Requirement for high mobility group protein HMGI-C interaction with STAT3 inhibitor PIAS3 in repression of a-subunit of epithelial Na+ channel (alpha-ENaC) transcription by Ras activation in salivary epithelial cells

Citation
Md. Zentner et al., Requirement for high mobility group protein HMGI-C interaction with STAT3 inhibitor PIAS3 in repression of a-subunit of epithelial Na+ channel (alpha-ENaC) transcription by Ras activation in salivary epithelial cells, J BIOL CHEM, 276(32), 2001, pp. 29805-29814
Citations number
39
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
JOURNAL OF BIOLOGICAL CHEMISTRY
ISSN journal
0021-9258 → ACNP
Volume
276
Issue
32
Year of publication
2001
Pages
29805 - 29814
Database
ISI
SICI code
0021-9258(20010810)276:32<29805:RFHMGP>2.0.ZU;2-G
Abstract
Previously, we have demonstrated that oxidative stress or Ras/ERK activatio n leads to the transcriptional repression of alpha -subunit of epithelial N a+ channel (ENaC in lung and salivary epithelial cells. Here, we further in vestigated the coordinated molecular mechanisms by which alpha -ENaC expres sion is regulated. Using both stable and transient transfection assays, we demonstrate that the overexpression of high mobility group protein I-C (HMG I-C), a Ras/ERK-inducible HMG-I family member, represses glucocorticoid rec eptor (GR)/dexamethasone (Dex)-stimulated alpha -ENaC/reporter activity in salivary epithelial cells. Northern analyses further confirm that the expre ssion of endogenous a-ENaC gene in salivary Pa-4 cells is suppressed by an ectopic HMGI-C overexpression. Through yeast two-hybrid screening and co-im munoprecipitation assays from eukaryotic cells, we also discovered the inte raction between HMGI-C and PIAS3 (protein inhibitor of activated STAT3 (sig nal transducer and activator of transcription 3)). A low level of ectopical ly expressed PIAS3 cooperatively inhibits GR/Dex-dependent alpha -ENaC tran scription in the presence of HMGI-C. Reciprocally, HMGI-C expression also c oordinately enhances PIAS3-mediated repression of STAT3-dependent transacti vation. Moreover, overexpression of antisense HMGI-C construct is capable o f reversing the repression mediated by Ras V12 on GR- and STAT3-dependent t ranscriptional activation. Together, our results demonstrate that Ras/ERK-m ediated induction of HMGI-C is required to effectively repress GR/Dex-stimu lated transcription of alpha -ENaC gene and STAT3-mediated transactivation. These findings delineate a network of inhibitory signaling pathways that c onverge on HMGI-C.PIAS3 complex, causally associating Ras/ERK activation wi th the repression of both GR and STAT3 signaling pathways in salivary epith elial cells.