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PubMed1983

A quantitative study of the position of the Golgi apparatus in the developing chick myocardium. Effects of colchicine administration.

This paper presents a quantitative study of the position of the Golgi apparatus in the developing chick myocardium between stages 8+ and 13+. In addition we have studied the effects of colchicine on the position and structure of the Golgi apparatus. During the formation of the heart tube and loop the position of the Golgi apparatus in the myocytes situated in the vicinity of the dorsal mesocardium is related to that found in the cells of the precardiac mesoderm, but it is completely different from that found in the bulk of myocytes of the heart tube and loop. The position of the Golgi apparatus in both pre- and myocardial cells shows clear significative patterns of polarity. The possible significance of the Golgi apparatus polarity is discussed. After colchicine treatment microtubules disappear, the Golgi apparatus loses its polarization and vacuoles filled with amorphous material and/or collagen fibrils are observed. A possible role of the microtubular system in the maintenance of the structure and polarity of the Golgi apparatus and in the intracytoplasmic transport of the cardiac jelly materials is proposed.

Animals↗
PubMed1994

Fragmentation of the Golgi apparatus of motor neurons in amyotrophic lateral sclerosis (ALS). Clinical studies in ALS of Guam and experimental studies in deafferented neurons and in beta,beta'-iminodipropionitrile axonopathy.

Previous morphological immunoenzymatic studies with organelle-specific antibodies have disclosed an apparent fragmentation of the Golgi apparatus in large numbers of motor neurons in 12 cases of sporadic, non-Guamanian amyotrophic lateral sclerosis (ALS) in three cases of other types of motor neuron disease and in one case of a mitochondrial myopathy with cytochrome c oxidase deficiency. Motor neurons with fragmented Golgi apparatus were moderately atrophic; in these cells, discrete immunostained elements of the organelle were twice as many as in normal neurons, and the size of each Golgi element and the percentage of the cytoplasmic area occupied by the Golgi apparatus were reduced (Am J Pathol 1992, 140: 731-737). In this report we have confirmed the fragmentation of the organelle of motor neurons in the spinal cord in six sporadic cases of Guamanian ALS. In four of the six cases the clinical course was 1 to 2 years. The percentages of motor neurons with fragmented Golgi apparatus varied from 38 to 92. Motor neurons from three additional cases of Guamanian ALS of clinical duration from 5 to 7 years did not show fragmentation of the Golgi apparatus. In two cases of Guamanian ALS and in one non-Guamanian ALS, all neurons with ubiquitin-positive skein-like or granular inclusions believed to be pathognomonic for ALS had fragmented Golgi apparatus. To examine whether the fragmentation of the Golgi apparatus results from reactions to either neuronal deafferentation or to lesions of proximal axons, we conducted two experimental studies. In the first study, we examined in cats the Golgi apparatus of deafferented neurons of the dorsal lateral geniculate nucleus. In the second study, we examined the Golgi apparatus of motor neurons in the spinal cord of rats with proximal axonopathy induced by beta,beta'-iminodipropionitrile. In these two experiments, the neuronal Golgi apparatus studied by immunoenzymatic techniques and morphometry, was not fragmented. Taken together, the results of these studies strongly suggest that the fragmentation of the Golgi apparatus of motor neurons in ALS represents an important and perhaps early change of the organelle that may be involved in the pathogenesis of ALS. The fragmentation of the Golgi apparatus of motor neurons is a fairly specific and easily recognizable marker of ALS and may be used together with other criteria for comparisons between the human disease and proposed animal models of the disorder.

Adult↗
PubMed1999

From the "apparato reticolare interno" to "the Golgi": 100 years of Golgi apparatus research.

The year 1998 is the centenary of the Golgi apparatus. It is an occasion to pay tribute to Camillo Golgi and the other pioneers of Golgi apparatus research. From the very beginning, the discussion of the Golgi apparatus was characterized by a great variety of theories and innovative terminology, with signs of keen interest already evident during the era of light microscopy.

