Proteolytic conversion of proinsulin into insulin. Identification of a Ca2+-dependent acidic endopeptidase in isolated insulin-secretory granules

Davidson, Howard W.; Peshavaria, Mina; Hutton, John C.

doi:10.1042/bj2460279

Cited by 64 publications

(19 citation statements)

References 46 publications

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“…It is possible that similar proteases are involved in the processing of other mammalian proproteins. Very recently, Davidson et al [20] identified a similar enzyme in insulin-secretory granules. This Ca2÷-dependent protease, which correctly processes proinsulin, is quite distinct from any previously proposed proinsulin convertase, but is remarkably similar to the proalbumin convertase described here in terms of its subcellular location, inhibitory properties and pH optimum (pH 5.0-6.0).…”

Section: Resultsmentioning

confidence: 97%

Calcium‐dependent KEX2‐like protease found in hepatic secretory vesicles converts proalbumin to albumin

Brennan

Peach

1988

FEBS Letters

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The yeast KEX2 protease is the only enzyme that has a proven role in the activation of polypeptide hormones through cleavage at pairs of basic residues. The enzyme that fulfils this role in higher eukaryotes has yet to be unequivocally identified. In this investigation, a KEX2-1ike calcium-dependent protease has been identified in rat hepatic microsomes. The enzyme is membrane-bound, has a pH optimum of 5-6 and converts proalbumin to albumin. More importantly, like the KEX2 protease, it meets two other exacting criteria defined by specific mutations in humans. Namely, it does not process proalbumin Christchurch (-1 Arg---,Gln) which lacks one of the requisite basic residues and, whilst not itself a serine protease, it is inhibited by the reactive center variant, al-antitrypsin Pittsburgh (358 Met~Arg) but not by normal ~l-antitrypsin.

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Section: Resultsmentioning

confidence: 97%

Calcium‐dependent KEX2‐like protease found in hepatic secretory vesicles converts proalbumin to albumin

Brennan

Peach

1988

FEBS Letters

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“…Various enzymes, including serine proteases, have been localized to insulin-producing cells (14,15,(35)(36)(37)(38)(39), which basically may cleave CGA into smaller fragments. Moreover, single basic residues in proline-containing regions of proteins (as in the C terminus of CST within the CGA sequence) define a preferential or specific cleavage site in various precursors of regulatory peptides including pancreatic icosapeptide, gastrin-releasing peptide, or atrial natriuretic polypeptide (26).…”

Section: Resultsmentioning

confidence: 99%

Chromostatin, a chromogranin A-derived bioactive peptide, is present in human pancreatic insulin (beta) cells.

Cetin¹,

Aunis²,

Bader³

et al. 1993

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

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Chromogranin A (CGA) is a secretory protein present in the adrenal medulla and in a variety ofendocrine organs. This protein may serve as precursor for pancreastatin (PST) and for other biologically active peptides. Recently, chromostatin (CST), a CGA derivative, has been identified that possesses high biological activity. The cellular distribution of CST in various endocrine organs is completely unknown. Using immunohistochemistry on plastic sections, we investigated the occurrence and cellular distribution of CST, PST, and CGA in human endocrine pancreas of healthy and diseased states and in the adrenal medulla. In the normal and diabetic pancreas, CST immunoreactivity was localized exclusively in 13 cells, which were mostly unreactive for PST and CGA. Both latter peptides were confined mainly to glucagon (a) cells. Insulinoma cells displayed strong insulin, PST, and CGA immunoreactivities, but they were faintly immunoreactive for CST or unreactive. Adrenal chromaffm cells exhibited strong immunoreactivity for CGA but lacked CST and PST immunoreactivities. Based on the peculiar distributive pattern of CST, PST, and CGA, we suggest that CGA is differentially processed in chromaffin and islet tissues and in insulinoma cells. The unique cellular localization of CST in the endocrine pancreas ofnormal and pathological conditions may indicate that CST is involved in 13-cell function.Chromogranin A (CGA) is an acidic glycoprotein originally detected in the adrenal medulla but more recently found also in a variety of peptide hormone-producing cells (see refs. 1 and 2 for review). Despite its widespread distribution, the physiological function of CGA is still largely unknown.The primary amino acid sequence of CGA, elucidated by cDNA analysis, includes several pairs of basic residues, which by analogy with other peptide hormone precursors constitute potential sites of proteolytic cleavage (3-5). Thus, it was speculated that CGA may be a putative precursor of biologically active peptides (2, 6, 7). Pancreastatin (PST), a peptide fully contained in the porcine CGA sequence (3, 7), was isolated from the porcine pancreas (8). This peptide inhibits insulin secretion (8). Moreover, tryptic digestion of CGA yielded various peptides that were able to modulate catecholamine secretion (7). Recently, chromostatin (CST) has been identified as a CGA derivative, which is localized between amino acids 124 and 143 in the bovine CGA sequence (9). In contrast to PST, CST had potent inhibitory action on chromaffin cell secretion (9).Previous studies demonstrated that pancreatic islet cells and islet cell tumors contain various CGA-derived peptides (10)(11)(12)(13)(14)(15)(16)(17). In the human pancreas, CGA has been localized mainly to glucagon (a) cells (18). The cellular distribution of PST, however, is still a matter of controversy (see ref. 19 for review), which in part may be due to species specificities (20). Data on tissue distribution of CST are completely lacking.Using specific antisera against CST, PST, and CGA, we inves...

