Nuclear and Cytoplasmic Triiodothyronine‐Binding Sites in Primary Sensory Neurons and Schwann Cells: Radioautographic Study During Development

Abstract

The effects of the thyroid hormones on target cells are mediated through nuclear T3 receptors. In the peripheral nervous system, nuclear T3 receptors were previously detected with the monoclonal antibody 2B3 mAb in all the primary sensory neurons throughout neuronal life and in peripheral glia at the perinatal period only (Eur. J. Neurosci. 5, 319, 1993). To determine whether these nuclear T3 receptors correspond to functional ones able to bind T3, cryostat sections and in vitro cell cultures of dorsal root ganglion (DRG) or sciatic nerve were incubated with 0.1 nM [125I]-labeled T3, either alone to visualize the total T3-binding sites or added with a 10(3) fold excess of unlabeled T3 to estimate the part due to the non-specific T3-binding. After glutaraldehyde fixation, radioautography showed that the specific T3-binding sites were largely prevalent. The T3-binding capacity of peripheral glia in DRG and sciatic nerve was restricted to the perinatal period in vivo and to Schwann cells cultured in vitro. In all the primary sensory neurons, specific T3-binding sites were disclosed in foetal as well as adult rats. The detection of the T3-binding sites in the nucleus indicated that the nuclear T3 receptors are functional. Moreover the concomitant presence of both T3-binding sites and T3 receptors alpha isoforms in the perikaryon of DRG neurons infers that: 1) [125I]-labeled T3 can be retained on the T3-binding 'E' domain of nascent alpha 1 isoform molecules newly-synthesized on the perikaryal ribosomes; 2) the alpha isoforms translocated to the nucleus are modified by posttranslational changes and finally recognized by 2B3 mAb as nuclear T3 receptor. In conclusion, the radioautographic visualization of the T3-binding sites in peripheral neurons and glia confirms that the nuclear T3 receptors are functional and contributes to clarify the discordant intracellular localization provided by the immunocytochemical detection of nuclear T3 receptors and T3 receptor alpha isoforms.

Differential Distribution of Thyroid Hormone Receptor Isoform in Rat Dorsal Root Ganglia and Sciatic Nerve in vivo and in vitro

“…Schwann cells express a nuclear triiodothyronine receptor (NT 3 R). By autoradiography we demonstrated that the immuno-TRa-common (a1 and a2) detected NT 3 R corresponds to a specific [125I ]-labeled T 3 binding site (39)(40)(41). Since both sensory neurons and Schwann cells At embryonic stages ( E17-E21), TRa-common was weakly possess functional T 3 receptors, the present study was designed expressed by DRG cells (Fig.…”

“…receptors and by the correlation between distribution of NT 3 R in which non neuronal cells were eliminated. Also T 3 stimulates the neurite outgrowth of sensory neurons in DRG explant cul-immunoreactivity and T 3 binding capacity (38)(39)(40)(41). tures.…”

Regulation of herpes simplex virus type 1 thymidine kinase gene expression by thyroid hormone receptor in cultured neuronal cells

“…Both sensory neurons and peripheral glial cells in dorsal root ganglia have been shown to possess specific T 3 binding sites (Walter & Droz, 1995). During development, sensory neurons express TRβ rather than TRα and the amount of TRβ positive neurons increased during the postnatal stages and remained stable in adults.…”

Distribution of thyroid hormone and thyrotropin receptors in reproductive tissues of adult female rabbits

“…Thus, thyroid hormones and TSH could be able to affect the synaptic contacts of these ganglia cells. In this regard, the presence of TRs has been described in neurons and glia cells of the dorsal root ganglia and sciatic nerve of postnatal rats (45). The presence of TRs and TSHR in the smooth musculature and corpus cavernosum of the clitoris, as well as in the glial cells of the dorsal nerve of the clitoris has not been previously approached in any species.…”