Effect of cell proliferation on H-ferritin receptor expression in human T lymphoid (MOLT-4) cells

We have previously demonstrated the presence of receptors specific for human recombinant H ferritin (HrHF) on human T lymphoid cells (MOLT-4), and changes in receptor number and binding affinity with growth and cell cycling have now been examined. Specific binding of HrHF was maximal in MOLT-4 cells harvested during exponential growth with the cells in the DNA synthesis phase of the cell cycle. Specific binding decreased progressively to the plateau phase of growth with the cells in the resting phase of the cell cycle. Scatchard analysis of the competitive binding data for HrHF demonstrated that this decrease in binding was associated with a reduction in receptor number, from 42,140 per cell to 10,306 per cell. Receptor binding affinity increased only minimally over this period, from 7.1 x 10(7) L/mol to 14.9 x 10(7) L/mol. These results indicate that growth- and cell cycle-induced changes in H-ferritin receptor expression are primarily associated with changes in receptor number rather than receptor binding affinity. The present study demonstrates that the expression of this receptor is associated with the proliferative status of the cell and suggests that the H-ferritin receptor may mediate the putative regulatory role of H-ferritin.