Molecular cloning, characterisation and tissue-specific expression of human LAG3, a member of the novel Lag1 protein family.

We identified and characterised the cDNA coding for human Lag3, a member of the novel eukaryotic Lag1 protein family which was related to the Saccharomyces cerevisiae longevity-assurance gene LAG1. The composite nucleotide sequence revealed a coding region of 1140 bp, a 5'-UTR of 210 bp and a 3'-UTR of 900 bp. The deduced sequence of 380 amino acids had six transmembrane regions and the conserved Lag1 motif. Northern blot analysis revealed that the approximately 2.2 kb LAG3Hs transcript was expressed in all 12 human tissues, high in kidney and liver, moderate in brain, heart, skeletal muscle, placenta and lung and low in colon, thymus, spleen, small intestine and peripheral blood leukocyte. Because of its structural similarity to LAG1, it was postulated that LAG3Hs may mediate sphingolipids metabolism.