The human growth factor-inducible immediate early gene, CYR61, maps to chromosome 1p

Fine-tuning osteoclastogenesis: An insight into the cellular and molecular regulation of osteoclastogenesis

Osteoclasts, the bone-resorbing cells, are essential for the bone remodeling process and are involved in the pathophysiology of several bone-related diseases. The extensive corpus of in vitro research and crucial mouse model studies in the 1990s demonstrated the key roles of monocyte/macrophage colony-stimulating factor, receptor activator of nuclear factor kappa B ligand (RANKL) and integrin αvβ3 in osteoclast biology. Our knowledge of the molecular mechanisms by which these variables control osteoclast differentiation and function has significantly advanced in the first decade of this century. Recent developments have revealed a number of novel insights into the fundamental mechanisms governing the differentiation and functional activity of osteoclasts; however, these mechanisms have not yet been adequately documented. Thus, in the present review, we discuss various regulatory factors including local and hormonal factors, innate as well as adaptive immune cells, noncoding RNAs (ncRNAs), etc., in the molecular regulation of the intricate and tightly regulated process of osteoclastogenesis. ncRNAs have a critical role as epigenetic controllers of osteoclast physiologic activities, including differentiation and bone resorption. The primary ncRNAs, which include micro-RNAs, circular RNAs, and long noncoding RNAs, form a complex network that affects gene transcription activities associated with osteoclast biological activity. Greater knowledge of the involvement of ncRNAs in osteoclast biological activities will contribute to the treatment and management of several skeletal diseases such as osteoporosis, osteoarthritis, rheumatoid arthritis, etc. Moreover, we further outline potential therapies targeting these regulatory pathways of osteoclastogenesis in distinct bone pathologies.

Association between CCN1 gene polymorphism and acute coronary syndrome in Chinese Han and Uygur populations

Background

CCN1 plays a crucial role in the modulation of cardiovascular diseases. However, whether CCN1 genetic variants are involved in the susceptibility of ACS remains unknown. Hence, the present study investigates the association between CCN1 polymorphisms and ACS among Han and Uygur populations in Xinjiang, China.

Results

In this case-control study, 1234 Han (547 ACS patients and 687 controls) and 932 Uygur (471 ACS patients and 461 controls) were genotyped using SNPscan^TM for three single-nucleotide polymorphisms (SNPs, rs6576776, rs954353, and rs3753794) of the human CCN1 gene. In the Uygur population, we found that the detected frequencies of the C allele (25.3% vs. 18.3%, P<0.001) and CC genotype (6.4% vs. 3.0%, P=0.001) of rs6576776 were significantly higher in the ACS patients than in the control participants. Differences in rs6576776 regarding the dominant model (CC+CG vs. GG, 44.2% vs. 55.8%, P=0.001) and the recessive model (CC vs. CG+GG, 6.4% vs. 93.6%, P=0.016) were observed between the two groups. The frequencies of the GGC and AGC haplotypes in those with ACS were significantly higher than those in the control group (all P<0.05) in the Uygur population. After adjusting for hypertension, diabetes, lipids and smoking, all of which indicate that the rs6576776 C allele is associated with higher risk of ACS (odds ratio (OR)=1.798, 95% confidence interval (CI), 1.218-2.656, P=0.003). In Han population, neither the distribution of genotypes and alleles of the CCN1 gene three SNPs nor the distribution of haplotypes constructed with the three SNPs exhibited a significant difference between the ACS patients and control participants.

Conclusions

Our study document that the CCN1 gene rs6576776 C allele is associated with higher susceptibility of ACS and that the frequencies of GGC and AGC haplotypes are higher among the Uygur ACS patients.

Cyr61 Promotes Inflammation of a Gouty Arthritis Model in Rats

Background

Cyr61 is considered a novel proinflammatory factor. Gouty arthritis (GA) is a self-limited inflammatory reaction caused by monosodium urate (MSU) crystals. In this study, we assessed the role of Cyr61 in the inflammatory process of GA.

Methods

We investigated the expression of Cyr61 in MSU-induced rat gout models and MSU-stimulated rat fibroblast-like synovial (FLS) cells. After inhibiting the expression of Cyr61, levels of IL-1β, TNF-α, and IL-6 were detected by ELISA, qPCR, western blot, and immunohistochemical methods. We probed the downstream NF-κB signaling pathway using the NF-κB inhibitor PDTC, and levels of NF-κB and p-NF-κB were detected by western blot and qPCR.

Results

Our results demonstrate that Cyr61 plays a potent role in the formation of local inflammation in vitro and in vivo. Cyr61 was highly expressed in synovial tissues of gout models, and the expression of Cyr61 protein was also significantly increased in MSU-stimulated FLS cells. Cyr61 promoted MSU-induced acute inflammation via the NF-κB signaling pathway.

Conclusions

Our study has revealed that Cyr61 is an important regulatory factor for the initiation of inflammation in GA. The high expression of Cyr61 protein can induce synovial cells to produce many inflammatory cytokines, such as IL-1β, TNF-α, and IL-6, partly in an NF-κB-dependent manner. Thus, inhibition of Cyr61 could be a new target and strategy for the prevention and treatment of GA.

Pancreatic neuroendocrine tumors: Therapeutic challenges and research limitations

Pancreatic neuroendocrine tumors (PNETs) are known to be the second most common epithelial malignancy of the pancreas. PNETs can be listed among the slowest growing as well as the fastest growing human cancers. The prevalence of PNETs is deceptively low; however, its incidence has significantly increased over the past decades. According to the American Cancer Society’s estimate, about 4032 (> 7% of all pancreatic malignancies) individuals will be diagnosed with PNETs in 2020. PNETs often cause severe morbidity due to excessive secretion of hormones (such as serotonin) and/or overall tumor mass. Patients can live for many years (except for those patients with poorly differentiated G3 neuroendocrine tumors); thus, the prevalence of the tumors that is the number of patients actually dealing with the disease at any given time is fairly high because the survival is much longer than pancreatic ductal adenocarcinoma. Due to significant heterogeneity, the management of PNETs is very complex and remains an unmet clinical challenge. In terms of research studies, modest improvements have been made over the past decades in the identification of potential oncogenic drivers in order to enhance the quality of life and increase survival for this growing population of patients. Unfortunately, the majority of systematic therapies approved for the management of advanced stage PNETs lack objective response or at most result in modest benefits in survival. In this review, we aim to discuss the broad challenges associated with the management and the study of PNETs.

