Purification and characterization of UDP-Gal: Ceramide Galactosyltransferase and recostitution of its activity by incorporation into liposomes.

Purification and characterization of UDP-Gal: Ceramide Galactosyltransferase and recostitution of its activity by incorporation into liposomes

Galactosylceramidase deficiency causes sperm abnormalities in the mouse model of globoid cell leukodystrophy

The classical recessive mouse mutant, bthe twitcher,Q is one of the several animal models of the human globoid cell leukodystrophy (Krabbe disease) caused by a deficiency in the gene encoding the lysosomal enzyme galactosylceramidase (GALC). The failure to hydrolyze galactosylceramide (gal-cer) and galactosylsphingosine (psychosine) leads to degeneration of oligodendrocytes and severe demyelination. Substrate for GALC is also the galactosyl-alkyl-acyl-glycerol (GalAAG), precursor of the seminolipid, the most abundant glycolipid in spermatozoa of mammals. In this paper, we report the pathobiology of the testis and sperm in the twitcher mouse and demonstrate the importance of GALC for normal sperm maturation and function. The GALC deficit results in accumulation of GalAAG in the testis of the twitcher mouse. Morphological studies revealed that affected spermatozoa have abnormally swollen acrosomes and angulation of the flagellum mainly at midpiece–principal piece junction. Multiple folding of the principal piece was also observed. Electron microscopy analysis showed that in the twitcher sperm, acrosomal membrane is redundant, detached from the nucleus and folded over. Disorganization and abnormal arrangements of the axoneme components were also detected. These results provide in vivo evidence that GALC plays a critical role in spermiogenesis

New insight in the interaction between the gp120 and the HIV receptor in human sperms

The human immunodeficiency virus (HIV) can infect some cell types which lack CD4. Galactosylceramide, a glycolipid present in the nervous system and colonic epithelial cells, has been implicated in the virus entry in these cells. Our data demonstrate that the HIV surface glycoprotein gp120 binds to the galactosyl-alkyl-acylglycerol (GalAAG), a glycolipid structurally related to galactosylceramide present on the surface membrane of the spermatozoa. In this paper, we review our previous data and further confirm the specificity of the interaction between this galactoglycerolipid and the gp120. Consistent with the structural similarity to galactosylceramide, the sperm GalAAG is capable of specifically binding the gp120. The specificity of the binding of antibodies antigalactosylceramide and the gp120 to the sperm extract and to the purified GalAAG fraction prepared from the same extract has been demonstrated utilizing an ELISA assay which favors sensitivity and specificity. Immunofluorescence and immunoelectron microscopy data show a different localization for the GalAAG and its sulfated form the seminolipid (SGalAAG). The GalAAG is preferentially localized in the equatorial segment and the middle piece of the sperm tail, while the seminolipid is widely distributed on the membrane of the spermatozoa. These data indicate that human sperm express on their surface membrane a glycolipid similar in structure to galactosylceramide, the receptor for HIV identified in the CD4 cells, that could function as a HIV receptor and possibly be implicated in its transmission

New players in the infertility of a mouse model of lysosomal storage disease:the hypothalamus-pituitary-gonadal axis.

Mammalian spermatogenesis is a complex hormone-dependent developmental program where interactions between different cell types are finely regulated. Mouse models in which any of the sperm maturation steps are perturbed provide major insights into the molecular control of spermatogenesis. The Twitcher mouse is a model for the Krabbe disease, characterized by the deficiency of galactosylceramidase (GALC), a lysosomal enzyme that hydrolyzes the terminal galactose from galactosylceramide, a typical component of the myelin membrane. In addition, GALC catalyzes the hydrolysis of the terminal galactose from galactosyl-alkyl-acyl-glycerol, precursor of seminolipids, specifically expressed on the membrane of germ cells. Previous data reported by our group demonstrated that glycolipids play an important role in sperm maturation and differentiation. Moreover, we hypothesized that the severe impairment of the central nervous system that affects the Twitcher mouse could interfere with the hypothalamus-pituitary-gonadal axis function, contributing to infertility. To highlight this hypothesis we have determined, at molecular level, the potential variation in expression pattern of brain hormones involved in spermatogenesis regulation