Influence of colchicine and vinblastine on the intracellular migration of secretory and membrane glycoproteins: I. Inhibition of glycoprotein migration in various rat cell types as shown by light microscope radioautography after injection of 3H-fucose

Intracellular 3',5'-adenosine cyclic monophosphate level regulates house dust mite-induced interleukin-13 production by T cells from mite-sensitive patients with atopic dermatitis

We studied the relationship between cAMP and house dust mite-induced cytokine production in T cells from mite-sensitive patients with atopic dermatitis. T cells from atopic dermatitis patients secreted high level of interleukin-13 (mean 851.1 pg per ml) when cultured with autologous monocytes pulsed with Dermatophagoides pteronyssinus extract. Dermato- phagoides pteronyssinus-induced interleukin-13 secretion was not detected in normal subjects. Adenylate cyclase inhibitor MDL 12,330A and cyclic nucleotide phosphodiesterase type 4 inhibitor rolipram blocked Dermatophagoides pteronyssinus-induced interleukin-13 secretion in atopic dermatitis T cells. In atopic dermatitis T cells, cAMP level rose at 5 min after Dermatophagoides pteronyssinus stimulus then decreased to the basal level at 1 h. MDL 12,330A blocked the Dermatophagoides pteronyssinus-induced cAMP elevation while rolipram blocked its reversal. In atopic dermatitis T cells, adenylate cyclase activity increased at 5 min after Dermatophagoides pteronyssinus stimulus, followed by the increase of cyclic nucleotide phosphodiesterase activity at 15 min. In atopic dermatitis T cells, phospholipase C inhibitor ET-18-OCH3 blocked Dermatophagoides pteronyssinus-induced activation of adenylate cyclase, while rolipram, protein kinase A inhibitor H-89, and MDL 12,330A blocked the activation of cyclic nucleotide phosphodiesterase. These results suggest that Dermatophagoides pteronyssinus may first increase cAMP in atopic dermatitis T cells by activating adenylate cyclase via phospholipase C, and next decrease cAMP by activating cyclic nucleotide phosphodiesterase 4 via protein kinase A, which may be activated by adenylate cyclase-generated cAMP signal. These events are required for interleukin-13 response Dermatophagoides pteronyssinus.

Differential colchicine effects on the transport of membrane and secretory proteins in rat hepatocytes in vivo: bipolar secretion of albumin

We carried out a comparative investigation on the effects of colchicine (25 mumoles/100 gm body wt) on the intracellular transport, processing and discharge by secretion or proteolytic processing of a membrane protein (i.e., the polymeric IgA receptor) and a secretory protein (i.e., albumin) in rat hepatocytes. The results obtained indicated the following: (a) the transport and processing of polymeric IgA receptor is strongly inhibited and delayed, but the appearance of secretory component in the bile is not arrested; (b) polymeric IgA receptor reaches the sinusoidal plasmalemma in colchicine-treated specimens, as it does in controls; (c) albumin discharge into the plasma is strongly inhibited and markedly delayed in colchicine-treated as compared with control animals; (d) the reverse applies for albumin secretion in the bile, which is increased by a large factor; (e) newly synthesized albumin secreted directly from hepatocytes in control and in colchicine-treated animals is the major source of bile albumin; and (f) colchicine affects in different ways the polymeric IgA receptor and albumin arrival at the sinusoidal front and especially at the biliary front of the hepatocyte.

Histochemical and radioautographic study of glycoprotein secretion in the epithelium lining the uterine tubes of mice

Two-month-old female Swiss mice that had come into estrus were injected intravenously with L-3H-fucose and killed at 5, 15, 40 min, and 4 h after injection. Pieces of the isthmus and of the ampulla of the uterine tubes were processed for light- and electron-microscopic radioautography. Incorporation of 3H-fucose was more intense in the isthmian secretory cells than in the ciliated cells of the ampulla. Electron-microscopic radioautography of the isthmian secretory cells demonstrated that 3H-fucose was incorporated into newly synthesized glycoproteins in the Golgi apparatus from where labelled glycoproteins migrated mainly to secretory granules and apical microvilli. The histochemical technique using ruthenium red confirmed the presence of glycoproteins in the contents of the secretory granules released to the lumen of the uterine tubes as demonstrated by radioautography. Other glycoproteins are transported inside small vesicles and most likely are related to the renewal of the plasma membrane. The role of the secretory glycoproteins in various events of mammalian reproduction is discussed.

