- Rab3D is not required for exocrine exocytosis but for maintenance of normally sized secretory granules. Riedel, D., Antonin, W., Fernandez-Chacon, R., Alvarez de Toledo, G., Jo, T., Geppert, M., Valentijn, J.A., Valentijn, K., Jamieson, J.D., Südhof, T.C., Jahn, R. Mol. Cell. Biol. (2002)