Transplantation of human endometrial perivascular cells with elevated CYR61 expression induces angiogenesis and promotes repair of a full-thickness uterine injury in rat

Background

Disruptions of angiogenesis can have a significant effect on the healing of uterine scars. Human endometrial perivascular cells (CD146+PDGFRβ+) function as stem cells in the endometrium. Cysteine-rich angiogenic inducer 61 (CYR61) plays an important role in vascular development. The purpose of this study was to observe the effects of the transplantation of human endometrial perivascular cells (En-PSCs) overexpressing CYR61 on structural and functional regeneration in rat models of partial full-thickness uterine excision.

Methods

We first sorted human En-PSCs from endometrial single-cell suspensions by flow cytometry. Human En-PSCs expressing low or high levels of CYR61 were then generated via transfection with a CYR61-specific small interfering ribonucleic acid (si-CYR61) construct or overexpression plasmid. To establish a rat model of uterine injury, a subset of uterine wall was then resected from each uterine horn in experimental animals. Female rats were randomly assigned to five groups, including a sham-operated group and four repair groups that received either PBS loaded on a collagen scaffold (collagen/PBS), En-PSCs loaded on a collagen scaffold (collagen/En-PSCs), En-PSCs with low CYR61 expression loaded on a collagen scaffold (collagen/si-CYR61 En-PSCs), and En-PSCs overexpressing CYR61 loaded on a collagen scaffold (collagen/ov-CYR61 En-PSCs). These indicated constructs were sutured in the injured uterine area to replace the excised segment. On days 30 and 90 after transplantation, a subset of rats in each group was sacrificed, and uterine tissue was recovered and serially sectioned. Hematoxylin and eosin staining and immunohistochemical staining were then performed. Finally, the remaining rats of each group were mated with fertile male rats on day 90 for a 2-week period.

Results

Sorted En-PSCs expressed all recognized markers of mesenchymal stem cells (MSCs), including CD10, CD13, CD44, CD73, CD90, and CD105, and exhibited differentiation potential toward adipocytes, osteoblasts, and neuron-like cells. Compared with En-PSCs and En-PSCs with low CYR61 expression, En-PSCs with elevated CYR61 expression enhanced angiogenesis by in vitro co-culture assays. At day 90 after transplantation, blood vessel density in the collagen/ov-CYR61 En-PSCs group (11.667 ± 1.287) was greater than that in the collagen/En-PSCs group (7.167 ± 0.672) (P < 0.05) and the collagen/si-CYR61 En-PSCs group (3.750 ± 0.906) (P < 0.0001). Pregnancy rates differed among groups, from 40% in the collagen/PBS group to 80% in the collagen/En-PSCs group, 12.5% in the collagen/si-CYR61 En-PSCs group, and 80% in the collagen/ov-CYR61 En-PSCs group. In addition, four embryos were evident in the injured uterine horns of the collagen/ov-CYR61 En-PSCs group, while no embryos were identified in the injured uterine horns of the collagen/PBS group.

Conclusions

The results showed that CYR61 plays an important role in angiogenesis. Collagen/ov-CYR61 En-PSCs promoted endometrial and myometrial regeneration and induced neovascular regeneration in injured rat uteri. The pregnancy rate of rats treated with transplantation of collagen/En-PSCs or collagen/ov-CYR61 En-PSCs was improved. Moreover, the number of embryos implantation on the injured area in uterus was increased after transplantation of collagen/ov-CYR61 En-PSCs.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1272-3) contains supplementary material, which is available to authorized users.

IL-1β-induced miR-34a up-regulation inhibits Cyr61 to modulate osteoarthritis chondrocyte proliferation through ADAMTS-4

Osteoarthritis (OA) is the most prevalent degenerative joint disease with multifactorial etiology caused by risk factors. The degradation of aggrecan by upregulated ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) is the key event in the development of OA. ADAMTS-4 contributes to aggrecan degradation in human OA. Cysteine-rich angiogenic inducer 61 (Cyr61), which is associated with diseases related to chronic inflammation, is found in articular cartilage from patients with osteoarthritis and appears to suppress ADAMTS-4 activity, possibly leading to chondrocyte cloning. Herein, we first revealed that Cyr61 and ADAMTS-4 protein levels were remarkably increased in OA cartilage tissues and OA chondrocytes, and verified Cyr61 regulation of ADAMTS-4 in normal and OA chondrocyte. Further, we revealed that Cyr61 could promote OA chondrocyte proliferation through inhibiting ADAMTS-4. Overproduction of inflammatory cytokines plays a vital role in the pathological development of OA; herein, we demonstrated that IL-1β inhibited Cyr61, while promoted ADAMTS-4 expression. By using online tools and luciferase assays, we confirmed that miR-34a, a regulatory miRNA of chondrocyte proliferation, could directly bind to the 3'-UTR of Cyr61 to inhibit its expression; further, IL-1β regulated Cyr61 and ADAMTS-4 expression through miR-34a. In OA cartilage tissues, miR-34a, and IL-1β mRNA expression was up-regulated and positively correlated; miR-34a and Cyr61 mRNA was positively correlated, further indicating that suppressing miR-34a expression might rescue IL-1β-induced Cyr61 suppression, and promote OA chondrocyte proliferation. Taken together, we provided novel experimental basis for rescuing OA chondrocyte proliferation through miR-34a/Cyr61 axis.

Biological functions and role of CCN1/Cyr61 in embryogenesis and tumorigenesis in the female reproductive system (Review)

Cysteine-rich angiogenic inducer 61 (CCN1/Cyr61) is a prompt response transcription product activated by growth factors. As a member of the CCN family, it mediates cell survival, proliferation, differentiation, migration, adhesion and synthesis of the extracellular matrix by binding directly to the integrins and heparin sulfate proteoglycans or activating multiple signaling transduction pathways. It has previously been demonstrated that CCN1/Cyr61 exhibits an important role in the female reproductive system during embryogenesis and tumorigenesis. However, the functions of CCN1/Cyr61 in the female reproductive system have not been systematically investigated, therefore, the primary aim of the present review is to introduce the role and function of CCN1/Cyr61 in the female reproductive system. The current review presents the molecular structure and biological function of CCN1/Cyr61 and provides detailed data on its expression pattern and contribution to the female reproductive system, including the role in embryogenesis and tumorigenesis.

