Abstract
Cellular localization of sphingomyelin synthase 2 in the seminiferous epithelium of adult rat testes
Lee,Nikki P.Y.; Mruk,Dolores D.; Xia,Weiliang; Cheng,Chuen-yan
Journal of Endocrinology 192(1): 17-32
Publication date: 2007
Sphingomyelin synthase 2 (SMS2) is an enzyme that catalyzesthe conversion of phosphatidylcholine and ceramide to sphingomyelinand diacylglycerol, and it is crucial to cellular lipid metabolism.Using the technique of subtraction hybridization, we have isolateda full-length cDNA encoding SMS2 from rat testes, which shared93 and 87% identity at the nucleotide level with SMS2 in miceand humans respectively. A specific polyclonal antibody wasprepared against a 20 amino acid peptide of NH-FSWPLSWPPGCFKSSCKKYS-COOHnear the C-terminus of SMS2. Studies by RT-PCR and immunoblottinghave shown that the expression of SMS2 was limited to late roundspermatids and elongating spermatids, but it was not detectedin late elongate spermatids and Sertoli cells. Furthermore,SMS2 was shown to associate with the developing acrosome beginningin late round spermatid through elongating spermatids (but notlate elongate spermatids) and the cell membrane in studies usingfluorescent microscopy and immunohistochemistry. These datawere further confirmed by studies using immunogold electronmicroscopy. The expression of SMS2 in the seminiferous epitheliumis stage-specific with its highest expression detected in theacrosome region in late round spermatids from stages VIII-IX,and also in the acrosome in elongating spermatids with diminishedintensity in stages X-V; however, it was not found inthe acrosome in elongate spermatids in stages VI-VIII.Collectively, these results suggest that SMS2 may play a crucialrole in the lipid metabolism in acrosome formation and the plasmamembrane restructuring from late round spermatids to early elongatingspermatids.
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