title: Stable RNA interference of synaptotagmin I in PC12 cells results in differential regulation of transmitter release.
abstract: In sympathetic neurons, it is well-established that the neurotransmitters, norepinephrine (NE), neuropeptide Y (NPY), and ATP are differentially coreleased from the same neurons. In this study, we determined whether synaptotagmin (syt) I, the primary Ca(2+) sensor for regulated release, could function as the protein that differentially regulates release of these neurotransmitters. Plasmid-based RNA interference was used to specifically and stably silence expression of syt I in a model secretory cell line. Whereas stimulated release of NPY and purines was abolished, stimulated catecholamine (CA) release was only reduced by approximately 50%. Although expression levels of tyrosine hydroxylase, the rate-limiting enzyme in the dopamine synthesis pathway, was unaffected, expression of the vesicular monoamine transporter 1 was reduced by 50%. To evaluate whether NPY and CAs are found within the same vesicles and whether syt I is found localized to each of these NPY- and CA-containing vesicles, we used immunocytochemistry to determine that syt I colocalized with large dense core vesicles, with NPY, and with CAs. Furthermore, both CAs and NPY colocalized with one another and with large dense core vesicles. Electron micrographs show that large dense core vesicles are synthesized and available for release in cells that lack syt I. These results are consistent with syt I regulating differential release of transmitters.
authors.affiliation: Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St Louis, MO 63104, USA.
authors.forename: William H
authors.initials: WH
authors.lastname: Roden
authors.forename: Jason B
authors.initials: JB
authors.lastname: Papke
authors.forename: Johnnie M
authors.initials: JM
authors.lastname: Moore
authors.forename: Anne L
authors.initials: AL
authors.lastname: Cahill
authors.forename: Heather
authors.initials: H
authors.lastname: Macarthur
authors.forename: Amy B
authors.initials: AB
authors.lastname: Harkins
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D004298:Dopamine / Q000378:metabolism*; D015870:Gene Expression; D007150:Immunohistochemistry; D046529:Microscopy, Electron, Transmission; D009478:Neuropeptide Y / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D016716:PC12 Cells; D034622:RNA Interference; D051381:Rats; D013572:Synaptic Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D050863:Synaptotagmin I / Q000235:genetics / Q000378:metabolism*; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D009478:Neuropeptide Y; D050863:Synaptotagmin I; C494312:Syt1 protein, rat; D000255:Adenosine Triphosphate; D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine; D009638:Norepinephrine