Changes of differentiation and proliferation in k562 cells with various levels of knockdown of cationic amino acid transporter 1.

We recently showed that arginine transport via cationic amino acid transporter 1 (CAT1), which transports arginine, lysine, ornithine, and histidine, is essential for erythropoiesis. In the present study, to confirm the importance of both arginine and CAT1 in erythropoiesis, we investigated the relationship of arginine uptake activity and differentiation and proliferation of blood cells by knockdown of the CAT1 gene using shRNA. Five short hairpin RNA (shRNA)-transfected K562 cell clones, in which the CAT1 mRNA expression level is decreased, and a vector-transfected clone were obtained. The differentiation to erythrocytes and proliferation of K562 cells were decreased by knockdown of CAT1. In addition, the initial uptake rate of [(3)H]arginine was decreased in the shRNA-transfected cell clones. The ratio of differentiation of CAT1-knockdown K562 cells was well correlated with the uptake activity for arginine by the cells (R(2)=0.59). These findings indicate that CAT1 is directly involved in erythropoiesis through supplying arginine to the blood cells.