Parallel regulation of procollagen I and colligin, a collagen-binding protein and a member of the serine protease inhibitor family

The heat shock protein 47 as a potential biomarker and a therapeutic agent in cancer research

Heat shock protein 47 (HSP47) is an important chaperone required for the correct folding and secretion of collagen. Several studies revealed that HSP47 has a role in numerous steps of collagen synthesis, preventing procollagen aggregation and inducing hydroxylation of proline and lysine residues. HSP47 is encoded by the SERPINH1 gene, which is located on chromosome 11q13.5, one of the most frequently amplified regions in human cancer. The altered expression levels of HSP47 have been correlated with several types of cancer, such as cervical, breast, pancreatic and gastric cancers. Studies have shown that HSP47 promotes tumor angiogenesis, growth, migration and metastatic capacity. In this review, we highlight the fundamental aspects of the interaction between HSP47 and collagen and the recent discoveries of the role of this chaperone in different types of malignant neoplasias. We also discuss recent treatments using HSP47 as a therapeutic target, and present evidences that HSP47 is an essential protein for cancer biology and a potential molecular target for chemotherapy.

Proteomic profiling of epileptogenesis in a rat model: Focus on inflammation

Detailed knowledge about the patterns of molecular alterations during epileptogenesis is a presupposition for identifying targets for preventive or disease-modifying approaches, as well as biomarkers of the disease. Large-scale differential proteome analysis can provide unique and novel perspectives based on comprehensive data sets informing about the complex regulation patterns in the disease proteome. Thus, we have completed an elaborate differential proteome analysis based on label-free LC-MS/MS in a rat model of epileptogenesis. Hippocampus and parahippocampal cortex tissues were sampled and analyzed separately at three key time points chosen for monitoring disease development following electrically-induced status epilepticus, namely, the early post-insult phase, the latency phase, and the chronic phase with spontaneous recurrent seizures. We focused the bioinformatics analysis on proteins linked to immune and inflammatory responses, because of the emerging evidence of the specific pathogenic role of inflammatory signalings during epileptogenesis. In the early post-insult and the latency phases, pathway enrichment analysis revealed an extensive over-representation of Toll-like receptor signaling, pro-inflammatory cytokines, heat shock protein regulation, and transforming growth factor beta signaling and leukocyte transendothelial migration. The inflammatory response in the chronic phase proved to be more moderate with differential expression in the parahippocampal cortex exceeding that in the hippocampus. The data sets provide novel information about numerous differentially expressed proteins, which serve as interaction partners or modulators in key disease-associated inflammatory signaling events. Noteworthy, a set of proteins which act as modulators of the ictogenic Toll-like receptor signaling proved to be differentially expressed. In addition, we report novel data demonstrating the regulation of different Toll-like receptor ligands during epileptogenesis. Taken together, the findings deepen our understanding of modulation of inflammatory signaling during epileptogenesis providing an excellent and comprehensive basis for the identification of target and biomarker candidates.

Pigment epithelium-derived factor upregulates collagen I and downregulates matrix metalloproteinase 2 in osteosarcoma cells, and colocalises to collagen I and heat shock protein 47 in fetal and adult bone

Objective

Pigment epithelium-derived factor (PEDF) has proven anti-osteosarcoma activity. However, the mechanism(s) underpinning its ability to reduce primary bone tumour (osteosarcoma) metastasis is unknown.

Methods

Adult and fetal murine bone were immunostained for PEDF, collagen I (major protein in bone) and its processing proteins, heat shock protein 47 (HSP47, a chaperone protein for collagen I), membrane type I matrix metalloproteinase (MT1-MMP, a collagenase), and matrix metalloproteinase 2 (MMP-2, which is activated by MT1-MMP). Immunoblotting and immunocytochemistry were used to observe levels of the above biomarkers when human osteosarcoma cells were treated with PEDF.

Key findings

Immunohistochemical staining in adult and fetal bone mirrors collagen I. PEDF localised to ridges of trabecular bone in tibial cortex and to megakaryocytes within bone marrow. Second, we observed that PEDF upregulates collagen I, HSP47 and MT1-MMP, while downregulating MMP-2 in osteosarcoma cells in vitro.

Conclusion

PEDF is a promising antagonist to osteosarcoma cell metastasis via downregulation of MMP-2, and can induce tumour cells to further adopt differentiative properties, thereby possibly reducing their aggressive growth in vitro and in vivo.

The molecular chaperone Hsp47 is essential for cartilage and endochondral bone formation

Heat shock protein 47 kDa (Hsp47) is considered as a molecular chaperone essential for the correct folding of type I and type IV procollagen in the ER. However, the function of Hsp47 for other types of procollagen and its importance for chondrogenesis have never been elucidated. To examine the function of Hsp47 in cartilage formation and endochondral ossification, we conditionally inactivated the Hsp47 gene in chondrocytes using Hsp47 floxed mice and mice carrying a chondrocyte-specific Col2a1-Cre transgene. Hsp47 conditional null mutant mice died just before or shortly after birth, and exhibited severe generalized chondrodysplasia and bone deformities with lower levels of type II and type XI collagen. Second-harmonic generation (SHG) analysis and electron microscopy revealed the accumulation of misaligned type I collagen molecules in the intervertebral discs and a substantial decrease in type II collagen fibers, respectively. Whole-mount skeletal staining showed no calcified region in the vertebral bodies of sacral vertebrae, and revealed that the endochondral bones were severely twisted and shortened. These results demonstrate that Hsp47 is indispensable for well-organized cartilage and normal endochondral bone formation.

