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Internalization of human sex steroid-binding protein in the monkey epididymis. 1990

A Gerard, and M Egloff, and H Gerard, and A el Harate, and M Domingo, and J L Gueant, and C D Dang, and H Degrelle
Laboratoire d'Histologie-Embryologie II, Faculté de Médecine de Nancy, Vandoeuvre-les-Nancy, France.

Human sex steroid-binding protein (hSBP) has been purified from late-pregnancy serum and labelled either by iodination (125I) or by photoaffinity with [3H]delta 6-testosterone. Using a micromanipulator, each labelled protein was separately injected into the lumen of epididymal tubules isolated from the head epididymis of the cynomologus monkey (Macaca fascicularis). Tubules were sampled from 3 to 90 min after the injection and processed for electron microscope autoradiography. Localization of the label occurred over the epididymal epithelium whichever tracer was used. The labelling was not randomly distributed over the different cell types constituting the epithelium, since only the 'principal cells' exhibited a silver grain count significantly greater than the background count. In these cells, labelled protein was found over endocytic organelles (coated structures, endosomes, multivesicular bodies and the trans Golgi network) and nuclei (including the nuclear envelope). Quantitative analysis demonstrated the same pattern of cellular and subcellular distribution for each tracer. Pretreatment with excess unlabelled protein significantly reduced the uptake of radioactivity by the principal cells, demonstrating the specificity of this phenomenon. This is the first study to show direct histological evidence for the internalization of hSBP in the primate epididymis, consistent with earlier immunohistochemical or biochemical localization of this protein. It is concluded that head epididymal cells are able to take up labelled hSBP across their apical membrane. The mechanism of internalization seems to involve endocytosis by the principal cells and leads to labelling of the nuclear compartment. This is strikingly similar to the pattern of uptake of rat androgen-binding protein (rABP) by rat epididymal cells previously demonstrated by our group. To what extent the chemical and structural homology between hSBP and rABP can be held responsible for the common cytophysiological behaviour of these sex steroid-binding proteins remains to be determined.

UI MeSH Term Description Entries
D008252 Macaca fascicularis A species of the genus MACACA which typically lives near the coast in tidal creeks and mangrove swamps primarily on the islands of the Malay peninsula. Burmese Long-Tailed Macaque,Crab-Eating Monkey,Cynomolgus Monkey,M. f. aurea,M. fascicularis,Macaca fascicularis aurea,Monkey, Crab-Eating,Monkey, Cynomolgus,Crab-Eating Macaque,Burmese Long Tailed Macaque,Crab Eating Macaque,Crab Eating Monkey,Crab-Eating Macaques,Crab-Eating Monkeys,Cynomolgus Monkeys,Long-Tailed Macaque, Burmese,Macaque, Burmese Long-Tailed,Macaque, Crab-Eating,Monkey, Crab Eating
D008297 Male Males
D008845 Microinjections The injection of very small amounts of fluid, often with the aid of a microscope and microsyringes. Microinjection
D002467 Cell Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (CELL NUCLEOLUS). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the ENDOPLASMIC RETICULUM. A cell may contain more than one nucleus. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed) Cell Nuclei,Nuclei, Cell,Nucleus, Cell
D003034 Coated Pits, Cell-Membrane Specialized regions of the cell membrane composed of pits coated with a bristle covering made of the protein CLATHRIN. These pits are the entry route for macromolecules bound by cell surface receptors. The pits are then internalized into the cytoplasm to form the COATED VESICLES. Bristle-Coated Pits,Cell-Membrane Coated Pits,Bristle Coated Pits,Bristle-Coated Pit,Cell Membrane Coated Pits,Cell-Membrane Coated Pit,Coated Pit, Cell-Membrane,Coated Pits, Cell Membrane,Pit, Bristle-Coated,Pit, Cell-Membrane Coated,Pits, Bristle-Coated,Pits, Cell-Membrane Coated
D004705 Endocytosis Cellular uptake of extracellular materials within membrane-limited vacuoles or microvesicles. ENDOSOMES play a central role in endocytosis. Endocytoses
D004822 Epididymis The convoluted cordlike structure attached to the posterior of the TESTIS. Epididymis consists of the head (caput), the body (corpus), and the tail (cauda). A network of ducts leaving the testis joins into a common epididymal tubule proper which provides the transport, storage, and maturation of SPERMATOZOA.
D006056 Golgi Apparatus A stack of flattened vesicles that functions in posttranslational processing and sorting of proteins, receiving them from the rough ENDOPLASMIC RETICULUM and directing them to secretory vesicles, LYSOSOMES, or the CELL MEMBRANE. The movement of proteins takes place by transfer vesicles that bud off from the rough endoplasmic reticulum or Golgi apparatus and fuse with the Golgi, lysosomes or cell membrane. (From Glick, Glossary of Biochemistry and Molecular Biology, 1990) Golgi Complex,Apparatus, Golgi,Complex, Golgi
D000345 Affinity Labels Analogs of those substrates or compounds which bind naturally at the active sites of proteins, enzymes, antibodies, steroids, or physiological receptors. These analogs form a stable covalent bond at the binding site, thereby acting as inhibitors of the proteins or steroids. Affinity Labeling Reagents,Labeling Reagents, Affinity,Labels, Affinity,Reagents, Affinity Labeling
D000727 Androgen-Binding Protein Carrier proteins produced in the Sertoli cells of the testis, secreted into the seminiferous tubules, and transported via the efferent ducts to the epididymis. They participate in the transport of androgens. Androgen-binding protein has the same amino acid sequence as SEX HORMONE-BINDING GLOBULIN. They differ by their sites of synthesis and post-translational oligosaccharide modifications. Androgen Binding Protein,Binding Protein, Androgen,Protein, Androgen Binding,Protein, Androgen-Binding

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