Activation of MAP kinase after reversible ATP depletion in LLC-PK 1 cells

We examined the effect of recovery following reversible ATP depletion on MAP kinase activity in cultured renal cells of proximal tubular origin (LLC-PK1). We induced ATP depletion by 0.1 micromol/l antimycin A in combination with substrate deprivation, and obtained recovery by restoration of substrate supply. MAP kinase activity increased from 374+/-45 pmol/mg protein/mm during ATP depletion to 768 +/- 77 pmol/mg protein/mm after 15 min of recovery. We used ATP to activate a representative G-protein coupled receptor, or epidermal growth factor (EGF) to activate receptors with intrinsic tyrosine kinase activity, and measured the effect of these manipulations on MAP kinase activity during ATP depletion or following recovery. ATP and EGF stimulated MAP kinase activity under control conditions, but not during ATP depletion or after recovery. This shows that two distinct signal transduction pathways represented by ATP and EGF are blocked during ATP depletion and recovery. The lack of energy during ATP depletion and the already maximally stimulated MAP kinase during recovery is likely to be the reason for these results. In summary, these findings suggest that MAP kinase may be involved in the physiological response of cells injured by hypoxia.