Animals↗
PubMed1991

Cyclic localization change of Golgi apparatus in Sertoli cells induced by mature spermatids in rats.

Previously we reported that the intracellular localization of the Golgi apparatus of rat Sertoli cells changes during the seminiferous epithelial cycle, and that the cyclic changes seem to be correlated to specific generations of germ cells. To ascertain which generations of germ cells are responsible for the cyclic changes, we determined the relative volume of the Golgi apparatus within the basal, mid, and apical cytoplasm of Sertoli cells in testes with and without mature spermatids. In normal adult rats, the Golgi apparatus was usually localized exclusively in the basal cytoplasm, whereas at stages VII-IX it increased remarkably in mid and apical cytoplasm, with a concomitant decrease in the basal cytoplasm. In young adult testes without spermatids at steps 15-19 of spermiogenesis (2nd layer spermatids), the Golgi apparatus was localized in the basal cytoplasm throughout the seminiferous epithelial cycle. Orchiopexy maintained for 35 days following 60 days of cryptorchidism allowed germ cells to regenerate to spermatids at steps 1-14 of sperminogenesis (1st layer spermatids), but failed to change the intracellular localization of the Golgi apparatus in Sertoli cells. At 50 days after orchiopexy, when all generations of germ cells appeared in the tubules, the cyclic changes in localization of the Golgi apparatus were restored similar to those in normal adult testes. These findings indicate that the cyclic change in localization of the Golgi apparatus in Sertoli cells is evoked by the presence of 2nd layer spermatids.

Animals↗
PubMed1970

The Golgi apparatus in chick corneal epithelium: changes in intracellular position during development.

The intracellular position of the Golgi apparatuses in the basal cell layer of the corneal epithelium in embryonic and hatched chicks has been studied in the light microscope by impregnating the Golgi apparatus with silver. During two distinct periods in development the Golgi apparatuses in the basal cells shift from an apical to basal position. Each of these periods correlates in time with the appearance of an acellular collagenous matrix beneath the epithelium. Examination of the basal epithelial cells in the electron microscope confirms the intracellular shifts in position of the Golgi apparatus. The results suggest that the Golgi apparatus shifts to the basal cell pole of the corneal epithelium in order to excrete connective tissue materials into the developing corneal stroma.

Animals↗
PubMed1984

Role of microtubules in the organization and localization of the Golgi apparatus.

Normal interphase PtK2 and A549 cells display long microtubules radiating from the microtubule-organizing center (MTOC) to the plasma membrane. Both MTOC and Golgi apparatus are contained in the same perinuclear area. Treatment of cells with 1 microM colcemid for 2 h results in microtubule depolymerization and fragmentation of the Golgi apparatus into elements scattered throughout the cytoplasm. Both normal microtubules and the Golgi apparatus assemble again following removal of colcemid. Injection of the alpha, beta-nonhydrolyzable GTP analog, guanosine 5'(alpha, beta-methylene)diphosphate [pp(CH2)pG], into interphase cells growing in normal medium results in the formation of microtubule bundles resistant to colcemid and prevents the fragmentation of the Golgi apparatus. Injection of pp(CH2)pG into cells incubated with colcemid results in substitution of tubulin ribbons for microtubules and has no effect on the Golgi-derived elements scattered throughout the cytoplasm. Removal of colcemid 1 h after the injection of pp(CH2)pG results in polymerization of large numbers of short, single randomly oriented microtubules, whereas the Golgi apparatus remains fragmented. Treatment of cells with 10 microM taxol for 3 h results both in polymerization of microtubule bundles without relation to the MTOC in the cell periphery and fragmentation of the Golgi apparatus. The Golgi-derived fragments are present exclusively in regions of the peripheral cytoplasm enriched in microtubules. The codistribution of microtubules and Golgi elements can be reversed in taxol-treated cells by injection of a monoclonal (YL 1/2) antibody reacting specifically with the tyrosylated form of alpha-tubulin. Cells incubated with colcemid after treatment with taxol have large numbers of Golgi-derived elements in close association with colcemid-resistant microtubule bundles. Incubation of cells with 50 microM vinblastine for 90 min results in microtubule dissembly, formation of tubulin paracrystals, and fragmentation of the Golgi apparatus into elements without relation to the tubulin paracrystals.

