The Rat Epididymis-specific Antimicrobial Peptides Bin1b Its Expression Characteristics Of The Homologous Gene In Mice And Function Of Research

Bin1b is a rat epididymis-specific antimicrobial peptide that belongs to beta-defensin gene family. The expression of its mRNA is temporally and spatially regulated, which is suggestive of its reproduction-related functions. Our research focused on obtaining of Bin1b specific antiserum and functionally active protein. Bin1b homology in mouse was generated for establishment of Bin1b deficient or overexpression animal models, which may pave ways for exploration of Bin1b function in vivo. The full length cDNA and genomic DNA of rat Bin1b homology in mouse, mBin1b were obtained by EST searching and PCR based procedures. The mRNA of mBin1b was located in middle-caput epididymis. Its expression was androgen-regulated and highlighted in adult male mouse. The size of mBin1b native mature protein was about 5kD as was detected by western blot, which matched that deduced from its nucleic acid sequence. In immunohistochemical staining, signals were detected in middle-caput epidiymis where signals were also seen in the luman. Culture medium from mBin1b transfected cells showed potent antimicrobial activity. In the mean time, an effective method for producing beta-defensin antibodies was established by expression of mBin1b double-copy protein. The rat Bin1b specific antiserum has been prepared. Bin1b showed its sperm binding capacity in immunofluorescence. In a collaborative study with Dr. Chen Xiaozhang in Chinese University in Hongkong, we found rat Bin1b involved in initiation of sperm motility, which was blocked by Bin1b antiserum. This effect was mediated by L-type Ca2+ channel. By fusion expression with thioredoxin followed by protease cleavage, Bin1b protein with antimicrobial activity was achieved. To seek a comparison, we looked into the expression pattern of RBD-1, a beta-defensin universally distributed in rat, in epidiymis at protein level. Immunohistochemistry showed that it expressed in clear cells all along the epididymis.