Calcium signaling of thyrocytes is modulated by TSH through calcium binding protein expression.
TSH is an important stimulus to maintain thyroid epithelial differentiation. Impairment of TSH signal transduction can cause thyroid pathologies such as hot nodules, goiter and hyperthyroidism. In a gene expression study in Fischer rat thyroid cells (FRTL-5) using cDNA microarrays we found a TSH-dependent regulation of several calcium binding proteins, S100A4, S100A6 and annexin A6. Expression of these genes in FRTL-5 and regulation by TSH was confirmed with LightCycler qPCR and Western blotting. The differential expression of S100A4 was confirmed for cultured primary human thyrocytes. Calcium-imaging experiments showed that prestimulation with TSH attenuates ATP-elicited P2Y-mediated calcium signaling. Experiments with thapsigargin, TSH and calcium-free perfusion excluded an involvement of other purinergic receptors or an involvement of SERCA regulation. Instead, we find a correlation between S100A4 expression and the effects of TSH on calcium signaling. Overexpression of S100A4 in FRTL-5 and shRNA-mediated knockdown of S100A4 in follicular thyroid cancer cells (FTC133) confirm the ability of S100A4 to attenuate calcium signals. Under repeated stimulations with ATP the calcium retention of these cells is also modulated by S100A4, suggesting a role of S100A4 as calcium buffering protein. As a biological consequence of S100A4 overexpression we detected reduced ATP-stimulated cFos induction. Taken together, the results suggest that S100A4 and other calcium binding proteins are part of a signaling network connecting TSH signaling to calcium-mediated events which play a role in thyroid physiology like H2O2 production or even thyroid cancer.
Lorenz
Stephan
S
III. Medical Department, Faculty of Medicine, University of Leipzig, D-04103 Leipzig, Germany.
Eszlinger
Markus
M
Paschke
Ralf
R
Aust
Gabriela
G
Weick
Michael
M
Führer
Dagmar
D
Krohn
Knut
K
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism; D051381:Rats; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins / Q000235:genetics / Q000378:metabolism; D019284:Thapsigargin / Q000378:metabolism; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism; D013972:Thyrotropin / Q000378:metabolism*
D002135:Calcium-Binding Proteins; D004791:Enzyme Inhibitors; D016760:Proto-Oncogene Proteins c-fos; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins; C499412:S100a4 protein, rat; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D013972:Thyrotropin; D002118:Calcium