Alkaloids↗
PubMed2004

Dynamic nucleation of Golgi apparatus assembly from the endoplasmic reticulum in interphase hela cells.

Models of Golgi apparatus biogenesis and maintenance are focused on two possibilities: one is self-assembly from the endoplasmic reticulum, and the other is nucleation by a stable template. Here, we asked in three different experimental situations whether assembly of the Golgi apparatus might be dynamically nucleated. During microtubule depolymerization, the integral membrane protein p27 and the peripheral Golgi protein GM130, appeared in newly formed, scattered Golgi elements before three different Golgi apparatus cisternal enzymes, whereas GRASP55, a medial peripheral Golgi protein, showed, if anything, a tendency to accumulate in scattered Golgi elements later than a cisternal enzyme. During Golgi formation after brefeldin A washout, endoplasmic reticulum exit of Golgi resident enzymes could be completely separated from that of p27 and GM130. p27 and GM130 accumulation was onto newly organized perinuclear structures, not brefeldin A remnants, and preceded that of a cisternal enzyme. Reassembly was completely sensitive to guanosine 5'-diphosphate-restricted Sar1p. When cells were microinjected with Sar1pWT DNA to reverse a guanosine 5'-diphosphate-restricted Sar1p endoplasmic reticulum-exit block phenotype, GM130 and p27 collected perinuclearly with little to no exit of a cisternal enzyme from the endoplasmic reticulum. The overall data strongly indicate that the assembly of the Golgi apparatus can be nucleated dynamically by GM130/p27 associated structures. We define dynamic nucleation as the first step in a staged organelle assembly process in which new component association forms a microscopically visible structure onto which other components add later, e.g. Golgi cisternae.

Antineoplastic Agents↗
PubMed1982

A cytochemical study of the Golgi apparatus of the spermatid during spermiogenesis in the rat.

The reactivity of the various components of the Golgi apparatus of rat spermatids for three phosphatase activities (nicotinamide adenine dinucleotide phosphatase, NADPase; thiamine pyrophosphatase, TPPase; cytidine monophosphatase, CMPase) and the incorporation of 3H-fucose by the spermatids was analyzed at the 19 steps of spermiogenesis, i.e., during and after this organelle elaborated the glycoprotein-rich acrosomic system. During steps 1-3, the Golgi apparatus produced, in addition to the proacrosomic granules, multivesicular bodies that became associated with the chromatoid body. NADPase was located within the four of five intermediate saccules of Golgi stacks, and TPPase was found in the last one or two saccules on the trans aspect of the stacks from steps 1 to 17 of spermiogenesis. CMPase was located within the thick saccular GERL elements found in the trans region of the Golgi apparatus from steps 1 to 7 of spermiogenesis, but the CMPase-positive GERL disappeared from the Golgi apparatus after its detachment from the acrosomic system at step 8. Th acrosomic system itself was reactive from CMPase and TPPase but was negative for NADPase, while the multivesicular bodies were CMPase and NADPase positive but unreactive for TPPase. Tritiated-fucose was readily incorporated within the Golgi apparatus of steps 1-17 spermatids; in steps 1-7 it was subsequently incorporated within the acrosomic system and multivesicular bodies. These various data indicated (1) that the Golgi apparatus of spermatids, although it loses its CMPase-positive GERL element in step 8, retains evidence of functional capacity until it degenerates in step 17; (2) that in early spermatids the various saccular components of the Golgi are specialized with respect to enzymatic activities; and (3) that each Golgi region may contribute in a coordinated fashion to the formation of the acrosomic system and multivesicular bodies.

Animals↗
PubMed1992

NADH-activated cell-free transfer between Golgi apparatus and plasma membranes of rat liver.

