title: Heterotypic tubular connections at the endoplasmic reticulum-Golgi complex interface.
abstract: Electron microscopy and cryoimmunocytochemistry were used to characterize tubular connections in the secretory pathway using rat spermatids as model. Our results support the existence of a complex tubular network enriched in the Golgi matrix protein GM130 that transiently joins the cis-Golgi side and the endoplasmic reticulum. These tubules occasionally contain the endoplasmic reticulum resident protein PDI but not COPII complexes or KDEL receptor. At the lateral edges of the stacks tubules were seen to connect cisternae belonging to the same or adjacent stacks. These connections were observed in all cisternae but preferentially on the cis side. Giantin, Gos28 and Rab6 were detected in the tubules; importantly, we reported the presence of cis-trans heterotypic connections between cisternae. On the trans-Golgi side, we occasionally observed tubules highly immunoreactive for Rab6 connecting the stack with the forming acrosome. Together, our results support the existence of transient continuities throughout the secretory pathways.
authors.affiliation: Department of Cell Biology and Histology, School of Medicine, University of Murcia, 30100, Murcia, Spain.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Vivero-Salmerón
authors.forename: José
authors.initials: J
authors.lastname: Ballesta
authors.forename: José A
authors.initials: JA
authors.lastname: Martínez-Menárguez
mesh_terms: D000818:Animals; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000378:metabolism* / Q000648:ultrastructure; D007150:Immunohistochemistry; D008297:Male; D008854:Microscopy, Electron; D051381:Rats; D017208:Rats, Wistar; D013087:Spermatids / Q000166:cytology* / Q000648:ultrastructure