Extracellular proteoglycans modify TGF-β bio-availability attenuating its signaling during skeletal muscle differentiation

The onset and progression of skeletal muscle regeneration are controlled by a complex set of interactions between muscle precursor cells and their environment. Satellite cells constitute the main source of muscle precursor cells for growth and repair. After skeletal muscle injury, cell-derived signals induce their re-entry into the cell cycle and their migration into the damaged zone, where they proliferate and differentiate into mature myofibers. The surrounding extracellular matrix (ECM) together with inhibitory growth factors, such as transforming growth factor-beta (TGF-beta), also likely play an important role in growth control and muscle differentiation. Decorin, biglycan and betaglycan are proteoglycans that bind TGF-beta during skeletal muscle differentiation. In this paper, we show that the binding of TGF-beta to the receptors TGF-betaRI and-betaRII diminished in a satellite cell-derived cell line during differentiation, in spite of an increase expression of both receptors. In contrast, during the differentiation of decorin-null myoblasts (Dcn null), which lack decorin expression, the binding of TGF-beta to TGF-betaRI and -betaRII increased concomitantly with receptors levels. Both the addition and re-expression of decorin, in these myoblasts, diminished the binding of TGF-beta to its transducing receptors. Similar results were obtained when biglycan was added or over-expressed in Dcn null myoblasts. The binding of TGF-beta to TGF-betaRIII, alternatively known as betaglycan, was also augmented in Dcn null myoblasts and diminished by decorin, biglycan and betaglycan. These results suggest that decorin, biglycan and betaglycan compete for the binding of TGF-beta to its transducing receptors. Transfection studies with the TGF-beta-dependent promoter of the plasminogen activator inhibitor-1, coupled with luciferase, revealed that the addition of each proteoglycan diminished TGF-beta-dependent activity, for both TGF-beta1 and -beta2. The modulation of TGF-beta signaling by ECM proteoglycans diminishing the bio-availability of TGF-beta for its transducing receptors appears to be a feasible mechanism for the attenuation of this inhibitory growth factor during skeletal muscle formation.

Cyclosporine A induces vascular fibrosis and heat shock protein expression in rat

The immunosuppressive drug Cyclosporine A (CsA) has been successfully used in several diseases with immunological basis and in transplant patients. However, the therapeutic treatment induces several side effects, which include the development of severe hypertension, renal failure and cardiotoxicity in the majority of the patients. Since the mechanism by which CsA induces hypertension is not well defined, the aim of this study is to evaluate the morphological changes and the expression of heat shock proteins (HSPs) in the thoracic aorta of CsA-treated rats. The study was carried out on 40 male Wistar rats with an average weight of 200-250 g. The animals were divided into four groups. Groups I and II were injected subcutaneously (sc) daily with castor oil for 15 or 30 days and used as control; group III and IV were injected sc daily with CsA (15 mg/Kg/day) for 15 or 30 days. After the end of the treatment, the thoracic aortae were removed and treated for morphological (Sirius Red) and immunohistochemical evaluation (HSP 25, alphaB-crystallin and HSP 47). The results indicate that CsA induces (1) time-dependent vascular damage visible as fibrosis mainly in intima-media tunica of aorta, and (2) a clear increase in HSP expression. In fact, after 30 days of treatment, HSP and alphaB-crystallin are increased in all tunicas, whereas HSP47 only in tunica media and adventitia. These findings could suggest that these proteins are up-regulated after CsA treatment in order to play a defensive role in vascular damage.

Dermatan sulfate exerts an enhanced growth factor response on skeletal muscle satellite cell proliferation and migration

Skeletal muscle regeneration is a complex process in which many agents are involved. When skeletal muscle suffers an injury, quiescent resident myoblasts called satellite cells are activated to proliferate, migrate, and finally differentiate. This whole process occurs in the presence of growth factors, the extracellular matrix (ECM), and infiltrating macrophages. We have shown previously that different proteoglycans, either present at the plasma membrane or the ECM, are involved in the differentiation process by regulating growth factor activity. In this article, we evaluated the role of glycosaminoglycans (GAGs) in myoblast proliferation and migration, using C2C12, a satellite cell-derived cell line. A synergic stimulatory effect on myoblast proliferation was observed with hepatocyte growth factor (HGF) and fibroblast growth factor type 2 (FGF-2), which was dependent on cell sulfation. The GAG dermatan sulfate (DS) enhanced HGF/FGF-2-dependent proliferation at 1-10 ng/ml. However, decorin, a proteoglycan containing DS, was unable to reproduce this enhanced proliferative effect. On the other hand, HGF strongly increased myoblast migration. The HGF-dependent migratory process required the presence of sulfated proteoglycans/GAGs present on the myoblast surface, as inhibition of both cell sulfation, and heparitinase (Hase) and chondroitinase ABC (Ch(abc)) treatment of myoblasts, resulted in a very strong inhibition of cell migration. Among the GAGs analyzed, DS most increased HGF-dependent myoblast migration. Taken together, these findings showed that DS is an enhancer of growth factor-dependent proliferation and migration, two critical processes involved in skeletal muscle formation.