This report concerns development of a cell-free system from rat liver to study transport of membrane constituents from the Golgi apparatus to the plasma membrane. Highly purified Golgi apparatus as donor and a mixture of sheets and vesicles as plasma membrane acceptor fractions were combined to analyze requirements for lipid and protein transport. In the reconstituted system, the Golgi apparatus donor was in suspension. To measure transfer, membrane constituents of the donor membranes were radiolabeled with [3H]acetate (lipids) or [3H]leucine (proteins). The plasma membrane vesicles were used as the acceptor and were unlabeled and immobilized on nitrocellulose for ease of recovery and analysis. The reconstituted cell-free transfer was dependent on temperature, but even at 37 degrees C, the amount of transfer did not increase with added ATP, was not specific for any particular membrane fraction or subfraction nor was it facilitated by cytosol. ATP was without effect both in the presence or absence of a cytosolic fraction capable of the support of cell-free transfer in other systems. In contrast to results with ATP, NADH added to the reconstituted system resulted in an increased amount of transfer. A further increase in transfer was obtained with NADH plus a mixture of ascorbate and dehydroascorbate to generate ascorbate free radical. The transfer of labeled membrane constituents from the Golgi apparatus to the plasma membrane supported by NADH plus ascorbate radical was stimulated by a cytosol fraction enriched in less than 10 kDa components. This was without effect in the absence of NADH/ascorbate radical or with ATP as the energy source. Specific transfer was inhibited by both N-ethylmaleimide and GTP gamma S. The findings point to the possibility of redox activities associated with the trans region of the Golgi apparatus as potentially involved in the transport of membrane vesicles from the Golgi apparatus to the cytoplasmic surface of the plasma membrane.

Animals↗
PubMed1987

Polypeptides of the Golgi apparatus of neurons from rat brain.

An antiserum was raised against fractions of the Golgi apparatus of neurons from rat brain. Immunoblots of these fractions with the antiserum showed two principal bands of 185 and 150 kilodaltons (kd) in apparent molecular mass. The antiserum reacted with five or six bands of 200, 150, 130, 100-110, 64, and 40 kd in apparent molecular mass in immunoblots of several crude brain membrane fractions. Affinity-purified antibodies from the different gel bands transferred to nitrocellulose paper were used in immunoblot and immunocytochemical studies. Antibodies eluted from the 200-, 150-, 100-110-, and 64-kd bands reacted not only with the corresponding band but also with the other three bands. Antibodies eluted from the 40-kd band stained only the corresponding band. On light and/or electron microscopic immunocytochemistry, the antiserum stained the Golgi apparatus of rat neurons, glia, liver, and kidney tubule cells. Weaker, segmented, and less consistent staining was observed in nuclear envelopes, rough endoplasmic reticulum, and plasma membranes of neurons. Antibodies eluted from the bands at 200, 150, 100-110, and 64 kd stained intermediate cisterns of the Golgi apparatus of neurons. These findings suggest that a group of related polypeptides of brain membranes is preferentially expressed or enriched in the Golgi apparatus of neurons. Polypeptides with apparent molecular masses of 185 and 150 kd probably represent moieties endogenous to membranes of the neuronal Golgi apparatus.

Animals↗
PubMed1988

Isolation of a vesicular intermediate in the cell-free transfer of membrane from transitional elements of the endoplasmic reticulum to Golgi apparatus cisternae of rat liver.

