Effect of Protein Kinase C Activation on Thyroid Cell Growth and Function
Activation of protein kinases and alterations in calcium fluxes are early events in the transduction of signals leading to cell proliferation and/or differentiation by hormones and other agents with cell-surface receptors (1). TSH is known to stimulate cAMP production and the cAMP-dependent protein kinase, protein kinase A. TSH stimulation results in many differentiated functions, e.g., iodide uptake and organification and thyroglobulin synthesis (2,3). In addition, there are reports of stimulation of Ca2+ efflux (3) and activation of another kinase known as protein kinase C (4) in response to TSH. We have previously shown that both the tumor-promoting phorbol ester, tetradecanoylphorbol acetate (TPA), a known stimulator of protein kinse C and epidermal growth factor (EGF) antagonize TSH-mediated differentiated functions, i.e., cAMP accumulation, iodide uptake and organification and thyroglobulin synthesis (5,6). This inhibition is not due to toxic effects on the cells, since both factors stimulate thyroid cell growth while inhibiting differentiation. The interaction of pathways stimulated by protein kinase A, protein kinase C, and Ca2+ remain unexplored in the thyroid gland. In several other systems, calcium mobilization and protein kinase C activation have been shown to act synergistically to produce a biological effect (1,7). In this paper we examine the effects of putative stimulators of protein kinase C on thyroid cell growth and differentiation.
KeywordsEpidermal Growth Factor Receptor Thyroid Cell Calcium Ionophore Iodide Uptake Stimulate cAMP Production
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- 2.Errick JE, Eggo MC, and Burrow GN. In MC Eggo and GN Burrow (eds), Thyroglobulin - The Prothyroid Hormone, Raven Press, 1985, p 271.Google Scholar
- 3.Dumont JE, Roger P, Servis P, et al. In MC Eggo and GN Burrow (eds), Thyroglobulin - The Prothyroid Hormone, Raven Press, 1985, p 283.Google Scholar
- 4.Friedman Y, Poleck T, and Burke G. 67th Annual Meeting Endocine Soc, abstract 700, 1985.Google Scholar
- 7.Rasmussen H, Kojima I, Kojima K, et al. Adv in Cyclic Nucleotide and Protein Phosphorylation 18: 159, 1985.Google Scholar
- 11.Kaibuchi K, Takai Y, and Nishizuka Y. J Biol Chem 200: 1366, 1985.Google Scholar