Role of CCN5 (WNT1 inducible signaling pathway protein 2) in pancreatic islets

In search of direct targets of insulin-like growth factor (IGF)-1 action, we discovered CCN5 (WNT1 inducible signaling pathway protein 2 [WISP2]) as a novel protein expressed in pancreatic β-cells. As a member of the "CCN" ( C ysteine-rich angiogenic inducer 61 [Cyr61], C onnective tissue growth factor [CTGF in humans], and N ephroblastoma overexpressed [Nov; in chickens]) family, the expression of CCN5/WISP2 is stimulated by IGF-1 together with Wnt signaling. When overexpressed in insulinoma cells, CCN5 promotes cell proliferation and cell survival against streptozotocin-induced cell death. The cell proliferation effect seems to be caused by AKT phosphorylation and increased cyclin D1 levels. These properties resemble those of CCN2/CTGF, another isoform of the CCN family, although CCN5 is the only one within the family of six proteins that lacks the C-terminal repeat. Treatment of primary mouse islets with recombinant CCN5 protein produced similar effects to those of gene transfection, indicating that either as a matricellular protein or a secreted growth factor, CCN5 stimulates β-cell proliferation and regeneration in a paracrine fashion. This review also discusses the regulation of CCN5/WISP2 by estrogen and its involvement in angiogenesis and tumorigenesis.

The matricellular protein CYR61 interferes with normal pancreatic islets architecture and promotes pancreatic neuroendocrine tumor progression

The significance of matricellular proteins during development and cancer progression is widely recognized. However, how these proteins actively contribute to physiological development and pathological cancer progression is only partially elucidated. In this study, we investigated the role of the matricellular protein Cysteine-rich 61 (CYR61) in pancreatic islet development and carcinogenesis. Transgenic expression of CYR61 in β cells (Rip1CYR mice) caused irregular islets morphology and distorted sorting of α cells, but did not alter islets size, number or vascularization. To investigate the function of CYR61 during carcinogenesis, we crossed Rip1CYR mice with Rip1Tag2 mice, a well-established model of β cell carcinogenesis. Beta tumors in Rip1Tag2CYR mice were larger, more invasive and more vascularized compared to tumors in Rip1Tag2 mice. The effect of CYR61 on angiogenesis was fully abrogated by treating mice with the anti-VEGFR2 mAb DC101. Results from in vitro assays demonstrated that CYR61 modulated integrin α6β1-dependent invasion and adhesion without altering its expression. Taken together, these results show that CYR61 expression in pancreatic β cells interferes with normal islet architecture, promotes islet tumor growth, invasion and VEGF/VERGFR-2-dependent tumor angiogenesis. Taken together, these observations demonstrate that CYR61 acts as a tumor-promoting gene in pancreatic neuroendocrine tumors.

CYR61 suppresses growth of human malignant melanoma

Cysteine-rich protein 61 (CCN1/CYR61) is an important marker of proliferation and metastasis in malignant melanoma, making it a potential target for melanoma treatment. In this study, we compared the expression of CRY61 in Chinese patients with malignant melanoma with its expression in patients with other skin tumors or with no skin pathological conditions. We examined the effects of anti-human CYR61 monoclonal antibody on proliferation and evaluated the changes in CYR61 expression and cell proliferation in response to treatment with either epirubicin or interferon (IFN)-α. CYR61 was expressed at lower levels in patients with malignant melanoma than in patients with other skin tumors or with no pathology. Following the treatment of B16 cells with epirubicin and IFN-α, CYR61 levels increased, cell growth was inhibited, and proliferating cell nuclear antigen expression decreased. Thus, CYR61 could become a therapeutic target for malignant melanoma patients with high CYR61 expression.

Study of Cysteine-Rich Protein 61 Genetic Polymorphism in Predisposition to Fracture Nonunion: A Case Control

Background. Many factors are responsible for this impaired healing, especially in long bones, but a possible genetic predisposition for the development of this complication remains unknown till now. In the present study, we aim to examine the CYR61 gene polymorphism in fracture nonunion patients and the correlation with clinical findings. Materials and Methods. We performed SNP analysis of the CYR61 gene in 250 fracture nonunion patients and 250 healthy subjects were genotyped in this hospital-based case control study, and 56 cases were further evaluated for mRNA expression of CYR61 by real-time quantitative reverse-transcription PCR. Results. CYR61 gene TT, TG, and GG genotype frequencies of total fracture nonunion cases were 41.6%, 49.2%, and 9.20% and 54.4%, 39.2%, and 6.40% in healthy controls. Heterozygous TG genotype was found statistically significant in fracture nonunion cases compared with that in controls, whereas homozygous mutant GG genotype was not found significant. Moreover, we found that TG + GG genotypes were significantly different in serum expression of CYR61 mRNA when compared with cases (TT genotypes). Conclusions. Our result signifies that genotype of CYR61 affects the mRNA expression and acts as a risk factor that could synergistically increase the susceptibility of a patient to develop fracture nonunion.

O-Fucosylation of CCN1 is required for its secretion

The matricellular protein CCN1, also known as Cyr61, is a secreted ligand and has numerous functions. Human CCN1 contains one predicted O-fucosylation site in the thrombospondin type-1 repeat (TSR1) domain at Thr(242). In this report, we demonstrated that CCN1 is O-fucosylated at Thr(242) using mass spectrometry. Deficiency of O-fucosylation resulted in the decrement of the cell surface localization and the secretion of CCN1. Furthermore, knockdown of protein O-fucosyltransferase 2, which modifies a specific Ser/Thr residue in the TSR1 domain, decreased secreted levels of CCN1. These results demonstrated that O-fucosylation of CCN1 at Thr(242) regulates its secretion.

Eyeing the Cyr61/CTGF/NOV (CCN) group of genes in development and diseases: highlights of their structural likenesses and functional dissimilarities

“CCN” is an acronym referring to the first letter of each of the first three members of this original group of mammalian functionally and phylogenetically distinct extracellular matrix (ECM) proteins [i.e., cysteine-rich 61 (CYR61), connective tissue growth factor (CTGF), and nephroblastoma-overexpressed (NOV)]. Although “CCN” genes are unlikely to have arisen from a common ancestral gene, their encoded proteins share multimodular structures in which most cysteine residues are strictly conserved in their positions within several structural motifs. The CCN genes can be subdivided into members developmentally indispensable for embryonic viability (e.g., CCN1, 2 and 5), each assuming unique tissue-specific functions, and members not essential for embryonic development (e.g., CCN3, 4 and 6), probably due to a balance of functional redundancy and specialization during evolution. The temporo-spatial regulation of the CCN genes and the structural information contained within the sequences of their encoded proteins reflect diversity in their context and tissue-specific functions. Genetic association studies and experimental anomalies, replicated in various animal models, have shown that altered CCN gene structure or expression is associated with “injury” stimuli—whether mechanical (e.g., trauma, shear stress) or chemical (e.g., ischemia, hyperglycemia, hyperlipidemia, inflammation). Consequently, increased organ-specific susceptibility to structural damages ensues. These data underscore the critical functions of CCN proteins in the dynamics of tissue repair and regeneration and in the compensatory responses preceding organ failure. A better understanding of the regulation and mode of action of each CCN member will be useful in developing specific gain- or loss-of-function strategies for therapeutic purposes.

