Document Detail

Mechanism of cell entry and toxicity of an affinity- purified lectin from Ricinus communis and its differential effects on normal and virus-transformed fibroblasts.
MedLine Citation:
PMID:  162859     Owner:  NLM     Status:  MEDLINE    
An affinity-purified plant lectin from Ricinus communis (RCAII) was shown to exhibit differential toxicity toward SV40-transformed 3T3 fibroblasts grown in vitro. When macromolecular synthesis was examined in SV3T3 and 3T3 cells, RCAII suppressed cell protein synthesis in the transformed line at lower concentrations (1/50 to 1/100) compared to the 3T3 line, and these effects were blocked by the RCAII inhibitors D-galactose or lactose. RNA and DNA synthesis and L-leucine transport were relatively unaffected by RCAII concentrations (greater than 1 mug/ml) that completely suppressed protein synthesis in both cell lines. The RCAII-mediated inhibition of cell protein synthesis required incubation times longer than 60 min, but quantitative cell binding studies with 125-I-RCAII indicated that the lectin binds to maximal levels in approximately 5 to 10 min, even at 4 degrees. During 10-min labeling experiments with 125-I-RCAII (1 mug/ml), it was demonstrated that the cell-bound lectin could be almost quantitatively removed from cells up to an additional 15 min after labeling without subsequent inhibition of protein synthesis. However, longer incubation times (greater than 30 min) after RCAII cell labeling and washing resulted in incomplete removal of cell-bound lectin (less than 20 to 30% of cell-bound lectin could be removed after a 60-min incubation). The longer incubation times (greater than 60 min) also resulted in almost complete inhibition of protein synthesis. Ferritin-conjugated RCAII (ferritin-RCAII) was used to follow the fate of the cell-bound lectin. Ferritin-RCAII bound rapidly (less than 10 min) to SV3T3 cell surfaces and could be blocked from labeling with lactose. After a 10-min incubation at 4 degrees in ferritin-RCAII solutions, the ferritin label was exclusively located at the extracellular surface in a random distribution. After washing and incubation at 37 degrees, the ferritin-RCAII induced clustering of its receptors (15 to 30 min) and eventually induced endocytosis (30 to 60 min). Further incubation (greater than 60 min) resulted in a predominantly intracellular localization of ferritin-RCAII inside endocytotic vesicles and free in the cell cytoplasm. That RCAII acts directly on protein synthesis after cell entry was confirmed with rabbit reticulocyte and mouse Krebs II ascites S30 cell-free protein synthesis system in diameter wit
G L Nicolson; M Lacorbiere; T R Hunter
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Cancer research     Volume:  35     ISSN:  0008-5472     ISO Abbreviation:  Cancer Res.     Publication Date:  1975 Jan 
Date Detail:
Created Date:  1975-04-16     Completed Date:  1975-04-16     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2984705R     Medline TA:  Cancer Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  144-55     Citation Subset:  IM    
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MeSH Terms
Binding Sites
Carcinoma, Krebs 2 / metabolism
Cell Division / drug effects
Cell Transformation, Neoplastic*
Cell-Free System
Cytoplasm / metabolism
DNA, Neoplasm / biosynthesis
Depression, Chemical
Fibroblasts / drug effects
Galactose / pharmacology
Iodine Radioisotopes
Lactose / pharmacology
Lectins / metabolism*,  pharmacology*
Leucine / metabolism
Neoplasm Proteins / biosynthesis
RNA, Neoplasm / biosynthesis
Reticulocytes / metabolism
Simian virus 40*
Time Factors
Reg. No./Substance:
0/DNA, Neoplasm; 0/Iodine Radioisotopes; 0/Lectins; 0/Neoplasm Proteins; 0/RNA, Neoplasm; 26566-61-0/Galactose; 61-90-5/Leucine; 63-42-3/Lactose; 9007-73-2/Ferritins

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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