Condensation-sorting events in the rough endoplasmic reticulum of exocrine pancreatic cells.

摘要: In guinea pig exocrine pancreatic cells intracisternal granules (ICGs) occur at a low frequency within the lumen of RER. By starving and refeeding pigs or injecting them in CoCl2 solution, number these is greatly increased. We show here that ICGs contain complete set secreted digestive enzymes proenzymes. Two other soluble proteins RER, GRP 78/BiP protein disulphide isomerase (PDI), are specifically excluded from ICGs. The formation ICGs, which occurs without acidification RER cisternae, therefore sorting event involving cocondensation secretory proenzymes, for brevity we refer to collectively as zymogens. With exception approximately 50% RNase, zymogens covalently cross-linked by intermolecular bonds. synthesis all three resident ER cisternal proteins--PDI, 78/BiP, 94--with carboxy-terminal sequence KDEL, induced response accumulation massive amounts misfolded After injection rats with large doses parachlorophenylalanine-methylester, crystals form appear be lattice amylase incorporated between layers. Both PDI crystals. inclusion is, therefore, also event. These data establish can cocondense into either amorphous aggregates exclude proteins. This demonstrates mechanism capable pathway.