Potential role of Cyr61 induced degeneration of human Müller cells in diabetic retinopathy

The degeneration of Müller cells has been recognized to involve in the pathogenesis of diabetic retinopathy. However, the mechanism is not yet clear. This study is to explore the potential role of Cyr61, a secreted signaling protein in extracellular matrix, in inducing human Müller cell degeneration in diabetic retinopathy (DR). Twenty patients with proliferative diabetic retinopathy (PDR) and twelve non-diabetic patients were recruited for this study. Vitreous fluid was collected during vitrectomy surgery for Cyr61 ELISA. Human Müller cell line MIO-M1 were cultured to be subconfluent, and then treated with glucose (0–20 mM) or Cyr61 (0–300 ng/ml). Cyr61 expression induced by increasing concentrations of glucose was evaluated by RT-qPCR and Western blot. Effects of Cyr61 on Müller cells viability, migration and apoptosis were observed by MTT assay, Transwell assay, and TUNEL assay. Vitreous Cyr61 levels were observed to be 8-fold higher in patients with PDR (3576.92±1574.58 pg/mL), compared with non-diabetic controls (436.14±130.69 pg/mL). Interestingly, the active PDR group was significantly higher than the quiescent PDR group (P<0.01). In retinal Müller cells culture, high glucose significantly and dose-dependently elevated Cyr61 expression at both mRNA and protein levels. Cyr61 at high concentrations dose-dependently inhibited the viability and migration of Müller cells. TUNEL assay further revealed that high concentration of Cyr61 significantly promoted the cell apoptosis. In conclusion, these findings demonstrated for the first time that the expression of Cyr61 was elevated by high glucose in Müller cells, and Cyr61 inhibited cell viability and migration while induced apoptosis, suggesting the potential role of Cyr61 in Müller cell degeneration. The elevated Cyr61 levels in vitreous fluid of PDR patients further support its role in diabetic retinopathy (DR).

CCN1 expression in hepatocytes contributes to macrophage infiltration in nonalcoholic fatty liver disease in mice

Our objective was to investigate the potential roles of CCN1 in the inflammation and macrophage infiltration of nonalcoholic fatty liver disease (NAFLD). The regulation of hepatic CCN1 expression was investigated in vitro with murine primary hepatocytes treated with free fatty acids or lipopolysaccharide (LPS) and in vivo with high-fat (HF) diet-fed mice or ob/ob mice. CCN1 protein and a liver-specific CCN1 expression plasmid were administered to mice fed a normal diet (ND) or HF diet. Myeloid-derived macrophages and RAW264.7 cells were also treated with CCN1 in vitro to determine the chemotactic effects of CCN1 on macrophages. LPS treatment significantly increased hepatic CCN1 expression in HF diet-fed mice and ob/ob mice. LPS and FFAs induced CCN1 expression in primary murine hepatocytes in vitro through the TLR4/MyD88/AP-1 pathway. CCN1 protein and overexpression of CCN1 in the liver induced more severe hepatic inflammation and macrophage infiltrates in HF mice than in ND mice. CCN1 recruited macrophages through activation of the Mek/Erk signaling pathway in myeloid-derived macrophages and RAW264.7 cells in vitro. Endotoxin and FFA-induced CCN1 expression in hepatocytes is involved in the hepatic proinflammatory response and macrophage infiltration in murine NAFLD.

A functional polymorphism in the CYR61 (IGFBP10) gene is associated with prostate cancer risk

BACKGROUND

CYR61 (cysteine-rich protein 61, also named IGFBP10) is a secreted signaling molecule that promotes angiogenesis and tumor growth. The goal of this study is to determine whether a functional polymorphism in the promoter region of the CYR61 gene (rs3753793) is associated with prostate cancer (PCa) risk and gene expression in Chinese patients.

METHODS

A total of 665 patients diagnosed with PCa and 703 cancer-free controls were genotyped in this hospital-based case-control study, and 26 PCa tissue samples were evaluated for mRNA expression of CYR61 by real-time quantitative reverse-transcription PCR.

RESULTS

Men carrying the G allele of rs3753793 (TG+GG) had significantly lower risk of PCa when compared with the TT genotype (odds ratio (OR) = 0.76, 95% confidence interval (CI) = 0.61-0.95). The association was generally more pronounced among subgroups of PCa patients with advanced stage (OR = 0.70, 95% CI = 0.53-0.94), Gleason score >7 (OR = 0.63, 95% CI = 0.46-0.86) and PSA>20 ng ml(-1) (OR = 0.68, 95% CI = 0.53-0.88). Prostate tumors derived from cases with the GT/GG genotypes had significantly lower levels of CYR61 mRNA when compared with cases with the TT genotypes (P = 0.02).

CONCLUSIONS

Our results indicate that the genetic variation of rs3753793 in the CYR61 promoter may contribute to genetic predisposition to PCa and intra-tumor expression gene expression.

CCN1/CYR61: the very model of a modern matricellular protein

CCN1 (CYR61) is a dynamically expressed, multifunctional matricellular protein that plays essential roles in cardiovascular development during embryogenesis, and regulates inflammation, wound healing and fibrogenesis in the adult. Aberrant CCN1 expression is associated with myriad pathologies, including various cancers and diseases associated with chronic inflammation. CCN1 promotes diverse and sometimes opposing cellular responses, which can be ascribed, as least in part, to disparate activities mediated through its direct binding to distinct integrins in different cell types and contexts. Accordingly, CCN1 promotes cell proliferation, survival and angiogenesis by binding to integrin α(v)β(3), and induces apoptosis and senescence through integrin α(6)β(1) and heparan sulfate proteoglycans. The ability of CCN1 to trigger the accumulation of a robust and sustained level of reactive oxygen species underlies some of its unique activities as a matrix cell-adhesion molecule. Emerging studies suggest that CCN1 might be useful as a biomarker or therapeutic target in certain diseases.

