Abstract
After the completion of human genome project, about 350 transporters have been identified in human, including those identified from the genomic sequences. The recent progresses in transporter research have revealed numbers of transporter function, although many orphan transporters still remain. Now the transporter research moves the interests to physiological and pathological roles of transporters. For such analyses, the quantitative information is essential in addition to the qualitative information, e.g. functional changing of transporters in disease conditions, and functional regulation of interacting proteins including scaffold proteins. To accelerate this movement, we have developed two fundamental techniques by means of HPLC-linked tandem mass-spectrometry (LC-MS/MS). Identification of substrates and evaluate the transport activity is one of limiting steps in transporter research, since transport activity was examined using single radio-labeled compound. We have developed the technique to analyze transport function using mixture of non-radio-labeled compounds. The expression was usually analyzed in mRNA levels and there is no method to quantify the transporter protein comprehensively. We have succeeded to quantify the absolute protein amount of multiple transporters simultaneously with high-sensitivity. This method can produce the transporter map, which is necessary to evaluate the physiological and pathological contribution of transporters. The new techniques will open the new field in transporter research. [J Physiol Sci. 2007;57 Suppl:S43]
