Regulation of protein turnover versus growth state: Ascites hepatoma as a model for studies both in the animal and in vitro

Luciana Tessitore, Gabriella Bonelli, Giovanni Cecchini, Joseph S. Amenta, Francesco M. Baccino

Risultato della ricerca: Contributo su rivistaArticolo in rivistapeer review

Abstract

Cell protein turnover states as related to growth phase have been analyzed in a rat ascites hepatoma (Yoshida AH-130), which after transplantation entered a period of exponential growth, followed by a quasi-stationary state. Evaluation of AH-130 cell protein turnover in the animal (slow-turnover protein pool) was combined with rapid assays of proteolytic rates of cells transferred in vitro. Protein accumulation in the exponential phase reflected the balance between sustained synthetic rates and relatively low degradative rates. Cessation of growth resulted from convergent reduction of synthesis (from 3.10 to 1.49%/h) and enhancement of protein breakdown (from 0.61 to 1.43%/h).Endogenous proteolytic rates in vitro were very close to the above degradation rates. As shown by incubation with ammonia or other lysosomal inhibitors, the acidic vacuolar pathway for protein degradation, while totally suppressed in exponential tumor cells, was activated in cells from stationary tumors to such an extent that it fully accounted for the enhanced proteolysis. In contrast, energy metabolism inhibitors were effective on cells in either growth state, the residual ongoing proteolysis being similar in both cells. The possible contribution of cell death to activation of the acidic vacuolar proteolysis in stationary tumors is discussed.

Lingua originaleInglese
pagine (da-a)372-384
Numero di pagine13
RivistaArchives of Biochemistry and Biophysics
Volume255
Numero di pubblicazione2
DOI
Stato di pubblicazionePubblicato - giu 1987
Pubblicato esternamente

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