Identification of a conserved anti-apoptotic protein that modulates the mitochondrial apoptosis pathway

Here we identified an evolutionarily highly conserved and ubiquitously expressed protein (C9orf82) that shows structural similarities to the death effector domain of apoptosis-related proteins. RNAi knockdown of C9orf82 induced apoptosis in A-549 and MCF7/casp3-10b lung and breast carcinoma cells, respectively, but not in cells lacking caspase-3, caspase-10 or both. Apoptosis was associated with activated caspases-3, -8, -9 and -10, and inactivation of caspases 10 or 3 was sufficient to block apoptosis in this pathway. Apoptosis upon knockdown of C9orf82 was associated with increased caspase-10 expression and activation, which was required for the generation of an 11 kDa tBid fragment and activation of Caspase-9. These data suggest that C9orf82 functions as an anti-apoptotic protein that modulates a caspase-10 dependent mitochondrial caspase-3/9 feedback amplification loop. We designate this ubiquitously expressed and evolutionarily conserved anti-apoptotic protein Conserved Anti-Apoptotic Protein (CAAP). We also demonstrated that treatment of MCF7/casp3-10b cells with staurosporine and etoposides induced apoptosis and knockdown of CAAP expression. This implies that the CAAP protein could be a target for chemotherapeutic agents.     

Identification of mRNA/protein (mRNP) complexes containing Puralpha,mStaufen, fragile X protein,and myosin Va and their association with rough endoplasmic reticulum equipped with a kinesin motor

Puralpha, which is involved in diverse aspects of cellular functions, is strongly expressed in neuronal cytoplasm. Previously, we have reported that this protein controls BC1 RNA expression and its subsequent distribution within dendrites and that Puralpha is associated with polyribosomes. Here, we report that, following treatment with EDTA, Puralpha was released from polyribosomes in mRNA/protein complexes (mRNPs), which also contained mStaufen, Fragile X Mental Retardation Protein (FMRP), myosin Va, and other proteins with unknown functions. As the coimmunoprecipitation of these proteins by an anti-Puralpha antibody was abolished by RNase treatment, Puralpha may assist mRNP assembly in an RNA-dependent manner and be involved in targeting mRNPs to polyribosomes in cooperation with other RNA-binding proteins. The immunoprecipitation of mStaufen- and FMRP-containing mRNPs provided additional evidence that the anti-Puralpha detected structurally or functionally related mRNA subsets, which are distributed in the somatodendritic compartment. Furthermore, mRNPs appear to reside on rough endoplasmic reticulum equipped with a kinesin motor. Based on our present findings, we propose that this rough endoplasmic reticulum structure may form the molecular machinery that mediates and regulates multistep transport of polyribosomes along microtubules and actin filaments, as well as localized translation in the somatodendritic compartment.     

The C1orf9 gene encodes a putative transmembrane member of a novel protein family

Here we report the characterization of a human mRNA encoding a novel protein denoted C1orf9 (chromosome 1 open reading frame 9). The cDNA sequence, derived from a testis cDNA library, contains 5700 bp which encodes an open reading frame of 1254 amino acids. The deduced protein contains a putative N-terminal signal peptide and one putative transmembrane region, indicating membrane localization. No significant homology was found with known characterized proteins. However, a 150 amino acid region has significant homology to deduced protein sequences from other organisms, including Caenorhabditis elegans (43% identity), Saccharomyces cerevisiae (47% identity), Schizosaccharomyces pombe (48% identity), and two proteins from Arabidopsis thaliana (42% and 40% identity), suggesting a novel family of conserved domains. The C1orf9 gene was assigned to chromosome 1q24. The gene spans approximately 78.7 kb and is organized into at least 24 exons. Expression analysis revealed a single C1orf9 mRNA species of approximately 6.0 kb with a predominant expression in pancreas and testis, and only low levels of expression in other tissues examined.     

Cloning and expression of a novel human C5orf12 gene,a member of the TMS_TDE family

We report here cloning and characterization of a novel human gene, termed C5orf12, which is a putative membrane protein belonging to the TMS_TDE family. The cDNA encodes 42 animo acid with a putative molecular weight of about 47 KDa. Secondary structure prediction showed that C5orf12 contained 10 putative transmembrane helices, which has high identity with other family members. We performed RT-PCR to examine its expression pattern. The result showed that C5orf12 was highly expressed in placenta, skeletal muscle, spleen, thymus, testis and peripheral leukocyte while expressed weakly in heart and liver. C5orf12 has high identity with the rat TPO1, so we speculate that C5orf12 may also have a role in the brain development.     

