Overexpression of JKTBP1 induces androgen-independent LNCaP cell proliferation through activation of epidermal growth factor-receptor (EGF-R)

Heterogenous nuclear ribonucleoprotein D-like protein (JKTBP) belongs to a new member of hnRNPs. Previous studies implied that JKTBP1 may be associated with the progression of androgen-independent (AI) prostate cancer. In this study, we generated three stable LNCaP cell lines which expressed exogenous JKTBP1. Furthermore, the effect of ectopic JKTBP1 on the proliferation of LNCaP cells and its mechanism was investigated. We originally found that the ectopic JKTBP1 expression resulted in the proliferation of LNCaP cells in an AI way, as well as inducing the upregulated expression of EGF-R and prostate-specific antigen (PSA), but did not influence the expression level of AR. Moreover, AG1478 suppressed the effect of proliferation induced by JKTBP1. In addition, immunohistochemistry showed that JKTBP1 expression was significantly elevated in AI prostate cancer tissues when compared with the androgen-dependent (AD) prostate cancer and benign prostatic hyperplasia. Our data indicated that overexpression of JKTBP1 in LNCaP cells leads to abnormal cell proliferation and may be involved in the process of AD to AI through induction of EGF-R expression.     

Molecular cloning and functional expression of nucleolar phospholipid hydroperoxide glutathione peroxidase in mammalian cells

We cloned a full-length cDNA for phospholipid hydroperoxide glutathione peroxidase (PHGPx) including exon Ib from rat and mouse testis. The nuclear signal sequence of the N terminal of rat nuclear PHGPx possessed a different sequence from that previously reported for rat sperm nuclei GPx (SnGPx). Expression of this PHGPx-YFP (yellow fluorescent protein) fusion protein including a novel nuclear signal sequence was exclusively localized in nucleolus; although YFPs fused with only a novel nuclear signal sequence were distributed in the whole nucleus, indicating that preferential translocation of nucleolar PHGPx into nucleoli was required for the nuclear signal sequence and internal sequence of PHGPx. Low level expression of nucleolar PHGPx was detected in several tissues, but the expression of nucleolar PHGPx was extensively high in testis. Immunohistochemical analysis with anti-nucleolar PHGPx indicated that expression of nucleolar PHGPx was observed in the nucleoli in the spermatogonia, spermatocyte, and spermatid. Overexpression of 34kDa nucleolar PHGPx in RBL2H3 cells significantly suppressed cell death induced by actinomycin D and doxorubicin that induced damage in the nucleolus. These results indicated that nucleolar PHGPx plays an important role in prevention of nucleolus from damage in mammalian cells.     

Presenilin-1 protein specifically expressed in Leydig cells with its expression level increased during rat testis development

Presenilin-1, mutations of which cause the early-onset of Alzheimer's disease, was shown to be abundantly expressed in the testis as well as the brain. In spite of the high expression level of this protein in the testis, no further analysis has been undertaken. We aimed to study the distribution and developmental changes in presenilin-1 protein, and to provide clues so as to elucidate the role of this protein in the rat testis. To evaluate the specificity of the anti presenilin-1 antibody, rat presenilin-1 protein was expressed in COS-7 cells and the recombinant protein was used for western blot analysis. A positive band of approximately 20 kDa corresponding to the C-terminal fragment of proteolyzed presenilin-1 protein was observed. Using testis and brain tissue samples, a 20 kDa band was detected in both tissues suggesting a similar proteolytic process, but the expression level in the testis was higher than that in the brain. The expression level increased significantly during postnatal testis development. By an immunohistochemical analysis of the rat testis, a strong signal was observed in interstitial cells and further study with cultured TM3 murine Leydig cells revealed an abundant expression of presenilin-1 in Leydig cells. Our study suggests that presenilin-1 expression in Leydig cells may play an important role in Leydig cell function and testis development.     

CUX1 transcription factors: from biochemical activities and cell-based assays to mouse models and human diseases

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.     

Localization of lysosomal acid phosphatase mRNA in mouse tissues.

We studied the expression of lysosomal acid phosphatase (LAP) in mouse by hybridizing Northern blots and tissue sections with the mouse LAP cDNA. Three mRNA species of 2.3, 3.2 and 5.2 KB were identified, which differ in the length of their 3' untranslated region (UTR). The 3.2 KB mRNA is expressed in equal amounts in all tissues and represents the major species in most tissues, whereas the amounts of the 2.3 and 5.2 KB species differ. In situ hybridization of different tissues of adult mice showed a uniform expression of LAP, as expected for a housekeeping gene, except in testis and brain. In testis we found an increase in the LAP mRNA level in spermatocytes. By Northern blot analysis of young mouse testis, this increase could be attributed to late pachytene primary spermatocytes or secondary spermatocytes. In brain tissue the neurons were predominantly labeled, especially the Purkinje and pyramidal cells, whereas glial cells expressed only low amounts of LAP mRNA. Very high LAP expression was also found in the epithelial cells of the choroid plexus. Analysis of LAP expression during mouse embryonic development between Days 9.5 and 17.5 revealed a prominent expression relative to other tissues in the neural tube from Day 9.5 to Day 13.5.     

