Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P56851 (epididymal)
 11,273 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Monoclonal antibodies directed against four different polypeptide epitopes on the Mr approximately 94,000 steroid-binding subunit of the rat liver cytosolic glucocorticoid receptor (GcR) were used to probe Western blots of epididymal spermatozoa from rats and mice. Two sperm polypeptides with apparent molecular weights of 94,000 (indistinguishable in size from the liver GcR subunit) and 150,000 reacted with these antibodies. Other polypeptides that are present in a wide variety of somatic cells [lamin-A, -B, and -C; topoisomerase-I; poly(ADP-ribose) polymerase; the 62-kilodalton internal nuclear matrix protein; the nucleolar protein B23; and histone H1] could not be detected in these preparations of spermatozoa, thus appearing to rule out contamination by somatic cells. Rat and mouse pachytene spermatocytes and round spermatids contained much lower amounts of the Mr approximately 94,000 and 150,000 polypeptides. These results suggested that the steroid-binding subunit of the GcR might be accumulated late in spermatogenesis. Consistent with this view, a 6-kilobase mRNA (identical in size to a mRNA detected in mouse somatic cell lines) was detected when Northern blots of mouse round spermatid RNA were probed with a cDNA to the steroid-binding GcR subunit. Although the results described above suggest the presence of GcR in rodent sperm, high affinity binding of glucocorticoids to epididymal sperm could not be detected in a whole cell binding assay. Further analysis revealed that the Mr approximately 90,000 heat shock protein (hsp90), a component reportedly required for high affinity ligand binding to the GcR, was present in early germ cells, but absent from rodent epididymal sperm. These results suggest that the Mr approximately 94,000 steroid-binding subunit of the GcR and an immunologically related Mr approximately 150,000 polypeptide are specifically accumulated during the later stages of rodent spermatogenesis, but are not assembled into receptor complexes capable of binding steroid. In addition, these results support the view that hsp90 is required for high affinity binding of glucocorticoids to the Mr approximately 94,000 GcR subunit in intact cells.
 ...
PMID:Evidence that rodent epididymal sperm contain the Mr approximately 94,000 glucocorticoid receptor but lack the Mr approximately 90,000 heat shock protein. 157 14

We previously identified an insoluble 50-kDa acrosomal matrix protein (AM50) localized to the ventral region of the guinea pig sperm apical segment. AM50 is converted to a 42-kDa polypeptide and released during matrix dispersion in acrosome-reacting sperm. This study examines the sorting pathways and assembly processes which generate the domain-specific distribution of AM50 in the acrosome. AM50 was expressed during early acrosome development and localized to the matrix of proacrosomal granules and the acrosomal vesicle. Initial sorting of AM50 occurred in Golgi phase spermatids, where it became concentrated in the matrix surrounding the acrosomal granule. AM50 remained restricted to the apical segment of acrosome phase spermatids and was finally sorted to the ventral matrix of the apical segment in maturation phase spermatids. By reducing SDS-PAGE testicular AM50 exhibited a slightly higher M(r) of 52 kDa than the 50-kDa form of cauda epididymal spermatozoa. Nonreducing SDS-PAGE demonstrated that testicular and epididymal AM50 were assembled into homomeric complexes of 480 and 450 kDa respectively. Cauda epididymal sperm apical segments contained a second disulfide-cross-linked homomeric complex of 520 kDa composed of a 68-kDa subunit. These studies indicate that AM50 is first assembled into a disulfide-cross-linked complex and subsequently processed into mature AM50. These data also suggest that disulfide-linked complexes of different structural proteins may assemble into distinct acrosomal matrix compartments.
 ...
PMID:Sorting of the domain-specific acrosomal matrix protein AM50 during spermiogenesis in the guinea pig. 785 54

The sperm acrosome contains a variety of hydrolytic enzymes that exhibit differential release during the acrosome reaction. The interaction between hydrolases and the acrosomal matrix, and their compartmentalization into chemically unique matrix domains may represent mechanisms by which this ordered release is achieved. This study characterizes an acrosomal matrix protein that is restricted to the ventral-most region of the apical segment of guinea pig cauda epididymal spermatozoa. Polyclonal antiserum, prepared against an SDS-PAGE-purified apical segment protein, recognized a 50-kDa band, termed AM50, on Western blots. Native AM50 is resistant to solubilization. However, during the acrosome reaction, AM50 is converted into a 42-43-kDa doublet protein (AM50AR) and released into the incubation medium. AM50 and AM50AR are not recognized by antiserum to guinea pig proacrosin and do not exhibit protease activity in a gelatinolytic SDS-PAGE assay. However, AM50AR does bind to p-aminobenzamidine affinity columns, suggesting that it may remain associated with proteases after the acrosome reaction. Light and electron microscopic immunocytochemistry established that AM50 was exclusively localized to the ventral aspect of the apical segment of the acrosome.
 ...
PMID:A domain-specific 50-kilodalton structural protein of the acrosomal matrix is processed and released during the acrosome reaction in the guinea pig. 791 64

The acrosome of the mature spermatozoon functions as a regulated secretory vesicle which performs several critical functions in mammalian fertilization. Acrosome assembly occurs throughout spermiogenesis and continues during posttesticular sperm maturation in the epididymis, resulting in a structurally polarized membrane-bounded organelle that contains an assortment of hydrolases and a stable infrastructure termed the acrosomal matrix. The role of stable acrosomal matrix assemblies in acrosomal biogenesis and function are poorly understood. This article presents ultrastructural, immunocytochemical, and biochemical data on the remodeling of the hamster acrosomal matrix during spermiogenesis and posttesticular sperm maturation in the epididymis. Specific posttranslational modifications of the major acrosomal matrix protein are evident in late, step 16, spermatids and matrix protein processing continues within specific acrosomal subdomains of caput epididymal spermatozoa. At the completion of sperm maturation, the acrosomal matrix consists of two structurally distinct domains which are adherent to the outer acrosomal membrane and exhibit a localized distribution pattern. Coincident with acrosomal matrix differentiation, a paracrystalline cytoskeletal complex is assembled onto the outer acrosomal membrane of epididymal spermatozoa. This cytoskeletal network appears to establish transmembrane structural interactions with the acrosomal matrix and may maintain attachment of the acrosomal cap to the sperm head during the early steps of the acrosome reaction.
 ...
PMID:Structural modification of the hamster sperm acrosome during posttesticular development in the epididymis. 1267 22