Intracellular transport and conformational maturation of intestinal brush border hydrolases.
Brush border hydrolases of the differentiated intestinal cell line Caco-2 are transported to the microvillar membrane at different rates. This asynchronism is due to at least two rate-limiting events, a pre- and an intra-Golgi step. The retardation of sucrase-isomaltase, a slowly migrating hydrolase, versus dipeptidylpeptidase IV, a rapidly transported enzyme, is neither due to differential trimming of N-linked carbohydrates nor due to oligomerization. In this study, the conformational maturation of biosynthetically labeled sucrase-isomaltase and dipeptidylpeptidase IV was probed by conformation-specific antibodies and proteases. These assays enabled us to correlate the conformational maturation of the two enzymes with their rates of transport. Furthermore, two naturally occurring mutants of sucrase-isomaltase with impaired intracellular transport displayed an immature conformation. It is proposed that differential kinetics of folding might be the underlying cause for both the pre- and the intra-Golgi steps of asynchronous intracellular transport. Furthermore, a proper tertiary structure might be a prerequisite for sucrase-isomaltase to leave the Golgi apparatus.
Matter
K
K
Department of Pharmacology, Biocenter of the University of Basel, Switzerland.
Hauri
H P
HP
D000230:Adenocarcinoma; D000911:Antibodies, Monoclonal; D002460:Cell Line; D003110:Colonic Neoplasms; D018819:Dipeptidyl Peptidase 4; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism; D006801:Humans; D006867:Hydrolases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008871:Microvilli / Q000201:enzymology*; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D013394:Sucrase-Isomaltase Complex / Q000096:biosynthesis / Q000378:metabolism
D000911:Antibodies, Monoclonal; D006867:Hydrolases; D013394:Sucrase-Isomaltase Complex; D010450:Endopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D018819:Dipeptidyl Peptidase 4