The expression of mRNA of cytokines and of extracellular matrix proteins in triiodothyronine-treated rat hearts

In various models of cardiac hypertrophy, e.g. treatment of rats with norepinephrine infusion or pressure overload, increased expression of cytokines together with increase in extracellular matrix proteins (ECMP) was reported. In this study the effect of triiodothyronine (T3) on the expression of mRNA for cytokines and ECMP was investigated. Female Sprague-Dawley rats were treated daily with T3 in a dose of 0.2 mg x kg(-1) of body weight s.c. Changes in the left (LV) and right (RV) ventricular function were measured 6, 24, 48, 72 h and 7 and 14 days after the first T3-injection using Millar ultraminiature pressure catheter transducers. RNA was isolated from LV and RV tissue, and the expression of cytokines and ECMP was measured using the ribonuclease protection assay. T3-treatment induced a significant increase in LV dP/dtmax and RV dP/dtmax, (p < 0.05) 24 h after the first injection of T3 together with an increase in heart rate (p < 0.01). The RV systolic pressure increased 48 h after the first T3 injection, whereas the LV systolic pressure remained unchanged. After 48 h the heart weight to body weight ratio was increased (p < 0.01). Hypertrophy of the RV was more prominent than that of the LV (155.9 vs. 137.7%). In all groups the expression of mRNA for interleukins (IL) IL-6, IL-1beta, IL-1alpha and tumour necrosis factor (TNF)-alpha in both ventricles did not change (p > 0.05). There was a significant increase in the mRNA for colligin 24 h after the T3 injection in both LV (p < 0.01) and RV (p < 0.05). This was followed by an increase in the mRNA for collagen I and III 72 h after the first T3-dose (p < 0.05 in RV; p < 0.01 in LV). At this point, the mRNA for tissue inhibitor of matrix metalloproteinases-2 (TIMP-2) was increased (p < 0.01) in the LV only. Moreover, after 7 days also the mRNA for matrix metalloproteinase (MMP)-2 increased (p < 0.01) in the LV. Both, TIMP-2 and MMP-2 were increased in the RV only after 14 days (p < 0.05). The gelatinase activity of MMP-2, however, was unchanged in both ventricles. The T3-induced cardiac hypertrophy was not accompanied by fibrosis as measured by the Sirius red staining after 14-days of T3-treatment. The moderate increase in mRNA for ECMP and MMP may be attributed more to the increasing mass of the ventricles with the accompanying remodelling of the ECM than to increased fibrosis.

Immunohistochemical expression of angiogenesis-related markers in oral squamous cell carcinomas with multiple metastatic lymph nodes

The aim of this study was to evaluate the histopathologic features and the expression of angiogenesis-related markers in primary tumors and metastatic lymph nodes of oral squamous cell carcinomas (SCCs) with multiple lymph node involvement in comparison with oral SCCs without nodal metastasis. The protein levels of the angiogenesis inhibitor endostatin, as well as those of the related molecules collagen XVIII, collagen-binding protein (CBP) 2/heat shock protein (HSP) 47, and cathepsin L, were evaluated by immunohistochemical analysis. Compared with nonmetastatic cases, primary tumors of the metastatic group exhibited significantly decreased protein levels of endostatin and its precursor collagen XVIII. Comparison between primary tumors and positive nodes of the metastatic cases revealed decreased expression of collagen XVIII and CBP2/HSP47 in metastases. Angiogenesis is essential for tumor growth and metastasis; accordingly, the observed differences in the immunohistochemical expression of angiogenesis-related proteins in oral SCC with multiple lymph node involvement may provide an explanation for the increased metastatic potential of these tumors.

Cloning, expression, and characterization of chicken transforming growth factor beta 4

Transforming growth factor beta 4 (TGF-beta 4) is unique to avian species, though its roles in vivo have not yet been well established. In this paper we describe the expression and partial characterization of recombinant chicken TGF-beta 4. By using a GC-rich PCR system in a modified 5'RACE methodology we generated the 5'-end of cDNA sequence encoding the TGF-beta 4 precursor, which was in-frame cloned into pcDNA3.1/V5-His-TOPO and transfected into the Chinese hamster ovary cell line (CHO-K1). A cell line stably expressing TGF-beta 4 precursor protein was established from CHO-K1 cells. Acid-activated mature TGF-beta 4 inhibited the growth of mink lung epithelial (Mv1Lu) cell line. TGF-beta 4 also stimulated the expression of type I procollagen and enhanced heat shock protein 47 (Hsp47) expression in chicken tendon fibroblasts. Hsp47 expression by TGF beta 4 is likely regulated through activation of heat shock transcription factor 1 (HSF1). Because the presence of TGF-beta 1 has not been documented in avian cells and our data show that TGF-beta 4 elicits biological activities in chicken tendon cells, which closely parallel that of TGF-beta 1, we propose that TGF-beta 4 plays roles in avian species similar to what TGF-beta 1 plays in mammalian species.

Regulation of heat shock protein 47 and type I procollagen expression in avian tendon cells

Heat shock protein 47 (Hsp47) is a collagen-binding stress protein that acts as a collagen-specific molecular chaperone during the biosynthesis and secretion of procollagen. Type I collagen is a major component of tendons. Coexpression of genes for both proteins has been reported in various tissues, where many growth factors likely regulate their expressions in different ways. Here we describe the effects of increased temperature, mechanical stress and growth factors on Hsp47 and type I procollagen expression in embryonic chicken tendon cells. The expression of Hsp47 mRNA at 45 degrees C increased within 60 min and returned to baseline in 4 h after the temperature decreased to 37 degrees C. Our data also show that transforming growth factor beta1 (TGF-beta1) is another regulator of Hsp47 expression as the addition of TGF-beta1 led to a moderate increase in the expression of Hsp47 mRNA. TGF-beta2 and TGF-beta3 exerted only a small effect; epidermal growth factor and tumor necrosis factor alpha (TNF-alpha) had none. TGF-beta1 increased type I procollagen mRNA expression and TNF-alpha reduced this expression. TGF-beta1 delayed the degradation of Hsp47 mRNA after heat shock likely via post-transcriptional regulation of the Hsp47 gene. We also report that mechanical stress increased Hsp47 mRNA expression and Hsp47 protein synthesis. Induction of Hsp47 protein expression by heat shock, mechanical stress and TGF-beta1 was likely achieved through activation and translocation of heat shock transcription factor 1 into the nucleus. Our data indicate that TGF-beta1 is a major regulator of both procollagen and Hsp47 genes.

