Taxol induces paraptosis independent of both protein synthesis and MAPK pathway.
Our recent studies have shown that high concentration of taxol induced a caspase-independent paraptosis-like cell death and cytoplasmic vacuolization derived predominantly from endoplasmic reticulum (ER) swelling in human lung carcinoma cell lines (ASTC-a-1). In this report, we further explored the relationship between taxol-induced cell death and vacuolization, and the roles of protein synthesis, mitogen-activated protein kinase kinases (MEK), c-jun N-terminal kinase (JNK) and P38 in taxol-induced paraptosis. Enhanced green fluorescent protein (EGFP) was used to probe the cell morphological change, while ER-targeted red fluorescent protein (er-RFP) was used to probe ER spatial distribution. Real-time monitoring of the ER swelling dynamics during the formation of vacuolization inside single living cells co-expressing EGFP and er-RFP further demonstrated that taxol-induced cytoplasmic vacuolization was from the ER restructuring due to fusion and swelling. PI staining showed that taxol-induced vacuolization was not necrosis. These results further demonstrated that the taxol-induced cell death was neither apoptosis nor necrosis, and fitted the criteria of paraptosis characterized by cytoplasmic vacuolization, caspase-independence, lack of apoptotic morphology and insensitivity to broad caspase inhibitor. Our data further indicated that taxol-induced paraptosis required neither protein synthesis nor the participation of MEK, JNK, and P38, which was different from the insulin-like growth factor I receptor (IGFIR)-induced paraptosis. These results suggest that high concentration of taxol activates an alternative paraptotic cell death pathway.
Sun
Qingrui
Q
MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, South China Normal University, Guangzhou, China.
Chen
Tongsheng
T
Wang
Xiaoping
X
Wei
Xunbin
X
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D031541:Fluorescence Resonance Energy Transfer; D005455:Fluorescent Antibody Technique; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000235:genetics; D020935:MAP Kinase Signaling System / Q000187:drug effects; D018613:Microscopy, Confocal; D008933:Mitochondrial Swelling / Q000187:drug effects; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D009369:Neoplasms / Q000201:enzymology / Q000473:pathology*; D017239:Paclitaxel / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors; D013997:Time Factors; D014162:Transfection; D014617:Vacuoles / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051020:bcl-X Protein / Q000378:metabolism; D000097573:Red Fluorescent Protein
D000972:Antineoplastic Agents, Phytogenic; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D009363:Neoplasm Proteins; D017239:Paclitaxel; D047428:Protein Kinase Inhibitors; D011500:Protein Synthesis Inhibitors; D051020:bcl-X Protein; D000097573:Red Fluorescent Protein; C494811:BCL2L1 protein, human; C485184:enhanced green fluorescent protein