CCN3 inhibits neointimal hyperplasia through modulation of smooth muscle cell growth and migration

OBJECTIVE

CCN3 belongs to the CCN family, which constitutes multifunctional secreted proteins that act as matrix cellular regulators. We investigated the pathophysiological roles of CCN3 in the vessels.

METHODS AND RESULTS

We examined the effects of CCN3 on the proliferation and migration of rat vascular smooth muscle cells (VSMC). CCN3 knockout mice were created, and vascular phenotypes and neointimal hyperplasia induced by photochemically induced thrombosis were investigated. CCN3 suppressed the VSMC proliferation induced by fetal bovine serum. The neutralizing antibody for transforming growth factor-beta did not affect the growth inhibitory effect of CCN3. Moreover, CCN3 enhanced the mRNA expression of cyclin-dependent kinase inhibitors, p21 and p15. Gamma secretase inhibitor, an inhibitor of Notch signaling, partially inhibited the enhanced expression of p21 induced by CCN3. CCN3 also inhibited the VSMC migration. Finally, the histopathologic evaluation of the arteries 21 days after the endothelial injury revealed a 6-fold enhancement of neointimal thickening in the null mice compared with the wild-type mice.

CONCLUSIONS

CCN3 suppresses neointimal thickening through the inhibition of VSMC migration and proliferation. Our findings indicate the involvement of CCN3 in vascular homeostasis, especially on injury, and the potential usefulness of this molecule in the modulation of atherosclerotic vascular disease.

Cyr61 is up-regulated in prostate cancer and associated with the p53 gene status

Cysteine-rich 61 (Cyr61) is a member of the CCN protein family that has been implicated in diverse biological processes such as cell adhesion, proliferation, angiogenesis, and tumorigenesis. Altered expression of Cyr61 is found to be associated with human cancers. Here we show that Cyr61 was up-regulated in prostate cancer cell lines and tumor tissues. A significant correlation of Cyr61 expression was found between benign prostatic hyperplasia and prostate cancer (P = 0.002). However, there was no significant correlation between levels of PSA and Cyr61 expression (P = 0.2). Cyr61 may represent an independent prostate cancer biomarker and potentially a useful therapeutic target for prostate cancer treatment. In addition, our analysis based on published data and data present in this report indicted that levels of Cyr61 expression associated with the status of the tumor suppressor gene p53 in 32 cancer cell lines analyzed, high levels of Cyr61 expression were found in cell lines with mutant or null p53 gene, whereas lower expression levels of Cyr61 in the cell lines with wild-type p53. We further show that over-expression of dominant negative p53 or down-expression of endogenous wild-type p53 resulted in up-regulation of Cyr61 expression, suggesting a functional link between Cyr61 and p53 in cancers.

Functions and mechanisms of action of CCN matricellular proteins

Members of the CCN (CYR61/CTGF/NOV) family have emerged as dynamically expressed, extracellular matrix-associated proteins that play critical roles in cardiovascular and skeletal development, injury repair, fibrotic diseases and cancer. The synthesis of CCN proteins is highly inducible by serum growth factors, cytokines, and environmental stresses such as hypoxia, UV exposure, and mechanical stretch. Consisting of six secreted proteins in vertebrate species, CCNs are typically comprised of four conserved cysteine-rich modular domains. They function primarily through direct binding to specific integrin receptors and heparan sulfate proteoglycans, thereby triggering signal transduction events that culminate in the regulation of cell adhesion, migration, proliferation, gene expression, differentiation, and survival. CCN proteins can also modulate the activities of several growth factors and cytokines, including TGF-beta, TNFalpha, VEGF, BMPs, and Wnt proteins, and may thereby regulate a broad array of biological processes. Recent studies have uncovered novel CCN activities unexpected for matricellular proteins, including their ability to induce apoptosis as cell adhesion substrates, to dictate the cytotoxicity of inflammatory cytokines such as TNFalpha, and to promote hematopoietic stem cell self-renewal. As potent regulators of angiogenesis and chondrogenesis, CCNs are essential for successful cardiovascular and skeletal development during embryogenesis. In the adult, the expression of CCN proteins is associated with injury repair and inflammation, and has been proposed as diagnostic or prognostic markers for diabetic nephropathy, hepatic fibrosis, systemic sclerosis, and several types of cancer. Targeting CCN signaling pathways may hold promise as a strategy of rational therapeutic design.

CYR61 polymorphisms are associated with plasma HDL-cholesterol levels in obese individuals

We have recently characterized the transcriptome of the omental adipose tissue of non-diabetic, obese men with and without the metabolic syndrome (MS). The cysteine-rich protein 61 (CYR61) is one of the most differentially expressed genes between the groups and has been selected for a detailed molecular investigation. Direct sequencing of complete CYR61 gene revealed five polymorphisms with minor allele frequency >5% in the promoter region (rs 3753794, rs 3753793 and rs 2297140), intron 1 (rs 2297141) and intron 2 (IVS 2+50). Chi-square test and logistic regression were applied to test for association between CYR61 polymorphisms and the individual MS components in a cohort of 697 obese individuals. In men and women, rs 3753794 and rs 3753793 (r2 = 0.77) were associated plasma HDL-cholesterol levels (p = 0.016 and p = 0.008). Carriers of the A allele for rs 3753794 were more likely to have high plasma HDL-cholesterol levels (1.50-fold; p = 0.016), as compared with G/G homozygotes and the A/A homozygotes for rs 3753793 were more likely to exhibit low plasma HDL-cholesterol levels (1.56-fold; p = 0.008), as compared with C/C homozygotes. Furthermore, an association between IVS 2+50 polymorphism and HDL-cholesterol was found in women and in men analyzed separately (p = 0.002 and p = 0.038, respectively). These results suggest that CYR61 is a promising candidate gene for lipoprotein/lipid perturbations.

Endometrial Expression of Cyr61

OBJECTIVE

To compare the expression of Cyr61 in normal cycling endometrium with endometrium from women with polycystic ovarian syndrome (PCOS) and endometrial hyperplasia and adenocarcinoma.

