INS and diabetes mellitus: We thank Tom Jetton, Dhananjay Gupta and Mina Peshavaria from the University of Vermont Division of Endocrinology, Diabetes and Metabolism for supplying the INS-1 cell line and helpful discussion during the course of these experiments, Douglas Taatjes and Nicole Bouffard from the University of Vermont microscopy and imaging center for their assistance in acquiring the super resolution STORM images, David Piston (Vanderbilt University) for the kind gift of the proinsulin-eGFP plasmid and Jason Stumpff (University of Vermont) for use of his Nikon Ti-E inverted microscopy.