Isolation, characterization and chromosomal assignment of human colligin-2 gene (CBP2)

Quantitative proteomics characterization of a mouse embryonic stem cell model of Down syndrome

Down syndrome, caused by the trisomy of chromosome 21, is a complex condition characterized by a number of phenotypic features, including reduced neuron number and synaptic plasticity, early Alzheimer disease-like neurodegeneration, craniofacial dysmorphia, heart development defects, increased incidence of childhood leukemia, and powerful suppression of the incidence of most solid tumors. Mouse models replicate a number of these phenotypes. The Tc1 Down syndrome model was constructed by introducing a single supernumerary human chromosome 21 into a mouse embryonic stem cell, and it reproduces a large number of Down syndrome phenotypes including heart development defects. However, little is still known about the developmental onset of the trisomy 21-induced mechanisms behind these phenotypes or the proteins that are responsible for them. This study determined the proteomic differences that are present in undifferentiated embryonic stem cells and are caused by an additional human chromosome 21. A total of 1661 proteins were identified using two-dimensional liquid chromatography followed by tandem mass spectrometry from whole embryonic stem cell lysates. Using isobaric tags for relative and absolute quantification, we found 52 proteins that differed in expression by greater than two standard deviations from the mean when an extra human chromosome 21 was present. Of these, at least 11 have a possible functional association with a Down syndrome phenotype or a human chromosome 21-encoded gene. This study also showed that quantitative protein expression differences in embryonic stem cells can persist to adult mouse as well as reproduce in human Down syndrome fetal tissue. This indicates that changes that are determined in embryonic stem cells of Down syndrome could potentially identify proteins that are involved in phenotypes of Down syndrome, and it shows that these cell lines can be used for the purpose of studying these pathomechanisms.

Genetic and expression analyses of the STOP (MAP6) gene in schizophrenia

Accumulating evidence suggests that the pathologic lesions of schizophrenia may in part be due to the altered cytoskeletal architecture of neurons. Microtubule-associated proteins (MAPs) that bind to cytoskeletal microtubules to stabilize their assembly are prominently expressed in neurons. Of the MAPs, MAP6 (STOP) has a particular relevance to schizophrenia pathology, since mice deficient in the gene display neuroleptic-responsive behavioral defects. Here we examined the genetic contribution of MAP6 to schizophrenia in a case (n = 570) -control (n = 570) study, using dense single nucleotide polymorphism (SNP) markers. We detected nominal allelic (p = 0.0291) and haplotypic (global p = 0.0343 for 2 SNP-window, global p = 0.0138 for 3 SNP-window) associations between the 3' genomic interval of the gene and schizophrenia. MAP6 transcripts are expressed as two isoforms. A postmortem brain expression study showed up-regulation of mRNA isoform 2 in the prefrontal cortex (Brodmann's area 46) of patients with schizophrenia. These data suggest that the contribution of MAP6 to the processes that lead to schizophrenia should be further investigated.

Expression of heat shock proteins and heat shock protein messenger ribonucleic acid in human prostate carcinoma in vitro and in tumors in vivo

Heat shock proteins (HSPs) are thought to play a role in the development of cancer and to modulate tumor response to cytotoxic therapy. In this study, we have examined the expression of hsf and HSP genes in normal human prostate epithelial cells and a range of prostate carcinoma cell lines derived from human tumors. We have observed elevated expressions of HSF1, HSP60, and HSP70 in the aggressively malignant cell lines PC-3, DU-145, and CA-HPV-10. Elevated HSP expression in cancer cell lines appeared to be regulated at the post-messenger ribonucleic acid (mRNA) levels, as indicated by gene chip microarray studies, which indicated little difference in heat shock factor (HSF) or HSP mRNA expression between the normal and malignant prostate cell lines. When we compared the expression patterns of constitutive HSP genes between PC-3 prostate carcinoma cells growing as monolayers in vitro and as tumor xenografts growing in nude mice in vivo, we found a marked reduction in expression of a wide spectrum of the HSPs in PC-3 tumors. This decreased HSP expression pattern in tumors may underlie the increased sensitivity to heat shock of PC-3 tumors. However, the induction by heat shock of HSP genes was not markedly altered by growth in the tumor microenvironment, and HSP40, HSP70, and HSP110 were expressed abundantly after stress in each growth condition. Our experiments indicate therefore that HSF and HSP levels are elevated in the more highly malignant prostate carcinoma cells and also show the dominant nature of the heat shock-induced gene expression, leading to abundant HSP induction in vitro or in vivo.

