Fig. 2.

The importin β-dependent import pathway is functional in HGPS fibroblasts. (A) Rate of importin β-dependent transport measured in living cells. A fluorescent reporter protein (Alexa 544-labeled IBB-β-galactosidase) that undergoes importin β-dependent import was injected into the cytoplasm of control (Normal 8469) and progeria (HGPS 1498) fibroblasts. For each injected cell, the initial rate was plotted versus the initial concentration. The slopes of the solid lines represent the relationship between the import rate and the reporter protein concentration. Dashed lines represent 95% confidence intervals. (B) Images of Normal 8469 and HGPS 1498 fibroblasts 3 s and 117 s after microinjection. Scale bar, 20 μm.