Role of the adenylate system and glycolytic flux in the control of protein synthesis in isolated rat lung cells.
(1) Glucose stimulates the incorporation of amino acids into protein in lung cells isolated by digestion of the lung stroma with collagenase. This effect reflects mainly an increase in protein synthesis since no effect of glucose had been found to the uptake of amino acid precursors and, although glucose decreases the rate of intracellular proteolysis by 15%, this effect cannot account for the increased incorporation of radioactivity into proteins. Furthermore, glucose did not induce any significant change in the intracellular content of valine. (2) For glucose to act on protein synthesis, it must be glycolyzed since its stereoisomer, L-glucose, which is not metabolized by lung cells, has no effect. (3) The mechanism of glucose action does not seem to be related simply to variations of cellular ATP content or energy charge. The following arguments seem to support this conclusion: (i) glucose does not bring about significant variations in the concentration of reactants of the adenylate system; (ii) the increase in protein synthesis induced by glucose in energy-depleted cells correlates with a rise in ATP content and energy charge; however, adenosine, which increases ATP levels in a form quantitatively similar to glucose, is unable to affect protein synthesis: (iii) glucose also accelerates the incorporation of amino acids into proteins in adenosine-treated lung cells in which the ATP concentration was almost double that of the control and the energy charge was considerably elevated, ruling out the possibility that a rise in the steady-state concentration of ATP and/or energy charge alone could be responsible for the acceleration of protein synthesis. (4) It can be concluded that the effect of glucose in increasing protein synthesis in lung cells is dependent on some signal arising from its breakdown and not to variations in the concentration of reactants or energy charge of the adenylate system.
D000227:Adenine Nucleotides / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D005947:Glucose / Q000494:pharmacology; D006019:Glycolysis; D066298:In Vitro Techniques; D007461:Iodoacetates / Q000494:pharmacology; D019807:Iodoacetic Acid; D007700:Kinetics; D008168:Lung / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008358:Mannose / Q000494:pharmacology; D003012:Microbial Collagenase; D014176:Protein Biosynthesis; D051381:Rats; D011919:Rats, Inbred Strains; D014633:Valine / Q000378:metabolism*
D000227:Adenine Nucleotides; D007461:Iodoacetates; D000255:Adenosine Triphosphate; D003012:Microbial Collagenase; D014633:Valine; D005947:Glucose; D008358:Mannose; D019807:Iodoacetic Acid