Intracellular trafficking and degradation of unassociated proalpha2 chains of collagen type I

Procollagen I is a trimer consisting of two proalpha1(I) chains and one proalpha 2(I) chain. In certain cases of mild osteogenesis imperfecta, abnormal proalpha1(I) chains are degraded very soon after synthesis. As a consequence, the cells produce excess proalpha2(I) chains, which cannot form trimers and are not secreted. The objective of this work was to determine the intracellular fate of unassociated proalpha2(I) chains. Mov13 mouse fibroblasts, which do not synthesize proalpha1(I) mRNA, but do produce proalpha2(I) mRNA, were incubated with radioactive amino acids using pulse-chase protocols, and proteins were analyzed by gel electrophoresis, autoradiography, and Western blotting. Mov13 cells produced proalpha2(I) chains that were degraded intracellularly within 30 min. Degradation was inhibited when cells were treated with brefeldin-A, which blocks transit from endoplasmic reticulum to Golgi. Fixed cells exposed to various immunofluorescence markers and imaged by confocal laser scanning microscopy showed that proalpha2(I) chains colocalized with Golgi and lysosome markers. Degradation was inhibited and chains were secreted when cells were treated with wortmannin, which blocks trafficking to lysosomes. These results demonstrate that unassociated proalpha2(I) chains leave the endoplasmic reticulum, transit the Golgi, and enter lysosomes where they are degraded.

Downregulation of a rheumatoid arthritis-related antigen (RA-A47) by ra-a47 antisense oligonucleotides induces inflammatory factors in chondrocytes

Previously we have shown that the expression of RA-A47 (rheumatoid arthritis-related antigen) which is identical to HSP47, a collagen-binding chaperon, is downregulated in chondrocytes by tumor necrosis factor alpha (TNFalpha). RA-A47 was also found on the surface of chondrocytes where it is recognized as an antigen in the serum of rheumatoid arthritis (RA) patients. Its translocation to the cell surface from endoplasmic reticulum membrane where it is normally located was also enhanced by TNFalpha. To understand the significance of RA-A47 downregulation in chondrocytes independent from other effects of TNFalpha, we used an antisense oligonucleotide approach and investigated the effect of this treatment on the expression of molecules related to matrix degradation and production of growth factors for chondrocytic, endothelial, and synovial cells. Here we show that treatment of rabbit chondrocyes and human chondrosarcoma cells HCS-2/8 by ra-a47 antisense S-oligonucleotides significantly reduced the expression of ra-a47 both at mRNA and protein level. Interestingly, this TNFalpha-independent RA-A47 downregulation was associated with a strong induction of matrix metalloproteinase (MMP)-9 mRNA and inducible NO synthase (iNOS) mRNA. The induction of active-type MMP-9 was further detected by gelatin zymography. Under the same conditions, the release of basic fibroblast growth factor (bFGF) and connective tissue growth factor (CTGF) from HCS-2/8 cells into the conditioned medium (CM) was strongly enhanced. These effects were not a result of TNFalpha upregulation, since the ra-a47 antisense oligonucleotide treatment did not enhance TNFalpha synthesis. These observations indicate that downregulation of RA-A47 induces TNFalpha-independent cartilage-degrading pathways involving iNOS and MMP-9. Furthermore, the stimulation of bFGF and CTGF release from chondrocytes may stimulate the proliferation of adjacent endothelial and/or synovial cells.

Functional linkage between the endoplasmic reticulum protein Hsp47 and procollagen expression in human vascular smooth muscle cells