Preparations enriched in part-smooth (lacking ribosomes), part-rough (with ribosomes) transitional elements of the endoplasmic reticulum when incubated with ATP plus a cytosol fraction responded by the formation of blebbing profiles and approximately 60-nm vesicles. The 60-nm vesicles formed resembled closely transition vesicles in situ considered to function in the transfer of membrane materials between the endoplasmic reticulum and the Golgi apparatus. The transition elements following incubation with ATP and cytosol were resolved by preparative free-flow electrophoresis into fractions of differing electronegativity. The main fraction contained the larger vesicles of the transitional membrane elements, while a less electronegative minor shoulder fraction was enriched in the 60-nm vesicles. If the vesicles concentrated by preparative free-flow electrophoresis were from material previously radiolabeled with [3H]leucine and then added to Golgi apparatus immobilized to nitrocellulose, radioactivity was transferred to the Golgi apparatus membranes. The transfer was rapid (T1/2 of about 5 min), efficient (10-30% of the total radioactivity of the transition vesicle preparations was transferred to Golgi apparatus), and independent of added ATP but facilitated by cytosol. Transfer was specific and apparently unidirectional in that Golgi apparatus membranes were ineffective as donor membranes and endoplasmic reticulum vesicles were ineffective as recipient membranes. Using a heterologous system with transition vesicles from rat liver and Golgi apparatus isolated from guinea pig liver, coalescence of the small endoplasmic reticulum-derived vesicles with Golgi apparatus membranes was demonstrated using immunocytochemistry. Employed were polyclonal antibodies directed against the isolated rat transition vesicle preparations. When localized by immunogold procedures at the electron microscope level, regions of rat-derived vesicles were found fused with cisternae of guinea pig Golgi apparatus immobilized to nitrocellulose strips. Membrane transfer was demonstrated from experiments where transition vesicle membrane proteins were radioiodinated by the Bolton-Hunter procedure. Additionally, radiolabeled peptide bands not present initially in endoplasmic reticulum appeared following coalescence of the derived vesicles with Golgi apparatus. These bands, indicative of processing, required that both Golgi apparatus and transition vesicles be present and did not occur in incubated endoplasmic reticulum preparations or on nitrocellulose strips to which no Golgi apparatus were added.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphate↗
PubMed1985

The Golgi apparatus remains associated with microtubule organizing centers during myogenesis.

In vitro myogenesis involves a dramatic reorganization of the microtubular network, characterized principally by the relocalization of microtubule nucleating sites at the surface of the nuclei in myotubes, in marked contrast with the classical pericentriolar localization observed in myoblasts (Tassin, A. M., B. Maro, and M. Bornens, 1985, J. Cell Biol., 100:35-46). Since a spatial relationship between the Golgi apparatus and the centrosome is observed in most animal cells, we have decided to follow the fate of the Golgi apparatus during myogenesis by an immunocytochemical approach, using wheat germ agglutinin and an affinity-purified anti-galactosyltransferase. We show that Golgi apparatus in myotubes displays a perinuclear distribution which is strikingly different from the polarized juxtanuclear organization observed in myoblasts. As a result, the Golgi apparatus in myotubes is situated close to the microtubule organizing center (MTOC), the cis-side being situated at a fixed distance from the nuclear envelope, a situation which suggests the existence of a structural association between the Golgi apparatus and the nuclear periphery. This is supported by experiments of microtubule depolymerization by nocodazole, in which a minimal effect was observed on Golgi apparatus localization in myotubes in contrast with the dramatic scattering observed in myoblasts. In both cell types, electron microscopy reveals that microtubule disruption generates individual dictyosomes; this suggests that the connecting structures between dictyosomes are principally affected. This structural dependency of the Golgi apparatus upon microtubules is not apparently accompanied by a reverse dependency of MTOC structure or function upon Golgi apparatus activity. Golgi apparatus modification by monensin, as effective in myotubes as in myoblasts, is without apparent effect on MTOC localization or activity and on microtubule stability. The main result of our study is to show that in a cell type where the MTOC is dissociated from centrioles and where antero-posterior polarity has disappeared, the association between the Golgi apparatus and the MTOC is maintained. The significance of such a tight association is discussed.

Animals↗
PubMed2003

The Golgi apparatus at the cell centre.

In non-polarised mammalian cells, the Golgi apparatus is localised around the centrosome and actively maintained there. Microtubules and molecular motor activity are required for determining both the localisation and organisation of the Golgi apparatus. Other factors, however, also appear necessary for regulating both the static steady-state distribution of this organelle and its relationship with microtubule minus-end-anchoring activities of the centrosome. Several non-motor microtubule-binding proteins have now been found to be associated with the Golgi apparatus. Recent advances suggest that, in addition to important roles in cell motility, polarisation and differentiation, the interplay between Golgi apparatus and centrosome could participate in other physiological processes such as intracellular signalling, mitosis and apoptosis.

