Modulation of actin filament dynamics by actin-binding proteins residing in lamellipodia.
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.
Department of Anatomy and Embryology, Ruhr-University, Bochum, Germany.
Antonina Joanna
AJ
Mazur
Dagmar
D
Gremm
Temuujin
T
Dansranjavin
Monika
M
Litwin
Brigitte M
BM
Jockusch
Albrecht
A
Wegner
Alan G
AG
Weeds
Hans Georg
HG
Mannherz
D008841:Actin Cytoskeleton / Q000378:metabolism*; D051339:Actin Depolymerizing Factors / Q000378:metabolism; D000199:Actins / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D000918:Antibody Specificity; D002478:Cells, Cultured; D051345:Destrin / Q000378:metabolism; D018260:Gelsolin / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism*; D041681:NIH 3T3 Cells; D021122:Protein Subunits / Q000378:metabolism; D021381:Protein Transport; D011554:Pseudopodia / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D014335:Tropomyosin / Q000378:metabolism
D051339:Actin Depolymerizing Factors; D000199:Actins; D051345:Destrin; D018260:Gelsolin; D008840:Microfilament Proteins; D021122:Protein Subunits; D014335:Tropomyosin; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D000251:Adenosine Triphosphatases