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p38 MAP kinase and MAPKAP kinases MK2/3 cooperatively phosphorylate epithelial keratins

Manoj B Menon1, Jessica Schwermann1, Anurag Kumar Singh2

  • 1From the Institute of Biochemistry, Hannover 30625, Germany.

The Journal of Biological Chemistry
|August 21, 2010
PubMed

Insights

Mitogen-activated protein kinase-activated protein kinases (MAPKAP kinases) MK2 and MK3, alongside p38 MAPK, regulate cellular stress responses. This study reveals their coordinated role in phosphorylating keratins K8, K18, and K20, impacting intestinal epithelial function.

Area of Science:

  • Cellular Biology
  • Molecular Signaling
  • Protein Phosphorylation

Background:

  • MAPKAP kinases MK2 and MK3 are activated by p38 MAPK and involved in stress response.
  • Their substrate repertoire is expanding, necessitating further investigation into their roles.
  • Understanding MK2/3 function is crucial for deciphering cellular signaling pathways.

Purpose of the Study:

  • To compare protein phosphorylation in MK2/3-deficient cells versus rescued cells using phosphoproteomics.
  • To identify novel substrates and phosphorylation sites regulated by MK2/3 and p38 MAPK.
  • To elucidate the functional interplay between p38 MAPK, MK2, and keratin phosphorylation in intestinal epithelia.

Main Methods:

  • Phosphoproteomics analysis of MK2/3-deficient and rescued cells.
  • In vitro kinase assays to determine direct phosphorylation events.
  • Pharmacological inhibition of p38 MAPK and MK2 pathways.
  • Analysis of keratin phosphorylation in mouse ileum and HT29 cells.
  • Assessment of mucin secretion.

Main Results:

  • Identified significant differences in keratin 8 (K8) phosphorylation at Ser(73) in MK2/3-deficient cells.
  • p38 MAPK directly phosphorylates K8-Ser(73), with MK2 influencing its expression.
  • MK2 directly phosphorylates K18-Ser(52) and K20-Ser(13), which are not direct p38 substrates.
  • p38 and MK2 inhibitors reduced phosphorylation of K18-Ser(52) and K20-Ser(13).
  • MK2 knockdown reduced K20-Ser(13) phosphorylation in HT29 cells.
  • Differences in K20-Ser(13) phosphorylation observed between wild-type and MK2/3-deficient mouse ileum.
  • p38 and MK2 signaling regulate mucin secretion in HT29 cells.

Conclusions:

  • MK2 and p38 MAPK function in concert to regulate the phosphorylation of keratins K8, K18, and K20.
  • This coordinated action plays a role in intestinal epithelial function, including mucin secretion.
  • The findings expand the understanding of MK2/3 and p38 MAPK signaling networks in cellular stress and epithelial biology.

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