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PMID:18511498

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Citation

Arnaoutova, I, Cawley, NX, Patel, N, Kim, T, Rathod, T and Loh, YP (2008) Aquaporin 1 is important for maintaining secretory granule biogenesis in endocrine cells. Mol. Endocrinol. 22:1924-34

Abstract

Aquaporins (AQPs), a family of water channels expressed in epithelial cells, function to transport water in a bidirectional manner to facilitate transepithelial fluid absorption and secretion. Additionally, AQP1 and AQP5 are found in pancreatic zymogen granules and synaptic vesicles and are involved in vesicle swelling and exocytosis in exocrine cells and neurons. Here, we show AQP1 is in dense-core secretory granule (DCSG) membranes of endocrine tissue: pituitary and adrenal medulla. The need for AQP1 in endocrine cell function was examined by stable transfection of AQP1 antisense RNA into AtT20 cells, a pituitary cell line, to down-regulate AQP1 expression. These AQP1-deficient cells showed more than 60% depletion of DCSGs and significantly decreased DCSG protein levels, including proopiomelanocotin/pro-ATCH and prohormone convertase 1/3, but not non-DCSG proteins. Pulse-chase studies revealed that whereas DCSG protein synthesis was unaffected, approximately 50% of the newly synthesized proopiomelanocortin was degraded within 1 h. Low levels of ACTH were released upon stimulation, indicating that the small number of DCSGs that were made in the presence of the residual AQP1 were functionally competent for exocytosis. Analysis of anterior pituitaries from AQP1 knockout mice showed reduced prohormone convertase 1/3, carboxypeptidase E, and ACTH levels compared to wild-type mice demonstrating that our results observed in AtT20 cells can be extended to the animal model. Thus, AQP1 is important for maintaining DCSG biogenesis and normal levels of hormone secretion in pituitary endocrine cells.

Links

PubMed PMC2725772 Online version:10.1210/me.2007-0434

Keywords

Adrenocorticotropic Hormone/metabolism; Animals; Aquaporin 1/genetics; Aquaporin 1/metabolism; Cell Line; Clone Cells; Down-Regulation; Endocrine Glands/cytology; Endocrine Glands/metabolism; Endocrine Glands/ultrastructure; Mice; Mice, Knockout; Pituitary Gland, Anterior/metabolism; Pro-Opiomelanocortin/biosynthesis; Pro-Opiomelanocortin/genetics; Protein Biosynthesis; Protein Processing, Post-Translational; RNA, Messenger/genetics; RNA, Messenger/metabolism; Secretory Vesicles/metabolism; Secretory Vesicles/ultrastructure; Transfection; Up-Regulation

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

BOVIN:AQP1

located_in

GO:0032127: dense core granule membrane

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete

MOUSE:AQP1

located_in

GO:0016020: membrane

ECO:0000314: direct assay evidence used in manual assertion

C

  • part_of:(EMAPA:17515)|part_of:(EMAPA:18426)

Seeded From UniProt

complete

MOUSE:AQP1

acts_upstream_of_or_within

GO:0051458: corticotropin secretion

ECO:0000315: mutant phenotype evidence used in manual assertion

MGI:MGI:1857807

P

  • occurs_in:(EMAPA:17515)

Seeded From UniProt

complete

MOUSE:AQP1

acts_upstream_of_or_within

GO:0051458: corticotropin secretion

ECO:0000315: mutant phenotype evidence used in manual assertion

MGI:MGI:1857807

P

occurs_in:(EMAPA:17515)

Seeded From UniProt

complete

MOUSE:AQP1

acts_upstream_of_or_within

GO:0033363: secretory granule organization

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

MOUSE:AQP1

acts_upstream_of_or_within

GO:0032940: secretion by cell

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

MOUSE:AQP1

part_of

GO:0016020: membrane

ECO:0000314: direct assay evidence used in manual assertion

C

part_of:(EMAPA:17515)|part_of:(EMAPA:18426)

Seeded From UniProt

complete


See also

References

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