Mapping of endolysosomes in neurons has revealed that Lamp1 associates with a number of compartments in the endolysosomal pathway, some of which do not contain lysosomal degradative enzymes,46 and that differentiation of endolysosomal compartments is possible only with using more than one immunofluorescent marker.47 Therefore, a more complete mapping of glucagon trafficking through the endolysosomal system in diabetes will require the use of more than one lysosomal marker. The gene discussed is GCG; the disease is diabetes mellitus.