Modulation of actin filament dynamics by actin-binding proteins residing in lamellipodia

• Published in: European journal of cell biology 2010-05, Vol.89 (5), p.402-413
• Main Authors: Mazur, Antonina Joanna, Gremm, Dagmar, Dansranjavin, Temuujin, Litwin, Monika, Jockusch, Brigitte M., Wegner, Albrecht, Weeds, Alan G., Mannherz, Hans Georg
• Format: Article
• Language: English
• Subjects: Actin; Actin Cytoskeleton - metabolism; Actin Depolymerizing Factors - metabolism; Actins - metabolism; Adenosine Triphosphatases - metabolism; ADF/cofilin; Animals; Antibody Specificity; Cells, Cultured; Destrin - metabolism; Gelsolin; Gelsolin - metabolism; Green Fluorescent Proteins - metabolism; HeLa Cells; Humans; Lamellipodia; Mice; Microfilament Proteins - metabolism; NIH 3T3 Cells; Protein Subunits - metabolism; Protein Transport; Pseudopodia - metabolism; Rabbits; Rats; Tropomyosin; Tropomyosin - metabolism
• ISSN: 0171-9335; 1618-1298
• DOI: 10.1016/j.ejcb.2009.10.017

Lamellipodial extension depends essentially on the polymerisation cycle of actin. In this cellular compartment the rate and extent of actin polymerisation is tightly regulated by a large number of actin-binding proteins. The main regulators comprise proteins of the actin-depolymerising factor (ADF)/cofilin family, which stimulate actin cycling, but there are also minor constituents like gelsolin and certain variants of tropomyosin that have so far not been considered to be lamellipodial constituents. A number of cell lines express ADF and cofilin simultaneously as shown here for the fibroblastic normal rat kidney (NRK) cell line. Both proteins co-localise in the lamellipodial region. We furthermore demonstrate the presence of gelsolin in lamellipodia by immunostaining with anti-gelsolin antibodies and transfection with EGFP-tagged gelsolin constructs. The presence of tropomyosins in lamellipodia has recently been reported ( Hillberg et al., 2006. Tropomyosins are present in lamellipodia of motile cells. Eur. J. Cell Biol. 85, 399-409). In order to evaluate the effect of the simultaneous presence of ADF and cofilin together with tropomyosin and/or gelsolin on the polymerisation cycle of actin, we analysed their effect or combinations of these actin-binding proteins on the steady-state F-actin-ATPase activity in biochemical assays. Our results demonstrate stimulatory effects of ADF/cofilin on actin cycling and a further modulation of ADF/cofilin-stimulated F-actin-ATPase activity by gelsolin and tropomyosin in a complex manner.