Human cytosolic sialidase (NEU2) has been identified and characterized using a NEU2 cDNA constructed from a genomic library of human skeletal muscle. However, the tissue distribution of NEU2 mRNA and the physiological functions of the enzyme remain unclear. In the present study, unlike other human sialidases, NEU2 expression as assessed by quantitative real-time PCR was found to be extremely low or undetectable in many human tissues and cells, with notable exceptions like the placenta and testis. The gene forms obtained by PCR with cDNAs synthesized from poly (A)(+) RNA of human brain and colon were verified to encode cytosolic sialidase with appropriate activity, regardless of the brain gene feature of SNPs. Among a series of human cancer cell lines examined, only prostate cancer PC-3 cells exhibited relatively high expression and NEU2-silencing with an siRNA resulted in decreased cell survival and motility. To gain insights into the significance of the high levels, transcription factors in the promoter region of the NEU2 gene were surveyed for involvement. PC-3 cells were characterized by high expression of Runx2 and Sp3, and their silencing reduced NEU2, suggesting regulatory roles.
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