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.jpg): Failed to open stream: No such file or directory in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 117 Asian+J+Androl
2015 ; 17
(5
): 726-9
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Epididymosomes: a heterogeneous population of microvesicles with multiple
functions in sperm maturation and storage
#MMPMID26112475
Sullivan R
Asian J Androl
2015[Sep]; 17
(5
): 726-9
PMID26112475
show ga
Extracellular microvesicles present in the epididymal fluid have been named
epididymosomes. Many epididymosome-associated proteins are transferred to
spermatozoa during their maturation in the excurrent duct. Epididymosomes are
heterogeneous, with their size varying between 50 and 250 nm. Two distinct
population of epididymosomes characterized by different protein compositions and
diameters have been isolated from the bovine epididymal fluid using different
centrifugation protocols. One subpopulation of epididymosomes was characterized
by CD9 and other tetraspanin partners. Transfer of proteins from these
epididymosomes to maturing spermatozoa in co-incubation experiments was inhibited
by antibodies against tetraspanin proteins. This suggests that this subpopulation
of epididymosomes is involved in the acquisition of proteins involved in
maturation by spermatozoa in the epididymis. The other population of
epididymosomes was characterized by ELSPBP1 (epididymal sperm binding protein 1),
known for its affinity for the phospholipid choline group. Flow cytometric
analyses showed that ELSPBP1-positive epididymosomes only interacted with dying
or dead epididymal spermatozoa in a Zn 2 + -dependent manner. BLVRA (biliverdin
reductase) was identified as a partner of ELSPBP1. This enzyme reduces biliverdin
to bilirubin: two molecules with powerful anti-oxidant properties. We hypothesize
that BLVRA is involved in an ROS-scavenging mechanism protecting live epididymal
spermatozoa against detrimental molecules (ROS) released by dying cells.
Therefore, it appears that there are at least two epididymosome population with
distinct functions: targeting specific proteins to transiting spermatozoa by
tetraspanin-mediated membrane fusion, and protection of epididymal spermatozoa
against ROS released from dying cells. Further work is needed to understand
functions of epididymosomes in epididymal physiology and sperm maturation and
storage.