METHODS

This is a retrospective study of 59 samples of normal and abnormal endometrium. Endometrial biopsies were obtained from normal fertile controls throughout the menstrual cycle and compared with endometrium from ovulatory and anovulatory women with PCOS and complex endometrial hyperplasia and endometrioid adenocarcinoma. Cyr61 expression was evaluated by using immunohistochemistry and reverse transcription PCR for Cyr61, estrogen receptor (ER)-alpha, a marker of cell proliferation (Ki67), and another marker of early estrogen action, cFos. Regulation of Cyr61 protein was studied in a steroid-responsive endometrial carcinoma cell line, ECC1.

RESULTS

Cyr61 protein was regulated by estrogen. In normal endometrium, Cyr61 was highest in the proliferative phase and lowest in the normal midsecretory phase. In contrast, elevated levels of Cyr61, ER-alpha, Ki67, and cFos were all found in the midsecretory endometrium of ovulatory PCOS patients, endometrial cancer patients, and hyperplasia patients.

CONCLUSION

Cyr61 is overexpressed in PCOS endometrium, reflecting a heightened responsiveness to estrogen. As a unique marker of estrogen action, Cyr61 may be an early biomarker for the development of hyperplasia or adenocarcinoma in this group of women.

The matricellular protein CCN1 is essential for cardiac development

The matricellular protein CCN1 (formerly named CYR61) regulates cell adhesion, migration, proliferation, survival, and differentiation through binding to integrin receptors and heparan sulfate proteoglycans. Here we show that Ccn1-null mice are impaired in cardiac valvuloseptal morphogenesis, resulting in severe atrioventricular septal defects (AVSD). Remarkably, haploinsufficiency for Ccn1 also results in delayed formation of the ventricular septum in the embryo and persistent ostium primum atrial septal defects (ASD) in approximately 20% of adults. Mechanistically, Ccn1 is not required for epithelial-to-mesenchymal transformation or cell proliferation and differentiation in the endocardial cushion tissue. However, Ccn1 deficiency leads to precocious apoptosis in the atrial junction of the cushion tissue and impaired gelatinase activities in the muscular component of the interventricular septum at embryonic day 12.5, when fusion between the endocardial cushion tissue and the atrial and ventricular septa occurs, indicating that these defects may underlie the observed AVSD. Moreover, human CCN1 maps to 1p21-p31, the chromosomal location of an AVSD susceptibility gene. Together, these results provide evidence that deficiency in matrix signaling can lead to autosomal dominant AVSD, identify Ccn1(+/-) mice as a genetic model for ostium primum ASD, and implicate CCN1 as a candidate gene for AVSD in humans.

Elevated cysteine-rich 61 mediates aberrant collagen homeostasis in chronologically aged and photoaged human skin

Alterations of human skin connective tissue structure and function are prominent features of chronological aging and solar UV irradiation-induced premature aging (photoaging). These skin connective tissue abnormalities result, in part, from reduced synthesis and elevated degradation of type I collagen, the major structural protein in skin. Here, we report that cysteine-rich 61 (CYR61/CCN1), a novel mediator of collagen homeostasis, is predominantly expressed in human skin connective tissue and is significantly elevated in fibroblasts in chronologically aged (80+ years) and photoaged human skin in vivo. In cultured human skin fibroblasts, elevated CYR61 expression substantially reduces type I procollagen and concurrently increases matrix metalloproteinase-1 (MMP-1), which initiates fibrillar collagen degradation. Elevated CYR61 caused down-regulation of transforming growth factor-beta type II receptor mRNA and protein levels, thereby impairing the transforming growth factor-beta pathway, which reduced type I procollagen and raised MMP-1 expression. Furthermore, elevated CYR61 induced transcription factor activator protein-1 (AP-1), which functions to stimulate MMP-1 expression. Thus, elevated expression of CYR61 in human skin fibroblasts acts through multiple pathways to cause alterations of collagen homeostasis similar to those pathways observed in aged human skin in vivo. These data identify CYR61 as a pivotal regulator of collagen production and degradation in aged and photoaged human skin.

Dinucleotide repeats negatively modulate the promoter activity of Cyr61 and is unstable in hepatocellular carcinoma patients

Cyr61 is a secreted, cysteine-rich, heparin-binding protein that mediates diverse functions including extracellular matrix formation, differentiation, cell proliferation, adhesion, migration, survival, as well as angiogenesis and tumorigenesis. In this study, we found that Cyr61 gene expression is significantly downregulated in the tumors of hepatocellular carcinoma (HCC) patients. To elucidate its mechanism of gene regulation, we examined the promoter of Cyr61 which contains two long stretches of repeats, each comprising d(CA) dinucleotide repeats downstream of HNF3beta- and ATF-binding sites. We hypothesized that the d(CA) repeats may play an important role in regulating Cyr61 promoter activity and performed promoter reporter assays to examine this. We found that a greater number of d(CA) repeats resulted in significantly lower promoter activity of the Cyr61 gene in the KB3-1 and HepG2 cell lines, but not in the MCF-7 cell line. In addition, the d(CA) repeats, but not other random sequences, were found to be important for Cyr61 promoter activity. We further demonstrate that the ATF- and HNF3beta-binding sites upstream the d(CA) repeats positively and negatively modulate Cyr61 promoter activity, respectively. An examination of the d(CA) dinucleotide patterns in the Cyr61 promoter in HCC patients revealed that approximately 32% of these patients exhibited either loss of heterozygosity or somatic mosaicism in either the tumors, adjacent normal liver tissues or both.

Up-regulation of cyr61 in vascular smooth muscle cells of spontaneously hypertensive rats

In the present study, we applied a fluorescent differential display method to mRNAs from aortae of spontaneously hypertensive rats (SHRs), stroke-prone spontaneously hypertensive rats (SPSHRs), and their parental strain, Wistar Kyoto rats (WKYRs), to identify the genes involved in the development of hypertension. Through this screen we came across a gene that is consistently up-regulated in hypertensive rats. Nucleotide sequence determination of the corresponding cDNA revealed that the gene is the rat orthologue of cyr61. Northern blot analysis showed that cyr61 expression increases in SHR and SPSHR before the onset of hypertension and is sustained thereafter at higher levels than in age-matched WKYRs. In situ hybridization analysis demonstrated that cyr61 is expressed strongly in smooth muscle cells (SMCs) in media of SHR and SPSHR but not WKYR aorta. Fluorescent in situ hybridization mapped the cyr61 gene to rat chromosome 1p12-13, which is located in close proximity to a recently defined quantitative trait locus including NHE3 Na(+)/H(+) exchanger. Overexpression of the cyr61 gene in stably transfected rat SMC line A7r5 caused rather inhibitory effects on the proliferation and DNA and protein synthesis. Our results thus demonstrate for the first time that cyr61 can also act as a growth inhibitor in SMC of genetically hypertensive rats. This may reveal a new route for investigation of the pathogenesis of hypertension.

