Overview Cell Structures Cell Migration Cell Division  

Flux of Actin Subunits at the Leading Edge of Fibroblasts

Wang, J. Cell Biol. 101:597-602 (1985)

Lamellipodia, where cultured cells undergo active forward protrusion, are packed with actin filaments. To investigate the dynamics of these actin filaments, cultured IMR33 gerbil fibroma cells were microinjected with fluorescently labeled actin. A laser micro-beam was then used to bleach the fluorescence and create a small dark spot. Flux of actin subunits was detected as directional movement of the spot relative to the edge of the cell.

Rearward Movement of Bleached Spot in Stationary Cells

This cell had an active lamellipodium but remained stationary during the period of observation. The bleached spot, created at the very edge of the cell, moves toward the cell center, suggesting that actin monomers are adding continuously at the leading edge and pushing the filaments backwards. In addition the other end of the filament must undergo disassembly or fragmentation to maintain a constant width of lamellipodia. Large number indicates the time in seconds after photobleaching. Recording time, 5 min.

Stationary Bleached Spot in Forward Moving Cells

In this cell, the leading edge moves forward while the bleached spot remains stationary relative to the substrate. Recording time, 4 min.