Dynamic processes that reflect anti-apoptotic strategies set up by HspB1 (Hsp27).
Human HspB1 (also denoted Hsp27) is an oligomeric anti-apoptotic protein that has tumorigenic and metastatic roles. To approach the structural organizations of HspB1 that are active in response to apoptosis inducers acting through different pathways, we have analyzed the relative protective efficiency induced by this protein as well its localization, oligomerization and phosphorylation. HeLa cells, that constitutively express high levels of HspB1 were treated with either etoposide, Fas agonist antibody, staurosporine or cytochalasin D. Variability in HspB1 efficiency to interfere with the different apoptotic transduction pathways induced by these agents were detected. Moreover, inducer-specific dynamic changes in HspB1 localization, native size and phosphorylation were observed, that differed from those observed after heat shock. Etoposide and Fas treatments gradually shifted HspB1 towards large but differently phosphorylated oligomeric structures. In contrast, staurosporine and cytochalasin D induced the rapid but transient formation of small oligomers before large structures were formed. These events correlated with inducer-specific phosphorylations of HspB1. Of interest, the formation of small oligomers in response to staurosporine and cytochalasin D was time correlated with the rapid disruption of F-actin. The subsequent, or gradual in the case of etoposide and Fas, formation of large oligomeric structures was a later event concomitant with the early phase of caspase activation. These observations support the hypothesis that HspB1 has the ability, through specific changes in its structural organization, to adapt and interfere at several levels with challenges triggered by different signal transduction pathways upstream of the execution phase of apoptosis.
Laboratoire Stress, Chaperons et Mort Cellulaire, CNRS UMR 5534, Université Claude Bernard Lyon1, Villeurbanne, France.
Catherine
C
Paul
Stéphanie
S
Simon
Benjamin
B
Gibert
Sophie
S
Virot
Florence
F
Manero
André-Patrick
AP
Arrigo
D000199:Actins / Q000378:metabolism; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D015638:Cytochalasin D / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D055551:HSP27 Heat-Shock Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006360:Heat-Shock Proteins; D018869:Heat-Shock Response; D006801:Humans; D008928:Mitochondria / Q000187:drug effects; D018832:Molecular Chaperones; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction; D019311:Staurosporine / Q000494:pharmacology; D019014:fas Receptor / Q000378:metabolism
D000199:Actins; D000972:Antineoplastic Agents, Phytogenic; D004791:Enzyme Inhibitors; C491901:FAS protein, human; D055551:HSP27 Heat-Shock Proteins; C057725:HSPB1 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D019384:Nucleic Acid Synthesis Inhibitors; D019014:fas Receptor; D015638:Cytochalasin D; D005047:Etoposide; D045304:Cytochromes c; D053148:Caspase 3; D019311:Staurosporine