COPI-positive clusters are observed near all ARFs. (A–D) Fixed ARF1^EN-, ARF3^EN-, ARF4^EN-, and ARF5^EN-2xALFA KI HeLa cells were immunostained with anti-ALFA (magenta) and anti-β′COP (CM1, green) and secondary antibodies labeled with either ATTO647N or AlexaFluor594 to be able to perform dual-color STED experiments. Line profiles in each panel correspond to the dotted boxes in the cropped images. All images were deconvolved, background subtracted, and smoothed with a Gaussian filter as described in Materials and methods. Scale bars are 5 and 1 µm in the cropped images.