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“…There are important sequence differences at both the B-chain/ C-peptide and C-peptide/A-chain cleavage sites between the human and rodent proinsulins (Sizonenko & Halban 1991). The processing of human proinsulin occurs at sites marked by the sequence Lys-Thr-Arg-Arg and Leu-GlnLys-Arg, which are cleaved by the endoproteases PC1 and PC2 respectively (Davidson et al 1987). These enzymes work sequentially and thus little cleavage of the C-peptide/A-chain junction by PC2 occurs in the absence of prior cleavage at the B-chain/C-peptide junction by PC1 (Jackson et al 1997).…”

Section: Discussionmentioning

confidence: 99%

Proinsulin processing in the diabetic Goto-Kakizaki rat

Guest¹,

Abdel‐Halim²,

Gross³

et al. 2002

Journal of Endocrinology

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The biosynthesis and processing of proinsulin was investigated in the diabetic Goto-Kakizaki (GK) rat. Immunofluorescence microscopy comparing GK and Wistar control rat pancreata revealed marked changes in the distribution of -cells and pronounced -cell heterogeneity in the expression patterns of insulin, prohormone convertases PC1, PC2, carboxypeptidase E (CPE) and the PC-binding proteins 7B2 and ProSAAS. Western blot analyses of isolated islets revealed little difference in PC1 and CPE expression but PC2 immunoreactivity was markedly lower in the GK islets. The processing of the PC2-dependent substrate chromogranin A was reduced as evidenced by the appearance of intermediates. No differences were seen in the biosynthesis and post-translational modification of PC1, PC2 or CPE following incubation of islets in 16·7 mM glucose, but incubation in 3·3 mM glucose resulted in decreased PC2 biosynthesis in the GK islets. The rates of biosynthesis, processing and secretion of newly synthesized (pro)insulin were comparable. Circulating insulin immunoreactivity in both Wistar and GK rats was predominantly insulin 1 and 2 in the expected ratios with no (pro)insulin evident. Thus, the marked changes in islet morphology and PC2 expression did not impact the rate or extent of proinsulin processing either in vitro or in vivo in this experimental model.

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Proteolytic conversion of proinsulin into insulin. Identification of a Ca2+-dependent acidic endopeptidase in isolated insulin-secretory granules

Cited by 64 publications

References 46 publications

Calcium‐dependent KEX2‐like protease found in hepatic secretory vesicles converts proalbumin to albumin

Calcium‐dependent KEX2‐like protease found in hepatic secretory vesicles converts proalbumin to albumin

Chromostatin, a chromogranin A-derived bioactive peptide, is present in human pancreatic insulin (beta) cells.

Proinsulin processing in the diabetic Goto-Kakizaki rat

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