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Isolation of Intermediate Filament Proteins from Multiple Mouse Tissues to Study Aging-associated Post-translational Modifications
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Keratin 8 phosphorylation by p38 kinase regulates cellular keratin filament reorganization: modulation by a keratin

Nam-On Ku1, Salman Azhar, M Bishr Omary

  • 1Department of Medicine, and Geriatric Research, Education and Clinical Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, California 94304, USA.

The Journal of Biological Chemistry
|January 15, 2002
PubMed

Insights

Keratin 8 Serine-73 phosphorylation by p38 kinase is crucial for keratin filament organization. Mutations affecting this site can lead to keratin filament collapse and may impact disease pathogenesis.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Keratin 8 (K8) Serine-73 is a phosphorylation site involved in cellular processes like mitosis and apoptosis.
  • Understanding K8 phosphorylation is vital for comprehending keratin filament dynamics and associated diseases.

Purpose of the Study:

  • To elucidate the specific kinase responsible for K8 Ser-73 phosphorylation.
  • To investigate the functional role of K8 Ser-73 phosphorylation in keratin filament organization.
  • To explore the impact of disease-associated keratin mutations on phosphorylation and filament stability.

Main Methods:

  • In vitro kinase assays using p38 mitogen-activated protein kinase.
  • Cell transfection with wild-type and mutant K8 constructs.
  • Treatment with specific kinase inhibitors (SB203580, PD98059) and okadaic acid.
  • Immunoprecipitation and in vitro overlay assays to assess protein interactions.

Main Results:

  • p38 kinase exclusively phosphorylates K8 Ser-73 in vitro.
  • Ser-73 phosphorylation occurs in cells with activated p38 kinase and is inhibited by SB203580.
  • Mutating Ser-73 to Alanine (Ala) or Aspartic acid (Asp) affects filament stability upon okadaic acid treatment.
  • A disease-associated K8 mutation (Leu-71 --> Pro) leads to hyperphosphorylation and filament collapse.

Conclusions:

  • K8 Ser-73 is a physiological phosphorylation site for p38 kinase, regulating keratin filament reorganization.
  • Phosphorylation at Ser-73 is essential for maintaining keratin filament stability.
  • Keratin mutations can alter phosphorylation patterns and filament organization, potentially contributing to disease pathogenesis.

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