title: Thymosin beta4 inhibits ADF/cofilin stimulated F-actin cycling and hela cell migration: reversal by active Arp2/3 complex.
abstract: F-actin treadmilling plays a key part in cell locomotion. Because immunofluorescence showed colocalisation of thymosin beta4 (Tβ4) with cofilin-1 and Arp2/3 complex in lamellipodia, we analyzed combinations of these proteins on F-actin-adenosine triphosphate (ATP)-hydrolysis, which provides a measure of actin treadmilling. Actin depolymerising factor (ADF)/cofilin stimulated treadmilling, while Tβ4 decreased treadmilling, presumably by sequestering monomers. Tβ4 added together with ADF/cofilin also inhibited the treadmilling, relative to cofilin alone, but both the rate and extent of depolymerization were markedly enhanced in the presence of both these proteins. Arp2/3 complex reversed the sequestering activity of Tβ4 when equimolar to actin, but not in the additional presence of cofilin-1 or ADF. Transfection experiments to explore the effects of changing the intracellular concentration of Tβ4 in HeLa cells showed that an increase in Tβ4 resulted in reduced actin filaments bundles and narrower lamellipodia, and a conspicuous decrease of cell migration as seen by two different assays. In contrast, cells transfected with a vector leading to Tβ4 knockdown by small interfering RNA (siRNA) displayed prominent actin filament networks within the lamellipodia and the leading lamella and enhanced migration. The experiments reported here demonstrate the importance of the interplay of these different classes of actin-binding proteins on cell behaviour.
authors.affiliation: Department of Anatomy and Molecular Embryology, Ruhr-University, Bochum, Germany.
authors.forename: Abdulatif
authors.initials: A
authors.lastname: Al Haj
authors.forename: Antonina Joanna
authors.initials: AJ
authors.lastname: Mazur
authors.forename: Sabine
authors.initials: S
authors.lastname: Buchmeier
authors.forename: Christine
authors.initials: C
authors.lastname: App
authors.forename: Carsten
authors.initials: C
authors.lastname: Theiss
authors.forename: Unai
authors.initials: U
authors.lastname: Silvan
authors.forename: Cora-Ann
authors.initials: CA
authors.lastname: Schoenenberger
authors.forename: Brigitte M
authors.initials: BM
authors.lastname: Jockusch
authors.forename: Ewald
authors.initials: E
authors.lastname: Hannappel
authors.forename: Alan G
authors.initials: AG
authors.lastname: Weeds
authors.forename: Hans Georg
authors.initials: HG
authors.lastname: Mannherz
mesh_terms: D051339:Actin Depolymerizing Factors / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D002465:Cell Movement / Q000502:physiology; D051345:Destrin / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D013947:Thymosin / Q000378:metabolism*; D000099201:Thymosin beta(4)
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D051345:Destrin; D013947:Thymosin; D000099201:Thymosin beta(4)
keywords: Arp2/3 complex; actin; actin depolymerising factor/cofilin; thymosin beta4