Live-cell imaging is performed using an epi-fluorescence inverted microscope equipped with a CCD camera (Retiga; QImaging). For epi-fluorescence inverted microscope, excitation is provided by a xenon arc lamp with the beam passing through a monochromator (Cairn Research) and emission was reflected through a long-pass filter to a cooled CCD camera and digitized to 12-bit resolution (Digital Pixel Ltd, UK).