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A‐kinase anchor protein 4 precursor (pro‐AKAP4) in human spermatozoa
Author(s) -
Jumeau F.,
Sigala J.,
DossouGbete F.,
Frimat K.,
Barbotin A. L.,
Buée L.,
Béhal H.,
Sergeant N.,
Mitchell V.
Publication year - 2018
Publication title -
andrology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.947
H-Index - 43
eISSN - 2047-2927
pISSN - 2047-2919
DOI - 10.1111/andr.12524
Subject(s) - sperm , biology , western blot , semen , blot , motility , immunogold labelling , sperm motility , andrology , flagellum , microbiology and biotechnology , anatomy , immunology , antibody , biochemistry , genetics , gene , medicine
Background A‐kinase anchor protein 4 ( AKAP 4) and its precursor pro‐ AKAP 4 are two major proteins in spermatozoa of rodents and mammals. Although researchers have characterized the AKAP 4 expression in various species, the protein's expression in humans has not been described in detail. Objectives The objective of this study was to characterize human pro‐ AKAP 4 more precisely (notably the definition of its localization and expression levels in human spermatozoa and testes). Materials and Methods pro‐ AKAP 4 protein expression levels were assessed by Western blotting. The pro‐ AKAP 4's localization in spermatozoa and testes was determined using immunofluorescence staining and immunogold electron microscopy. Furthermore, pro‐ AKAP 4 protein expression levels were assessed in a series of 77 human semen samples, and associations with semen parameters were evaluated. Results Western blotting revealed a 100‐ kD a band in human sperm protein extracts. The pro‐ AKAP 4 was immunolocalized in the fibrous sheath of the flagellum of ejaculated spermatozoa and in elongated spermatids in human testes. A Western blot analysis of 77 normozoospermic semen samples evidenced striking differences in pro‐ AKAP 4 levels from one to another sample (median [interquartile range] integrated optical density = 305 [49–1038]). No correlations were found for pro‐ AKAP 4 levels on one hand and semen volume, sperm concentration, sperm count, sperm motility, or sperm morphology on the other ( p > 0.05 for all). However, pro‐ AKAP 4 levels were positively correlated with motility after density gradient centrifugation of the semen ( r = 0.224, p = 0.049). Discussion AKAP 4 protein might be activated as an alternative pathway to rescue sperm motility. In human spermatozoa, pro‐ AKAP 4 might therefore be a ‘reservoir’ of mature AKAP 4. Conclusion This study generated new knowledge about pro‐ AKAP 4 in human semen, which may be of interest in the management of male infertility.