title: Drugs that influence tubulin polymerization modulate thyrotropin-releasing hormone receptor number in AtT-20 cells.
abstract: In order to examine the role of cytoskeleton in modulating the cell surface receptors, AtT-20 cells (stably expressing thyrotropin-releasing hormone receptors) were incubated with drugs that are known to modify the tubulin-microtubule system. The binding of [3H]methyl thyrotropin-releasing hormone ([3H]mTRH) to intact cells increased as a function of time, and was linear from 1.25 x 10(6) to 6.25 x 10(6) cells/ml. Cells incubated with colchicine, vinblastine, and taxol for 16 hr were harvested and the cell concentration was determined using a haemocytometer. Because the drugs inhibited the cell proliferation at 100 nM, it was decided to examine the effect of 100 nM of each of the three drugs on the ability of [3H]mTRH to bind cell surface receptors. Cells were incubated with the drugs for 16 hr at 37 degrees. After the incubation, cells (5 x 10(6) cells/ml) from each group were assayed for [3H]mTRH binding. Colchicine, vinblastine, and taxol stimulated [3H]mTRH binding by up to 27, 27, and 21%, respectively, without altering the Ka of the ligand to the receptor. These results suggest that perturbation of cytosolic microtubules leads to a reorganization of the spatial location of hormone receptors.
authors.affiliation: Veterans Affairs Medical Center, North Chicago, IL 60064, USA.
authors.forename: R
authors.initials: R
authors.lastname: Ravindra
authors.forename: P J
authors.initials: PJ
authors.lastname: McIlroy
authors.forename: S A
authors.initials: SA
authors.lastname: Patel
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects; D003078:Colchicine / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D017239:Paclitaxel / Q000494:pharmacology; D010911:Pituitary Neoplasms / Q000378:metabolism*; D018025:Receptors, Thyrotropin-Releasing Hormone / Q000235:genetics / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism; D014162:Transfection; D014404:Tubulin / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured; D014747:Vinblastine / Q000494:pharmacology
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D018025:Receptors, Thyrotropin-Releasing Hormone; D014404:Tubulin; D014747:Vinblastine; D013973:Thyrotropin-Releasing Hormone; D017239:Paclitaxel; D003078:Colchicine