ATP DEPLETION CAUSES TRANSLATIONAL IMMOBILIZATION OF CELL-SURFACE TRANSFERRIN RECEPTORS IN K562 CELLS

We have used quantitative fluorescence microscopy and fluorescence pho tobleaching recovery to examine the role of metabolic energy in the tr anslational movement of transferrin receptors in the plasma membrane o f K562 erythroleukemia cells. Cellular ATP depletion caused a signific ant decrease in the translational mobility of cell surface transferrin receptors and a significant increase in the number of receptors on th e cell surface. ATP repletion restored receptor translational mobility and cell surface expression to control values. Inhibition of ATP hydr olases by orthovanadate also immobilized cell surface transferrin rece ptors and altered cell surface receptor expression, in a concentration -dependent manner. Vanadate-induced changes in receptor mobility and c ell surface expression were reversible upon washing out the drug. Cell ular ATP depletion did not affect the translational mobility of plasma membrane glycophorins or a fluorescent phospholipid analogue. We conc lude that the translational movement of cell surface transferrin recep tors specifically requires metabolic energy and ATP hydrolysis. (C) 19 96 Wiley-Liss, Inc.