Scar/WAVE is localised at the tips of protruding lamellipodia in living cells

Cell motility entails the extension of cytoplasmic processes, termed lamell ipodia and filopodia. Extension is driven by actin polymerisation at the ti ps of these processes via molecular complexes that remain to be characteris ed. We show here that a green fluorescent protein (GFP) fusion of the Wisko tt-Aldrich syndrome protein family member Scar1/WAVE1 is specifically recru ited to the tips of lamellipodia in living B16F1 melanoma cells. Scar1-GFP was recruited only to protruding lamellipodia and was absent from filopodia . The localisation of Scar was facilitated by the finding that the formerly described inhibition of lamellipodia formation by ectopical expression of Scar, could be overcome by the treatment of cells with aluminium fluoride. These findings show that Scar is strategically located at sites of actin po lymerisation specifically engaged in the protrusion of lamellipodia. (C) 20 01 Federation of European Biochemical Societies. Published by Elsevier Scie nce B.V. All rights reserved.