Avtor/Urednik		Goncalves, Paula P; Stenovec, Matjaž; Chowdhury-Haque, Helena; Grilc, Sonja; Kreft, Marko; Zorec, Robert
Naslov		Prolactin secretion sites contain syntaxin-1 and differ from ganglioside monosialic acid rafts in rat lactotrophs
Tip		članek
Vir		Endocrinology
Vol. in št.		Letnik 149, št. 10
Leto izdaje		2008
Obseg		str. 4948-57
Jezik		eng
Abstrakt		In neuroendocrine cells, discharge of hormones follows the fusion of exocytotic vesicles with the plasma membrane at confined sites; however, the molecular nature of these distinct sites remains poorly understood. We studied intact pituitary lactotrophs and plasma membrane lawns by confocal microscopy in conjunction with antibodies against rat prolactin (rPRL), soluble N-ethylmaleimide-sensitive factor-attachment protein receptor (SNARE) proteins (syntaxin-1 and synaptobrevin-2,) and fluorescent cholera toxin subunit B (CT-B), a marker of ganglioside monosialic acid (GM1) lipid rafts, to examine 1) whether rPRL vesicles discharge cargo at GM1 rafts, 2) whether discharging rPRL vesicles interact with SNAREs, and 3) to examine the overlap of GM1 rafts, rPRL, and syntaxin-1 sites in plasma membrane lawns. In intact cells, immunofluorescently labeled rPRL poorly colocalized (<6%) with CT-B. In conditions favoring endocytotic trafficking, vesicle SNARE synaptobrevin-2 modestly colocalized (35%) with CT-B, whereas it highly colocalized (58%) with retrieved rPRL. Although partial mixing between rPRL and CT-B intracellular trafficking pathways is likely, our results indicated that rPRL discharge involves interactions with plasma membrane SNAREs, but not with GM1 rafts. In support of this, the plasma membrane SNARE syntaxin-1 poorly colocalized with CT-B (<5%), whereas it highly colocalized (75%) with rPRL in inside-out plasma membrane lawns. Spontaneous and stimulated rPRL discharge in live lactotrophs is thus associated with plasma membrane sites enriched with SNARE proteins, however, spatially confined to plasma membrane areas other than GM1 rafts.
Deskriptorji		PITUITARY GLAND, ANTERIOR EXOCYTOSIS PROLACTIN SYNAPSINS ETHYLMALEIMIDE MICROSCOPY, CONFOCAL CHOLERA TOXIN GANGLIOSIDES CELLS, CULTURED IMMUNOHISTOCHEMISTRY RATS, WISTAR