The effects of vinblastine on the secretory ameloblasts: an ultrastructural, cytochemical, and immunocytochemical study in the rat incisor

Secretory ameloblasts synthesize the organic matrix of enamel and secrete it at two distinct "putative secretory sites" characterized by membrane infoldings (Nanci and Warshawsky, 1984a). The antimicrotubular agent vinblastine sulphate interferes with secretion. We have examined the effect of this drug on the ameloblast secretory sites and re-evaluated the effect on the intracellular organization of the cell by using conditions that optimize fixation, cytochemistry (ZI0), and immunocytochemistry. Associated with the disappearance of secretory granules and Golgi-related structures from Tomes' process was the loss of membrane infoldings at secretory sites. The Golgi apparatus appeared fragmented and numerous granule clusters were found throughout the cell body. These clusters were often seen in relation to extracellular patches of material in which no crystallites were seen. Immunocytochemistry revealed the presence of enamel proteins in the protein synthetic organelles, including various granule types, in lysosomes and in the extracellular patches. These data suggest that ameloblasts under the effect of vinblastine carry on secretory activities, but the product is not routed to the usual sites. It was confirmed that membrane infoldings characterize the sites where enamel proteins are normally secreted.

Loss of microtubules and alteration of glycoprotein migration in organ cultures of mouse intestine exposed to nocodazole or colchicine

Explants from mouse jejunum were cultured for 3-7 h in the absence (control) or presence of colchicine (100 micrograms/ml) or nocodazole (10 micrograms/ml). In recovery experiments, explants were cultured in fresh medium for an additional period. To label glycoproteins, 3H-fucose was added during the last 3 or 6 h of the initial culture or recovery period. Subcellular fractionation studies revealed that colchicine and nocodazole inhibited migration of labelled glycoproteins to the brush border (P2) by 40-45%. Radioautographic studies of absorptive cells showed that colchicine and nocodazole inhibited labelling of the microvillous border by 67% and 87%, while labelling of the basolateral plasma membrane increased by 114% and 275%. Immunocytochemical studies revealed that both colchicine and nocodazole caused the virtual disappearance of the microtubular network in the absorptive cells. It is possible that some glycoproteins normally destined for the microvillous border are rerouted to the basolateral membrane. The observed loss of microtubules after drug treatment suggests that microtubules may play a role in the intracellular migration of membrane glycoproteins. Additional support for this concept is provided by the fact that in recovery experiments the distribution of label returned to control values after the microtubular network became re-established.

The role of microtubules in human natural killer cell-mediated cytotoxicity

The effect of four different microtubule (MT) inhibitors on the various stages of human natural killer (NK) cell-mediated cytotoxicity was studied. The MT-disrupting effect of the drugs was monitored by indirect immunofluorescence microscopy and transmission electron microscopy. All the drugs tested, vinblastine sulfate, demecolcine, nocodazole, and taxol, had only a slight inhibitory effect on NK activity. Cells with nonfunctional MT were capable of normal conjugate formation and polarization of actin-containing microfilaments. Natural killer cell cytotoxic factor (NKCF) activity produced by cells with nonfunctional MT was slightly diminished. MT disruption caused enlargement of Golgi cisternae, but did not, however, dissociate the overall structural organization of the Golgi complex. The results indicate that fresh human NK cells are capable of lytic activity without functional MT although MT play a small supportive role in production or secretion of NKCF and mediation of the lytic activity. Previous experiments by us and others have strongly suggested that NK cells mediate their cytolytic activity by directed secretion of toxic material. As NK cells with unfunctional microtubules are capable of close to normal secretion the results presented in this report are not inconsistent with the earlier suggested stimulus-secretion model.

