Activation of the β₂-adrenergic receptor promotes growth and differentiation in thyroid cells

We have introduced the β₂-adrenergic receptor into the unnatural environment of the thyroid cell to demonstrate that the activation of this receptor initiates diverse cellular programs in different cell types. The thyroid-stimulating hormone (TSH) receptor and the β₂-adrenergic receptor stimulate a common signaling pathway in distinct populations of cells. In this study, we demonstrate that the activation of the β₂-adrenergic receptor, transfected into a thyroid epithelial cell, elicits a program of growth and differentiation normally observed with TSH. In thyroid cells expressing β₂ receptors, the β₂ agonist isoproterenol activates adenylate cyclase, induces the expression of a thyroid-specific iodide carrier system, and can substitute for TSH to promote growth. Thus, in thyroid cells expressing β₂-adrenergic receptors, isoproterenol elicits the entire array of thyroid-specific functions normally activated by TSH.