Expression of C9orf72 hexanucleotide repeat expansion leads to formation of RNA foci and dipeptide repeat proteins but does not influence autophagy or proteasomal function in neuronal cells

C9orf72 hexanucleotide repeat expansion (HRE) is the major genetic cause underpinning frontotemporal lobar degeneration (FLTD) and amyotrophic lateral sclerosis (ALS). C9orf72 HRE-associated pathogenesis involves both loss-of-function, through reduced C9orf72 levels, and gain-of-function mechanisms, including formation of RNA foci and generation of dipeptide repeat (DPR) proteins. In addition, dysfunctional protein degradation pathways, i.e. autophagy and ubiquitin-proteasome system (UPS), are suggested. Our aim was to study the gain-of-function mechanisms in the context of the function of protein degradation pathways as well as the regulation of the DPR proteins through these pathways. To this end, we expressed the pathological HRE in neuronal N2a cells and mouse primary cortical neurons. Protein degradation pathways were modulated to induce or block autophagy or to inhibit UPS. In addition, proteasomal activity was assessed. The C9orf72 HRE-expressing N2a cells and neurons were confirmed to produce RNA foci and DPR proteins, predominantly the Poly-GP proteins. However, the presence of these pathological hallmarks did not result in alterations in autophagy or proteasomal activity in either of the studied cell types. In N2a cells, Poly-GP proteins appeared in soluble forms and Lactacystin-mediated UPS inhibition increased their levels, indicating proteasomal regulation. Similar effects were not observed in cortical neurons, where the Poly-GP proteins formed also higher molecular weight forms. These results suggest a cell type-specific morphology and regulation of the DPR proteins. Further studies in other model systems may shed additional light onto the effects of the C9orf72 HRE on cellular protein degradation pathways and the regulation of the DPR protein levels.     

The C9orf72 protein interacts with Rab1a and the ULK1 complex to regulate initiation of autophagy

A GGGGCC hexanucleotide repeat expansion in the C9orf72 gene is the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia (C9ALS/FTD). C9orf72 encodes two C9orf72 protein isoforms of unclear function. Reduced levels of C9orf72 expression have been reported in C9ALS/FTD patients, and although C9orf72 haploinsufficiency has been proposed to contribute to C9ALS/FTD, its significance is not yet clear. Here, we report that C9orf72 interacts with Rab1a and the Unc‐51‐like kinase 1 (ULK1) autophagy initiation complex. As a Rab1a effector, C9orf72 controls initiation of autophagy by regulating the Rab1a‐dependent trafficking of the ULK1 autophagy initiation complex to the phagophore. Accordingly, reduction of C9orf72 expression in cell lines and primary neurons attenuated autophagy and caused accumulation of p62‐positive puncta reminiscent of the p62 pathology observed in C9ALS/FTD patients. Finally, basal levels of autophagy were markedly reduced in C9ALS/FTD patient‐derived iNeurons. Thus, our data identify C9orf72 as a novel Rab1a effector in the regulation of autophagy and indicate that C9orf72 haploinsufficiency and associated reductions in autophagy might be the underlying cause of C9ALS/FTD‐associated p62 pathology.     

Cloning and characterization of a novel gene（C17orf25）from the deletion region on chromosome 17p13.3 in hepatocelular carcinoma

INTRODUCTIONLoss of heterozygosity (LOH) at chromosoma1loci associated with tumor suppressor genes has beenimplicated in the genesis of many types of humanmalignancies. On the basis of frequent LOH in tu-mors, coupled with linkage analysis in some heredi-tary cancer syndromes, a number of tumor suppres-sor genes, such as RB[l], DCC[2], NF2[3], VHLI4],MTh1[5], DML/OM1[6], and PrsN/rmC1[7l have been successively isolated.It has beell reported that LOH occurred at l7p invarious ty…     