Synthesis and migration of 3H-fucose-labeled glycoproteins in the retinal pigment epithelium of albino rats, as visualized by radioautography

3H-fucose was injected into the vitreous body of the eye(s) of 250-gm rats, which were then killed by means of an intracardiac perfusion with glutaraldehyde after intervals of 10 min, 1 and 4 hr, and 1 and 7 days. The eyes were removed and further fixed, and pieces of retina were processed for light and electron microscope radioautography. Light microscope radioautography showed that the pigment epithelial cells actively incorporated 3H-fucose label. The intensity of reaction peaked at 4 hr after injection of the label and then slowly declined. Quantitative electron microscope radioautography revealed that, at 10 min after 3H-fucose injection, over 70% of the label was localized to the Golgi apparatus, indicating that fucose residues are added to newly synthesized glycoproteins principally at this site. With time the proportion of label associated with the Golgi apparatus decreased, but that assigned to the infolded basal plasma membrane, the apical microvilli, and various apical lysosomes increased. These results indicate that in retinal pigment epithelial cells newly synthesized glycoproteins continuously migrate from the Golgi apparatus to lysosomes and to various regions of the plasma membrane. In this case, the membrane glycoproteins may play specific roles in receptor functions of the basal plasma membrane or phagocytic activities at the apical surface. Very little label migrated to Bruch's membrane, indicating either a very slow turnover or a paucity of fucose-containing glycoproteins at this site.

Synthesis and migration of 3H-fucose-labeled glycoproteins in the ciliary epithelium of the eye: effects of microtubule-disrupting drugs

3H-fucose was injected intravenously or intravitreously into albino rats. After time intervals of 10, 40, and 50 min, 1, 1.5, and 4 hr, 1, 3, and 7 days, and 1, 2, and 4 weeks after injection, the animals were sacrificed by intracardiac perfusion with glutaraldehyde. Samples of the ciliary body were prepared for light and electron microscope radioautography. Light microscope autoradiographs showed that the cells of both the inner and outer layers of ciliary epithelium actively incorporated 3H-fucose label in a reaction that peaked in intensity at 4 hr after injection, and then progressively declined. Electron microscope radioautographs revealed that, at early time intervals, most of the label was localized to the Golgi apparatus. With time, the plasma membrane of both cell types became increasingly labeled, and accounted for 60-70% of the total silver grains at 4 hr after injection. Adjacent to the basal cell surface of the inner layer cells, the fibers of the zonula became increasingly labeled from 1.5 hr onwards, providing strong evidence that these cells secrete glycoproteins to the zonula. When vinblastine was administered 30 min before 3H-fucose injection, followed by sacrifice 1.5 hr later, a much larger proportion of label remained localized to the Golgi apparatus than in controls, and the plasma membrane and zonula were much less labeled. These results suggest that, as documented in other cell types, microtubules may play a role in the intracellular transport of membrane and secretory glycoproteins in these cells.

Golgi and secreted galactosyltransferase

Galactosyltransferase (GT) belongs to the glycosyltransferases. In several tissues and cell lines, the enzyme is localized by immunocytochemistry to the two to three trans cisternae of the Golgi complex and may thus be considered a specific membrane component of this type of endomembrane. As a consequence, it is the most common Golgi "marker" enzyme in cell fractionation studies. Study of its biosynthesis, membrane orientation, and turnover in several tissues and cultured cell lines has broadened our knowledge about Golgi function itself. The enzyme is oriented towards the lumen of the cisternal space. In this orientation, it catalyzes the transfer of galactose to glycoprotein-bound acetylglucosamine and, in the presence of alpha-lactalbumin, to glucose, as shown in the Golgi complex of mammary gland epithelial cells. The enzymatic properties of GT are well known. The metabolism of GT has been extensively studied in HeLa and human hepatoma cells. The enzyme is synthesized in the rough endoplasmic reticulum (RER) and provided with one N-linked oligosaccharide and palmitate residues. In the Golgi complex, terminal sugars are attached to the N-linked oligosaccharide and extensive O-glycosylation takes place. The half-life of the enzyme is about 20 hr, after which a soluble form appears in the culture medium. Release of GT into the medium is observed in all cell lines studied. This phenomenon is in accordance with the presence of soluble GT in body fluids such as serum, ascites, milk, and saliva. In patients suffering from ovarian and breast cancer, increased levels of GT enzyme activity have been reported. Whether extracellular GT is of biological significance is still a point of discussion.

