Neuronal expression, cytosolic localization, and developmental regulation of the organic solute carrier partner 1 in the mouse brain
Toxicology Laboratory, Pharmaceutical Research Center, Meiji Seika Kaisha, Ltd, Kanagawa, 230-0074, Japan. Histochemie
(Impact Factor: 3.05).
02/2011; 135(3):229-38. DOI: 10.1007/s00418-011-0790-6
Organic solute carrier partner 1 (OSCP1) is a mammalian, transporter-related protein that is able to facilitate the uptake of structurally diverse organic compounds into the cell when expressed in Xenopus laevis oocytes. This protein has been implicated in testicular handling of organic solutes because its mRNA expression is almost exclusive in the testis. However, in this study, we demonstrated significant expression of OSCP1 protein in mouse brain, the level of which was rather higher than that in the testis, although the corresponding mRNA expression was one-tenth of the testicular level. Immunohistochemistry revealed that OSCP1 was broadly distributed throughout the brain, and various neuronal cells were immunostained, including pyramidal cells in the cerebral cortex and hippocampus. However, there was no evidence of OSCP1 expression in glia. In primary cultures of cerebral cortical neurons, double-labeling immunofluorescence localized OSCP1 to the cytosol throughout the cell body and neurites including peri-synaptic regions. This was consistent with the subcellular fractionation of brain homogenates, in which OSCP1 was mainly recovered after centrifugation both in the cytosolic fraction and the particulate fraction containing synaptosomes. Immunoelectron microscopy of brain sections also demonstrated OSCP1 in the cytosol near synapses. In addition, it was revealed that changes in the expression level of OSCP1 correlated with neuronal maturation during postnatal development of mouse brain. These results indicate that OSCP1 may have a role in the brain indirectly mediating substrate uptake into the neurons in adult animals.
Available from: Seiji Miyata
- "Subcellular localization of OSCP1 is controversial. Although it has been reported to localize in plasma membranes of human trophoblast cells and mouse Sertoli cells
[9,11], cytoplasmic localization has also been reported in mouse cerebral neuronal cells
[8,21] and human HeLa cells
. Therefore, in this study, we examined subcellular localization of dOSCP1 and revealed its presence in the plasma membrane, endoplasmic reticulum, Golgi apparatus, mitochondria and nucleus of cells. "
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Organic solute carrier partner 1 (OSCP1) is known to facilitate the transport of various organic solutes into cells and reported to play a role in cell growth and cell differentiation. Moreover, OSCP1 is known as a tumor suppressor gene that is frequently down-expressed in nasopharyngeal carcinomas and acute myeloid leukemia. However, the underlying mechanisms of action remain unclear and the subcellular localization of OSCP1 has yet to be determined in detail.
Drosophila contains a single orthologue of OSCP1 (dOSCP1) that shares 58% homology with its human counterpart. To study the expression pattern and subcellular localization of dOSCP1, we prepared a specific antibody. Subcellular localization analyses of dOSCP1 with these revealed localization in the plasma membrane, endoplasmic reticulum, Golgi apparatus and mitochondria, but no detection in cytosol. dOSCP1 signals were also detected in the nucleus, although at weaker intensity than in plasma membranes and subcellular organelles. In addition, native polyacrylamide gel electrophoresis analysis with and without β-mercaptoethanol treatment revealed that recombinant dOSCP1 forms dimers and trimers in solution. The dimer form of dOSCP1 could also be detected by Western immunoblot analyses in third instar larval extracts.
The data revealed that dOSCP1 localizes not only in the plasma membrane but also in the nucleus, ER, Golgi apparatus and mitochondria. It is therefore conceivable that this protein may interact with various partners or form multimeric complexes with other proteins to play multiple roles in cells, providing clues to understanding the functions of dOSCP1 during Drosophila development.
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ABSTRACT: Oxidored nitro domain containing protein 1 (NOR1) is usually restrictively expressed in the brain and testis. Detection of altered NOR1 expression could help us to identify its functions in cell growth, differentiation, metabolism, or even carcinogenesis. In this study, NOR1 homologues were identified in multiple species through GenBank search. NOR1 is a novel protein conserved in multiple species. Mouse NOR1 shared high homology with human NOR1. Furthermore, NOR1 expression was analyzed in mouse tissues by using RT-PCR, Western blot, and immunohistochemistry. The data showed that NOR1 is broadly expressed in neurons of mouse brain and the expression profile changes during postnatal development of the mouse brain. Moreover, in non-nervous tissues, strong immunostaining for NOR1 protein was observed in the testis, epididymis and trachea. In addition, expression of human NOR1 protein in different normal and cancerous human tissues was analyzed via search of the human RNA and protein databases; the data showed that although most malignant cells weakly stained or were negative for NOR1 expression, the liver cancer cells displayed moderate to strong expression of NOR1. These data suggested that NOR1 might serve as a cancer/testis/brain antigen in cells, and that altered NOR1 expression in liver cancer may help us to elucidate the functions of NOR1 protein in liver carcinogenesis.
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ABSTRACT: Studies published in Histochemistry and Cell Biology in the year 2011 represent once more a manifest of established and newly sophisticated techniques being exploited to put tissue- and cell type-specific molecules into a functional context. The review is therefore the Histochemistry and Cell Biology's yearly intention to provide interested readers appropriate summaries of investigations touching the areas of tissue biology, developmental biology, the biology of the immune system, stem cell research, the biology of subcellular compartments, in order to put the message of such studies into natural scientific-/human- and also pathological-relevant correlations.
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