EXPRESSION OF THE SURFACE-ANTIGEN 4F2HC AFFECTS SYSTEM-L-LIKE NEUTRAL-AMINO-ACID-TRANSPORT ACTIVITY IN MAMMALIAN-CELLS

Mammalian cells possess a variety of amino acid-transport systems with overlapping substrate specificity. System L is one of the major amino acid-transport systems of non-epithelial cells. By expression cloning we have recently demonstrated that the surface antigen 4F2hc (CD98) i s a necessary component for expression of system-L-like amino acid-tra nsport activity in C6-BU-1 rat glioma cells [Broer, Broer and Hamprech t (1995) Biochem. J. 312, 863-870]. 4F2he mRNA was detected in CHO cel ls, COS cells, activated lymphocytes isolated from mouse spleen and pr imary cultures of astrocytes. In all these cell types, Na+-independent isoleucine transport was mediated by system L. No contribution of sys tem y(+)L to isoleucine or arginine transport was detected in C6-BU-1 cells. In lymphocytes, both system-L-like amino acid-transport activit y and 4F2hc mRNA levels increased after treatment with phorbol ester p lus ionomycin. Antisense oligonucleotides caused modest inhibition of Na+-independent isoleucine transport in C6-BU-1 cells and primary cult ures of astroglial cells, whereas arginine transport was unaffected. O verexpression of 4F2he cDNA in CHO cells resulted in an increase in Na +-independent isoleucine transport.