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Serine residue 115 of MAPK-activated protein kinase MK5 is crucial for its PKA-regulated nuclear export and

Sergiy Kostenko1, Alexey Shiryaev, Nancy Gerits

  • 1Faculty of Health Sciences, Institute of Medical Biology, University of Tromsø, Tromsø, Norway.

Cellular and Molecular Life Sciences : CMLS
|August 25, 2010
PubMed

Insights

Protein kinase A (PKA) regulates the nuclear export of mitogen-activated protein kinase-activated protein kinase-5 (MK5) via phosphorylation of Ser-115. This phosphorylation impacts MK5

Area of Science:

  • Cellular biology
  • Molecular signaling pathways
  • Protein kinase regulation

Background:

  • Mitogen-activated protein kinase-activated protein kinase-5 (MK5) is primarily nuclear in resting cells.
  • Various kinases, including p38(MAPK), ERK3/4, and PKA, can induce MK5 redistribution.
  • The precise mechanism of PKA-induced nuclear export of MK5 is not fully understood.

Purpose of the Study:

  • To elucidate the role of Ser-115 in PKA-mediated nuclear export of MK5.
  • To investigate the impact of Ser-115 phosphorylation on MK5 localization and function.
  • To determine if other kinases (p38(MAPK), ERK3, ERK4) utilize Ser-115 for MK5 redistribution.

Main Methods:

  • In vitro kinase assays to identify PKA phosphoacceptor sites on MK5.
  • Site-directed mutagenesis to create MK5 mutants (S115A, S115D, T182A, K51E).
  • Analysis of MK5 subcellular localization in response to kinase stimulation using mutant proteins.

Main Results:

  • Ser-115 was identified as a direct PKA phosphoacceptor site.
  • PKA, but not p38(MAPK), ERK3, or ERK4, induced cytoplasmic redistribution of MK5 S115A.
  • The phospho-mimicking mutant MK5 S115D localized to the cytoplasm in untreated cells.
  • Mutants S115D/T182A and K51E/S115D exhibited cytoplasmic localization, indicating Ser-115's critical role.
  • Mutations at Ser-115 altered the biological properties of MK5.

Conclusions:

  • Serine-115 is essential for PKA-regulated nuclear export of MK5.
  • Phosphorylation of Ser-115 by PKA is a key event controlling MK5 localization.
  • Ser-115 phosphorylation may also influence the biological functions of MK5.

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