IBYME   02675
INSTITUTO DE BIOLOGIA Y MEDICINA EXPERIMENTAL
Unidad Ejecutora - UE
artículos
Título:
NF-kappaB p65 subunit mediates lipopolysaccharide-induced Na(+)/I(-) symporter gene expression by involving functional interaction with the paired domain transcription factor Pax8.
Autor/es:
NICOLA JP, NAZAR M, MASCANFRONI ID, PELLIZAS CG, MASINI-REPISO AM
Revista:
MOLECULAR ENDOCRINOLOGY
Editorial:
ENDOCRINE SOC
Referencias:
Año: 2010 p. 1846 - 1862
ISSN:
0888-8809
Resumen:
The Gram-negative bacterial endotoxin lipopolysaccharide (LPS) elicits a
variety of biological responses. Na(+)/I(-) symporter (NIS)-mediated
iodide uptake is the main rate-limiting step in thyroid hormonogenesis.
We have recently reported that LPS stimulates TSH-induced iodide uptake.
Here, we further analyzed the molecular mechanism involved in the
LPS-induced NIS expression in Fisher rat thyroid cell line 5 (FRTL-5)
thyroid cells. We observed an increase in TSH-induced NIS mRNA
expression in a dose-dependent manner upon LPS treatment. LPS enhanced
the TSH-stimulated NIS promoter activity denoting the NIS-upstream
enhancer region (NUE) as responsible for the stimulatory effects. We
characterized a novel putative conserved kappaB site for the
transcription factor nuclear factor-kappaB (NF-kappaB) within the NUE
region. NUE contains two binding sites for the transcription factor
paired box 8 (Pax8), main regulator of NIS transcription. A physical
interaction was observed between the NF-kappaB p65 subunit and paired
box 8 (Pax8), which appears to be responsible for the synergic effect
displayed by these transcription factors on NIS gene transcription.
Moreover, functional blockage of NF-kappaB signaling and site-directed
mutagenesis of the kappaB cis-acting element abrogated LPS stimulation.
Silencing expression of p65 confirmed its participation as an effector
of LPS-induced NIS stimulation. Furthermore, chromatin
immunoprecipitation corroborated that NIS is a novel target gene for p65
transactivation in response to LPS. Moreover, we were able to
corroborate the LPS-stimulatory effect on thyroid cells in vivo in
LPS-treated rats, supporting that thyrocytes are capable of responding
to systemic infections. In conclusion, our results reveal a new
mechanism involving p65 in the LPS-induced NIS expression, denoting a
novel aspect in thyroid cell differentiation.