Title

Thyroxine-dependent modulation of actin polymerization in cultured astrocytes. A novel, extranuclear action of thyroid hormone

UMMS Affiliation

Department of Physiology; Department of Cellular and Molecular Physiology

Publication Date

3-25-1990

Document Type

Article

Subjects

Actins; Animals; Astrocytes; Bucladesine; Cell Nucleus; Cells, Cultured; Cycloheximide; Cytoskeleton; Dactinomycin; Iodide Peroxidase; Kinetics; Macromolecular Substances; Thyroxine

Disciplines

Life Sciences | Medicine and Health Sciences

Abstract

Actin depolymerization specifically blocks the rapid thyroid hormone-dependent inactivation of type II iodothyronine 5'-deiodinase. Thyroid hormone appears to regulate enzyme inactivation by modulating actin-mediated internalization of this plasma membrane-bound protein. In this study, we examined the interrelationships between thyroxine-dependent enzyme inactivation and the organization of the actin cytoskeleton in cultured astrocytes. Steady-state enzyme levels were inversely related to actin content in dibutyryl cAMP-stimulated astrocytes, and increases in filamentous actin resulted in progressively shorter enzyme half-lives without affecting enzyme synthesis. In the absence of thyroxine, filamentous actin decreased by approximately 40% and soluble actin correspondingly increased; thyroxine normalized filamentous actin levels without changing total cell actin. Thyroxine treatment for only 10 min resulted in an approximately 50% loss of enzyme and increased filamentous actin 2-fold. Neither cycloheximide nor actinomycin D affected the thyroxine-induced actin polymerization. Astrocytes grown without thyroxine also showed a disorganized actin cytoskeleton, and 10 nM thyroxine or 10 nM reverse triiodothyronine normalized the actin cytoskeleton appearance within 20 min; 10 nM 3,3',5-triiodothyronine had no effect. These data show that thyroxine modulates the organization of the actin cytoskeleton in astrocytes and suggest that regulation of actin polymerization may contribute to thyroid hormone's influence on arborization, axonal transport, and cell-cell contact in the developing brain.

Rights and Permissions

Citation: J Biol Chem. 1990 Mar 25;265(9):5296-302.

Related Resources

Link to Article in PubMed

Journal/Book/Conference Title

The Journal of biological chemistry

PubMed ID

2156867