• Microtubule ring structure;
  • Apoptosis;
  • Trichosanthin;
  • Intracellular free calcium;
  • Plasma membrane integrity


This study investigates the role of dysregulated cytosolic free calcium ([Ca2+]c) homeostasis on microtubule (MT) ring structure in apoptotic cervical cancer (HeLa) cells induced by trichosanthin (TCS), a type I ribosome inactivating protein (RIP). The TCS-induced decrease in cell viability was significantly enhanced in combination with the specific calcium chelator, EGTA-AM. Sequestration of [Ca2+]c markedly disrupted the special MT ring structure. Furthermore, TCS tended to increase LDH release, whereas no significant differences were observed until 48 h of the treatment. In contrast, combined addition of EGTA-AM or colchicine (an inhibitor of tubulin polymerization) significantly reinforced LDH release. The data suggest that TCS-elevated [Ca2+]c maintains plasma membrane integrity via the formation of the MT ring structure in apoptotic HeLa cells.