Cationic amino acid transport through system y+L in erythrocytes of patients with lysinuric protein intolerance

We test the hypothesis that lysinuric protein intolerance (LPI), a rare aut osomal recessive defect of cationic amino acid transport, results from the absence of the recently described y(+)L amino acid transporter. We compare fluxes of lysine (1 mu M) into erythrocytes of normal subjects with those o f patients homozygous for the LPI mutation. No significant differences infl uxes through system y(+)L in normal or LPI cells were found, excluding the possibility that system y(+)L cannot be expressed in patients with LPI. Rea sons for supposing that there may be tissue-specific processing of two rece ntly described genes encoding the y(+)L transporter are discussed. Polymera se chain reaction measurement of expression of these two genes in an erythr oleukemic cell line suggests that alternatively there may be an as-yet-unid entified additional member of this gene family.