NKCT1 (purified Naja kaouthia protein toxin) conjugated gold nanoparticles induced Akt/mTOR inactivation mediated autophagic and caspase 3 activated apoptotic cell death in leukemic cell

Toxicon. 2016 Oct;121:86-97. doi: 10.1016/j.toxicon.2016.08.004. Epub 2016 Aug 12.


Background: Gold nanoparticle (GNP) and snake venom protein toxin NKCT1 was conjugated as stated earlier (Bhowmik et al., 2013). The aim of this study was to explore the caspase dependent apoptotic pathway and autophagy inducing ability of gold nanoparticles tagged snake venom protein toxin NKCT1 (GNP-NKCT1) in human leukemic U937 and K562 cell line.

Methods: GNP-NKCT1 induced apoptosis in U937 and K562 cell line were assessed through mitochondrial membrane potential assay, ROS generation assay, caspase 3 pathways and western blotting. GNP-NKCT1 induced autophagic pathway was detected through Akt, mTOR and PI3K expression by western blotting. Autophagic cell death also checked after addition of caspase 3 inhibitor and which also reconfirmed by western blotting of autophagic marker protein, lysosomal staining.

Results: Loss of mitochondrial membrane potential was occurred in both the leukemic cell line after induction by GNP-NKCT1 and treatment of which also exhibited high ROS generation. Caspase 3 expression of cell was also increased. With caspase 3 inhibitor, GNP-NKCT1 downregulated PI3K/Akt and mTOR expression and thus undergoing autophagic cell death. Lysosomal staining confirmed lysosomal enzyme involvement in the autophagic response. Up regulation of Atg 3, Atg12, Beclin 1, LC3-II protein and BIF-1 and down regulation of Atg4B were also showed by blotting.

Conclusion: The results demonstrated that conjugation of Gold nanoparticles with NKCT1 could induce an alternate cell death pathway other than apoptosis in the form of autophagy in leukemic cell.

General significance: This study might provide the understanding area of chemotherapeutic drug development from natural resources like snake venoms.

Keywords: Apoptosis; Autophagy; Caspase 3; Gold nanoparticles; Lysosome; NKCT1.

MeSH terms

  • Apoptosis / drug effects*
  • Autophagy / drug effects*
  • Caspase 3 / metabolism*
  • Cell Line, Tumor
  • Elapid Venoms / chemistry*
  • Elapid Venoms / toxicity*
  • Gold / chemistry*
  • Humans
  • Leukemia / metabolism
  • Leukemia / pathology*
  • Membrane Potential, Mitochondrial / drug effects
  • Metal Nanoparticles / chemistry*
  • Proto-Oncogene Proteins c-akt / antagonists & inhibitors*
  • Reactive Oxygen Species / metabolism
  • TOR Serine-Threonine Kinases / antagonists & inhibitors*


  • Elapid Venoms
  • NKCT1 protein, Naja kaouthia
  • Reactive Oxygen Species
  • Gold
  • TOR Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Caspase 3