Document Detail

Protein synthesis, ribosomal protein S6 phosphorylation in vitro and the effects of amiloride: SDS gel electrophoresis studies in the Yoshida ascites tumor (AH 130) grown in vivo.
MedLine Citation:
PMID:  3022947     Owner:  NLM     Status:  MEDLINE    
Cell-free cytosolic extracts from the Yoshida (AH 130) rat ascites hepatoma cell line, grown in vivo, showed high ribosomal protein S6 kinase activity in vitro, as measured by transfer of 32P to exogenous 40S rat liver ribosomal subunits, in both exponential growing and stationary phase cells. A significant decrease of protein synthesis (3H-leucine incorporation into total cell protein) was found to occur in cells reaching the stationary phase of growth, suggesting that S6 phosphorylation was not tightly coupled to the rate of the intraperitoneal cell growth and of protein synthesis in these tumor cells. When the cell-free cytosolic extracts were prepared from cells exposed to amiloride, at concentrations that inhibit the Na+/H+ exchange, a decrease of S6 kinase activity was observed only in exponential growing cells, suggesting the possibility of coupling of the Na+/H+ exchange with phosphorylation of intracellular proteins in these tumor cells. Actually, stationary phase cells showed unchanged S6 kinase activity under the same conditions, possibly due to the extremely low Na+/H+ exchange activity, previously demonstrated (Cell Biol. Int. Rep., 1985, 9, 1017-1025). The present experiments support the hypothesis that the regulation of protein synthesis is not tightly coupled to phosphorylation-dephosphorylation cycles, at least of ribosomal protein S6, in cells characterized by a rather uncontrolled growth such as the Yoshida (AH 130) rat ascites hepatoma. In this connection, an elevated degree of protein phosphorylation, such as that of the ribosomal protein S6, could be a general phenomenon of neoplastic transformation.
R Comolli; M G Leonardi; P Alberti; M Frigerio
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Cell biology international reports     Volume:  10     ISSN:  0309-1651     ISO Abbreviation:  Cell Biol. Int. Rep.     Publication Date:  1986 Oct 
Date Detail:
Created Date:  1987-01-15     Completed Date:  1987-01-15     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7708050     Medline TA:  Cell Biol Int Rep     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  821-31     Citation Subset:  IM    
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MeSH Terms
Amiloride / pharmacology*
Carrier Proteins / antagonists & inhibitors
Cell Cycle
Cell Line
Liver Neoplasms, Experimental / metabolism,  pathology
Phosphoproteins / metabolism
Ribosomal Proteins / metabolism*
Ribosomes / drug effects
Sodium-Hydrogen Antiporter
Reg. No./Substance:
0/Carrier Proteins; 0/Phosphoproteins; 0/Ribosomal Proteins; 0/Sodium-Hydrogen Antiporter; 2609-46-3/Amiloride

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