Actinin-4 in keratinocytes regulates motility via an effect on lamellipodia stability and matrix adhesions

FASEB J. 2013 Feb;27(2):546-56. doi: 10.1096/fj.12-217406. Epub 2012 Oct 19.

Abstract

During wound repair, epidermal cells at the edge of an injury establish front-rear polarity through orchestrated changes in their cytoskeleton and adhesion structures. The polarity and directed migration of such cells is determined by the assembly, extension, and stabilization of a lamellipodium. Actinin-4 associates with lamellipodia and has been implicated in regulating lamellipodial structure, function and assembly. To study the functions of actinin-4 in human keratinocytes, we used shRNA to generate knockdown cells and compared their motility behavior and matrix adhesion assembly to scrambled shRNA treated control keratinocytes. Actinin-4 knockdown keratinocytes lack polarity, assemble multiple lamellipodia with a 2× increased area over controls, display reduced activity of the actin remodeling protein cofilin, and fail to migrate in a directional manner. This motility defect is rescued by plating knockdown cells on preformed laminin-332 matrix. In actinin-4-knockdown keratinocytes, focal contact area is increased by 25%, and hemidesmosome proteins are mislocalized. Specifically, α6β4 integrin localizes to large lamellipodial extensions, displays reduced dynamics, and fails to recruit its bullous pemphigoid antigen binding partners. Together, our data indicate a role for actinin-4 in regulating the steering mechanism of keratinocytes via profound effects on their matrix adhesion sites.

Publication types

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

MeSH terms

  • Actin Depolymerizing Factors / physiology
  • Actinin / antagonists & inhibitors
  • Actinin / genetics
  • Actinin / physiology*
  • Cell Movement / physiology
  • Cells, Cultured
  • Focal Adhesions / physiology
  • Gene Knockdown Techniques
  • Hemidesmosomes / physiology
  • Humans
  • Integrin alpha6beta4 / genetics
  • Integrin alpha6beta4 / physiology
  • Keratinocytes / physiology*
  • Pseudopodia / physiology*
  • RNA, Small Interfering / genetics

Substances

  • ACTN4 protein, human
  • Actin Depolymerizing Factors
  • Integrin alpha6beta4
  • RNA, Small Interfering
  • Actinin