Pathways of protein secretion in eukaryotes

Protein secretion from cells can take several forms. Secretion is constitutive if proteins are secreted as fast as they are synthesized. In regulated secretion newly synthesized proteins destined for secretion are stored at high concentration in secretory vesicles until the cell receives an appropriate stimulus. When both constitutive and regulated protein secretion can take place in the same cell a mechanism must exist for sorting the correct secretory protein into the correct secretory vesicle. The secretory vesicle must then be delivered to the appropriate region of plasma membrane. Transfection of DNA encoding foreign secretory proteins into regulated secretory cells has provided insight into the specificity of sorting into secretory vesicles.

Influence of colchicine and vinblastine on the intracellular migration of secretory and membrane glycoproteins: III. Inhibition of intracellular migration of membrane glycoproteins in rat intestinal columnar cells and hepatocytes as visualized by light and electron-microscope radioautography after 3H-fucose injection

In the first paper of this series (Bennett et al., 1984), light-microscope radioautographic studies showed that colchicine or vinblastine inhibited intracellular migration of glycoproteins out of the Golgi region in a variety of cell types. In the present work, the effects of these drugs on migration of membrane glycoproteins have been examined at the ultrastructural level in duodenal villous columnar cells and hepatocytes. Young (40 gm) rats were given a single intravenous injection of colchicine (4.0 mg) or vinblastine (2.0 mg). At 10 min after colchicine and 30 min after vinblastine administration, the rats were injected with 3H-fucose. Control rats received 3H-fucose only. All rats were sacrificed 90 min after 3H-fucose injection and their tissues processed for radioautography. In duodenal villous columnar cells, 3H-fucose labeling of the apical plasma membrane was reduced by 51% after colchicine and by 67% after vinblastine treatment; but there was little change in labeling of the lateral plasma membrane. Labeling of the Golgi apparatus increased. This suggests that labeled glycoproteins destined for the apical plasma membrane were inhibited from leaving the Golgi region, while migration to the lateral plasma membrane was not impaired. In hepatocytes, labeling of the sinusoidal plasma membrane was reduced by 83% after colchicine and by 85% after vinblastine treatment. Labeling of the lateral plasma membrane also decreased, although not so dramatically. Labeling of the Golgi apparatus and neighboring secretory vesicles increased. This indicates that the drugs inhibited migration of membrane glycoproteins from the Golgi region to the various portions of the plasma membrane. Accumulation of secretory vesicles at the sinusoidal front suggests that exocytosis may also have been partially inhibited. In both cell types, microtubules almost completely disappeared after drug treatment. Microtubules may, therefore, be necessary for intracellular transport of membrane glycoproteins, although the possibility of a direct action of these drugs on Golgi or plasma membranes must also be considered.

Influence of colchicine and vinblastine on the intracellular migration of secretory and membrane glycoproteins: II. Inhibition of secretion of thyroglobulin in rat thyroid follicular cells as visualized by radioautography after 3H-fucose injection

Young (40 gm) rats were given a single intravenous injection of colchicine (4.0 mg) or vinblastine (2.0 mg). At 10 min after colchicine and 30 min after vinblastine administration, the rats were injected with 3H-fucose. Control rats received 3H-fucose only. All rats were sacrificed 90 min after 3H-fucose injection and their tissues processed for radioautography. In thyroid follicular cells of control animals, at this time interval, 57% of the total label was associated with colloid and secretory vesicles in the apical cytoplasm while 27% was localized in the Golgi apparatus and neighboring vesicles. In experimental animals, the proportion of label in colloid and apical vesicles was reduced by more than 69% after colchicine and more than 83% after vinblastine treatment. The proportion of label in the Golgi region, on the other hand, increased by more than 125% after colchicine and more than 179% after vinblastine treatment. Within the Golgi region, the great majority of the label was associated with secretory vesicles which accumulated adjacent to the trans face of the Golgi stacks. It is concluded that the drugs do not interfere with passage of newly synthesized thyroglobulin from the Golgi saccules to nearby secretory vesicles, but do inhibit intracellular migration of these vesicles to the cell apex. In most cells the number of vesicles in the apical cytoplasm diminished, but this was not always the case, suggesting that exocytosis may also be partially inhibited. The loss of microtubules in drug-treated cells suggests that the microtubules may be necessary for intracellular transport of thyroglobulin.