Effect of transforming growth factor-beta1, interleukin-6, and interferon-gamma on the expression of type I collagen, heat shock protein 47, matrix metalloproteinase (MMP)-1 and MMP-2 by fibroblasts from normal gingiva and hereditary gingival fibromatosis

BACKGROUND

Increased collagen and extracellular matrix deposition within the gingiva is the main characteristic feature of hereditary gingival fibromatosis (HGF). To date, it is not well established if these events are a consequence of alterations in the collagen and other extracellular matrix molecules synthesis or disturbances in the homeostatic equilibrium between synthesis and degradation of extracellular matrix molecules. Cytokines are important regulators of expression of the profibrogenic genes, including type I collagen and its molecular chaperone heat shock protein (Hsp)47 and proteolytic enzymes degrading extracellular matrix such as matrix metalloproteinases-1 and -2 (MMP-1 and MMP-2).

METHODS

In this study, we analyzed the expression and production of type I collagen, Hsp47, MMP-1, and MMP-2 in normal gingiva (NG) and HGF fibroblasts, and investigated the effects of transforming growth factor-beta1 (TGF-beta1), interleukin-6 (IL-6) and interferon-gamma (IFN-gamma) on the expression of these genes by NG and HGF fibroblasts.

RESULTS

Our results obtained from semi-quantitative reverse transcription-polymerase chain reactions (RT-PCR), Western blots, enzyme-linked immunosorbent assays (ELISA), and enzymographies clearly demonstrated that the expression and production of type I collagen and Hsp47 were significantly higher in fibroblasts from HGF than from NG, whereas MMP-1 and MMP-2 expression and production were lower in fibroblasts from HGF patients. Addition of TGF-beta1 and IL-6, which are produced in greater amounts by HGF fibroblasts, promoted an increase in type I collagen and Hsp47 and a decrease in MMP-1 and MMP-2 expression. IFN-gamma reduced both type I collagen and Hsp47 expression, whereas it had a slight effect on the expression of MMP-1 and MMP-2.

CONCLUSION

These patterns of expression and production suggest that enhanced TGF-beta1 and IL-6 production simultaneously increase the synthesis and reduce the proteolytic activities of fibroblasts from patients with HGF, which may favor the accumulation of extracellular matrix observed in patients with this condition.

Induction of heat shock protein 47 synthesis by TGF-beta and IL-1 beta via enhancement of the heat shock element binding activity of heat shock transcription factor 1

With most immunological reactions, tissue fibrosis, collagen overproduction caused by immune cytokines, is inevitably associated. Among the various immune cytokines, heat shock protein 47 (HSP47) is a procollagen-specific molecular chaperon and is essential for secretion of procollagen from cells. Induction of HSP47 by TGF-beta has been previously reported in rat skeletal myoblasts and mouse osteoblasts, but not in human diploid fibroblasts. As for IL-1beta, its effect on HSP47 has not been elucidated. In the present study, using human embryonic lung fibroblast cells, we first disclosed that both TGF-beta and IL-1beta induced HSP47 synthesis. We then revealed that the binding of the heat shock element (HSE) by heat shock transcription factor 1 (HSF1) was enhanced by both cytokines. We further demonstrated that trimer formation of HSF1, which is essential for its binding to HSE, was induced by these cytokines. The enhancement of HSP47 synthesis and their trimer formation of HSF1 were augmented by using a combination of both cytokines. Collectively, TGF- beta and IL-1beta were found to induce trimer formation of HSF1 which in turn bound to HSE of HSP47, resulting in the enhancement of HSP47 expression. Thus, HSP47 could well be a good candidate for molecular targeting in controlling tissue fibrosis, given that both principal fibrinogenetic cytokines (TGF-beta, IL-1beta) are commonly involved in its induction through HSF1 trimerization.

Evidence for a direct interaction between the tumor suppressor serpin, maspin, and types I and III collagen

Maspin (mammary serine protease inhibitor) was originally identified as a tumor suppressor protein in human breast epithelial cells and is a member of the serine proteases inhibitor (serpin) superfamily. It inhibits tumor cell motility and angiogenesis, and although predominantly cytoplasmic, it is also localized to the cell surface. In this study we have investigated the use of the yeast two-hybrid interaction trap to identify novel maspin targets. A target human fibroblast cDNA library was screened, and the alpha-2 chain of type I collagen was identified as a potential interactant. Binding studies with isolated proteins showed interaction between recombinant maspin and types I and III collagen but not other collagen subtypes, a profile strikingly similar to mouse pigment epithelium-derived factor (caspin), which is similarly down-regulated in murine adenocarcinoma tumors and is a potent inhibitor of angiogenesis. Kinetic analysis using an IAsys resonant mirror biosensor determined the dissociation constant of maspin for collagen type I to be 0.63 microm. Further two-hybrid interactions with maspin truncation constructs suggest that collagen binding is localized to amino acids 84-112 of maspin, which aligns with the collagen-binding region of colligin. A direct interaction between exogenous or cell surface maspin and extracellular matrix collagen may contribute to a cell adhesion role in the prevention of tumor cell migration and angiogenesis.

hsp47 and hsp70 gene expression is differentially regulated in a stress- and tissue-specific manner in zebrafish embryos

We have examined differences in the spatial and temporal regulation of stress-induced hsp47 and hsp70 gene expression following exposure of zebrafish embryos to heat shock or ethanol. Using Northern blot analysis, we found that levels of hsp47 and hsp70 mRNA were dramatically elevated during heat shock in 2-day-old embryos. In contrast, ethanol exposure resulted in strong upregulation of the hsp47 gene whereas hsp70 mRNA levels increased only slightly following the same treatment. Whole-mount in situ hybridization analysis revealed that hsp47 mRNA was expressed predominantly in precartilagenous cells, as well as several other connective tissue cell populations within the embryo following exposure to either stress. hsp70 mRNA displayed a very different cell-specific distribution. For example, neither stress induced hsp70 mRNA accumulation in precartilagenous cells. However, high levels of hsp70 mRNA were detectable in epithelial cells of the developing epidermis following exposure to heat shock, but not to ethanol. These cells did not express the hsp47 gene following exposure to either of these stresses. The results suggest the presence of different inducible regulatory mechanisms for these genes which operate in a cell- and stress-specific manner in zebrafish embryos.

