Evidence for functional localization of the proenkephalin-processing enzyme, prohormone thiol protease, to secretory vesicles of chromaffin cells

Vivian Y H Hook, Stephen C Noctor, Catherine A. Sei, Thomas Toneff, Sukkid Yasothornsrikul, Yuan Hsu Kang

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

The biosynthesis of enkephalin opioid neuropeptides as well as numerous peptide hormones and neurotransmitters requires proteolyric processing of the respective prohormone precursors. We previously identified a novel cysteine protease known as prohormone thiol protease (PTP) as the major proenkephalin-processing enzyme in chromaffin granules (secretory vesicles) of bovine adrenal medulla. In this study, colocalization of PTP with (Met)enkephalin in regulated secretory vesicles was assessed by immunochemical approaches. Western blots demonstrated the presence of PTP in chromaffin granules, with equivalent levels of PTP protein in the soluble and membrane components of the vesicle. The presence of PTP in pituitary was also demonstrated by immunoblots. Immunoelectron microscopy demonstrated immunogold-labeled PTP and (Met)enkephalin within isolated chromaffin granules. In primary cultures of chromaffin cells, the discrete pattern of PTP and (Met)enkephalin immunofluorescence staining in neuritic extensions and cytoplasmic (perinuclear) regions of chromaffin cells is consistent with localization to secretory vesicles. Moreover, cosecretion of PTP and (Met)enkephalin from chromaffin cells occurred upon KCl depolarization in a calcium-dependent manner, indicating the localization of PTP and (Met)enkephalin within regulated secretory vesicles. Calcium-dependent secretion is a well known property of regulated secretory vesicle exocytosis. Overall, these results are consistent with the localization of PTP to functional, regulated secretory vesicles that contain (Met)enkephalin.

Original languageEnglish (US)
Pages (from-to)3744-3754
Number of pages11
JournalEndocrinology
Volume140
Issue number8
StatePublished - 1999
Externally publishedYes

Fingerprint

Chromaffin Cells
Secretory Vesicles
Methionine Enkephalin
Enzymes
Chromaffin Granules
prohormone thiol protease
proenkephalin
Calcium
Adrenal Medulla
Cysteine Proteases
Immunoelectron Microscopy
Peptide Hormones
Enkephalins
Exocytosis
Neuropeptides
Opioid Analgesics
Fluorescent Antibody Technique
Neurotransmitter Agents
Western Blotting
Staining and Labeling

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Evidence for functional localization of the proenkephalin-processing enzyme, prohormone thiol protease, to secretory vesicles of chromaffin cells. / Hook, Vivian Y H; Noctor, Stephen C; Sei, Catherine A.; Toneff, Thomas; Yasothornsrikul, Sukkid; Kang, Yuan Hsu.

In: Endocrinology, Vol. 140, No. 8, 1999, p. 3744-3754.

Research output: Contribution to journalArticle

Hook, Vivian Y H ; Noctor, Stephen C ; Sei, Catherine A. ; Toneff, Thomas ; Yasothornsrikul, Sukkid ; Kang, Yuan Hsu. / Evidence for functional localization of the proenkephalin-processing enzyme, prohormone thiol protease, to secretory vesicles of chromaffin cells. In: Endocrinology. 1999 ; Vol. 140, No. 8. pp. 3744-3754.
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