Differential toxicity profile of ricin isoforms correlates with their glycosylation levels.
Ricin is one of the most potent and deadly plant toxins from the seeds of Ricinus communis. In view of its high toxicity, ricin is being used as an immunotoxin in cancer therapy. Ricin also has several isoforms with differential glycosylation depending on the seed variety. Our study shows three isoforms designated 1, 2 and 3, which differed in their surface charge, resulting in a different behavior on cation exchange chromatography, two dimensional (pI 5.5-8.7) and native PAGE. The molecular masses of isoform-1, 2 and 3 were measured as 63.55 kDa, 64.03 kDa and 62.8 kDa, respectively, by MALDI-TOF/MS. In vitro studies with monkey kidney (Vero) cells showed a time dependent increase in cytotoxicity of the isoforms evaluated by extracellular lactate dehydrogenase activity and mitochondrial dehydrogenase assay. These isoforms also induce oxidative stress and DNA damage. Among the isoforms, isoform-3 was quick to generate reactive oxygen species (ROS), (in 90 min) and exhibited maximum cytotoxicity. Morphological changes, catalase activity and DNA fragmentation were significantly higher with isoform-3 treatment compared to others. The glycosylation studies by MALDI-TOF/MS showed that isoform-3 is highly glycosylated with high sugar levels containing more of hybrid/complex type glycopeptides with mannose as hexose units. These experimental evidences clearly suggest that isoform-3 is superior in its early ROS generation, potency to induce oxidative stress and cytotoxicity, that could be due to it's higher glycosylation levels which make isoform-3 as an ideal candidate for immunotoxin studies.
Division of Pharmacology and Toxicology, Defence Research and Development Establishment, Jhansi Road, Gwalior, India.
Payal
P
Sehgal
Om
O
Kumar
Mula
M
Kameswararao
Jayaraj
J
Ravindran
Mohsin
M
Khan
Shashi
S
Sharma
Rajagopalan
R
Vijayaraghavan
G B K S
GB
Prasad
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015415:Biomarkers / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002522:Chlorocebus aethiops; D053938:DNA Fragmentation / Q000187:drug effects; D006020:Glycopeptides / Q000737:chemistry; D006031:Glycosylation; D000922:Immunotoxins / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D020128:Inhibitory Concentration 50; D008358:Mannose / Q000032:analysis; D008970:Molecular Weight; D018384:Oxidative Stress / Q000187:drug effects; D010446:Peptide Fragments / Q000737:chemistry; D020033:Protein Isoforms / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D012276:Ricin / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D053719:Tandem Mass Spectrometry; D014709:Vero Cells
D015415:Biomarkers; D006020:Glycopeptides; D000922:Immunotoxins; D010446:Peptide Fragments; D020033:Protein Isoforms; D017382:Reactive Oxygen Species; D012276:Ricin; D008358:Mannose