The secretion of proteins in vitro from Xenopus oocytes and their accessory cells: a biochemical and morphological study

Development ◽  
1981 ◽  
Vol 61 (1) ◽  
pp. 367-383
Author(s):  
T. J. Mohun ◽  
C. D. Lane ◽  
A. Colman ◽  
C. C. Wylie
Keyword(s):  
Gel Electrophoresis ◽  
Messenger Rna ◽  
Morphological Study ◽  
Xenopus Oocytes ◽  
Secretory Proteins ◽  
Xenopus Laevis Oocytes ◽  
Follicular Cells ◽  
Two Dimensional Gel Electrophoresis ◽  
Accessory Cells

Protein secretion by Xenopus laevis oocytes and their surrounding follicular cells in vitro has been investigated using two-dimensional gel electrophoresis. Viable oocytes, devoid of follicle layers, were prepared by treatment with collagenase; they retain in full their capacity to synthesize, sequester and export secretory proteins following microinjection with heterologous messenger RNA. Both RNA-injected and normal cells export a large number of endogenous oocyte proteins and, as with heterologous secretory translation products, these proteins are found within the oocyte in a vesicle fraction. Electron microscopy indicates that secretion involves exocytotic release of cortical vesicle contents. The follicular cells themselves also seem to contribute a number of proteins to the incubation medium surrounding isolated oocytes, but the presence of follicle layers is not required for the export of endogenous oocyte proteins.

Protein synthesis and messenger RNA levels along the animal–vegetal axis during early Xenopus development

Development ◽  
1986 ◽  
Vol 95 (1) ◽  
pp. 15-35
Author(s):  
Rosamund C. Smith
Keyword(s):  
Protein Synthesis ◽  
Gel Electrophoresis ◽  
Messenger Rna ◽  
Xenopus Oocytes ◽  
Early Embryo ◽  
2D Gel Electrophoresis ◽  
Gastrula Stage ◽  
Cleavage Stage ◽  
2D Gel

The patterns of proteins synthesized in animal and vegetal regions of Xenopus oocytes, eggs and embryos were examined by 2D gel electrophoresis. In oocytes and eggs, the only proteins synthesized asymmetrically along the animal-vegetal axis were a small number of proteins synthesized predominantly in the vegetal hemisphere. At the cleavage stage there were a total of four proteins synthesized unevenly in animal and vegetal regions: three synthesized predominantly in the vegetal hemisphere and one synthesized predominantly in the animal hemisphere. By the gastrula stage, when maternal messages have largely been replaced by embryonic transcripts, the number of differences in proteins synthesized in the animal-derived ectoderm and mesoderm, and the vegetal-derived endoderm started to increase rapidly with time of development with many more animal-characteristic proteins than vegetal-characteristic proteins appearing. Comparison of protein synthesis patterns with those obtained when extracted RNA was translated in vitro and run on 2D gels, showed that the asymmetry in protein synthesis along the animal-vegetal axis in the oocyte and early embryo reflected directly the distribution of their mRNAs along the axis. There was no evidence for localized ‘masked’ abundant messages along the animal-vegetal axis of oocytes and cleavage embryos.

scholarly journals Involvement of single-stranded tails in homologous recombination of DNA injected into Xenopus laevis oocyte nuclei.

1991 ◽  
Vol 11 (6) ◽  
pp. 3268-3277 ◽  
Author(s):  
E Maryon ◽  
D Carroll
Keyword(s):  
Homologous Recombination ◽  
Xenopus Laevis ◽  
Gel Electrophoresis ◽  
Xenopus Laevis Oocyte ◽  
Molecular Models ◽  
Mixed Substrates ◽  
Two Dimensional Gel Electrophoresis ◽  
Recombination Pathway ◽  
Made In

