IL-6 activates serum and glucocorticoid kinase via p38alpha mitogen-activated protein kinase pathway

Am J Physiol Cell Physiol. 2005 Oct;289(4):C971-81. doi: 10.1152/ajpcell.00081.2005. Epub 2005 May 25.

Abstract

Interleukin-6 (IL-6) has been implicated as an autocrine factor involved in growth of several human cancers, such as tumors arising from the biliary tract or cholangiocarcinoma. In malignant biliary tract epithelia, IL-6 activates the p38 MAPK pathway, which mediates a dominant survival signaling pathway. Serum and glucocorticoid-stimulated kinase (SGK) has been implicated as a survival kinase, but its role in survival signaling by IL-6 is unknown. After IL-6 stimulation, p38 MAPK activation preceded phosphorylation of SGK at Ser78. Pretreatment with the pharmacological inhibitors of p38 MAPK SB-203580 or SB-202190 blocked IL-6-induced SGK phosphorylation at Ser78 and SGK activation. Overexpression of p38alpha increased constitutive SGK phosphorylation at Ser78, whereas dominant negative p38alpha MAPK blocked IL-6-induced SGK phosphorylation and nuclear translocation. Interestingly, in addition to stimulating SGK phosphorylation, both IL-6 stimulation and p38alpha MAPK overexpression increased SGK mRNA and protein expression. An increase in p38 MAPK and SGK occurred following enforced expression of IL-6 in vivo. Furthermore, inhibition of SGK expression by siRNA increased toxicity due to chemotherapeutic drugs. Taken together, these data identify SGK as both a downstream kinase substrate as well as a transcriptionally regulated gene target of p38 MAPK in response to IL-6 and support a role of SGK during survival signaling by IL-6 in human cancers, such as cholangiocarcinoma.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cell Line, Tumor
  • Enzyme Activation
  • Enzyme Inhibitors / pharmacology
  • Gene Expression Regulation
  • Humans
  • Imidazoles / pharmacology
  • Immediate-Early Proteins
  • Interleukin-6 / physiology*
  • Isoenzymes
  • Mitogen-Activated Protein Kinase 14 / antagonists & inhibitors
  • Mitogen-Activated Protein Kinase 14 / metabolism*
  • Nuclear Proteins / metabolism*
  • Protein Serine-Threonine Kinases / metabolism*
  • Pyridines / pharmacology
  • RNA, Messenger
  • Signal Transduction

Substances

  • Enzyme Inhibitors
  • Imidazoles
  • Immediate-Early Proteins
  • Interleukin-6
  • Isoenzymes
  • Nuclear Proteins
  • Pyridines
  • RNA, Messenger
  • Protein Serine-Threonine Kinases
  • serum-glucocorticoid regulated kinase
  • Mitogen-Activated Protein Kinase 14
  • SB 203580
  • 4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole