The golgi-associated COPI-coated buds and vesicles contain beta/gamma -actin.
It has been shown previously that the morphology and subcellular positioning of the Golgi complex is controlled by actin microfilaments. To further characterize the association between actin microfilaments and the Golgi complex, we have used the Clostridium botulinum toxins C2 and C3, which specifically inhibit actin polymerization and cause depolymerization of F-actin in intact cells by the ADP ribosylation of G-actin monomers and the Rho small GTP-binding protein, respectively. Normal rat kidney cells treated with C2 showed that disruption of the actin and the collapse of the Golgi complex occurred concomitantly. However, when cells were treated with C3, the actin disassembly was observed without any change in the organization of the Golgi complex. The absence of the involvement of Rho was further confirmed by the treatment with lysophosphatidic acid or microinjection with the constitutively activated form of RhoA, both of which induced the stress fiber formation without affecting the Golgi complex. Immunogold electron microscopy in normal rat kidney cells revealed that beta- and gamma-actin isoforms were found in Golgi-associated COPI-coated buds and vesicles. Taken together, the results suggest that the Rho signaling pathway does not directly regulate Golgi-associated actin microfilaments, and that beta- and gamma-actins might be involved in the formation and/or transport of Golgi-derived vesicular or tubular intermediates.
Valderrama
F
F
Departament de Biologia Cellular, Facultat de Medicina, Institut d'Investigacions Biomediques August pi i Sunyer (IDIBAPS), Universitat de Barcelona, 08036 Barcelona, Spain.
Luna
A
A
Babía
T
T
Martinez-Menárguez
J A
JA
Ballesta
J
J
Barth
H
H
Chaponnier
C
C
Renau-Piqueras
J
J
Egea
G
G
D036002:ADP Ribose Transferases / Q000494:pharmacology; D000199:Actins / Q000378:metabolism*; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000818:Animals; D001905:Botulinum Toxins / Q000494:pharmacology; D002478:Cells, Cultured; D020755:Coat Protein Complex I / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism*; D008845:Microinjections; D016253:Microscopy, Immunoelectron; D051381:Rats; D015398:Signal Transduction; D020741:rho GTP-Binding Proteins / Q000378:metabolism
D000199:Actins; D020755:Coat Protein Complex I; D000246:Adenosine Diphosphate Ribose; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D001905:Botulinum Toxins; D020741:rho GTP-Binding Proteins; C096324:botulinum toxin type C