Protein synthesis inhibition induces cytoresistance in cultured human proximal tubular (hk-2) cells. Iwata, Mineo, Ph. D, James B. Herrington, Ph. D, Richard A. Zager. Fred Hutchinson Cancer Research Center, and the Departments of Medicine and Physiology/Biophysics, the University of Washington, Seattle, WA
APStracts 2:0013F, 1995.
Following sublethal injury, proximal tubular cells acquire resistance to further attack. This study evaluated whether this could be a possible consequence of decreased protein synthesis, a potential correlate of cell damage. To this end, cultured human proximal tubular cells (HK-2) were subjected to 0-24 hrs of protein synthesis inhibition (>98%), either by adding protein synthesis inhibitors [cycloheximide (CH), or verrucarin A], or by inducing sublethal ATP depletion (antimycin A + 2-deoxyglucose). After 24 hrs of these treatments, significant resistance to Ca2+ ionophore/ATP depletion -induced attack was noted (assessed by vital dye exclusion; compared to normal cells). That <6 hrs of protein synthesis inhibition caused no cytoresistance implied the importance of evolving protein depletion, rather than non-specific drug effects or protein synthesis inhibition, per se. CH + ATP depletion did not induce additive benefits, suggesting a common mechanism. Cytoresistance was dissociated from the extent of free Ca2+ loading and ATP depletion, but was associated with a decrease in membrane deacylation. CH removal promptly restored protein synthesis and cytoresistance was lost; conversely, ATP recovery did not restore protein synthesis and cytoresistance persisted. The emergence of cytoresistance correlated with the disappearance/dephosphorylation of an unidentified 130 Kda tyrosine phosphorylated protein/protein complex (denoted "pp-130"). The functional significance of this change was suggested by the fact that tyrosine phosphatase inhibition with orthovanadate maintained pp-130 expression and prevented the cytoresistant state. Conclusions: Protein synthesis inhibition in HK-2 cells can induce a cytoresistant state. Suppression in phospholipase activity and altered tyrosine phosphorylation events may have functional significance in this regard. 

Received 23 August 1994; accepted in final form 30 January 1995.
APS Manuscript Number F302-4.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 February 1995.