title: Synaptic-like microvesicles, synaptic vesicle counterparts in endocrine cells, are involved in a novel regulatory mechanism for the synthesis and secretion of hormones.
abstract: Microvesicles in endocrine cells are the morphological and functional equivalent of neuronal synaptic vesicles. Microvesicles accumulate various neurotransmitters through a transmitter-specific vesicular transporter energized by vacuolar H(+)-ATPase. We found that mammalian pinealocytes, endocrine cells that synthesize and secrete melatonin, accumulate l-glutamate in their microvesicles and secrete it through exocytosis. Pinealocytes use l-glutamate as either a paracrine- or autocrine-like chemical transmitter in a receptor-mediated manner, resulting in inhibition of melatonin synthesis. In this article, we briefly describe the overall features of the microvesicle-mediated signal-transduction mechanism in the pineal gland and discuss the important role of acidic organelles in a novel regulatory mechanism for hormonal synthesis and secretion.
authors.affiliation: Department of Biochemistry, Faculty of Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan. moriyama@pheasant.pharm.okayama-u.ac.jp.
authors.forename: Y
authors.initials: Y
authors.lastname: Moriyama
authors.forename: M
authors.initials: M
authors.lastname: Hayashi
authors.forename: H
authors.initials: H
authors.lastname: Yamada
authors.forename: S
authors.initials: S
authors.lastname: Yatsushiro
authors.forename: S
authors.initials: S
authors.lastname: Ishio
authors.forename: A
authors.initials: A
authors.lastname: Yamamoto
mesh_terms: D018698:Glutamic Acid / Q000378:metabolism; D008550:Melatonin / Q000096:biosynthesis* / Q000378:metabolism; D015388:Organelles / Q000201:enzymology / Q000502:physiology*; D010870:Pineal Gland / Q000378:metabolism / Q000648:ultrastructure*; D006180:Proton-Translocating ATPases / Q000378:metabolism; D015398:Signal Transduction; D013572:Synaptic Vesicles; D025262:Vacuolar Proton-Translocating ATPases
chemical_list: D018698:Glutamic Acid; D025262:Vacuolar Proton-Translocating ATPases; D006180:Proton-Translocating ATPases; D008550:Melatonin