Browsing by Subject "Prosaposin"

Now showing 1 - 4 of 4
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    Age- and sex-associated changes in prosaposin and its receptors in the lacrimal glands of rats.
    (Universidad de Murcia, Departamento de Biologia Celular e Histiologia, 2020) Islam, Farzana; Khan, Md. Sakirul Islam; Nabeka, Hiroaki; Shimokawa, Tetsuya; Yamamiya, Kimiko; Matsuda, Seiji
    Prosaposin, a saposin precursor, is a potent neurotrophic factor found in several tissues and various biological fluids. Saposin-deficient patients have different ophthalmic disorders, indicating a relationship between ocular health and prosaposin. However, there is little information about prosaposin on the ocular surface. Because ocular functions are diverse and depend on age and sex, we examined whether prosaposin and its receptors, G protein-coupled receptor 37 (GPR37) and GPR37L1, are expressed in the major ocular glands, the extra orbital lacrimal gland (ELG), and harderian gland (HG) of rats and whether sex and aging affect their expression. Immunohistochemical analyses revealed that prosaposin and its receptors were expressed in the ELGs and HGs of rats, although their expression varied based on the type of gland, age, and sex. Prosaposin, GPR37, and GPR37L1 were expressed in the basolateral membranes and cytoplasm of acinar cells of the ELGs, and their immunoreactivities were higher in female rats of menopausal age than age-matched male rats. However, such age- and sex-related differences in the immunoreactivities of prosaposin, GPR37, and GPR37L1 were not observed in the HGs. Triple immunofluorescence labelling revealed that prosaposin, GPR37, and GPR37L1 were co-localised in the acinar and ductal cells in the ELGs, although the degrees of colocalization varied according to the age and sex of the rats. Together, the present results showed that prosaposin and its receptors were expressed in the major ocular glands of rats, and their immunoreactivities to the ELGs differed considerably with age and sex.
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    Molecular role of sulfated glycoprotein-1 (SGP-I/Prosaposin) in Sertoli cells
    (Murcia : F. Hernández, 1995) Morales, C.R.; El-Alfy, M.; Zhao, Q.; Igdoura, S.
    Sulfated Glycoprotein- 1 (SGP- 1) is a major polypeptide secreted by rat Sertoli cells. Sequence analysis revealed a 70% sequence similarity with human prosaposin and a 80% similarity with mouse prosaposin. Both human and mouse prosaposin are 65-70 kDa proteins cleaved in the lysosomes into four 10-15 kDa proteins designated saposins A, B, C and D. Lysosomal saposins function as enzymatic activators that promote the hydrolysis of certain glycolipids. SGP-1 (70 kDa) was first considered as being exclusively secreted to the extracellular space. However, recent immunocytochemical studies using an anti SGP-1 antibody demonstrated the presence of this protein in Sertoli cell lysosomes. In addition Sertoli cell lysosomes isolated by cellular fractionation were found to contain a 65 kDa form of SGP-1 or lysosomal prosaposin, as well as, the 15 kDa saposins. Morphological and immunocytochemical evidences also indicated that both prosaposin and saposins may reach Sertoli cell phagosomes by lysosomal fusion. These phagosomes contain cytoplasmic residual bodies detached from spermatids during spermiation. Thus, prosaposin and their derived saposins must play a role in the hydrolysis of membrane glycolipids present in phagocytosed residual bodies. On the other hand, the function of the secreted form of SGP- 1 is still unclear. However, SGP-1 was seen to interact with the plasma membrane of developing spermatids. Due to its capacity to bind certain types of gangliosides, SGP-1 appears to act as glycolipid transfer between Sertoli cells and the developing spermatids.
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    Prosaposin: a protein with differential sorting and multiple functions
    (F. Hernández y Juan F. Madrid. Universidad de Murcia: Departamento de Biología Celular e Histología, 2015) Carvelli, L.; Libin, Yuan; Morales, C.R.
    In eukaryotes the delivery of newly synthesized proteins to their final destination is dependent on a series of functionally distinct compartments, including the endoplasmic reticulum and the Golgi apparatus, which plays a role in posttranslational modification, sorting and distribution of proteins. Most cargo is sorted within, and exits from, the trans-Golgi network (TGN). Proteins delivered to lysosomes include hydrolytic enzymes and nonenzymic activator proteins. They are directed away from the cell surface by their binding to mannose-6-phosphate receptors (MPR). However, in I-cell disease, in which the MPR pathway is disrupted, the nonenzymic sphingolipid activator protein, prosaposin, continue to traffic to lysosomes. This observation led to discovery of a new lysosomal sorting receptor, sortilin. The targeting prosaposin to the lysosomes results from the interaction of its C-terminus with sortilin. Deletion of the Cterminus did not interfere with its secretion, but abolished its transport to the lysosomes. Mutational analysis revealed that the first half of the prosaposin Cterminus contains a motif required for its binding to sortilin and its transport to the lysosomes. Prosaposin can be also secreted to the extracellular space as oligomers. Extracellular prosaposin showed to exert a variety of responses in nervous tissues including the activation of G protein-coupled receptors and ERK phosphorylation. Lastly, prosaposin has been found to be expressed in other fluids of the body such as pancreaticjuice, bile, cerebrospinal fluid, milk and seminal fluid, indicating that prosaposin is not only a house keeping lysosomal protein but an essential factor in the development and maintenance of the nervous systems and other systems of the body.
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    Targeting exogenous β-Defensin to the endolysosomal compartment via a vehicle guided system
    (Universidad de Murcia. Departamento de Biología Celular e Histología, 2017) Carvelli, Lorena; Libin, Yuan; Esfandnia, Sherry; Zhang, Yan; Presley, John F.; Morales, Carlos R.
    A number of pathogens for which there are no effective treatments infect the cells via endocytosis. Once in the endosomes, the pathogens complete their life cycle by overriding normal lysosomal functions. Recently, our laboratory identified the lysosomal targeting signal of prosaposin, which is recognized by the sorting receptor “sortilin”. Based on this evidence, we tested whether the antimicrobial peptide β-Defensin linked to the targeting sequence of prosaposin (βDPSAP) could be redirected from its secretory pathway to the endolysosomal compartment. To this effect, βDPSAP was transfected into COS-7 cells. The sub-cellular distribution of βD-PSAP was analyzed by confocal microscopy and differential centrifugation. Confocal microscopy demonstrated that βD-PSAP overlaid with the lysosomal marker LAMP1, indicating that the construct reached endosomes and lysosomes. Differential centrifugation also showed that βD-PSAP was in the lysosomal fractions. In addition, our binding inhibition assay demonstrated that βD-PSAP bound specifically to sortilin. Similarly, the delivery of βDPSAP was abolished after overexpressing a truncated sortilin. These results indicate that the prosaposin Cterminus and D/C-domain (prosaposin targeting sequence) was an effective “guidance system” to redirect βD-PSAP to the endolysosomal compartment. In the future, this and other fusion proteins with antimicrobial properties will be assembled to our “biotic vehicle” to target pathogens growing within these compartments.