Homologous recombination of DNA molecules injected into Xenopus laevis oocyte nuclei is extremely efficient when those molecules are linear and have overlapping homologous ends. It was previously shown that a 5'----3' exonuclease activity in oocytes attacks injected linear DNAs and leaves them with single-stranded 3' tails. We tested the hypothesis that such tailed molecules are early intermediates on the pathway to recombination products. Substrates with 3' tails were made in vitro and injected into oocytes, where they recombined rapidly and efficiently. In experiments with mixed substrates, molecules with 3' tails entered recombination intermediates and products more rapidly than did molecules with flush ends. Molecules endowed in vitro with 5' tails also recombined efficiently in oocytes, but their rate was not faster than for flush-ended substrates. In most cases, the 5' tails served as templates for resynthesis of the 3' strands, regenerating duplex ends which then entered the normal recombination pathway. In oocytes from one animal, some of the 5' tails were removed, and this was exacerbated when resynthesis was partially blocked. Analysis by two-dimensional gel electrophoresis of recombination intermediates from 5'-tailed substrates confirmed that they had acquired 3' tails as a result of the action of the 5'----3' exonuclease. These results demonstrate that homologous recombination in oocytes proceeds via a pathway that involves single-stranded 3' tails. Molecular models incorporating this feature are discussed.

Characterization and purification of lupus antigen La, and RNA-binding protein

1985 ◽  
Vol 5 (3) ◽  
pp. 586-590
Author(s):  
A M Francoeur ◽  
E K Chan ◽  
J I Garrels ◽  
M B Mathews
Keyword(s):  
Hela Cell ◽  
Gel Electrophoresis ◽  
Rna Binding ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
In Vitro Translation ◽  
Cell Protein ◽  
Two Dimensional Gel Electrophoresis ◽  
La Antigen

HeLa cell La antigen, an RNA-binding protein, was characterized by using two-dimensional gel electrophoresis. Eight isoelectric forms (pI 6 to 7) were observed, many containing phosphate. An in vitro translation product similar in size and antigenicity was identified. The HeLa cell protein purified by using an assay based on ribonucleoprotein reconstitution with adenovirus VA RNAI also comprised several isoelectric forms.

Effect of terminal nonhomologies on homologous recombination in Xenopus laevis oocytes

1992 ◽  
Vol 12 (12) ◽  
pp. 5426-5437
Author(s):  
S Jeong-Yu ◽  
D Carroll
Keyword(s):  
Homologous Recombination ◽  
Xenopus Laevis ◽  
Gel Electrophoresis ◽  
Recombination Process ◽  
Xenopus Laevis Oocytes ◽  
Oligonucleotide Probes ◽  
Two Dimensional ◽  
Molecular Models ◽  
Two Dimensional Gel Electrophoresis ◽  
Time Courses

Homologous recombination of linear DNA molecules in Xenopus laevis oocytes is very efficient. The predictions of molecular models for this recombination process were tested with substrates with terminal nonhomologies (nonhomologous sequences). It was found that nonhomologies on one or both ends of an otherwise efficient substrate substantially reduced the yield of recombination products. In the case of a single nonhomology, inhibition was observed for all lengths of nonhomology, from 60 to 1,690 bp, being most dramatic for the longer blocks. Examination of time courses of recombination showed that the blocks were largely kinetic; that is, substrates with short nonhomologies eventually yielded substantial levels of completed products. Intermediates that accumulated after the injection of end-blocked substrates were characterized by two-dimensional gel electrophoresis and hybridization with strand-specific oligonucleotide probes. These blocked intermediates were shown to have base-paired junctions, but resolution was prevented by the failure to remove the 3'-ending strand of the original nonhomology. Continuing exonuclease action created a single-strand gap adjacent to the position of the persistent nonhomology. In contrast, the strand that included the unblocked side of the junction could be sealed. These results are consistent with a nonconservative, resection-annealing mechanism of homologous recombination in the oocytes and suggest the absence of any activity that can efficiently remove 3' tails.

