Molecular and cellular regulation of prohormone processing

Creemers, John W.M.; Jackson, Robert S.; Hutton, John C.

doi:10.1006/scdb.1997.0195

Cited by 63 publications

(45 citation statements)

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“…After synthesis in the ER, pro-insulin is transported into the Golgi apparatus where immature, pale secretory ''progranules'' are formed (6). These granules contain pro-insulin-zinc hexamers which are further processed into mature insulin and C-peptide by the prohormone convertases PC1/3 and PC2 (7). After maturation, the zincinsulin hexamers form water-insoluble crystals (3).…”

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confidence: 99%

Insulin crystallization depends on zinc transporter ZnT8 expression, but is not required for normal glucose homeostasis in mice

Lemaire

Ravier

Schraenen

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

300

346

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Zinc co-crystallizes with insulin in dense core secretory granules, but its role in insulin biosynthesis, storage and secretion is unknown. In this study we assessed the role of the zinc transporter ZnT8 using ZnT8-knockout (ZnT8 ؊/؊ ) mice. Absence of ZnT8 expression caused loss of zinc release upon stimulation of exocytosis, but normal rates of insulin biosynthesis, normal insulin content and preserved glucose-induced insulin release. Ultrastructurally, mature dense core insulin granules were rare in ZnT8 ؊/؊ beta cells and were replaced by immature, pale insulin ''progranules,'' which were larger than in ZnT8 ؉/؉ islets. When mice were fed a control diet, glucose tolerance and insulin sensitivity were normal. However, after high-fat diet feeding, the ZnT8 ؊/؊ mice became glucose intolerant or diabetic, and islets became less responsive to glucose. Our data show that the ZnT8 transporter is essential for the formation of insulin crystals in beta cells, contributing to the packaging efficiency of stored insulin. Interaction between the ZnT8 ؊/؊ genotype and diet to induce diabetes is a model for further studies of the mechanism of disease of human ZNT8 gene mutations.dense core granule ͉ diabetes ͉ zinc

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confidence: 99%

Insulin crystallization depends on zinc transporter ZnT8 expression, but is not required for normal glucose homeostasis in mice

Lemaire

Ravier

Schraenen

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

300

346

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“…The propeptides of mammalian PCs exhibit 30-67% sequence identity to each other [3]. These propeptide segments are required for the correct folding of their cognate catalytic domains, thus acting as intramolecular chaperones [4] and also function as potent autoinhibitors [5]. The catalytic domains contain the Ser-His-Asp catalytic triad, which effects substrate cleavage [6].…”

Section: Introductionmentioning

confidence: 99%

Processing and trafficking of a prohormone convertase 2 active site mutant

Lee

Kacprzak

Day

et al. 2007

Biochemical and Biophysical Research Communications

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Processing of most PC zymogens is required for successful folding and/or passage through the secretory pathway; active site mutants are retained in the ER and degraded. We here report that the active site serine mutant of PC2 (PC2-S383A) was efficiently secreted as the intact zymogen in CHO-K1 cells, suggesting that its propeptide can productively insert into the mutated binding pocket without causing misfolding. In AtT-20 cells, PC2-S383A was cleaved at the secondary cleavage site within the propeptide; this cleavage event was pH-dependent and was inhibited by a proprotein convertase inhibitor. In vitro digestion of PC2-S383A with various convertases indicates that this site is accessible to in trans cleavage. Abundant immunoreactive S383A PC2 was found in secretory granules, supporting the idea that this protein is efficiently trafficked through the secretory pathway.

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“…By analogy with bacterial subtilisin, the pro-region of furin is believed to serve numerous functions, such as promoting folding, stability, sorting and transiently inhibiting processing activity [17]. A recent study [18] investigated the inhibitory potency of PC Abbreviations used: ER, endoplasmic reticulum; PC, proprotein convertase; vWf, von Willebrand factor.…”

Section: Introductionmentioning

confidence: 99%

Identification of furin pro-region determinants involved in folding and activation

Bissonnette

Charest

Longpré

et al. 2004

Biochemical Journal

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The pro-region of the subtilisin-like convertase furin acts early in the biosynthetic pathway as an intramolecular chaperone to enable proper folding of the zymogen, and later on as an inhibitor to constrain the activity of the enzyme until it reaches the transGolgi network. To identify residues that are important for proregion function, we initially identified amino acids that are conserved among the pro-regions of various mammalian convertases. Site-directed mutagenesis of 17 selected amino acids within the 89-residue pro-region and biosynthetic labelling revealed that I60A-furin and H66A-furin were rapidly degraded in a proteasome-dependent manner, while W34A-furin and F67A-furin did not show any autocatalytic activation. Intriguingly, the latter mutants proteolytically cleaved pro-von Willebrand factor precursor to the mature polypeptide, suggesting that the mutations permitted proper folding, but did not allow the pro-region to exercise its role in inhibiting the enzyme. Homology modelling of furin's pro-region revealed that residues Ile-60 and His-66 might be crucial in forming the binding interface with the catalytic domain, while residues Trp-34 and Phe-67 might be involved in maintaining a hydrophobic core within the pro-region itself. These results provide structural insights into the dual role of furin's proregion.

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Molecular and cellular regulation of prohormone processing

Cited by 63 publications

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Insulin crystallization depends on zinc transporter ZnT8 expression, but is not required for normal glucose homeostasis in mice

Insulin crystallization depends on zinc transporter ZnT8 expression, but is not required for normal glucose homeostasis in mice

Processing and trafficking of a prohormone convertase 2 active site mutant

Identification of furin pro-region determinants involved in folding and activation

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