Actin filaments are involved in the maintenance of Golgi cisternae morphology and intra-Golgi pH.
Here we examine the contribution of actin dynamics to the architecture and pH of the Golgi complex. To this end, we have used toxins that depolymerize (cytochalasin D, latrunculin B, mycalolide B, and Clostridium botulinum C2 toxin) or stabilize (jasplakinolide) filamentous actin. When various clonal cell lines were examined by epifluorescence microscopy, all of these actin toxins induced compaction of the Golgi complex. However, ultrastructural analysis by transmission electron microscopy and electron tomography/three-dimensional modelling of the Golgi complex showed that F-actin depolymerization first induces perforation/fragmentation and severe swelling of Golgi cisternae, which leads to a completely disorganized structure. In contrast, F-actin stabilization results only in cisternae perforation/fragmentation. Concomitantly to actin depolymerization-induced cisternae swelling and disorganization, the intra-Golgi pH significantly increased. Similar ultrastructural and Golgi pH alkalinization were observed in cells treated with the vacuolar H+ -ATPases inhibitors bafilomycin A1 and concanamycin A. Overall, these results suggest that actin filaments are implicated in the preservation of the flattened shape of Golgi cisternae. This maintenance seems to be mediated by the regulation of the state of F-actin assembly on the Golgi pH homeostasis.
Lázaro-Diéguez
Francisco
F
Departament de Biologia Cellular i Anatomia Patològica, Facultat de Medicina, Universitat de Barcelona, 08036 Barcelona, Spain.
Jiménez
Nuria
N
Barth
Holger
H
Koster
Abraham J
AJ
Renau-Piqueras
Jaime
J
Llopis
Juan L
JL
Burger
Koert N J
KN
Egea
Gustavo
G
D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001905:Botulinum Toxins / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002522:Chlorocebus aethiops; D015638:Cytochalasin D / Q000494:pharmacology; D004847:Epithelial Cells / Q000502:physiology; D019084:Fluorescent Antibody Technique, Indirect; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000166:cytology; D008387:Marine Toxins / Q000494:pharmacology; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000494:pharmacology; D053778:Thiazolidines / Q000494:pharmacology; D014709:Vero Cells / Q000187:drug effects / Q000648:ultrastructure
D019086:Bridged Bicyclo Compounds, Heterocyclic; D008387:Marine Toxins; D019384:Nucleic Acid Synthesis Inhibitors; D010080:Oxazoles; D053778:Thiazolidines; C080978:mycalolide B; D015638:Cytochalasin D; D011065:Poly(ADP-ribose) Polymerases; D001905:Botulinum Toxins; C096324:botulinum toxin type C; C037068:latrunculin B