Uptake of biotin by native Xenopus laevis oocytes

1990 ◽  
Vol 259 (3) ◽  
pp. C397-C401 ◽  
Author(s):  
H. M. Said ◽  
L. Polenzani ◽  
S. Khorchid ◽  
D. Hollander ◽  
R. Miledi
Keyword(s):  
Xenopus Laevis ◽  
Mammalian Cells ◽  
Xenopus Oocytes ◽  
Sulfhydryl Group ◽  
Maximum Velocity ◽  
Significant Inhibition ◽  
Metabolic Inhibitors ◽  
Xenopus Laevis Oocytes ◽  
Uptake System

The present study examined biotin uptake by Xenopus laevis oocytes in vitro. Uptake of low (0.03 microM) and high (10 microM) concentrations of biotin was linear with time for up to 4 h of incubation and occurred with little initial binding to oocytes. Uptake of biotin was dependent on extracellular Na+ concentration [Na+]o and was severely inhibited when Na+ was replaced by other monovalent cations [choline, tetraethylammonia, Li+, and tris(hydroxymethyl)aminomethane]. The initial rate of biotin uptake was saturable as a function of concentration with an apparent Michaelis constant of 3.9 +/- 0.5 microM and maximum velocity of 1,559 +/- 70 fmol.oocyte-1.h-1. Addition to the incubation medium of biotin structural analogues desthiobiotin and thioctic acid caused significant and concentration-dependent inhibition in the uptake of [3H]biotin. This inhibition was found to be competitive in nature with inhibition constant values of 9 and 17.5 microM. In contrast, neither the structural analogue biocytin nor biotin methyl ester (compounds in which the carboxyl group of the valeric acid moiety is blocked) showed any effect on the uptake of [3H]biotin. Biotin uptake was significantly blocked by the metabolic inhibitors dinitrophenol, cyanide, and azide and by incubation at 4 degrees C. Also, the sulfhydryl group blocker p-(chloromercuri)phenylsulfonate caused significant inhibition in biotin uptake. These results demonstrate that Xenopus oocytes possess an uptake system for biotin in its cell membrane that is Na+, energy, and temperature dependent. These characteristics of biotin uptake are similar to those reported in mammalian cells. It is suggested that Xenopus oocytes might be a useful in vitro model system to study the details of the mechanisms and regulation of biotin movement across biological membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Remifentanil Directly Activates Human N-methyl-d-aspartate Receptors Expressed in Xenopus laevis Oocytes

2004 ◽  
Vol 100 (6) ◽  
pp. 1531-1537 ◽  
Author(s):  
Klaus Hahnenkamp ◽  
Joke Nollet ◽  
Hugo K. Van Aken ◽  
Hartmut Buerkle ◽  
Tobias Halene ◽  
...  
Keyword(s):  
Nmda Receptor ◽  
Postoperative Pain ◽  
Xenopus Laevis ◽  
Nmda Receptors ◽  
Messenger Rna ◽  
Xenopus Laevis Oocytes ◽  
Opiate Tolerance ◽  
Induced Currents ◽  
Pore Blocker

Background Clinical studies suggest that intraoperative administration of the clinical remifentanil formulation Ultiva (GlaxoWellcome GmbH & Co, Bad Oldesloe, Germany) increases postoperative pain and postoperative analgesic requirements, but mechanisms remain unclear. N-methyl-D-aspartate (NMDA) receptors are thought to play a major role in development of postoperative pain and opiate tolerance. The authors hypothesized that Ultiva directly stimulates human NMDA receptors. Methods To test this hypothesis, the authors expressed human NR1A/NR2A and NR1A/NR2B NMDA receptors in Xenopus laevis oocytes by injection of messenger RNA prepared in vitro. After protein expression, they used a two-electrode voltage clamp to measure currents induced by NMDA receptor agonists and opioids. Results Noninjected cells were unresponsive to all compounds tested. Glutamate/glycine (1 nM-1 mM each) or Ultiva (0.01 pM-0.1 mM) stimulated NMDA receptors concentration dependently. NR1A/2A EC50 values were 8.0 microM/12 microM for glutamate/glycine and 3.5 nM for Ultiva, and NR1A/2B EC50 values were 3.9 microM/1.9 microM for glutamate/glycine and 0.82 microM for Ultiva. Glycine in combination with Ultiva showed no additive effect compared with Ultiva alone. Ultiva-induced currents were inhibited by MK-801 (pore blocker) but not by 7-CK (glycine antagonist), D-AP5 (glutamate antagonist), or naloxone. Fentanyl (10 microM) did not stimulate NMDA receptors. Conclusion These data indicate that Ultiva but not fentanyl stimulates NMDA receptors of different subunit combinations (NR1A/2A, NR1A/2B). The mechanism seems to be allosteric activation of the NMDA receptor.