Expression of arginine decarboxylase in brain regions and neuronal cells

After our initial report of a mammalian gene for arginine decarboxylase, an enzyme for the synthesis of agmatine from arginine, we have determined the regional expression of ADC in rat. We have analyzed the expression of ADC in rat brain regions by activity, protein and mRNA levels, and the regulation of expression in neuronal cells by RNA interference. In rat brain, ADC was widely expressed in major brain regions, with a substantial amount in hypothalamus, followed by cortex, and with least amounts in locus coeruleus and medulla. ADC mRNA was detected in primary astrocytes and C6 glioma cells. While no ADC message was detected in fresh neurons (3 days old), significant message appeared in differentiated neurons (3 weeks old). PC12 cells, treated with nerve growth factor, had higher ADC mRNA compared with naive cells. The siRNA mixture directed towards the N-terminal regions of ADC cDNA down-regulated the levels of mRNA and protein in cultured neurons/C6 glioma cells and these cells produced lower agmatine. Thus, this study demonstrates that ADC message is expressed in rat brain regions, that it is regulated in neuronal cells and that the down-regulation of ADC activity by specific siRNA leads to lower agmatine production.     

C9orf72: At the intersection of lysosome cell biology and neurodegenerative disease

The discovery that expansion of a hexanucleotide repeat within a noncoding region of the C9orf72 gene causes amyotrophic lateral sclerosis and frontotemporal dementia raised questions about C9orf72 protein function and potential disease relevance. The major predicted structural feature of the C9orf72 protein is a DENN (differentially expressed in normal and neoplastic cells) domain. As DENN domains are best characterized for regulation of specific Rab GTPases, it has been proposed that C9orf72 may also act through regulation of a GTPase target. Recent genetic and cell biological studies furthermore indicate that the C9orf72 protein functions at lysosomes as part of a larger complex that also contains the Smith‐Magenis chromosome region 8 (SMCR8) and WD repeat‐containing protein 41 (WDR41) proteins. An important role for C9orf72 at lysosomes is supported by defects in lysosome morphology and mTOR complex 1 (mTORC1) signaling arising from C9orf72 KO in diverse model systems. Collectively, these new findings define a C9orf72‐containing protein complex and a lysosomal site of action as central to C9orf72 function and provide a foundation for the elucidation of direct physiological targets for C9orf72. Further elucidation of mechanisms whereby C9orf72 regulates lysosome function will help to determine how the reductions in C9orf72 expression levels that accompany hexanucleotide repeat expansions contribute to disease pathology.      

Predicted gene sequence C10orf112 is transcribed,exhibits tissue-specific expression,and may correspond to AD7

Case-control and prospective longitudinal studies have revealed an interaction of the anonymous D10S1423 234 bp allele with the APOE4 allele in determining the age-specific risk of Alzheimer's disease (AD). The D10S1423 polymorphism resides within intron 10 of open reading frame C10orf112, whose predicted product resembles a low-density lipoprotein receptor (NCBI Build 35.1). These observations suggest that the D10S1423 234 bp allele may be in linkage disequilibrium with a C10orf112 gene variant whose product interacts with the apoE4 lipoprotein. Our initial exploration of this hypothesis focused on validating the C10orf112 gene model. RT-PCR amplification from human hippocampal mRNA confirmed that 34 of the predicted 39 exons of C10orf112 were expressed in this brain region. Northern blots revealed 1.2 kb and 3.2 kb mRNA species that hybridize to a cDNA probe consisting of contiguous exons 23–26. Expression of these C10orf112 mRNA species was limited to a subset of brain regions and heart tissue.     

Novel human esophagus-specific gene c1orf10: cDNA cloning, gene structure, and frequent loss of expression in esophageal cancer

We have identified a novel human gene, designated C1orf10, using modified differential display PCR. The C1orf10 gene, which spans 5 kb in length, is composed of three exons. The deduced protein contains 495 amino acids with one transmembrane domain. The amino acid sequence of C1orf10 is characterized by the presence of a calcium-binding motif of about 90 amino acids at its N-terminal and a conserved consecutive repeat sequence of 60 amino acids that was identified previously only in bacterial ice nucleation proteins. In normal adult tissues, C1orf10 is highly expressed only in the esophagus and was undetectable in a total of 15 other tissues examined, suggesting its important role in esophageal cells. The expression of C1orf10 is either dramatically reduced or absent in esophageal cancer cell lines (3/3) as well as primary esophageal cancer tissues (35/37) compared with the corresponding normal esophageal mucosa. Using a radiation hybrid panel, C1orf10 was found to be located on chromosome 1q21. These findings suggest that expression of C1orf10 is unique to esophageal cells and that loss of its expression may play a role in the development of esophageal cancer.