Keratins Stabilize Hemidesmosomes through Regulation of β4-Integrin Turnover

J Invest Dermatol. 2015 Jun;135(6):1609-1620. doi: 10.1038/jid.2015.46. Epub 2015 Feb 10.

Abstract

Epidermal integrity and wound healing depend on remodeling of cell-matrix contacts including hemidesmosomes. Mutations in β4-integrin and plectin lead to severe epidermolysis bullosa (EB). Whether mutations in keratins K5 or K14, which cause EB simplex, also compromise cell-matrix adhesion through altering hemidesmosomal components is not well investigated. In particular, the dependence of β4-integrin endocytosis and turnover on keratins remains incompletely understood. Here, we show that the absence of keratins causes loss of plectin-β4-integrin interaction and elevated β4-integrin phosphorylation at Ser1354 and Ser1362. This triggered a caveolin-dependent endocytosis of β4-integrin but not of other integrins through Rab5 and Rab11 compartments in keratinocytes. Expressing a phospho-deficient β4-integrin mutant reduces β4-integrin endocytosis and rescues plectin localization in keratin-free cells. β4-integrin phosphorylation in the absence of keratins resulted from elevated Erk1/2 activity downstream of increased EGFR and PKCα signaling. Further, increased Erk1/2 phosphorylation and altered plectin localization occur in keratin-deficient mouse epidermis in vivo. Strikingly, expression of the K14-R125P EBS mutant also resulted in plectin mislocalization and elevated β4-integrin turnover, suggesting disease relevance. Our data underscore a major role of keratins in controlling β4-integrin endocytosis involving a plectin-Erk1/2-dependent mechanism relevant for epidermal differentiation and pathogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Caveolins / metabolism
  • Cell Separation
  • Endocytosis
  • Epidermis / metabolism
  • ErbB Receptors / metabolism
  • Flow Cytometry
  • Fluorescence Recovery After Photobleaching
  • Gene Expression Regulation*
  • Genotype
  • Hemidesmosomes / metabolism*
  • Integrin beta4 / metabolism*
  • Keratinocytes / cytology
  • Keratins / metabolism*
  • Lasers
  • Mice
  • Microscopy, Fluorescence
  • Mutation
  • Phenotype
  • Phosphorylation
  • Plectin / metabolism
  • Protein Binding
  • Protein Kinase C-alpha / metabolism
  • Serine / chemistry
  • rab GTP-Binding Proteins / metabolism
  • rab5 GTP-Binding Proteins / metabolism

Substances

  • Caveolins
  • Integrin beta4
  • Plectin
  • Serine
  • Keratins
  • ErbB Receptors
  • Protein Kinase C-alpha
  • rab11 protein
  • rab GTP-Binding Proteins
  • rab5 GTP-Binding Proteins