Intracellular transport of the major glycoprotein of zymogen granule membranes in the rat pancreas

Havinga, Johan R.; Strous, Ger J.; Poort, C.

doi:10.1111/j.1432-1033.1984.tb08446.x

Cited by 22 publications

(14 citation statements)

References 21 publications

(12 reference statements)

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“…Pulse-chase studies with dissociated rat pancreatic cells by Havinga et al (15,16) have indicated that GP-2 is a 73-kDa species in the rough endoplasmic reticulum (0-40 min of chase) and a 78-to 80-kDa species in the Golgi compartment and ZGs (60 min of chase), findings consistent with the N-linked-glycoprotein nature of GP-2 and the addition of terminal sugars within the Golgi apparatus. With longer chase periods (4-6 hr), GP-2 assumed a slightly smaller size (75 kDa), and this form was observed in a plasma membrane fraction and in the medium bathing acinar cells.…”

supporting

confidence: 54%

A single gene encodes membrane-bound and free forms of GP-2, the major glycoprotein in pancreatic secretory (zymogen) granule membranes.

Fukuoka

Freedman

Scheele

1991

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

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A single gene encodes membrane-bound and free forms of GP-2, the major glycoprotein in pancreatic secretory (zymogen) granule membranes (phosphatidylinositol-glycan-linked Communicated by George E. Palade, January 3, 1991 (received for review July 27, 1990) ABSTRACT GP-2, a 75-kDa glycoprotein, was isolated from dog pancreatic zymogen granule membranes (ZGMs). In a carbohydrate-shift strategy, N-terminal and internal peptide sequences were obtained on glycosylated and deglycosylated forms of GP-2, respectively, by gas-phase sequencing. Sets of mixed oligonucleotides and the polymerase chain reaction were used to obtain a double-stranded cDNA probe, which was used to isolate overlapping cDNA clones from a dog pancreatic cDNA library. The sequence of these clones revealed an open reading frame that encodes a protein of 509 amino acids, eight N-linked oligosaccharide attachment sites, and an N-terminal signal sequence absent from the mature form of GP-2 associated with ZGMs. The C terminus shows a 20-residue hydrophobic transmembrane domain preceded by a decapeptide containing potential phosphatidylinositol-glycan attachment sites. GP-2 completely released from ZGMs by exogenous phospholipase C showed similar immunochemical properties and electrophoretic mobilities compared to the form associated with ZGMs. A similar form of GP-2 was released from zymogen granules permeabilized with saponin and incubated in the absence of added phospholipase C. Kinetic analysis of GP-2 release at 0°C and 3rC suggested the presence of a granule enzyme responsible for endogenous release of GP-2 to granule contents and into the apical medium. The data indicate that GP-2 is a phosphatidylinositol-glycan-linked membrane protein released from the membrane of mature zymogen granules by an enzymatic mechanism. The cDNA structure presented here thus encodes both membrane-bound and free forms of GP-2.

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supporting

confidence: 54%

A single gene encodes membrane-bound and free forms of GP-2, the major glycoprotein in pancreatic secretory (zymogen) granule membranes.

Fukuoka

Freedman

Scheele

1991

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

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“…GP-2 has been localized in pancreatic acinar cells in transGolgi, condensing vacuoles, ZGs (spherical particles, =1000 nm), and apical plasma membranes (7)(8)(9)(10)21). Using similar methods, THP has been localized in kidney TALH cells in trans-Golgi, apical vesicles (oblong structures, 30-150 nm), and apical plasma membranes (42,43).…”

Section: Methodsmentioning

confidence: 99%

GP-2/THP gene family encodes self-binding glycosylphosphatidylinositol-anchored proteins in apical secretory compartments of pancreas and kidney.

