Paclitaxel and nocodazole differentially alter endocytosis in cultured cells

Pharm Res. 1996 Nov;13(11):1647-56. doi: 10.1023/a:1016432505275.

Abstract

Purpose: Microtubule-based transport facilitates the endocytosis of exogenous macromolecules. We have determined how microtubule accumulation and disassembly alter endocytosis.

Methods: The effects of paclitaxel, which promotes microtubule assembly, and nocodazole, which promotes microtubule disassembly, on fluid-phase and receptor-mediated endocytosis were measured using uptake of horseradish peroxidase and 125I-transferrin, respectively. Changes in membrane and microtubule organization were examined by fluorescence microscopy.

Results: Neither paclitaxel (4 microM, 60 min pretreatment) nor nocodazole (1 microgram/ml, 60 min pretreatment) significantly inhibited fluid-phase endocytosis. However, paclitaxel caused a redistribution of fluorescent fluid-phase marker to the periphery. Both paclitaxel and nocodazole treatment significantly (p < or = 0.05) reduced the initial uptake of 125I-transferrin at 5 min to approximately 50% of control. Despite the similarity of the effects on initial endocytic uptake, the effects on steady state accumulation of 125I-transferrin were quite distinct. Exposure of CV-1 cells to paclitaxel for an additional 30, 60 or 90 min also showed reduced accumulation of 125I-transferrin up to a maximum significant (p < or = 0.05) inhibition of 48% +/- 10% of control at 90 min. In contrast, nocodazole caused an initial significant (p < or = 0.05) increase in 125I-transferrin accumulation after 30 min (159% +/- 13% of control), while by 90 min 125I-transferrin accumulation had returned to control levels. Microtubule content, particularly of stable microtubules, was increased in CV-1 cells by paclitaxel, but abolished by nocodazole treatment.

Conclusions: Our data show that changes in the microtubule array can alter the dynamics of receptor movement through the endosomal pathway. However, microtubule assembly versus disassembly have different effects.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antineoplastic Agents / pharmacology*
  • Antineoplastic Agents, Phytogenic / pharmacology*
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Cells, Cultured
  • Chlorocebus aethiops
  • Endocytosis / drug effects*
  • Fluorescein-5-isothiocyanate / analogs & derivatives
  • Horseradish Peroxidase / pharmacokinetics
  • Iodine Radioisotopes
  • Kidney / drug effects
  • Kidney / metabolism
  • Lysosomes / drug effects
  • Lysosomes / metabolism
  • Microtubules / drug effects
  • Microtubules / metabolism
  • Nocodazole / pharmacology*
  • Paclitaxel / pharmacology*
  • Receptors, Transferrin / metabolism
  • Serum Albumin, Bovine
  • Transferrin / metabolism
  • Transferrin / pharmacokinetics

Substances

  • Antineoplastic Agents
  • Antineoplastic Agents, Phytogenic
  • Iodine Radioisotopes
  • Receptors, Transferrin
  • Transferrin
  • fluorescein isothiocyanate bovine serum albumin
  • Serum Albumin, Bovine
  • Horseradish Peroxidase
  • Fluorescein-5-isothiocyanate
  • Paclitaxel
  • Nocodazole