title: Doc2 is not associated with known regulated exocytotic or endosomal compartments in adrenal chromaffin cells.
abstract: Doc2 is a C2-domain-containing protein that is highly expressed in the nervous system and has a constitutively expressed isoform. It has been implicated as a potential Ca2+ sensor in regulated exocytosis, and has been suggested to be associated with synaptic vesicles. To examine whether Doc2 is associated with synaptic-like microvesicles (SLMVs) or dense-core granules in neuroendocrine cells, we examined the distribution of Doc2 in subcellular fractionation of chromaffin cells of the adrenal medulla and in PC12 cells. Doc2 did not co-distribute with SLMVs from either cell type, but did appear to co-distribute with dense-core granules from PC12 cells. In contrast, it was not associated with the dense-core granules during subcellular fractionation of the adrenal medulla, and nor did it appear to be associated with endosomes, cis-Golgi or the trans-Golgi network. In contrast, Doc2 co-distributed under all conditions with a mitochondrial marker. We conclude that Doc2 is not a general component of regulated secretory vesicles, but may instead be associated with mitochondria.
authors.affiliation: The Physiological Laboratory, University of Liverpool, Crown Street, Liverpool L69 3BX, UK.
authors.forename: N
authors.initials: N
authors.lastname: Charvin
authors.forename: G
authors.initials: G
authors.lastname: Williams
authors.forename: R D
authors.initials: RD
authors.lastname: Burgoyne
mesh_terms: D000313:Adrenal Medulla / Q000737:chemistry*; D000818:Animals; D002135:Calcium-Binding Proteins / Q000302:isolation & purification*; D002417:Cattle; D002451:Cell Compartmentation; D019439:Chromaffin Cells / Q000737:chemistry*; D003594:Cytoplasmic Granules; D011992:Endosomes; D005089:Exocytosis; D009419:Nerve Tissue Proteins / Q000302:isolation & purification*; D009490:Neurosecretory Systems / Q000737:chemistry* / Q000166:cytology; D016716:PC12 Cells; D051381:Rats; D013347:Subcellular Fractions / Q000737:chemistry; D013572:Synaptic Vesicles / Q000737:chemistry
chemical_list: D002135:Calcium-Binding Proteins; C490419:Doc2a protein, rat; D009419:Nerve Tissue Proteins