- Publication date : 2016-01-26
D'Amours O, Frenette G, Caron P, Belleannée C, Guillemette C, Sullivan R. Evidences of Biological Functions of Biliverdin Reductase A in the Bovine Epididymis. J. Cell. Physiol. 2016;231:1077-89. doi: 10.1002/jcp.25200. PubMed PMID: 26395865.
animals antioxidants bilirubin biliverdine blotting, western body fluids cattle chromatography, liquid epididymis hydrogen peroxide immunohistochemistry immunoprecipitation male oxidoreductases acting on ch-ch group donors protein binding recombinant proteins seminal plasma proteins spermatozoa tandem mass spectrometry testis zinc
Epididymal sperm binding protein 1 (ELSPBP1) is secreted by the epididymal epithelium via epididymosomes and is specifically transferred to dead spermatozoa during epididymal transit. We identified biliverdin reductase A (BLVRA) as a partner of ELSPBP1 by immunoprecipitation followed by tandem mass spectrometry. Pull down assays showed that these two proteins interact in the presence of zinc ions. The BLVRA enzyme is known to convert biliverdin to bilirubin, both of which possess antioxidant activity. Assessment by real-time RT-PCR showed that BLVRA is highly expressed in the caput and the corpus epididymis, but is expressed at lower levels in the testis and the cauda epididymis. It is primarily found in the soluble fraction of the caput epididymal fluid, is barely detectable in the cauda fluid, and is detectable to a lesser extent in the epididymosome fraction of both caput and cauda fluids. Immunocytometry on epididymal sperm showed that BLVRA is found on all sperm recovered from the caput region, whereas it is undetectable on cauda sperm. Biliverdin and bilirubin are found in higher concentrations in the caput epididymal fluid, as measured by mass spectrometry. Lipid peroxidation was limited by 1 μM of biliverdin, but not bilirubin when caput spermatozoa were challenged with 500 μM H2O2. Since immature spermatozoa are a source of reactive oxygen species, BLVRA may be involved in the protection of maturing spermatozoa. It is also plausible that BLVRA is implicated in haemic protein catabolism in the epididymal luminal environment.