Hsp47 is a heat stress protein that interacts with procollagen in the lumen of the endoplasmic reticulum, which is vital for collagen elaboration and embryonic viability. The precise actions of Hsp47 remain unclear, however. To evaluate the effects of Hsp47 on collagen production we infected human vascular smooth muscle cells (SMCs) with a retrovirus containing Hsp47 cDNA. SMCs overexpressing Hsp47 secreted type I procollagen faster than SMCs transduced with empty vector, yielding a greater accumulation of pro alpha1(I) collagen in the extracellular milieu. Interestingly, the amount of intracellular pro alpha1(I) collagen was also increased. This was associated with an unexpected increase in the rate of pro alpha1(I) collagen chain synthesis and 2.5-fold increase in pro alpha1(I) collagen mRNA expression, without a change in fibronectin expression. This amplification of procollagen expression, synthesis, and secretion by Hsp47 imparted SMCs with an enhanced capacity to elaborate a fibrillar collagen network. The effects of Hsp47 were qualitatively distinct from, and independent of, those of ascorbate and the combination of both factors yielded an even more intricate fibril network. Given the in vitro impact of altered Hsp47 expression on procollagen production, we sought evidence for interindividual variability in Hsp47 expression and identified a common, single nucleotide polymorphism in the Hsp47 gene promoter among African Americans that significantly reduced promoter activity. Together, these findings indicate a novel means by which type I collagen production is regulated by the endoplasmic reticulum constituent, Hsp47, and suggest a potential basis for inherent differences in collagen production within the population.

Procollagen folding and assembly: the role of endoplasmic reticulum enzymes and molecular chaperones

Procollagen assembly occurs within the endoplasmic reticulum, where the C-propeptide domains of three polypeptide alpha-chains fold individually, and then interact and trimerise to initiate folding of the triple helical region. This highly complex folding and assembly pathway requires the co-ordinated action of a large number of endoplasmic reticulum-resident enzymes and molecular chaperones. Disease-causing mutations in the procollagens disturb folding and assembly and lead to prolonged interactions with molecular chaperones, retention in the endoplasmic reticulum, and intracellular degradation. This review focuses predominantly on prolyl 1-hydroxylase, an essential collagen modifying enzyme, and HSP47, a collagen-specific binding protein, and their proposed roles as molecular chaperones involved in fibrillar procollagen folding and assembly, quality control, and secretion.

Detection of specific antibodies against human cultured chondrosarcoma (HCS-2/8) and osteosarcoma (Saos-2) cells in the serum of patients with osteoarthritis of the temporomandibular joint

To find specific humoral antibodies in sera from patients with temporomandibular joint (TMJ) osteoarthritis (OA), an immortal human chondrocyte (HCS-2/8) and osteoblast (Saos-2) cell line derived from a chondrosarcoma and an osteosarcoma, respectively, were used as source proteins of human antigens. Patients with chronically painful TMJ OA (n = 18) but no other joints symptoms were selected from a consecutive series of patients with temperomandibular disorders and sex-matched asymptomatic controls (n = 8) were also recruited. Cellular proteins of the HCS-2/8 and Saos-2 cells were subjected to Western blotting with the OA and control sera as probes. Band-recognition frequency and the peak optical density of the band were compared between groups by chi2 and t-tests. OA sera recognized various bands for the chondrocytes, and one of these (47-kDa) was specific for the OA sera. In two OA patients whose treatment outcome was less favorable, the reactivity against the 47-kDa protein was relatively high. In addition, the OA sera clearly cross-reacted with recombinant HSP47. Based on these findings, an autoimmune reaction against chondrocytes could be one of the exaggerating and/or perpetuating mechanisms in the pathophysiology of osteoarthritic TMJs, and the humoral antibody titre against the HSP47-like protein derived from the chondrocytes could be one of the possible markers for the prognosis of the joint pathology.

The human genome has only one functional hsp47 gene (CBP2) and a pseudogene (pshsp47)

Among all the species investigated to date, only in humans is hsp47 reported to exist as two separate genes. Here we examined whether hsp47 forms a gene family, and if so, how many genes constitute the family. Cloning and sequencing of human hsp47 cDNA revealed that only one gene, identical to CBP2, was transcribed. No transcript corresponding to colligin, which was reported to be a human homologue of hsp47, was found. Genomic southern hybridization using the exon III fragment of mouse hsp47 as a probe, however, showed two bands for several restriction enzyme digests. We cloned and sequenced the gene corresponding to the extra band and found that a pseudogene (pshsp47) existed in the human genome. We have mapped this pseudogene to chromosome 9p12-p13 by fluorescent in situ hybridization (FISH) using a 3.5kb genomic fragment containing the entire pshsp47 sequence as a probe. These results suggested that functional hsp47 exists as CBP2, not as colligin, and a highly conserved pseudogene is present in the human genome.

