title: Actinin-4 in keratinocytes regulates motility via an effect on lamellipodia stability and matrix adhesions.
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.
authors.affiliation: Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Hamill
authors.forename: Susan B
authors.initials: SB
authors.lastname: Hopkinson
authors.forename: Omar
authors.initials: O
authors.lastname: Skalli
authors.forename: Jonathan C R
authors.initials: JC
authors.lastname: Jones
mesh_terms: D051339:Actin Depolymerizing Factors / Q000502:physiology; D000185:Actinin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured; D022001:Focal Adhesions / Q000502:physiology; D055785:Gene Knockdown Techniques; D022002:Hemidesmosomes / Q000502:physiology; D006801:Humans; D039161:Integrin alpha6beta4 / Q000235:genetics / Q000502:physiology; D015603:Keratinocytes / Q000502:physiology*; D011554:Pseudopodia / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: C111453:ACTN4 protein, human; D051339:Actin Depolymerizing Factors; D039161:Integrin alpha6beta4; D034741:RNA, Small Interfering; D000185:Actinin