Synaptic-like microvesicles, synaptic vesicle counterparts in endocrine cells, are involved in a novel regulatory mechanism for the synthesis and secretion of hormones

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.

Published with permission from the copyright holder. This is the institute's copy, as published in The Journal of Experimental Biology, January 2000, Volume 203, Issue 1, Pages 117-125.
Publisher URL:http://jeb.biologists.org/cgi/reprint/203/1/117
Copyright © 2000 The Company of Biologists Limited. All rights reserved.