title: Heterogeneity of Ca2+ handling among and within Golgi compartments.
abstract: The Golgi apparatus (GA) is a dynamic intracellular Ca(2+) store endowed with complex Ca(2+) homeostatic mechanisms in part distinct from those of the endoplasmic reticulum (ER). We describe the generation of a novel fluorescent Ca(2+) probe selectively targeted to the medial-Golgi. We demonstrate that in the medial-Golgi: (i) Ca(2+) accumulation takes advantage of two distinct pumps, the sarco/endoplasmic reticulum Ca(2+) ATPase and the secretory pathway Ca(2+) ATPase1; (ii) activation of IP3 or ryanodine receptors causes Ca(2+) release, while no functional two-pore channel was found; (iii) luminal Ca(2+) concentration appears higher than that of the trans-Golgi, but lower than that of the ER, suggesting the existence of a cis- to trans-Golgi Ca(2+) concentration gradient. Thus, the GA represents a Ca(2+) store of high complexity where, despite the continuous flow of membranes and luminal contents, each sub-compartment maintains its Ca(2+) identity with specific Ca(2+) homeostatic characteristics. The functional role of such micro-heterogeneity in GA Ca(2+) handling is discussed.
authors.affiliation: Department of Biomedical Sciences, University of Padua, 35121 Padua, Italy.
authors.forename: Andrea K C
authors.initials: AK
authors.lastname: Wong
authors.forename: Paola
authors.initials: P
authors.lastname: Capitanio
authors.forename: Valentina
authors.initials: V
authors.lastname: Lissandron
authors.forename: Mario
authors.initials: M
authors.lastname: Bortolozzi
authors.forename: Tullio
authors.initials: T
authors.lastname: Pozzan
authors.forename: Paola
authors.initials: P
authors.lastname: Pizzo
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D000252:Calcium-Transporting ATPases / Q000378:metabolism / Q000502:physiology; D002460:Cell Line; D006224:Cricetinae; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism* / Q000648:ultrastructure; D006367:HeLa Cells; D006706:Homeostasis; D006801:Humans
chemical_list: D000252:Calcium-Transporting ATPases; D002118:Calcium
keywords: Ca2+ homeostasis; FRET-based Ca2+ probes; Golgi apparatus; SERCA; SPCA1; intracellular Ca2+-releasing channels