Distribution of prolyl oligopeptidase in the mouse whole-body sections and peripheral tissues

Prolyl oligopeptidase (POP) is a serine endopeptidase that hydrolyses proline-containing peptides shorter than 30-mer, including many bioactive peptides. The distribution of POP in the brain has been studied but little is known about the distribution of peripheral POP. We used immunohistochemistry to localize POP in mouse whole-body sections and at the cellular level in peripheral tissues. Furthermore, we used a POP activity assay to reveal the associations between POP protein and its enzymatic activity. The highest POP protein densities were found in brain, kidney, testis and thymus, but in the liver the amounts of POP protein were small. There were remarkable differences between the distribution of POP protein and activity. The highest POP activities were found in the liver and testis while kidney had the lowest activity. In peripheral tissues, POP was present in various cell types both in the cytoplasm and nucleus of the cells, in contrast to the brain where no nuclear localization was detected. These findings support the proposed role of POP in cell proliferation in peripheral tissues. The dissociation of the distribution of POP protein and its enzymatic activity points to nonhydrolytic functions of POP and to strict endogenous regulation of POP activity.     

Transcriptomic analyses support the similarity of gene expression between brain and testis in human as well as mouse

We previously revealed similarity in gene expression patterns between human brain and testis, based on digital differential display analyses of 760 human Unigenes. In the present work, we reanalyzed the gene expression data in many tissues of human and mouse for a large number of genes almost covering the respective whole genomes. The results indicated that both in human and in mouse, the gene expression profiles exhibited by brain, cerebellum and testis are most similar to each other compared with other tissues.     

cDNA Cloning and Characterization ofNpap60:A Novel Rat Nuclear Pore-Associated Protein with an Unusual Subcellular Localization during Male Germ Cell Differentiation

We have cloned and characterized a cDNA,Npap60,encoding a rat nuclear pore-associated protein. The 3-kb cDNA was obtained by antibody screening of a rat testis expression library. The predicted NPAP60 contains 381 amino acids with a composition of 25.6% charged residues and is highly hydrophilic. TheNpap60gene appears to be conserved in mouse, rat, and human. Immunofluorescence studies with anti-NPAP60 fusion protein antibody show that the NPAP60 protein colocalizes with nuclear pore complexes in RAT1A cells. The expression ofNpap60is about 10–20 times higher in rat testis than in somatic tissues. The subcellular localization of NPAP60 protein changes dramatically during male germ cell differentiation, from nuclear pore complex-like staining in spermatocytes to whole nucleus staining in spermatids and finally to a nuclear surface staining in mature spermatozoa. These changes are temporally and spatially related to nuclear reorganization during male germ cell differentiation.     

Molecular cloning and characterization of the human NIMA-related protein kinase 3 gene (NEK3)

NEKs (NIMA-related kinases) are a group of protein kinases sharing high amino acid sequence identities with NIMA (never in mitosis gene a) which control mitosis in Aspergillus nidulans. We have cloned a cDNA for human NEK3, a novel human gene structurally related to NIMA, by RT-PCR. Its open reading frame encodes a protein of 489 amino acid residues with the calculated molecular mass of 56.0 kDa and a predicted pI of 6.58. Phylogenetic analysis suggests that mouse and human NEK3s constitute a subfamily within the NIMA family of protein kinases. The expression pattern of NEK3 was studied by RT-PCR and a high level of expression was detected in testis, ovary, and brain, with low-level expression being detected in most of the tissues studied. NEK3 mRNA was detected in all the proliferating cell lines studied, and the amount did not change during the cell cycle. The human NEK3 gene was assigned to human chromosome 13 by somatic cell hybrids and 13q14.2 by radiation hybrid mapping.     

MSJ-1, a New Member of the DNAJ Family of Proteins, Is a Male Germ Cell-Specific Gene Product

A cDNA encoding for a new member of the DnaJ protein family has been isolated by screening a mouse spermatogenic cell expression library. The full-length cDNA obtained by extension of the original clone with RT-PCR has been characterized with respect to its DNA sequence organization and expression. The predicted open reading frame encodes a protein of 242 amino acid residues whose sequence is similar to that of bacterial DnaJ proteins in the amino-terminal portion since it contains the highly conserved J domain which is present in all DnaJ-like proteins and is considered to have a critical role in DnaJ protein–protein interactions. In contrast, the middle and carboxyl-terminal regions of the protein are not similar to any other DnaJ proteins, with the exception of the human neuronal HSJ-1 with which displays a 48% identity in a 175-amino-acid overlap. Analysis of RNAs from a wide spectrum of mouse somatic tissues, including the brain, and from ovary and testis reveals that the gene is specifically expressed in testis only. Developmental Northern blot analysis of testis RNA from mice of different ages andin situhybridization on juvenile and adult testis sections demonstrate that the mRNA is first transcribed in spermatids. A similar pattern of expression is exhibited also in rat testis. Based upon all these observations, we have named this novel mouse gene, MSJ-1, for mouse sperm cell-specific DNAJ first homolog.