Greater than normal expression of the collagen-binding stress protein heat-shock protein-47 in the infarct zone in rats after experimentally-induced myocardial infarction

BACKGROUND

The heat-shock protein with relative molecular mass 47,000 (HSP47) can bind to procollagen molecules in the endoplasmic reticulum, and acts as a molecular chaperone during the processing and secretion of procollagen.

OBJECTIVE

To test our hypothesis that HSP47 is expressed in the myocardial infarct zone.

METHODS

We induced myocardial infarction in male Sprague-Dawley rats by ligation of left coronary artery. The expression of HSP47 was examined by Northern blotting, in-situ hybridization, Western blotting and immunohistochemistry. The time-dependent change in the distribution of HSP47 messenger RNA (mRNA) signal was compared with the changes in expression of alpha 1(I) and alpha 1(III) collagen mRNA by in-situ hybridization. The hypoxic induction of HSP47 in cultured cardiac fibroblasts was examined by Northern-blot analysis.

RESULTS

Northern blotting demonstrated that the expression of HSP47 mRNA had increased on day 2, reaching a maximum level around day 14 (induced 3.5-fold compared with the preligation hearts) and was maintained at a high level up to day 28. In-situ hybridization analysis revealed HSP47 mRNA signals in spindle-shaped mesenchymal cells located between surviving myocytes in the infarct's peripheral zone 24 h after the ligation, and in the entire infarct zone on day 14. The sequential changes in distribution of HSP47 mRNA signal were identical to those of the alpha 1(I) and alpha 1(III) collagen mRNA. Western blotting demonstrated that expression of HSP47 protein in the infarct zone had increased. Immunofluorescent staining revealed positivity for HSP47 in the infarct's peripheral zone on day 2 and in the entire infarct zone on day 14. Northern blotting revealed that the expression of HSP47 mRNA in cultured cardiac fibroblasts in hypoxic cultures was greater than that in normoxic cultures.

CONCLUSION

The present data demonstrated that an increase in expression of HSP47 is produced by spindle-shaped mesenchymal cells in the infarct zone. Expression of HSP47 mRNA was concurrent with the expression of collagen mRNA of types I and III. Hypoxia is one of the factors which induces expression of HSP47.

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.

Effect of HSP47 on prolyl 4-hydroxylation of collagen model peptides

Prolyl 4-hydroxylation, the most important post-translational modification in collagen biosynthesis, is catalyzed by prolyl 4-hydroxylase, an endoplasmic reticulum-resident enzyme. HSP47 is a collagen-binding stress protein which also resides in the endoplasmic reticulum (Nagata, K. and Yamada, K.M. (1986) J. Biol. Chem., 261, 7531-7536). Both prolyl 4-hydroxylase and HSP47 interact with procollagen alpha-chains during their folding and/or modification in the endoplasmic reticulum. Recent study has revealed that a simple collagen model peptide, (Pro-Pro-Gly)n, is recognized by HSP47 as well as by prolyl 4-hydroxylase in vitro (Koide et al., manuscript submitted). In the present study, we investigated the effect of HSP47 on the prolyl 4-hydroxylation of such collagen model peptides. To monitor the enzymatic hydroxylation of the peptides, we developed a non-RI assay system based on reversed-phase HPLC. When HSP47 was added to the reaction mixture, substrate and less-hydroxylated materials accumulated. This effect depended on the peptide-binding activity of HSP47, because a mutant HSP47 without collagen-binding activity did not show any inhibitory effect on prolyl 4-hydroxylation. Kinetic analysis and other biochemical analyses suggest that HSP47 retards the enzymatic reaction competing for the substrate peptide.

Increased expression of heat-shock protein 47 is associated with overproduction of type I procollagen in systemic sclerosis skin fibroblasts

Heat-shock protein 47 (HSP47) is a collagen-binding stress protein that is thought to act as a collagen-specific molecular chaperon during the biosynthesis and secretion of procollagen. In this study we examined the expression of HSP47 mRNA and protein in systemic sclerosis (SSc) skin fibroblasts. HSP47 mRNA and protein levels were significantly higher in fibroblast cultures from SSc patient-involved skin samples than in fibroblasts from normal skin from healthy individuals, as assessed by northern blot and immunoblot analyses, respectively. SSc cultured fibroblasts with increased levels of HSP47 mRNA and protein showed high expression of type I procollagen. By in situ hybridization, SSc skin had a higher number of fibroblasts with high HSP47 and procollagen alpha1(I) mRNA levels than normal skin, and the distribution of HSP47 mRNA was similar to that of procollagen alpha1(I) mRNA. We also investigated the effects of cytokines on the expression of HSP47 in normal cultured fibroblasts. Transforming growth factor-beta1 and interleukin-4 increased HSP47 mRNA and protein levels, whereas interferon-gamma reduced HSP47 expression. The same pattern of cytokine-regulated expression was observed for type I procollagen levels. These results indicate that HSP47 expression is closely associated with that of type I procollagen in skin fibroblasts, and that increased expression of HSP47 may be involved in the abundant production of type I procollagen by SSc fibroblasts.

