Localization of metallocarboxypeptidase D in atT-20 cells: Potential role in prohormone processing

Oleg Varlamov, Francis J. Eng, Elena G. Novikova, Lloyd D. Fricker

Research output: Contribution to journalArticle

69 Citations (Scopus)

Abstract

Carboxypeptidase D (CPD) is a recently discovered metallocarboxypeptidase that is predominantly located in the trans-Golgi network (TGN), and also cycles between the cell surface and the TGN. In the present study, the intracellular distribution of CPD was examined in AtT-20 cells, a mouse anterior pituitary-derived corticotroph. CPD-containing compartments were isolated using antibodies to the CPD cytosolic tail. The immunopurified vesicles contained TGN proteins (TGN38, furin, syntaxin 6) but not lysosomal or plasma membrane proteins. The CPD-containing vesicles also contained neuropeptide-processing enzymes and adrenocorticotropic hormone, a product of proopiomelanocortin proteolysis. Electron microscopic analysis revealed that CPD is present within the TGN and immature secretory granules but is virtually absent from mature granules, suggesting that CPD is actively removed from the regulated pathway during the process of granule maturation. A second major finding of the present study is that a soluble truncated form of CPD is secreted mainly via the constitutive pathway in AtT-20 cells, indicating that the lumenal domain does not contain signals for the sorting of CPD to mature secretory granules. Taken together, these data are consistent with the proposal that CPD participates in the processing of proteins within the TGN and immature secretory vesicles.

Original languageEnglish (US)
Pages (from-to)14759-14767
Number of pages9
JournalJournal of Biological Chemistry
Volume274
Issue number21
DOIs
StatePublished - May 21 1999

Fingerprint

trans-Golgi Network
Processing
Secretory Vesicles
carboxypeptidase D
metallocarboxypeptidase D
Corticotrophs
Furin
Qa-SNARE Proteins
Proteolysis
Pro-Opiomelanocortin
Cell membranes
Neuropeptides
Sorting
Adrenocorticotropic Hormone
Tail
Blood Proteins
Cell Cycle
Membrane Proteins
Proteins
Cell Membrane

ASJC Scopus subject areas

  • Biochemistry

Cite this

Localization of metallocarboxypeptidase D in atT-20 cells : Potential role in prohormone processing. / Varlamov, Oleg; Eng, Francis J.; Novikova, Elena G.; Fricker, Lloyd D.

In: Journal of Biological Chemistry, Vol. 274, No. 21, 21.05.1999, p. 14759-14767.

Research output: Contribution to journalArticle

Varlamov, Oleg ; Eng, Francis J. ; Novikova, Elena G. ; Fricker, Lloyd D. / Localization of metallocarboxypeptidase D in atT-20 cells : Potential role in prohormone processing. In: Journal of Biological Chemistry. 1999 ; Vol. 274, No. 21. pp. 14759-14767.
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