A clathrin-coated, Golgi-related compartment of the insulin secreting cell accumulates proinsulin in the presence of monensin.
When the intracellular transit of 3H-labeled (pro)-insulin polypeptides is perturbed by monensin in the pancreatic B-cell, proinsulin conversion is impaired and the radioactive peptides accumulate in a clathrin-coated membrane compartment related to the Golgi apparatus. Clathrin was demonstrated by immunocytochemistry using the postembedding protein A-gold technique. The coated compartment, which is dilated by monensin, comprises Golgi cisternae with condensing secretory material and newly formed secretory granules; under monensin block, the noncoated (storage) secretory granules do not become significantly labeled. These data suggest that an unperturbed passage through a Golgi-related, clathrin-coated membrane compartment which subsequently matures into noncoated secretory granules is needed for the normal processing of (pro)insulin polypeptides.
D000818:Animals; D001345:Autoradiography; D002966:Clathrin / Q000032:analysis*; D005663:Furans / Q000494:pharmacology*; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D008985:Monensin / Q000494:pharmacology*; D011384:Proinsulin / Q000378:metabolism*; D051381:Rats; D014316:Tritium
D002966:Clathrin; D005663:Furans; D007328:Insulin; D014316:Tritium; D011384:Proinsulin; D008985:Monensin