Molecular aspects of thyroid hormone actions

Area of Science:

• Endocrinology and Molecular Biology
• Cellular and Molecular Physiology
• Genetics and Disease Pathogenesis

Background:

• Thyroid hormone (TH) mediates cellular functions through nuclear receptors (TRs) and extranuclear pathways.
• TRs regulate gene transcription via binding to thyroid hormone response elements.
• TH actions can be genomic (nuclear) or nongenomic (membrane/cytoplasmic).

Purpose of the Study:

• To elucidate the diverse cellular mechanisms of thyroid hormone action.
• To investigate the role of TRs and their isoforms in transcriptional regulation.
• To explore nongenomic pathways initiated at the plasma membrane and cytoplasm.

Main Methods:

• Analysis of TR gene products and their interaction with coregulatory proteins.
• Investigation of TR mutations using genetically engineered mouse models.
• Characterization of plasma membrane-initiated signaling pathways involving integrin alphavbeta3 and ERK1/2.
• Examination of mitochondrial and cytoskeletal effects of thyroid hormones.

Main Results:

• TRs regulate gene transcription dependent on T(3), coregulators, and response elements.
• TR mutations cause resistance to thyroid hormones and other abnormalities like cancer and dwarfism.
• Nongenomic actions, initiated at the plasma membrane (integrin alphavbeta3) or cytoplasm, influence cell proliferation, angiogenesis, and ion transport.
• Thyroid hormone affects mitochondrial energetics, cytoskeleton dynamics, and neuronal development.

Conclusions:

• Thyroid hormone actions are multifaceted, involving both nuclear and non-nuclear pathways.
• TRs are critical for normal development and function; their mutations have severe consequences.
• Nongenomic actions contribute significantly to cellular events and disease processes, such as cancer.
• Further research using mouse models is essential to understand unliganded TR actions and hypothyroidism pathogenesis.