IRON UPTAKE IN CULTURED SCHWANN CELLS. EVIDENCE FOR A NON TRANSFERRIN MEDIATED PATHWAY

摘要

Schwann cells (SCs) synthesize the myelin sheath in the peripheral nervous system. We have previously described that Fe~(3+) and holotransferrin (hTf) prevent SCs from dedifferentiation through the cAMP/protein kinase A pathway. A major route for the delivery of iron to the cells is the receptor mediated import although a non-Tf mediated pathway has also been described. The aim of the present work is to study the effect of serum deprivation on the kinetics of iron uptake. Cultured SCs were submitted to serum deprivation and supplemented with Fe~(3+), aTf, hTf for 3,6,24 and 72 hs in the presence of ~(59)Fe (FeCl_3). Intracellular iron content was measured by atomic absorption. The presence of Tf receptors (TfR) was evaluated by western blot. Our results demonstrate that there is no uptake of ~(59)Fe in the cells incubated in the presence of serum or apoTf. However, in the cells supplemented with Fe~(3+) or hTf the uptake of ~(59)Fe increases from 1 h to 24hs. These results agree with those referred to intracellular iron content. Deferroxamine blocks the effects promoted by Fe~(3+) or hTf. The expression of TfR increased in SCs submitted to serum deprivation. The supplementation with aTf decreases TfR levels to 66% while hTf supplementation decreases levels to 30%. Our results suggest the existence of an iron uptake mechanism independent of Tf which SCs would express when submitted to a harsh environment.