Fluorescence Dynamics in the Endoplasmic Reticulum of a Live Cell: Time-Resolved Confocal Microscopy

摘要

Fluorescence dynamics in the endoplasmic reticulum (ER) of a live non-cancer lung cell (WI38) and a lung cancer cell (A549) are studied by using time-resolved confocal microscopy. To selectively study the organelle, ER, we have used an ER-Tracker dye. From the emission maximum (lambda(em)(max)) of the ER-Tracker dye, polarity (i.e. dielectric constant, epsilon) in the ER region of the cells (approximate to 500 nm in WI38 and approximate to 510 nm in A549) is estimated to be similar to that of chloroform (lambda(em)(max) = 506 nm, epsilon approximate to 5). The red shift by 10 nm in lambda(em)(max) in the cancer cell (A549) suggests a slightly higher polarity compared to the non-cancer cell (WI38). The fluorescence intensity of the ER-Tracker dye exhibits prolonged intermittent oscillations on a timescale of 26 seconds for the cancer cell (A549). For the non-cancer cell (WI38), such fluorescence oscillations are much less prominent. The marked fluorescence intensity oscillations in the cancer cell are attributed to enhanced calcium oscillations. The average solvent relaxation time () of the ER region in the lung cancer cell (A549, 250 +/- 50 ps) is about four times faster than that in the non-cancer cell (WI38, 1000 +/- 50 ps).