1999 Volume 14 Issue supplement Pages 114-115
In the present study, we characterized novel Na+-dependent carnitine transporter family, OCTNs from human and mouse. At present, we isolated two and three members of OCTN family from human and mouse, respectively. OCTN1 and 2 are present in various tissues, including kidney, while mouse OCTN3 was strongly detected in testis and weakly in kidney. By immunohistochemical analysis in kidney, mouse OCTNs were distributed commonly in luminal membrane of tubular epithelial cells, while other subcellular distribution seemed to be distinct among members. Most of human and mouse OCTNs exhibited multifunctionality by transporting both of carnitine and organic cation, TEA. Furthermore, sodium ions were essential for carnitine transport by human and mouse OCTN1 and 2. Interestingly, sodium ions were not essential for carnitine transport by mouse OCTN3. Furthermore, TEA transport was sodium independent. Some of mutations of human OCTN2 lost both of carnitine and TEA transport activity and others lost only carnitine transport activity with normal TEA transport activity. These observations suggested that carnitine and TEA have partially common functional site on OCTN2 and are transported by distinct but mutually coupled mechanism.
