Hepatocyte Growth Factor Suppresses Proinflammatory NFκB Activation through GSK3β Inactivation in Renal Tubular Epithelial Cells

Abstract

Activation of NF B is a fundamental cellular event central to all inflammatory diseases. Hepatocyte growth factor (HGF) ameliorates both acute and chronic inflammation in a multitude of organ systems through modulating NF B activity; nevertheless, the exact molecular mechanism remains uncertain. Here we report that HGF through inactivation of GSK3␤ suppresses NF B p65 phosphorylation specifically at position Ser-468. The Ser-468 of RelA/p65 situates in a GSK3␤ consensus motif and could be directly phosphorylated by GSK3␤ both in vivo and in vitro, signifying Ser-468 of RelA/p65 as a putative substrate for GSK3␤. In addition, the C terminus of RelA/p65 harbors a highly conserved domain homologue of the consensus docking sequence for GSK3␤. Moreover, this domain was required for efficient phosphorylation of Ser-468 and was indispensable for the physical interaction between RelA/p65 and GSK3␤. HGF substantially intercepted this interaction by inactivating GSK3␤. Functionally, phosphorylation of Ser-468 of RelA/p65 was required for the induced expression of a particular subset of proinflammatory NF B-dependent genes. Diminished phosphorylation at Ser-468 by HGF resulted in a gene-specific inhibition of these genes' expression. The action of HGF on proinflammatory NF B activation was consistently mimicked by a selective GSK3␤ inhibitor or GSK3␤ knockdown by RNA interference but largely abrogated in cells expressing the mutant uninhibitable GSK3␤. Collectively, our findings suggest that HGF has a potent suppressive effect on NF B activation, which is mediated by GSK3␤, an important signaling transducer controlling RelA/p65 phosphorylation specificity and directing the transcription of selective proinflammatory cytokines implicated in inflammatory kidney disease.

Zac1 is a histone acetylation-regulated NF-κB suppressor that mediates histone deacetylase inhibitor-induced apoptosis

“…Although a negative regulatory role of Ser468 phosphorylation in NF-kB activation has been observed, 34 some later reports showed that phosphorylation of Ser468 serves to enhance NF-kB-dependent gene transcription in different systems. 29,35 Our findings support a positive role of p65 Ser468 phosphorylation in NF-kB activity, and suggest that repression of p65 phosphorylation at both Ser468 and Ser536 residues is involved in the inhibition of NF-kB activity and cell apoptosis.…”

“…29,[35][36][37] However, very little is known about factors that inhibit the phosphorylation of these residues. In this study, we showed that Zac1 inhibits the phosphorylation of p65 Ser468 and Ser536.…”

GSK-3 Represses Growth Factor-inducible Genes by Inhibiting NF-κB in Quiescent Cells

“…In most cases, GSK-3 did not affect activation of IKK, degradation of IB, or nuclear translocation of p65 but instead appeared to affect the DNA binding or transcriptional activity of nuclear p65 (16 -20). One possible mechanism for these effects is phosphorylation of p65 by GSK-3 (17,20). It is also noteworthy that inhibition of GSK-3 can lead to the accumulation of nuclear ␤-catenin, which directly interacts with p65 to inhibit its transcriptional activity (47,48).…”

The Pivotal Roles of GSK3β in Glioma Biology

“…GSK3 is also involved in inflammation that accompanies various kinds of diseases (reviewed in Jope et al, 2007). GSK3 inhibition attenuates activation of the pro-inflammatory transcription factor NF-κB and activates the immunomodulatory transcription factor -catenin (Gong et al, 2008). GSK3 inhibition also induces secretion of the anti-inflammatory cytokine IL-10 (Hu et al, 2006).…”