TY - JOUR
T1 - Regulation of protein turnover versus growth state
T2 - Ascites hepatoma as a model for studies both in the animal and in vitro
AU - Tessitore, Luciana
AU - Bonelli, Gabriella
AU - Cecchini, Giovanni
AU - Amenta, Joseph S.
AU - Baccino, Francesco M.
N1 - Funding Information:
’ This work was supported in part by grants from CNR, Rome (Special Project Oncology, Grant 85.020013.44; bilateral Italy-USA program, CT 85.00403.04), Minister0 PI, Rome, and AIRC, Milan. ’ To whom correspondence should be addressed at Istituto di Patologia Generale, Corso Raffaello 30, 10125 Torino, Italy. ’ Abbreviations used: PD, protein degradation; AVP, acidic vacuolar pathway (for protein degradation); log
PY - 1987/6
Y1 - 1987/6
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=0023355738&partnerID=8YFLogxK
U2 - 10.1016/0003-9861(87)90405-X
DO - 10.1016/0003-9861(87)90405-X
M3 - Article
SN - 0003-9861
VL - 255
SP - 372
EP - 384
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 2
ER -