Secretory protein traffic: Chromogranin a contains a dominant targeting signal for the regulated pathway

Robert J. Parmer, Xiao Ping Xi, Hong Jiang Wu, Lee J. Helmen, Larry N. Petz

Research output: Contribution to journalArticle

Abstract

Secretory proteins are targeted into either constitutive (secreted upon synthesis) or regulated (stored in vesicles and released in response to a secretagogue) pathways. To investigate mechanisms of protein targeting into catecholamine storage vesicles (CSV), we stably expressed human chromogranin A (CgA), the major soluble protein in human CSV, in the rat pheochromocytoma PC-12 cell line. Chromaffin cell secretagogues (0.1 mM nicotinic cholinergic agonist, 55 mM K+, or 2 mM Ba++) caused cosecretion of human CgA and catecholamines from human CgA-expressing cells. Sucrose gradients colocalized human CgA and catecholamines to subcellular particles of the same buoyant density. Chimeric proteins, in which human CgA (either full-length [457 amino acids] or truncated [amino-terminal 226 amino acids]) was fused in-frame to the ordinarily nonsecreted protein chloramphenicol acetyltransferase (CAT), were expressed transiently in PC-12 cells. Both constructs directed CAT activity into regulated secretory vesicles, as judged by secretagogue-stimulated release. These data demonstrate that human CgA expressed in PC-12 cells is targeted to regulated secretory vesicles. In addition, human CgA can divert an ordinarily non-secreted protein into the regulated secretory pathway, consistent with the operation of a dominant targeting signal for the regulated pathway within the peptide sequence of CgA.

Original languageEnglish (US)
Pages (from-to)1042-1054
Number of pages13
JournalJournal of Clinical Investigation
Volume92
Issue number2
DOIs
StatePublished - Aug 1993

Keywords

  • Catecholamine
  • Chromaffin cells
  • Chromogranin A
  • PC-12
  • Pheochromocytoma
  • Regulated secretion

ASJC Scopus subject areas

  • Medicine(all)

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