The biogenesis of the Golgi ribbon: the roles of membrane input from the ER and of GM130.
The Golgi complex in mammalian cells forms a continuous ribbon of interconnected stacks of flat cisternae. We show here that this distinctive architecture reflects and requires the continuous input of membranes from the endoplasmic reticulum (ER), in the form of pleiomorphic ER-to-Golgi carriers (EGCs). An important step in the biogenesis of the Golgi ribbon is the complete incorporation of the EGCs into the stacks. This requires the Golgi-matrix protein GM130, which continuously cycles between the cis-Golgi compartments and the EGCs. On acquiring GM130, the EGCs undergo homotypic tethering and fusion, maturing into larger and more homogeneous membrane units that appear primed for incorporation into the Golgi stacks. In the absence of GM130, this process is impaired and the EGCs remain as distinct entities. This induces the accumulation of tubulovesicular membranes, the shortening of the cisternae, and the breakdown of the Golgi ribbon. Under these conditions, however, secretory cargo can still be delivered to the Golgi complex, although this occurs less efficiently, and apparently through transient and/or limited continuities between the EGCs and the Golgi cisternae.
Marra
Pierfrancesco
P
Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, 66030 Santa Maria Imbaro, Chieti, Italy.
Salvatore
Lorena
L
Mironov
Alexander
A
Di Campli
Antonella
A
Di Tullio
Giuseppe
G
Trucco
Alvar
A
Beznoussenko
Galina
G
Mironov
Alexander
A
De Matteis
Maria Antonietta
MA
D000818:Animals; D001324:Autoantigens / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001693:Biological Transport, Active; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D004247:DNA / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure*; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism* / Q000648:ultrastructure*; D006367:HeLa Cells; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism / Q000648:ultrastructure; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats
D001324:Autoantigens; C097741:Golgin subfamily A member 2; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D004247:DNA