Microtubules and protein secretion in rat lacrimal glands: localization of short-term effects of colchicine on the secretory process.

Abstract

ABSlRACl The pathway and kinetics of the secretory protein transport in rat lacrimal exorbital gland have been established by an in vitro time-course radioautographic study of pulse-labeled protein secretion.The colchicine-sensitive steps have been localized by using the drug at various times with respect to the pulse labeling of proteins. Colchicine (10/IM) does not block any step of the secretory protein transport, but when introduced before the pulse it decreases the transfer of labeled proteins from the rough endoplasmic reticulum to the Golgi area, suppressing their temporary accumulation in the Golgi area before any alteration of this organelle is detectable. Moreover, colchicine inhibits protein release only from the secretory granules formed in its presence because the peroxidase discharge is diminished I h after colchicine addition, and the secretion of newly synthesized proteins is strongly inhibited only when colchicine is introduced before secretory granule formation.Morphometric studies show that there is a great increase of secondary lysosomes, related to crinophagy, as early as 40-50 rain after colchicine is added. However, changes in lysosomal enzymatic activities remained biochemically undetectable.We conclude that: (a) the labile microtubular system does not seem indispensable for protein transport in the rough endoplasmic reticulum-Golgi area but may facilitate this step, perhaps by maintaining the spatial organization of this area; and (b) in the lacrimal gland, colchicine inhibits protein release not by acting on the steps of secretion following the secretory granule formation, but by acting chiefly on the steps preceding secretory granule formation, perhaps by making the secretory granules formed in its presence incapable of discharging their content.From data obtained with various secretory tissues, it appears that the microtubular system could be involved in the secretory process (62). We have previously shown in rat lacrimal #ands that colchicine inhibited the release of newly synthesized proreins by impairing their intraceUular transport (9), and simultaneously induced a disorganization of the labile microtubular system. This latter effect could result from the shift of the equilibrium between microtubules and tubulin and from the impediment of microtubule assembly due to the colchicinetubulin complex (10). The intraceUular transport alterations produced by colchicine have also been observed in other tissues that produce exportable proteins (liver: 17, 52-55; pancreas B-]FIE JOURNAL Of CELL BIOLOGY • VOtUME 95 OCTOBER 1982 105-117 @The Rockefeller University Press -0021-9525/82/10/0105/13 $1.00 cells: 36, 37; fibroblasts: 12, 14, 38; anterior pituitary: 1, 26, 48; mammary gland: 30, 41, 42; parotid gland: 46; exocrine pancreas: 61; parathyroid gland: 11, 29). Although there is no definite proof, the hypothesis that both events (i.e., inhibition of protein secretion and disruption of labile microtubules) might be related by a causal effect is favored.The aim of the present work is to lo...

Golgi dispersal during microtubule disruption: regeneration of Golgi stacks at peripheral endoplasmic reticulum exit sites.

“…Alternatively, Golgi membrane enroute to peripheral sites could move through existing membrane structures, like the ER (Saraste and Svensson, 1991;Saraste and Kuismanen, 1992), which extend peripherally throughout the cytoplasm even during nocodazole treatment (Terasaki, 1986). Both of these models are consistent with previous observations on Golgi fragmentation after microtubule disruption, which found that fragmentation is sensitive to energy depletion and membrane traffic perturbants (Turner and Tartakoff, 1991; Table 1), and that rudimentary Golgi formations appear at peripheral sites before central Golgi structures are affected (Busson-Mabillot et al, 1982;Pavelka and Ellinger, 1983). Our observations that ERGIC-53 moves through the ER before accumulating in peripheral fragments during nocodazole treatment ( Figure 3), and that Golgi reassembly at peripheral ER sites during nocodazole treatment occurs whether Golgi enzymes are redistributed from centrosomal stacks or from the ER (during BFA washout), however, favor the latter of these models.…”

Cytoskeleton, microtubules, tubulin and colchicine : A review.

“…Cell functions affected at molecular level are enzyme activities (Volpe 1979, Wilfred 1977, Ewart 1982, Chen et al 1976, Nicklas et al 1973, redistribution of enzymes and proteins (Borensztajn et al 1975, Brimijoin 1974, Parish and Pelli 1974, Ray mackers and Hugon 1973, Thyberg et al 1980, Kreutzberg 1969, Sjostrand et al 1970, James et al 1970, permeability of cells (Berlin 1973, Mizel and Wilson 1972, Cheng and Katsoyannis 1975, Tauber and Reutter 1980, distribution of receptors on membrane (Whittaker et al 1981b), release of secretory products (Busson-Mabillot et al 1982, Jansen and Bornstein 1974, Gordon and Werb 1976, Ehrlich et al 1974, Reaven and Reaven 1980, and DNA and protein synthesis (Piatigorsky et al 1972, Daniels 1972, Redman et al 1978, Friedkin and Rozengurt 1980. Movement or shape changes of cells, division, phagocytosis, endocytosis, and translocations of organelles are examples of cell events affected at supramolecular level (Mori et al 1982, Bhisey and Freed 1971, Malawista 1975.…”

Microtubule perturbation inhibits intracellular transport of an apical membrane glycoprotein in a substrate-dependent manner in polarized Madin-Darby canine kidney epithelial cells.

“…With the use of various microtubule-perturbing drugs, the role of microtubules in protein transport has been extensively studied in different cell systems (Busson-Mabillot et al, 1982;Achler et al, 1989;Stults et al, 1989). Nocodazole, a depolymerizing drug (De Brabander et al, 1976), and taxol, a hyperpolymerizing drug (De Brabander et al, 1981;Horwitz et al, 1986), have been used to examine the role of the microtubular cytoskeleton in sorting in MDCK cells.…”