular proliferation, inhibits cell spreading in vitro and exhibits Ca2+-dependent binding to the extracellular matrix J. Cell Biol, 1989, 109, 341-356.
[http://dx.doi.org/10.1083/jcb.109.1.341] [PMID: 2745554]
[26] Maurer, P; Mayer, U; Bruch, M; Jenö, P; Mann, K; Landwehr, R; Engel, J; Timpl, R High-affinity and low affinity calcium binding and stability of the multidomain extracellular 40-kDa basement membrane glycoprotein (BM-40/SPARC/osteonectin) Eur. J. Biochem, 1992, 205, 233-240.
[http://dx.doi.org/10.1111/j.1432-1033.1992.tb16773.x] [PMID: 1555584]
[27] Chen, Y; Bal, BS; Gorski, JP Calcium and collagen binding properties of osteopontin, bone sialoprotein, and bone acidic glyco-protein-75 from bone J. Biol. Chem, 1992, 267, 24871-24878.
[PMID: 1447223]
[28] Thormodsson, FR; Parker, TS; Grafstein, B Immunochemical studies of extracellular glycoproteins (X-GPs) of goldfish brain Exp. Neurol, 1992, 118, 275-283.
[http://dx.doi.org/10.1016/0014-4886(92)90184-R]
[29] Maurer, P; Hohenester, E Structural and functional aspects of calcium binding in extracellular matrix proteins Matrix Biol, 1997, 15, 569-580.
[http://dx.doi.org/10.1016/S0945-053X(97)90033-0]
[30] Nicholson, C Modulation of extracellular calcium and its functional implications Fed. Proc, 1980, 39, 1519-1523.
[PMID: 6244979]
[31] Benninger, C; Kadis, J; Prince, DA Extracellular calcium and potassium changes in hippocampal slices Brain Res, 1980, 187, 165-182.
[http://dx.doi.org/10.1016/0006-8993(80)90502-8]
[32] Krnjevic, K; Morris, ME; Reiffenstein, RJ Stimulation-evoked changes in extracellular K+ and Ca2+ in pyramidal layers of the rat's hippocampus Can. J. Physiol. Pharmacol, 1982, 60, 1643-1657.
[http://dx.doi.org/10.1139/y82-243] [PMID: 7165860]
[33] Pumain, R; Heinemann, U Stimulus- and amino acid induced calcium and potassium changes in rat neocortex J. Neurophysiol, 1985, 53, 1-14.
[PMID: 2857775]
[34] Pumain, R; Kurcewicz, I; Louvel, J Ionic changes induced by excitatory amino acids in the rat cerebral cortex Can. J. Physiol. Pharmacol, 1987, 65, 1067-1077.
[http://dx.doi.org/10.1139/y87-168] [PMID: 3040202]
[35] Shashoua, VE Monomeric and polymeric forms of ependymin: a brain extracellular glycoprotein implicated in memory consolidation processes Neurochem. Res, 1988, 13, 649-655.
[http://dx.doi.org/10.1007/BF00973283] [PMID: 3412554]
[36] Kouznetsova, I; Chwieralski, CE; Bälder, R; Hinz, M; Braun, A; Krug, N; Hoffmann, W Induced trefoil factor family 1 expression by trans-differentiating Clara cells in a murine asthma model Am. J. Respir. Cell Mol. Biol, 2007, 36, 286-295.
[http://dx.doi.org/10.1165/rcmb.2006-0008OC] [PMID: 16990615]

Endorsements



"We have always had a fruitful cooperation and long-term experience of publishing with Bentham Open."

"A number of our original papers have appeared in its different journals, as the Bentham Open Publishers provides sufficient research in the field of science and technologies (belonging to the pharmaceutical, biotechnology, biomedical industries etc). The staff of the Bentham Open always treat our papers very seriously and gently during the rutile paper reviewing process, so far we always felt their kindness and highly cooperative support. Today, Bentham Open is providing a great support to science and research, giving opportunities of high standard publishing as well as promoting and enhancing selected papers around the world through communication and exchange of global scientific education."


Kholmirzo T. Kholmurodov
Leading Scientist
FLNP (Frank Laboratory of Neutron Physics) JINR (Joint Institute of Nuclear Research) Moscow region, Russia


Browse Contents



Webmaster Contact: info@benthamopen.net
Copyright © 2019 Bentham Open