scholarly journals Multiple forms of tubulin in the cytoskeletal and flagellar microtubules of polytomella

1981 ◽  
Vol 91 (2) ◽  
pp. 352-360 ◽  
Author(s):  
TW McKeithan ◽  
JL Rosenbaum
Keyword(s):  
Protein Synthesis ◽  
Gel Electrophoresis ◽  
Cold Temperature ◽  
Two Dimensional ◽  
Multiple Forms ◽  
Cytoplasmic Fraction ◽  
Two Dimensional Gel Electrophoresis ◽  
Brain Tubulin ◽  
Β Tubulin

The alga polytomella contains several organelles composed of microtubules, including four flagella and hundreds of cytoskeletal microtubules. Brown and co-workers have shown (1976. J. Cell Biol. 69:6-125; 1978, Exp. Cell Res. 117: 313-324) that the flagella could be removed and the cytoskeletans dissociated, and that both structures could partially regenerate in the absence of protein synthesis. Because of this, and because both the flagella and the cytoskeletons can be isolated intact, this organism is particularly suitable for studying tubulin heterogeneity and the incorporation of specific tubulins into different microtubule-containing organelles in the same cell. In order to define the different species of tubulin in polytonella cytoplasm, a (35)S- labeled cytoplasmic fraction was subjected to two cycles of assembly and disassembly in the presence of unlabeled brain tubulin. Comparison of the labeled polytomella cytoplasmic tubulin obtained by this procedure with the tubulin of isolated polytomella flagella by two-dimensional gel electrophoresis showed that, whereas the β-tubulin from both cytoplasmic and flagellar tubulin samples comigrated, the two α-tubulins had distinctly different isoelectic points. As a second method of isolating tubulin from the cytoplasm, cells were gently lysed with detergent and intact cytoskeletons obtained. When these cytoskeletons were exposed to cold temperature, the proteins that were released were found to be highly enriched in tubulin; this tubulin, by itself, could be assembled into microtubules in vitro. The predominant α-tubulin of this in vitro- assembled cytoskeletal tubulin corresponded to the major cytoplasmic α-tubulin obtained by coassembly of labeled polytomella cytoplasmic extract with brain tubulin and was quite distinct from the α-tubulin of purified flagella. These results clearly show that two different microtubule-containing organelles from the same cell are composed of distinct tubulins.

scholarly journals Platelet-collagen adhesion: inhibition by a monoclonal antibody that binds glycoprotein IIb.

1984 ◽  
Vol 99 (6) ◽  
pp. 2056-2060 ◽  
Author(s):  
P J Shadle ◽  
M H Ginsberg ◽  
E F Plow ◽  
S H Barondes
Keyword(s):  
Monoclonal Antibody ◽  
Gel Electrophoresis ◽  
Polyclonal Antiserum ◽  
Platelet Glycoprotein ◽  
Two Dimensional Gel Electrophoresis ◽  
Vitro Assay ◽  
Platelet Surface ◽  
Reducing Conditions ◽  
Purified Antigen

To identify platelet surface structures involved in adhesion to collagen, the effect of 16 murine antiplatelet membrane hybridoma antibodies were tested in a defined, in vitro assay. Four of these antibodies inhibited platelet-collagen adhesion and reacted with a polypeptide with Mr approximately 125,000, as determined by immunoblots after gel electrophoresis under reducing conditions. Through detailed studies with one of these antibodies, the monoclonal antibody PMI-1, the relevant antigen was identified as platelet glycoprotein IIb alpha, based upon (a) co-migration with this glycoprotein in two-dimensional gel electrophoresis and (b) co-purification by immunoaffinity chromatography with a protein with apparent Mr identical to that of glycoprotein III, under conditions in which glycoproteins IIb and III form a complex. Univalent antibody fragments prepared from monoclonal antibody PMI-1 inhibited greater than 80% of platelet-collagen adhesion, and inhibition was completely blocked by the immunopurified antigen. These results indicate that glycoprotein IIb participates in some aspect of platelet-collagen adhesion. In contrast, the purified antigen only partially neutralized a polyclonal antiserum that blocked platelet-collagen adhesion, to a maximum of approximately 25%, at saturating antigen concentrations. Thus, by these immunological criteria, glycoprotein IIb is not the only molecule involved in this process.

