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Ubiquitination of prohibitin in mammalian sperm mitochondria: possible roles in the regulation of mitochondrial inheritance and sperm quality control.

Authors
Thompson-WE; Ramalho-Santos-J; Sutovsky-P
Source
Biol Reprod 2003 Jul; 69(1):254-260
NIOSHTIC No.
20029253
Abstract
Ubiquitination of the sperm mitochondria during spermatogenesis has been implicated in the targeted degradation of paternal mitochondria after fertilization, a mechanism proposed to promote the predominantly maternal inheritance of mitochondrial DNA in humans and animals. The identity of ubiquitinated substrates in the sperm mitochondria is not known. In the present study, we show that prohibitin, a highly conserved, 30- to 32-kDa mitochondrial membrane protein, occurs in a number of unexpected isoforms, ranging from 64 to greater than 185 kDa in the mammalian sperm mitochondria, which are the ubiquitinated substrates. These bands bind antiubiquitin antibodies, displaying a pattern consistent with polyubiquitinated "ladders." Immunoprecipitation of sperm extracts with antiprohibitin antibodies followed by probing of the resultant immunocomplexes with antiubiquitin yields a banding pattern identical to that observed by antiprohibitin Western blot analysis. In fact, the presumably nonubiquitinated 30-kDa prohibitin band shows no antiubiquitin immunoreactivity. We demonstrate that ubiquitination of prohibitin occurs in testicular spermatids and spermatozoa. Ubiquitinated prohibitin molecules also accumulate in the defective fractions of ejaculated spermatozoa, which are thought to undergo surface ubiquitination during epididymal passage. In such sperm fractions, ubiquitin also coprecipitates with tubulin and microtubule-associated proteins, presumably contributed by the axonemes of defective, ubiquitinated spermatozoa. The results of the present study suggest that prohibitin is one of the ubiquitinated substrates that makes the sperm mitochondria recognizable by the egg's ubiquitin-proteasome dependent proteolytic machinery after fertilization and most likely facilitates the marking of defective spermatozoa in the epididymis for degradation.
Keywords
Spermatozoa; Spermatogenesis; Fertility; Sexual-reproduction; Humans; Animals; Microscopy; Proteins
Contact
Peter Sutovsky, Assistant Professor, University of Missouri-Columbia, S141 ASRC, 920 East Campus Drive, Columbia, MO 65211-5300
CODEN
BIREBV
Publication Date
20030701
Document Type
Journal Article
Email Address
sutovskyp@missouri.edu
Funding Type
Grant
Fiscal Year
2003
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-007324
Issue of Publication
1
ISSN
0006-3363
Source Name
Biology of Reproduction
State
GA
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