Isolation and characterization of a rheumatoid arthritis-specific antigen (RA-A47) from a human chondrocytic cell line (HCS-2/8)

Two types of 47 kDa antigen specifically recognized by sera from rheumatoid arthritis (RA) patients were isolated from the membrane fraction of a human chondrosarcoma-derived chondrocytic cell line (HCS-2/8) by a 2-step procedure: preparative SDS-PAGE and reverse-phase HPLC. An N-terminal amino acid sequence in one of the 47 kDa antigens, named RA-A47, had 81% homology to that deduced from the DNA sequence of the colligin gene which is reported as human hsp47 gene, and 100% homology to that deduced from the DNA sequence of colligin-2 gene, a homologue of colligin. The RA-A47 cross-reacted with a monoclonal antibody raised against chick heat shock protein (Hsp) 47 and bound to gelatin. The expression of the ra-a47 gene was enhanced by heat shock treatment and TGF-beta stimulation. These findings suggest that RA-A47 is a Hsp47-like protein, presumably the product of the colligin-2 gene, and that a collagen-specific molecular chaperone(s) such as Hsp47 and/or RA-A47 is involved in cartilage destruction in RA.

Expression and function of heat shock protein 47: a collagen-specific molecular chaperone in the endoplasmic reticulum

Heat shock protein (HSP) 47 is a collagen-binding stress protein localized in the endoplasmic reticulum (ER). In addition to stress-inducibility through heat shock element-heat shock factor interaction, the expression of HSP47 under normal conditions always correlates with that of collagens in various cell types and tissues. Both HSP47 and types I and III collagens are also dramatically induced under pathophysiological conditions such as liver fibrosis. HSP47 transiently associates with procollagen in the ER and dissociates from it in the cis-Golgi compartment. Possible functions of HSP47 as a molecular chaperone specific for procollagen are discussed: prevention of nascent procollagen chains from forming aggregates, effect on the modification of procollagen, inhibition of intracellular degradation of procollagen, quality control mechanisms under stress conditions, and effect on the secretion from the ER to the Golgi compartment.

Cytoplasmic antiproteinase 2 (PI8) and bomapin (PI10) map to the serpin cluster at 18q21.3

High-molecular-weight serine proteinase inhibitors (serpins) regulate a diverse set of intracellular and extracellular processes such as complement activation, fibrinolysis, coagulation, cellular differentiation, tumor suppression, apoptosis, and cell migration. The ov-serpins are a subset of the serpin superfamily and are characterized by their high degree of homology to chicken ovalbumin, the lack of N- and C-terminal extensions, the absence of a signal peptide, and a Ser rather than an Asn residue at the penultimate position. Recently, we mapped four members of the family [SCCA1, SCCA2, PAI2, and PI5 (maspin)] to a 300-kb region within 18q21.3. Using a panel of 18q21.3 YAC clones, PCR, and DNA blotting, we mapped two additional ov-serpins, cytoplasmic antiproteinase 2 [CAP2 (PI8)] and bone marrow-associated serpin [bomapin (PI10)], to the same region. Three of the serpins, PI8, PI10, and PAI2 mapped to the same YACs, yA27D8 and yA24E4. We estimated that the size of the 18q21.3 serpin cluster spanned approximately 500 kb and contained at least six serpin genes. The order was cen-PI5, SCCA2, SCCA1, PAI2, PI10, PI8-tel. The clustering of serpins at 18q21 provides new opportunities to study coordinate gene regulation and the evolution of gene families.

Structure of the gene encoding human colligin-2 (CBP2)

Colligins are collagen-binding proteins localized to the endoplasmic reticulum that belong to the superfamily of serine protease inhibitors and play a role in collagen biosynthesis. Previously, we cloned the human colligin-2 gene (CBP2) and mapped it to chromosome 11q13.15. To further characterize the CBP2 gene, we have determined its genomic structure and the 5'-flanking sequence. The CBP2 gene spanned approximately 11 kb of genomic DNA and consisted of five exons. The promoter sequence of the human gene showed significant homology to that of its murine counterpart, which contained several regulatory sequences including heat-shock and retinoic acid-responsive elements. These findings suggest colligin may function as a collagen-specific molecular chaperon and play a role in the process of retinoic acid-induced differentiation.