Acetylation modulates thyroid hormone receptor intracellular localization and intranuclear mobility

Area of Science:

• Molecular Biology
• Cell Biology
• Endocrinology

Background:

• Thyroid hormone receptor (TR) is crucial for development and homeostasis.
• TR shuttles between the nucleus and cytoplasm, with primary nuclear localization.
• Post-translational modifications like acetylation and sumoylation may regulate TR localization.

Purpose of the Study:

• To investigate the role of TR acetylation and sumoylation in regulating its intracellular localization.
• To determine how specific modifications affect TR's nuclear import and export dynamics.
• To understand the functional consequences of altered TR localization on gene expression.

Main Methods:

• Utilized fluorescent protein-tagged TR variants (acetylation mimic, nonacetylation mimic, sumoylation-deficient).
• Quantified nuclear/cytosolic fluorescence ratio (N/C) in transfected mammalian cells.
• Performed Fluorescence Recovery After Photobleaching (FRAP) to assess intranuclear dynamics.
• Inhibited acetyltransferase CBP/p300 to observe effects on TR localization.

Main Results:

• Acetylation mimic TR showed significantly lower N/C ratio compared to wild-type.
• Nonacetylation mimic and sumoylation-deficient TRs exhibited wild-type N/C.
• FRAP revealed reduced mobility for the nonacetylation mimic TR within the nucleus.
• Inhibition of CBP/p300 enhanced TR's nuclear localization.

Conclusions:

• Acetylation of TR promotes its cytosolic localization, while nonacetylation correlates with nuclear retention.
• TR's intracellular localization is dynamically regulated by acetylation.
• Altered localization impacts TR's intranuclear dynamics and transcriptional activity.