Novel changes in NF-κB activity during progression and regression phases of hyperplasia: Role of MEK, ERK, and p38

Parthasarathy Chandrakesan, Ishfaq Ahmed, Tariq Anwar, Yu Wang, Shubhashish Sarkar, Pomila Singh, Sara Peleg, Shahid Umar

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

Utilizing the Citrobacter rodentium-induced transmissible murine colonic hyperplasia (TMCH) model, we measured hyperplasia and NF-κB activation during progression (days 6 and 12 post-infection) and regression (days 20-34 post-infection) phases of TMCH. NF-κB activity increased at progression in conjunction with bacterial attachment and translocation to the colonic crypts and decreased 40% by day 20. NF-κB activity at days 27 and 34, however, remained 2-3-fold higher than uninfected control. Expression of the downstream target gene CXCL-1/KC in the crypts correlated with NF-κB activation kinetics. Phosphorylation of cellular IκBα kinase (IKK)α/β (Ser176/180) was elevated during progression and regression of TMCH. Phosphorylation (Ser32/36) and degradation of IαBβ, however, contributed to NF-κB activation only from days 6 to 20 but not at later time points. Phosphorylation of MEK1/2 (Ser 217/221), ERK1/2 (Thr202/Tyr204), and p38 (Thr180/Tyr182) paralleled IKKα/β kinetics at days 6 and 12 without declining with regressing hyperplasia. siRNAs to MEK, ERK, and p38 significantly blocked NF-κB activity in vitro, whereas MEK1/2-inhibitor (PD98059) also blocked increases in MEK1/2, ERK1/2, and IKKα/β thereby inhibiting NF-κB activity in vivo. Cellular and nuclear levels of Ser536-phosphorylated (p65536) and Lys310-acetylated p65 subunit accompanied functional NF-κB activation during TMCH. RSK-1 phosphorylation at Thr359/Ser 363 in cellular/nuclear extracts and co-immunoprecipitation with cellular p65-NF-κB overlapped with p65536 kinetics. Dietary pectin (6%) blocked NF-κB activity by blocking increases in p65 abundance and nuclear translocation thereby down-regulating CXCL-1/KC expression in the crypts. Thus, NF-κB activation persisted despite the lack of bacterial attachment to colonic mucosa beyond peak hyperplasia. The MEK/ERK/p38 pathway therefore seems to modulate sustained activation of NF-κB in colonic crypts in response to C. rodentium infection.

Original languageEnglish (US)
Pages (from-to)33485-33498
Number of pages14
JournalJournal of Biological Chemistry
Volume285
Issue number43
DOIs
StatePublished - Oct 22 2010

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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