Inhibition of glioma cell growth and tumorigenic potential by CCN3 (NOV)

AIMS

To establish whether the ectopic expression of CCN3 (NOV) in glioma cells can interfere with their tumorigenic potential and assess its potential value in molecular medicine.

METHODS

Glioma cell lines were used to assess whether differences in the degree of intracellular communication induced by the expression of the gap junction protein connexin 43 (Cx43) is related to the differential expression of CCN3 (NOV). The antiproliferative activity of rat CCN3 (rCCN3; NOV) in glioma cells, has been assessed both in vitro and in vivo with glioma cell lines expressing different amounts of CCN3 (NOV).

RESULTS

Upon ectopic expression of Cx43, the growth of C6 glioma cells is decreased. An increase of CCN3 (NOV) expression matches the reduced tumorigenic potential of these transfected cells. The localisation of CCN3 (NOV) is affected by the increased expression of Cx43 in the Cx-13 transfected cells, in which it is detected at areas of cell-cell contact. In a xenograft model, CCN3 (NOV) transfected glioma cells were found to induce tumours to a lesser degree than their parental counterparts, which do not express detectable amounts of CCN3 (NOV).

CONCLUSIONS

Previous observations had suggested an inverse relation between CCN3 (NOV) expression in glioma cells and their tumorigenicity. These results establish a direct association between the establishment of functional gap junctional intercellular communication and the expression of rCCN3 (NOV). In addition to a negative effect on murine and human cell growth, CCN3 (NOV) has antiproliferative activity on tumour cells in vivo. Thus, the antiproliferative activity of the CCN3 (NOV) protein might involve reorganisation of cellular contacts that play a crucial role in tumorigenesis. The antiproliferative activity of CCN3 (NOV) established in this work sets the stage for the potential use of CCN proteins in molecular oncology.

5' flanking sequence of the human immediate early responsive gene ccn1 (cyr61) and mapping of polymorphic CA repeat sequence motifs in the human ccn1 (cyr61) locus

AIMS

The human ccn1 (hccn; hcyr61) gene has been identified previously at the mRNA and protein level as a 1,25-dihydroxyvitamin D(3) and growth factor regulated gene in human osteoblasts. This study aimed to analyse genomic clones containing the human ccn1 (cyr61) gene and to provide the 5' flanking region.

METHODS

Genomic clones were isolated by screening a lambda library and by array filter hybridisations of a genomic library. Sequencing was performed using the dye terminator method. Promoter activity was measured after transient transfection using a beta galactosidase assay. CA repeat motifs were studied by a combined PCR/fragment analysis protocol.

RESULTS

The human 5' flanking region of 870 nucleotides contains several stretches with high homology to the mouse promoter as well as CA repeat motifs. This first report on the human 5' flanking sequence of the hccn1 (hcyr61) gene provides important insights into regulation pathways for the expression of this 1,25-dihydroxyvitamin D(3) and growth factor responsive early gene. A genomic clone containing the hccn1 (hcyr61) gene region also yielded a CA sequence located 3' of the ccn1 (cyr61) gene. This CA repeat and one of the CA repeat motifs in the promoter were studied in detail and found to be polymorphic.

CONCLUSIONS

The 5' flanking sequence of the hccn1 (hcyr61) gene provides insights into the mechanisms of regulation of this immediate early gene product. The CA repeat polymorphisms within the gene region will be useful in the genetic study of disorders affecting bone metabolism.

Cyr61, a member of the CCN family, is required for MCF-7 cell proliferation: regulation by 17beta-estradiol and overexpression in human breast cancer

Cyr61, a member of the CCN (CTGF/Cyr61/NOV) family of growth regulators, is a secreted cysteine-rich proangiogenic factor that has been implicated in tumorigenesis. Previous studies have also demonstrated that Cyr61 is regulated by 17beta-estradiol (E(2)) in the uterus. Therefore, we hypothesized that hormonal regulation of Cyr61 may be important in estrogen-dependent pathogenic processes such as breast tumorigenesis. Our study demonstrates that both Cyr61 messenger RNA and protein are induced by E(2) in MCF-7 mammary adenocarcinoma cells that primarily overexpress estrogen receptor alpha (ERalpha) in a dose-dependent and immediate early fashion. Cyr61 gene induction by E(2) is transcriptionally regulated by ERalpha as the antiestrogen, ICI 182,780, and actinomycin D blocked induction completely. In addition, Cyr61 is up-regulated in MCF-7 cells by epidermal growth factor (EGF) in an immediate early fashion as well. The functional relevance of steroid induction of Cyr61 in breast cancer cell growth is demonstrated by anti-Cyr61 neutralizing antibodies, which diminished E(2) and EGF-dependent DNA synthesis and dramatically reduced E(2)-driven cell proliferation by more than 70%. Most importantly, Cyr61 is overexpressed in 70% (28 of 40) of breast cancer patients with infiltrating ductal carcinoma and is localized exclusively to hyperplastic ductal epithelial cells. Moreover, the levels of Cyr61 protein are higher in breast tumors that are ER(+)/EGF receptor(+) than those that are ER(-)/EGF receptor(+), suggesting that estrogens may mediate Cyr61 expression in vivo. Collectively, our data suggest that Cyr61 may play a critical role in estrogen- as well as growth factor-dependent breast tumor growth.