Alteration of myogenic regulatory components in a rat myoblast GLUT 3(-) mutant

Myogenesis is a complex process characterized by both biochemical and morphological differentiation. Recent transfection studies suggested a close relationship between the GLUT 3 transporter and the myogenic ability of rat skeletal L6 myoblast. In this study, the myogenic properties of GLUT 3- mutants were examined. Studies using three different GLUT 3- mutants (D2, D9 and D23) revealed that these mutants were defective not only in the GLUT 3 transporter, but also in the expression of myogenesis-associated genes. The properties of mutant D23 were further characterized. Overexpression of an exogenous functional GLUT 3 transporter was unable to restore the myogenic defects of this mutant. This mutant was subsequently found to be altered in components acting on at least two different sites of the L6 myogenic pathway. Transfection studies revealed that mutant D23 was deficient in component(s) essential for the myogenin promoter activity. The second component was required for the transcription of muscle-specific protein genes, as overexpression of myogenin was unable to rescue the inability of this mutant to express muscle-specific genes and to form myotubes. Mutant D23 was therefore thought to be deficient in a regulatory component which controlled the expression of GLUT 3, myogenin and muscle-specific genes.

Up-regulation of HSP47 in the mouse kidneys with unilateral ureteral obstruction

BACKGROUND

Unilateral ureteral obstruction (UUO) is a well established experimental model of renal injury leading to interstitial fibrosis. The molecular and cellular mechanism(s) of interstitial fibrosis in UUO are beginning to be elucidated. In the progression of interstitial fibrosis in UUO, up-regulation of collagen synthesis is commonly observed. HSP47 is a collagen-binding stress protein and is thought to be a collagen-specific molecular chaperone, which plays a pivotal role during the biosynthesis and secretion of collagen molecules in the endoplasmic reticulum. The synthesis of HSP47 has been demonstrated to always parallel that of collagen in physiological and pathophysiological conditions. It is well recognized that renin-angiotensin system (RAS) is enhanced in the setting of UUO and that enhanced RAS has been implicated in the pathogenesis of interstitial fibrosis in the obstructed kidneys.

METHODS

To investigate the role of HSP47 in the progression of interstitial fibrosis in mouse UUO, the expression of HSP47 was examined by Northern blotting, immunohistochemistry and in situ hybridization in the obstructed kidneys. To test the possible involvement of enhanced RAS on the HSP47 expression, we examined the effects of lisinopril, an angiotensin converting enzyme inhibitor, on interstitial fibrosis. HSP47 and type I collagen mRNA expression.

RESULTS

By Northern blot analysis, HSP47 mRNA was significantly up-regulated at 12 hours (about twice that of sham operated kidneys) after the onset of ureteral obstruction, further increased and stayed at the increased level until seven days (about 8 times that of sham operated kidneys). HSP47 mRNA and protein expression were observed in the periglomerular and peritubular interstitial regions of the obstructed kidneys. Distribution of smooth muscle alpha actin and type I collagen immunoreactivity were similar to the HSP47 distribution pattern, suggesting that HSP47 was up-regulated in the myofibroblasts. Lisinopril ameliorated the expansion of cortical interstitium in the obstructed kidneys at four and seven days after ureteral obstruction. HSP47 mRNA expression was suppressed at four and seven days, whereas type I collagen mRNA was suppressed only at seven days after the onset of ureteral obstruction.

CONCLUSIONS

These results demonstrate the early and persistent up-regulation of HSP47 during the progression of interstitial fibrosis in mouse UUO kidneys, and further suggest the potential role of HSP47 in the pathogenesis of interstitial fibrosis in the obstructed kidneys. Partial suppression of HSP47 mRNA expression by lisinopril at day 4 and day 7 after ureteral obstruction suggests that there are other immediate trigger(s) that induce the HSP47 mRNA expression. Identification of the molecular mechanism of HSP47 induction during UUO may give an insight into the novel aspects of the molecular pathophysiology of interstitial fibrosis in obstructive nephropathy.

Transcriptional activation of the mouse HSP47 gene in mouse osteoblast MC3T3-E1 cells by TGF-beta 1

HSP47 is a 47-kDa collagen-binding heat shock protein, the expression of which is always correlated with that of collagens in various cell lines. We examined the effects of TGF-beta 1, which is reported to induce the collagen genes, on the expression of HSP47 in mouse osteoblast MC3T3-E1 cells. Treatment of the cells with 5 ng/ml TGF-beta 1 for 24 h increased the level of HSP47 mRNA three-fold. Dose-dependent induction by TGF-beta 1 was observed for both HSP47 mRNA and collagen alpha 1 (I) mRNA, and actinomycin D inhibited this increase of HSP47 mRNA. To elucidate the TGF-beta 1 responsive element(s) in the mouse HSP47 gene, we generated a series of 5'-deletion promoters fused to luciferase reporter constructs. Transient transfection assays showed that TGF-beta 1 induced 4-6 fold the promoter activity of a region approximately -5.5 kbp upstream of the HSP47 gene. Two upstream regions, -3.9 to -2.7 kbp and -280 to -50 bp were shown to be involved in the activation in response to TGF-beta 1 treatment.

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.