scholarly journals Initiation and processing in vitro of the primary translation products of guinea-pig caseins

1979 ◽  
Vol 184 (2) ◽  
pp. 261-267 ◽  
Author(s):  
R K Craig ◽  
P A J Perera ◽  
A Mellor ◽  
A E Smith
Keyword(s):  
Guinea Pig ◽  
Sodium Dodecyl Sulphate ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Polyacrylamide Gel ◽  
Secretory Proteins ◽  
Post Translational Modifications ◽  
Microsomal Membranes

1. Guinea-pig caseins synthesized in a mRNA-directed wheat-germ cell-free protein-synthesizing system represent the primary translation products, even though they appear to be of lower molecular weight when analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis in parallel with caseins isolated from guinea-pig milk. 2. Identification of the N-terminal dipeptide of the primary translational product of caseins A, B and C and alpha-lactalbumin showed that all shared a common sequence, which was identified as either Met-Arg or Met-Lys. 3. Procedures utilizing methionyl-tRNAfMet or methionyl-tRNAMet in the presence or absence of microsomal membranes during translation provide a rapid method of distinguishing between N-terminal processing of peptides synthesized in vitro and other post-translational modifications (glycosylation, phosphorylation), which also result in a change in mobility of peptides when analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. 4. The results demonstrate that guinea-pig caseins, in common with most other secretory proteins, are synthesized with transient N-terminal ‘signal’-peptide extensions, which are cleaved during synthesis in the presence of microsomal membranes.

scholarly journals Functional expression of mammalian glucose transporters in Xenopus laevis oocytes: evidence for cell-dependent insulin sensitivity.

1989 ◽  
Vol 9 (10) ◽  
pp. 4187-4195 ◽  
Author(s):  
J C Vera ◽  
O M Rosen
Keyword(s):  
Glucose Uptake ◽  
Rat Brain ◽  
Xenopus Oocytes ◽  
Glucose Transporter ◽  
Glucose Transporters ◽  
Functional Expression ◽  
Xenopus Laevis Oocytes ◽  
Rat Brain And Liver ◽  
Insulin Responsiveness

We report the functional expression of two different mammalian facilitative glucose transporters in Xenopus oocytes. The RNAs encoding the rat brain and liver glucose transporters were transcribed in vitro and microinjected into Xenopus oocytes. Microinjected cells showed a marked increase in 2-deoxy-D-glucose uptake as compared with controls injected with water. 2-Deoxy-D-glucose uptake increased during the 5 days after microinjection of the RNAs, and the microinjected RNAs were stable for at least 3 days. The expression of functional glucose transporters was dependent on the amount of RNA injected. The oocyte-expressed transporters could be immunoprecipitated with anti-brain and anti-liver glucose transporter-specific antibodies. Uninjected oocytes expressed an endogenous transporter that appeared to be stereospecific and inhibitable by cytochalasin B. This transporter was kinetically and immunologically distinguishable from both rat brain and liver glucose transporters. The uniqueness of this transporter was confirmed by Northern (RNA) blot analysis. The endogenous oocyte transporter was responsive to insulin and to insulinlike growth factor I. Most interestingly, both the rat brain and liver glucose transporters, which were not insulin sensitive in the tissues from which they were cloned, responded to insulin in the oocyte similarly to the endogenous oocyte transporter. These data suggest that the insulin responsiveness of a given glucose transporter depends on the type of cell in which the protein is expressed. The expression of hexose transporters in the microinjected oocytes may help to identify tissue-specific molecules involved in hormonal alterations in hexose transport activity.

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