Fukuoka

Freedman

et al. 1992

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

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A family of homologous genes is shown to encode GP-2, the major glycosylphosphatidylinositol (GPI)-linked glycoprotein of pancreatic zymogen granule membranes, and Tamm-Horsfall protein (THP), a GPI-linked glycoprotein associated with apical vesicles in kidney thick ascending limb of Henle (TALH) cells. The C-terminal regions of GP-2 (Asp5s-Phe-5-) and THP (Asp'75-IHis'4") from rat show 53% identity, 86% similarity, and 26 conserved cysteine residues including one epidermal growth factor motif. The unique N-terminal domain of rat THP (unique-THP, shows four conserved epidermal growth factor motifs, three in tandem and one in reverse orientation. GP-2 homologues are observed in a wide variety of epithelial cells, several of which contain highly regulated secretory processes. GP-2 released from zymogen granule membranes with phosphatidylinositol phospholipase C reacts with anti-cross-reactive determinant antibody (anti-CRD), confirming the GPI nature of the pancreatic homologue. In contrast, GP-2 and THP, released endogenously from pancreas and kidney, respectively, do not react with anti-cross-reactive determinant antibody, suggesting alternative enzymatic mechanisms for their physiological release. Globular domains of GP-2 and THP, but not albumin,show pH-and ion-dependent self-association in vitro. The GP-2/THP family appears to represent a newly discovered class of GPI-anchored proteins, which may utilize pH-and ion-dependent self-association mechanisms for establishing membrane (micro)domains targeted to intracellular secretory compartments.A growing number of hydrophilic proteins have recently been shown to be linked to membranes via a glycosylphosphatidylinositol (GPI) anchor (1, 2). Demonstrating diverse activities in mammalian cells, including cell adhesion, T-cell activation, and hydrolytic activities, GPI-anchored proteins are normally found attached to the outer surface of the plasma membrane. In polarized Madin-Darby canine kidney cells in culture, endogenous GPI-anchored and phosphatidylinositol phospholipase C (PI-PLC)-releasable proteins appeared to be restricted to the apical plasma membrane (3). In some cell lines, the surface expression and release of GPIlinked proteins is modulated by serum starvation or insulin (4). However, it is not clear why these proteins are tethered to membranes by GPI-lipid anchors or what role might be served by their potential release from the membrane (1). We have recently cloned and characterized rat (5) and dog GP-2 (6), the major glycoprotein of zymogen granule membranes (ZGMs) in the exocrine pancreas, and demonstrated that the membrane form of GP-2, targeted to apical plasma membranes via regulated exocytosis, is attached to the ectoleaflet of granule membranes by a GPI anchor. After granule assembly, we have also shown that GP-2 is released to the granule content fraction by a pH-dependent anchorcleavage activity associated with granule membranes (6). However, the function of GP-2 in ZGMs has remained obscure and its release from granule membranes into...

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“…Since these early experiments, Havinga et al [35] have also demonstrated that a fraction of glyco protein-2 (GP2) molecules, a major zymogen granule membrane protein also found in Golgi apparatus, is transported to the plasma membrane by a route distinct from the one followed by the mass of the newly synthe sized zymogens. It was later found that un der resting conditions newly synthesized se cretory proteins come out of the cell in two waves [36,37].…”

Section: Alternative Route For the Release Of Secretory Proteins Undementioning

confidence: 99%

Pancreatic Juice Composition: New Views about the Cellular Mechanisms That Control the Concentration of Digestive and Nondigestive Proteins

Beaudoin¹,

St-Jean²,

Grondin³

1989

Dig Dis

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Intracellular transport of the major glycoprotein of zymogen granule membranes in the rat pancreas

Cited by 22 publications

References 21 publications

A single gene encodes membrane-bound and free forms of GP-2, the major glycoprotein in pancreatic secretory (zymogen) granule membranes.

A single gene encodes membrane-bound and free forms of GP-2, the major glycoprotein in pancreatic secretory (zymogen) granule membranes.

GP-2/THP gene family encodes self-binding glycosylphosphatidylinositol-anchored proteins in apical secretory compartments of pancreas and kidney.

Pancreatic Juice Composition: New Views about the Cellular Mechanisms That Control the Concentration of Digestive and Nondigestive Proteins

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