Animals↗
PubMed1976

Isolation of a Golgi-apparatus-enriched fraction from leukaemic cells.

1. A Golgi-apparatus-enriched fraction was isolated from acute leukaemic lymphoblasts of AKR mice by using an homogenate stabilized with 1 mM-glutaraldehyde. 2. The isolated fraction, which was shown morphologically to be enriched in dictyosomes, possessed between 44- and 76-fold increase in specific activity, compared with the tumour homogenate, of UDP-galactose-glycoprotein galactosyltransferase and between 3- and10.5-fold increase in relative specific activity of UDP-N-acetygalactosamine-polypeptide N-acetylgalactosaminyltransferase. 3. Plasma membranes isolated from the leukaemic lymphoblasts also possessed glycoprotein galactosyltransferase activity, though in contrast with Golgi-apparatus-enriched material had no detectable polypeptide N-acetygalactosaminyltransferase. 4. The difficulties associated with maintaining the morphological integrity of the Golgi apparatus in subcellular fractionation are discussed.

Animals↗
PubMed1982

Flow kinetics of a nucleoside phosphatase common to endoplasmic reticulum, Golgi apparatus, and plasma membrane of rat liver.

Nucleoside mono-, di- and triphosphatase activities of highly purified endoplasmic reticulum (ER), Golgi apparatus, and plasma membrane fractions of rat liver were compared. The highest rates of hydrolysis were always in ER or plasma membrane. Golgi apparatus activity was intermediate between those of ER and plasma membrane. This relationship was true for both freshly isolated fractions and salt-extracted membranes. Detergent solubilization of the membranes, polyacrylamide gel electrophoresis of the solubilized proteins, and localization of the enzyme activities on the gel revealed bands of enzyme activity which had identical mobilities in all three membrane fractions as well as other bands of activity that occurred only in ER and to a lesser degree in the Golgi apparatus. Antibodies raised against one of the phosphatase bands of plasma membrane which was common to all three membrane fractions cross-reacted with the corresponding phosphatase band in ER and Golgi apparatus. The anti-nucleoside phosphatase was utilized in combination with pulse-chase techniques to investigate the flow kinetics of transfer of newly synthesized enzyme among different cell compartments. Label first appeared in nucleoside phosphatase within the ER. Maximum specific activity was observed at about 5 min after injection of label and was followed by rapid loss of label. This was followed by appearance of label in Golgi apparatus 15 to 25 min after injection of label and by subsequent rapid loss of label. Plasma membranes were labeled last with no evidence of either rapid accumulation of label or of rapid turnover. Flow of nucleoside phosphatase from its site of synthesis and insertion into the membrane at the endoplasmic reticulum to the plasma membrane via the Golgi apparatus is indicated but in a manner whereby a significant fraction of the protein may be processed (removed?) from the membrane concomitant with the flow process.

Acid Anhydride Hydrolases↗
PubMed1995

The fate of the Golgi apparatus and the endoplasmic reticulum during lens fiber cell differentiation.

PURPOSE: To establish the fate of the Golgi apparatus and the endoplasmic reticulum (ER) during lens fiber differentiation. METHODS: Organelles were visualized by confocal or electron microscopy. For fluorescence microscopy, organelles were labeled with fluorescent probes or antibodies raised against organelle-resident proteins. The cytoplasmic volume was reconstructed from optical sections using volume rendering techniques. RESULTS: The Golgi apparatus was located apically in epithelial cells. In the annular pad, Golgi elements were transformed into ribbon-like structures running parallel to the long axes of the cells. Toward the lens equator, the Golgi apparatus fragmented. In the lens fibers, the Golgi apparatus was detected only in the superficial cells. The ER was present as vesicular or tubular elements in both epithelial and cortical fiber cells, and ER probes co-labeled the nuclear membrane and revealed that the ER and nuclei disappeared coincidentally in the deep cortex. Using a lipophilic dye and volume rendering, the relationships between organelles could be evaluated in three dimensions. CONCLUSIONS: The Golgi apparatus was not a prominent organelle in differentiating lens fibers. In contrast, the ER was more abundant and extended to the edge of the organelle-free region, where it was degraded along with the nuclei and mitochondria.

