| Institution: | 1. Graduate School of Science, Chiba University, 1-33 Yayoi-Cho, Inage-Ku, Chiba 263-8522, Japan;2. Graduate School of Science and Technology, Chiba University, 1-33 Yayoi-Cho, Inage-Ku, Chiba 263-8522, Japan;3. Department of Chemistry, Faculty of Science, Chiba University, 1-33 Yayoi-Cho, Inage-Ku, Chiba 263-8522, Japan;4. International Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology, Central 6, 1-1-1, Higashi, Tsukuba, Ibaraki 305-8566, Japan;5. Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba Science City, Ibaraki 305-8572, Japan;6. Research Team for Molecular Biomarkers, Tokyo Metropolitan Institute of Gerontology, Tokyo 173-0015, Japan |
| Abstract: | In mammalian spermiogenesis, sperm mature during epididymal transit to get fertility. The pig sharing many physiological similarities with humans is considered a promising animal model in medicine. We examined the expression profiles of proteins from boar epididymal caput, corpus, and cauda sperm by two-dimensional gel electrophoresis and peptide mass fingerprinting. Our results indicated that protein disulfide isomerase-P5 (PDI-P5) human homolog was down-regulated from the epididymal corpus to cauda sperm, in contrast to the constant expression of protein disulfide isomerase A3 (PDIA3) human homolog. To examine the functions of PDIA3 and PDI-P5, we cloned and sequenced cDNAs of pig PDIA3 and PDI-P5 protein precursors. Each recombinant pig mature PDIA3 and PDI-P5 expressed in Escherichia coli showed thiol-dependent disulfide reductase activities in insulin turbidity assay. Although PDIA3 showed chaperone activity to promote oxidative refolding of reduced denatured lysozyme, PDI-P5 exhibited anti-chaperone activity to inhibit oxidative refolding of lysozyme at an equimolar ratio. SDS-PAGE and Western blotting analysis suggested that disulfide cross-linked and non-productively folded lysozyme was responsible for the anti-chaperone activity of PDI-P5. These results provide a molecular basis and insights into the physiological roles of PDIA3 and PDI-P5 in sperm maturation and fertilization. |