Identification of tropoelastin as a ligand for the 65-kD FK506-binding protein, FKBP65, in the secretory pathway

The folding and trafficking of tropoelastin is thought to be mediated by intracellular chaperones, although the identity and role of any tropoelastin chaperone remain to be determined. To identify proteins that are associated with tropoelastin intracellularly, bifunctional chemical cross-linkers were used to covalently stabilize interactions between tropoelastin and associated proteins in the secretory pathway in intact fetal bovine auricular chondrocytes. Immunoprecipitation of tropoelastin from cell lysates after cross-linking and analysis by SDS-PAGE showed the presence of two proteins of approximately 74 kD (p74) and 78 kD (p78) that coimmunoprecipitated with tropoelastin. Microsequencing of peptide fragments from a cyanogen bromide digest of p78 identified this protein as BiP and sequence analysis identified p74 as the peptidyl-prolyl cis-trans isomerase, FKPB65. The appearance of BiP and FKBP65 in the immunoprecipitations could be enhanced by the addition of brefeldin A (BFA) and N-acetyl-leu-leu-norleucinal (ALLN) to the culture medium for the final 4 h of labeling. Tropoelastin accumulates in the fused ER/Golgi compartment in the presence of BFA if its degradation is inhibited by ALLN (Davis, E.C., and R.P. Mecham. 1996. J. Biol. Chem. 271:3787-3794). The use of BFA and other secretion-disrupting agents suggests that the association of tropoelastin with FKBP65 occurs in the ER. Results from this study provide the first identification of a ligand for an FKBP in the secretory pathway and suggest that the prolyl cis-trans isomerase activity of FKBP65 may be important for the proper folding of the proline-rich tropoelastin molecule before secretion.

Cellular localization of gp46 at the human fetal-maternal interface

gp46 is a collagen-binding heat-shock glycoprotein with a possible role in the biosynthesis of collagen as well as in cell differentiation and fusion. In this study, the relative levels of gp46 protein and its mRNA transcript were examined, as well as the mRNA levels of collagen types I and IV in first trimester and term human placental tissues. Western blot analysis revealed substantially higher levels of gp46 in first trimester placentae than in term placentae. Similarly, elevated levels of type IV collagen transcript were detected in first trimester relative to term issues. Interestingly, the levels of gp46 and type I collagen mRNA remained unchanged. Immunohistochemical analysis of first trimester tissues demonstrated intense gp46 staining in mononucleated villous and extravillous cytotrophoblasts, decidual cells and in the villous connective tissue stroma. Syncytiotrophoblast in the same tissues also exhibited gp46 staining but at a reduced intensity. In chronic villi of term placentae, faint gp46 staining was only observed in the syncytiotrophoblast layer. However, as in the first trimester placentae, intense labelling was evident in the extravillous cytotrophoblasts and decidual cells of these tissues. These results suggest a developmental regulation of gp46 expression at the fetal-maternal interface during pregnancy and suggest a possible functional link between gp46 and collagen type IV. during gestation.

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.

Expression of genes encoding the collagen-binding heat shock protein (Hsp47) and type II collagen in developing zebrafish embryos

Hsp47 is a heat-shock protein which interacts with newly synthesize procollagen chains in the endoplasmic reticulum (ER) of collagen-secreting cells and is thought to assist in procollagen triple helix assembly and subsequent transport to the cis-Golgi. This is supported by studies which have reported that genes encoding collagen and Hsp47 are subject to co-ordinate increases and decreases in expression in cultured cells. However, limited information is available regarding hsp47 expression in vivo, particularly during early embryonic development when a variety of collagen genes are expressed. Here we show that the zebrafish hsp47 gene is expressed in a dynamic spatiotemporal pattern in developing embryos. Strong expression of hsp47 mRNA is co-incident predominantly with expression of the type II collagen gene (col2a1) in a number of chondrogenic and non-chondrogenic tissues including the notochord, otic vesicle and developing fins. Notochordal expression of both genes is disrupted in floating head (flh) and no tail (ntl) embryos, which lack properly differentiated notochords. Surprisingly, no hsp47 mRNA is detectable in the strongly col2a1-expressing cells of the floor plate and hypochord, indicating that the two genes are not strictly co-regulated. Finally, Northern blot analysis revealed two alternative transcripts of col2a1 which are expressed in distinct temporal patterns. Appearance of the larger transcript occurs following somitogenesis, a time which coincides with the co-activation of hsp47 and col2a1 gene expression in tissues outside of the notochord.

Tissue distribution and immunohistochemical localization of the collagen-binding heat-shock protein gp46 in neonatal rats

Collagen-binding heat-shock proteins of M(r) 46-47 kDa have been postulated to function as putative molecular chaperones in the biosynthesis of collagen in several species. The rat homologue of this family of heat-shock proteins is called gp46. In the present study, we employed Western blotting and immunohistochemical methods to determine the tissue distribution and cellular localization of gp46 in the thoracic aorta, heart, kidney, liver and lung of eight-day-old Wistar rats. Highest levels of gp46 were detected in the thoracic aorta and lung, followed by the kidney and heart. Gp46 levels were low to undetectable by Western blot analysis in the liver. Immunohistochemistry revealed that gp46 labelling was observed almost exclusively in three distinct cell types: fibroblasts, muscle cells, and some epithelial cells. Gp46 was detected in the fibroblasts of the hepatic triad, in the interstitium of the alveolar wall and in the tunica adventitia of blood vessels in the majority of tissues examined, in atrial and ventricular cardiomyocytes, in vascular smooth muscle cells of the abluminal portion of the tunica media, in parietal epithelial cells and mesangial cells of the glomerulus, in epithelial cells of the distal tubules and collecting ducts in the kidney and clusters of immature renal tubules, in epithelial cells of the bile duct, and in mesodermal cells surrounding the liver. These results demonstrate that gp46 is present in collagen producing cells and cells undergoing rapid growth and development, suggesting that gp46 may play a significant role in these processes.