Amino Acid Sequence↗
PubMed1990

Influence of antimicrotubular drugs on the Golgi apparatus of stomach secretory mucoid cells and small intestine absorptive cells.

The effects of vinblastine and colchicine on the Golgi apparatus of stomach surface mucoid and absorptive intestinal cells were compared by cytochemical analysis. The two epithelial cells were chosen because of their different specific functions in the formation of secretory granules, the production of lysosomes and the intensity of membrane traffic in the cytoplasm. For the analysis, adult mice were injected with 1 mg/100 g b.w. of vinblastine and 1 mg/100 g b.w. of colchicine. For the demonstration of cis and trans cisternae of the Golgi apparatus, prolonged osmification, thiamine pyrophosphatase and acid phosphatase activity identification were applied. After treatment with vinblastine or colchicine, polarity of stacks in the Golgi apparatus of surface mucoid cells is preserved although the number of cisternae with thiamine pyrophosphatase or acid phosphatase activity decreases. However, the Golgi apparatus of intestinal absorptive cells completely disintegrates and only a few separated cis or trans cisternae can be identified. The main effect seems to be a reduction of vesicles which can be cytochemically identified as parts of the Golgi apparatus and an accumulation of vesicles which probably originate from budding ER. Communication between the ER and the Golgi apparatus seems to be interrupted.

Animals↗
PubMed1994

Retinoic acid disrupts the Golgi apparatus and increases the cytosolic routing of specific protein toxins.

All-trans retinoic acid can specifically increase receptor mediated intoxication of ricin A chain immunotoxins more than 10,000 times, whereas fluid phase endocytosis of ricin A chain alone or ricin A chain immunotoxins was not influenced by retinoic acid. The immunotoxin activation by retinoic acid does not require RNA or protein synthesis and is not a consequence of increased receptor binding of the immunotoxin. Vitamin D3 and thyroid hormone T3, that activate retinoic acid receptor (RAR) cognates, forming heterodimers with retinoid X receptor (RXR), do not affect the potency of immunotoxins. Among other retinoids tested, 13-cis retinoic acid, which binds neither RAR nor RXR, also increases the potency of the ricin A chain immunotoxin. Therefore, retinoic acid receptor activation does not appear to be necessary for immunotoxin activity. Retinoic acid potentiation of immunotoxins is prevented by brefeldin A (BFA) indicating that in the presence of retinoic acid, the immunotoxin is efficiently routed through the Golgi apparatus en route to the cytoplasm. Directly examining cells with a monoclonal antibody (Mab) against mannosidase II, a Golgi apparatus marker enzyme, demonstrates that the Golgi apparatus changes upon treatment with retinoic acid from a perinuclear network to a diffuse aggregate. Within 60 min after removal of retinoic acid the cell reassembles the perinuclear Golgi network indistinguishable with that of normal control cells. C6-NBD-ceramide, a vital stain for the Golgi apparatus, shows that retinoic acid prevents the fluorescent staining of the Golgi apparatus and eliminates fluorescence of C6-NBD-ceramide prestained Golgi apparatus. Electron microscopy of retinoic acid-treated cells demonstrates the specific absence of any normal looking Golgi apparatus and a perinuclear vacuolar structure very similar to that seen in monensin-treated cells. This vacuolization disappears after removal of the retinoic acid and a perinuclear Golgi stacking reappears. These results indicate that retinoic acid alters intracellular routing, probably through the Golgi apparatus, potentiating immunotoxin activity indepedently of new gene expression. Retinoic acid appears to be a new reagent to manipulate the Golgi apparatus and intracellular traffic. As retinoic acid and immunotoxins are both in clinical trials for cancer therapy, their combined activity in vivo would be interesting to examine.

4-Chloro-7-nitrobenzofurazan↗