The apoptotic microtubule network preserves plasma membrane integrity during the execution phase of apoptosis.
It has recently been shown that the microtubule cytoskeleton is reformed during the execution phase of apoptosis. We demonstrate that this microtubule reformation occurs in many cell types and under different apoptotic stimuli. We confirm that the apoptotic microtubule network possesses a novel organization, whose nucleation appears independent of conventional gamma-tubulin ring complex containing structures. Our analysis suggests that microtubules are closely associated with the plasma membrane, forming a cortical ring or cellular "cocoon". Concomitantly other components of the cytoskeleton, such as actin and cytokeratins disassemble. We found that colchicine-mediated disruption of apoptotic microtubule network results in enhanced plasma membrane permeability and secondary necrosis, suggesting that the reformation of a microtubule cytoskeleton plays an important role in preserving plasma membrane integrity during apoptosis. Significantly, cells induced to enter apoptosis in the presence of the pan-caspase inhibitor z-VAD, nevertheless form microtubule-like structures suggesting that microtubule formation is not dependent on caspase activation. In contrast we found that treatment with EGTA-AM, an intracellular calcium chelator, prevents apoptotic microtubule network formation, suggesting that intracellular calcium may play an essential role in the microtubule reformation. We propose that apoptotic microtubule network is required to maintain plasma membrane integrity during the execution phase of apoptosis.
Sánchez-Alcázar
José A
JA
Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide-CSIC, Carretera de Utrera Km 1, Sevilla, 41013, Spain. jasanalc@upo.es
Rodríguez-Hernández
Angeles
A
Cordero
Mario D
MD
Fernández-Ayala
Daniel J M
DJ
Brea-Calvo
Gloria
G
Garcia
Katherina
K
Navas
Plácido
P
D000199:Actins / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology* / Q000648:ultrastructure*; D002463:Cell Membrane Permeability / Q000187:drug effects; D003078:Colchicine / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism; D006801:Humans; D007382:Intermediate Filaments / Q000378:metabolism; D008870:Microtubules / Q000187:drug effects* / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism
D000199:Actins; D014404:Tubulin; D020169:Caspases; D003078:Colchicine; D002118:Calcium