Hsp47: a collagen-specific molecular chaperone

Hsp47 is a novel stress protein in the endoplasmic reticulum that binds specifically to various types of collagens and procollagens. Hsp47 transiently associates with procollagen and is involved in collagen processing and/or secretion under normal conditions. Under conditions of stress, Hsp47 is part of the quality control system for procollagen, including the prevention of the secretion of procollagen with abnormal conformation. In addition to its role as a molecular chaperone, Hsp47 synthesis always parallels that of collagen in developing tissues and various cell lines, and in collagen-related pathological conditions such as fibrosis.

Intracellular interaction of collagen-specific stress protein HSP47 with newly synthesized procollagen

Heat shock protein 47 (HSP47), a collagen-specific stress protein, has been postulated to be a collagen-specific molecular chaperone localized in the ER. We previously demonstrated that HSP47 transiently associated with newly synthesized procollagen in the ER (Nakai, A., M. Satoh, K. Hirayoshi, and K. Nagata. 1992. J. Cell Biol. 117:903-914). In the present work, we examined the location where HSP47 binds to and dissociates from newly synthesized procollagen within the cells, and whether HSP47 associates with nascent single procollagen polypeptide chains and/or with mature triple-helix procollagen. This was accomplished by biochemical coprecipitation with anti-HSP47 and anticollagen antibodies, combined with pulse-label and chase experiments in the presence or absence of various inhibitors for protein secretion, as well as by confocal laser microscopic observation of the cells double stained with both antibodies. We further examined whether the RDEL (Arg-Asp-Glu-Leu) sequence at the COOH terminus of HSP47 can act as an ER-retention signal, as the KDEL sequence does. When the secretion of procollagen was inhibited by the presence of alpha, alpha'-dipyridyl, an iron chelator that inhibits procollagen triple-helix formation, or by the presence of brefeldin A. which inhibits protein transport between the ER and the Golgi apparatus, procollagen was found to be bound to HSP47 during the chase period in the intermediate compartment. In contrast, the dissociation of procollagen chains from HSP47 was not inhibited when procollagen secretion was inhibited by monensin or bafilomycin A1, both of which are known to be inhibitors of post-cis-Golgi transport. These findings suggest that HSP47 and procollagen dissociated between the post-ER and the cis-Golgi compartments. HSP47 was shown to bind to nascent, single-polypeptide chains of newly synthesized procollagen, as well as to the mature triple-helix form of procollagen. HSP47 with the RDEL sequence deleted was secreted out of the cells, which suggests that the RDEL sequence actually acts as an ER-retention signal, as the KDEL sequence does. This secreted HSP47 did not acquire endoglycosidase H resistance. The biological significance of the interaction between HSP47 and procollagen in the central secretory pathway, as well as possible mechanisms for this pathway, will be discussed.

Cloning and characterization of a cDNA encoding the collagen-binding stress protein hsp47 in zebrafish

Hsp47 is a major stress-inducible protein that is localized to the endoplasmic reticulum of avian and mammalian cells and is thought to act as a molecular chaperone specific for the processing of procollagen. Although hsp47 is coordinately expressed together with several collagen types, and vertebrate embryos are known to express collagen genes in complex spatial and temporal patterns, limited information is available regarding the function or regulation of hsp47 during early embryonic development. We have initiated an examination of hsp47 in the zebrafish, Danio rerio, which offers a number of features that make it attractive as a model developmental system with which to examine the expression and function of hsp47. A polymerase chain reaction (PCR)-based cloning strategy was used to isolate a hsp47 cDNA from an embryonic zebrafish cDNA library. The deduced translation product of the cDNA is a 404-amino-acid polypeptide that is 72% identical to chicken, 64% identical to mouse and rat, and 69% identical to human hsp47. The protein contains a typical hydrophobic signal sequence, an RDEL endoplasmic reticulum retention signal, and a serine protease inhibitor signature sequence, all of which are characteristic of hsp47 in higher vertebrates. Thus, it is likely that hsp47 in zebrafish is also localized to the endoplasmic reticulum and may play a similar role to its counterpart in higher vertebrates. Northern blot analysis revealed that the hsp47 gene is expressed at relatively low levels in embryos during normal development but is strongly induced following exposure to heat shock at the gastrula, midsomitogenesis, 2-day, and 3-day larval stages. The level of induction was much higher than has previously been reported in chicken and mouse cells.

Developmental expression of the collagen-binding heat-shock protein GP46 and collagen types I and IV in rat tissues

The temporal expression of protein and mRNA encoding the collagen-binding heat-shock glycoprotein, gp46, were determined in the heart, kidney, and lung during early rat postnatal development. The steady-state levels of collagen types I and IV mRNA expression were also examined to determine if gp46 and these collagen types are co-regulated during ontogenesis. Western blot analysis using a monoclonal antibody to gp46 revealed that gp46 levels are developmentally regulated. In heart and kidney, gp46 levels were high on days 3 and 8, reduced significantly on day 25, and low to undetectable on day 69. Protein levels of gp46 in the lung exhibited a similar temporal pattern except on day 3, when very low levels of gp46 were detected. mRNA expression of gp46 during early postnatal development did not correlate with gp46 protein accumulation in these tissues, suggesting a complex pre- and post-translational regulatory scheme. In the heart, protein levels of gp46 correlated well with collagen type I alpha 1(I) mRNA expression but not with collagen type IV alpha 1(IV). In contrast, gp46 protein levels closely paralleled alpha 1(IV) expression in the kidney. Gp46 levels exhibited no apparent correlation with either alpha 1(I) or alpha 1(IV) levels in the lung. These results show that gp46 is developmentally regulated at both the protein and mRNA levels in a tissue specific manner. The relationship between gp46 and collagen alpha 1(I) and alpha 1(IV) chain mRNA expression also has been shown to be tissue specific.