NF-kappaB p65 S-nitrosylation inhibits TSH-induced Na+ /I- symporter expression

NICOLA, J.P; PEYRET, V; NAZAR, M; ROMERO, J M; LUCERO, A. M; MONTESINOS, M. M.; BOCCO, J. L; PELLIZAS, C. G; MASINI-REPISO, A. M

Lake Buena Vista, Orlando

Congreso; 15th International Thyroid Congress and 85th Annual Meeting of the American Thyroid Association; 2015

American Thyroid Association

Nitric oxide (NO) is a ubiquitous signaling molecule involved in awide variety of cellular physiological processes. In thyroid cells, NOsynthaseIII-endogenously produced NO reduces thyrotropin (TSH)-stimulated thyroid specific gene expression, suggesting a potentialautocrine role of NO in modulating thyroid function. Further studiesindicate that NO induces thyroid dedifferentiation, since NO donorsrepress TSH-stimulated I- uptake. Here, we investigated the molecularmechanism underlying the NO-inhibited Na+ /I- Symporter(NIS)-mediated I- uptake in thyroid cells FRTL-5 cells, a line of highly differentiated rat thyroid-derived cells, were incubated with different NO donors (sodium nitroprusside,S-nitrosoglutathione, Spermine NONOate). NIS function wasmeasured using 125I- transport assays, and NIS expression wasevaluated through western blot, RT/qPCR, and gene reporter assays.NIS post-transcriptional modifications were evaluated in FRTL-5cells stably expressing N-terminal HA-tagged NIS.NO donors reduced I- uptake in a concentration-dependent manner,which correlated with decreased NIS protein expression. NOreducedI- uptake resulted from transcriptional repression of NISgene rather than post-transcriptional modifications impairing functionalNIS expression at the plasma membrane. We observed that NOdonors repress TSH-induced NIS gene expression by reducing theNF-jB subunit p65-dependent transcriptional activity rather thanaffecting Pax8 expression or transcriptional activity. NO-promotedCys-38 p65 S-nitrosylation reduces p65-mediated transactivation ofthe NIS promoter in response to TSH stimulation.We demonstrated that exogenous NO-induced p65 S-nitrosylationrepressed TSH-stimulated NIS gene transcription, thus leading to asubsequent reduction of NIS-mediated I- uptake in rat thyrocytes.These findings support the participation of NO as an inhibitory signalmolecule to counterbalance TSH-stimulated NF-jB activation, thusmodulating TSH-induced thyroid specific gene expression.