Taurine-responsive genes related to signal transduction as identified by cDNA microarray analyses of HepG2 cells

Taurine-induced changes in the expression profiles of HepG2 cells were assessed using a cDNA microarray technology, and confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR) analyses. Of 8,298 human genes on the microarray, 128 genes (87 known genes) were up-regulated, and 349 (206 known genes) were down-regulated more than 2.0-fold by taurine. Among the 293 known genes regulated by taurine, a total of 44 genes were involved in signal transduction; 16 genes were up-regulated greater than 2.0-fold, and 28 genes were down-regulated more than 2.0-fold by taurine. The results of RT-PCR analyses for the five genes selected were consistent with our microarray data, although the fold changes in the expression level differed somewhat between the two analytical methods. Among signal transduction-related genes affected by taurine, four genes--mitogen-activated protein kinase (MAPK) kinase kinase 7, p21-activated kinase 4, sprouty homolog 2, and MAPK kinase 1--are implicated in the MAPK signaling pathway. Taurine also regulated the expression of signal transducer and activator of transcription (STAT) 3 gene involved in the Janus kinase-STAT pathway, and diacylglycerol kinase, zeta 104 kDa, the downstream mediator of the protein kinase C transmembrane signaling pathway. In conclusion, gene expression profiling of HepG2 cells treated with taurine provided us with new insights into the novel aspects of taurine as a possible regulator of MAPK signaling cascades and protein kinase C signaling pathways involved in cellular processes such as cell growth, differentiation, and apoptosis.