Promoter function of the angiogenic inducer Cyr61gene in transgenic mice: tissue specificity, inducibility during wound healing, and role of the serum response element

The cysteine-rich angiogenic protein 61 (Cyr61) is an extracellular matrix-associated, heparin-binding protein that mediates cell adhesion, stimulates cell migration, and enhances growth factor-induced cell proliferation. Cyr61 also promotes chondrogenic differentiation and induces neovascularization. In this study, we show that a 2-kb fragment of the Cyr61 promoter, which confers growth factor-inducible expression in cultured fibroblasts, is able to drive accurate expression of the reporter gene lacZ in transgenic mice. Thus, transgene expression was observed in the developing placenta and embryonic cardiovascular, skeletal, and central and peripheral nervous systems. The sites of transgene expression are consistent with those observed of the endogenous Cyr61 gene as determined by in situ hybridization and immunohistochemistry. The transgene expression in the cardiovascular system does not require the serum response element, a promoter sequence essential for transcriptional activation of Cyr61 by serum growth factors in cultured fibroblasts. Because the serum response element contains the CArG box, a sequence element implicated in cardiovascular-specific gene expression, the nonessential nature of this sequence for cardiovascular expression of Cyr61 is unexpected. Furthermore, the Cyr61 promoter-driven lacZ expression is inducible in granulation tissue during wound healing, as is synthesis of the endogenous Cyr61 protein, suggesting a role for Cyr61 in wound healing. Consistent with this finding, purified Cyr61 protein promotes the healing of a wounded fibroblast monolayer in culture. In addition, we mapped the mouse Cyr61 gene to the distal region of chromosome 3. Together, these results define the functional Cyr61 promoter in vivo, and suggest a role of Cyr61 in wound healing through its demonstrated angiogenic activities upon endothelial cells and its chemotactic and growth promoting activities upon fibroblasts.

Gene induction by coagulation factor Xa is mediated by activation of protease-activated receptor 1

Cell signaling by coagulation factor Xa (Xa) contributes to pro-inflammatory responses in vivo. This study characterizes the signaling mechanism of Xa in a HeLa cell line that expresses protease-activated receptor 1 (PAR-1) but not PAR-2, -3, or -4. Xa induced NF-kappaB in HeLa cells efficiently but with delayed kinetics compared to thrombin. This delay caused no difference in gene expression patterns, as determined by high-density microarray analysis. Both proteases prominently induced the angiogenesis-promoting gene Cyr61 and connective tissue growth factor. Inhibition of PAR-1 cleavage abolished MAP kinase phosphorylation and gene induction by Xa, demonstrating that Xa signals through PAR-1 and not through a novel member of the PAR family. Activation of cell surface prothrombin with the snake venom enzyme Ecarin also produced PAR-1-dependent signaling. However, though the response to Ecarin was completely blocked by the thrombin inhibitor hirudin, the response to Xa was not. This suggests that the Xa response is not mediated by locally generated thrombin. The concentration dependence of Xa for PAR-1 activation is consistent with previously characterized Xa-mediated PAR-2 signaling, suggesting that local concentration of Xa on the cell surface, rather than sequence-specific recognition of the PAR scissile bond, determines receptor cleavage. This study demonstrates that PAR-1 cleavage by Xa can elicit the same cellular response as thrombin, but mechanistic differences in receptor recognition may be crucial for specific roles for Xa in signaling during spatial or temporal separation from thrombin generation.

Aberrant expression of Cyr61, a member of the CCN (CTGF/Cyr61/Cef10/NOVH) family, and dysregulation by 17 beta-estradiol and basic fibroblast growth factor in human uterine leiomyomas

Uterine leiomyomas are the most common tumors of the reproductive tract, afflicting women between the ages of 30--55 yr. Although considered to be the leading cause of hysterectomies in the United States, little is known of the etiology and mechanisms of pathogenesis in leiomyomas. Accordingly, rapid analysis of differential expression (RADE) was employed to identify genes that are abnormally expressed in leiomyomas. Of the several genes identified, Cyr61, a member of the CCN family of growth and angiogenic regulators, was shown to be markedly down-regulated at the messenger ribonucleic acid (mRNA) and protein levels in leiomyoma tumors compared with the matched uterine myometrial controls (n = 38). In addition, in situ hybridization experiments corroborated the lack of Cyr61 expression in leiomyoma cells, whereas abundant transcript levels were identified in adjacent myometrial smooth muscle cells. To elucidate the mechanisms of Cyr61 gene regulation in leiomyomas, we determined the effects of ovarian steroids, basic fibroblast growth factor (bFGF), and serum, on Cyr61 expression using an ex vivo culture system. Treatment of human myometrial explants with 17 beta-estradiol and bFGF up-regulated Cyr61 transcripts, whereas the progesterone receptor agonist, R5020 (alone or in combination with 17 beta-estradiol), had no effect. Paradoxically, neither 17 beta-estradiol nor bFGF was capable of up-regulating Cyr61 mRNA in leiomyoma explants despite elevated levels of ER alpha mRNA, suggesting a possible defect in steroid and growth factor regulation. Thus, dysregulation of Cyr61 by estrogen and bFGF may contribute to down-regulation of Cyr61 in leiomyomas, which, in turn, may predispose uterine smooth muscle cells toward sustained growth.

Connective tissue growth factor: potential role in glomerulosclerosis and tubulointerstitial fibrosis

Transforming growth factor beta (TGF-beta) is a pivotal driver of glomerulosclerosis and tubulointerstitial fibrosis in renal diseases. Because TGF-beta also plays important anti-inflammatory and antiproliferative roles in mammalian systems, there has been a recent drive to elucidate downstream mediators of TGF-beta's pro-fibrotic effects with the ultimate goal of developing new anti-fibrotic strategies for treatment of chronic diseases. Connective tissue growth factor (CTGF) belongs to the CCN family of immediate early response genes. Several lines of evidence suggest that CTGF is an important pro-fibrotic molecule in renal disease and that CTGF contributes to TGF-beta bioactivity in this setting. CTGF expression is increased in the glomeruli and tubulointerstium in a variety of renal disease in association with scarring and sclerosis of renal parenchyma. In model systems in vitro, mesangial cell CTGF expression is induced by high extracellular glucose, cyclic mechanical strain and TGF-beta. Recombinant human CTGF augments the production of fibronectin and type IV collagen by mesangial cells and the effects of high glucose on mesangial cell CTGF expression and matrix production are attenuated, in part, by anti-TGF-beta antibody. In aggregate, these observations identify CTGF as an attractive therapeutic target in fibrotic renal diseases.

Muscarinic acetylcholine receptors induce the expression of the immediate early growth regulatory gene CYR61

In brain, muscarinic acetylcholine receptors (mAChRs) modulate neuronal functions including long term potentiation and synaptic plasticity in neuronal circuits that are involved in learning and memory formation. To identify mAChR-inducible genes, we used a differential display approach and found that mAChRs rapidly induced transcription of the immediate early gene CYR61 in HEK 293 cells with a maximum expression after 1 h of receptor stimulation. CYR61 is a member of the emerging CCN gene family that includes CYR61/CEF10, CTGF/FISP-12, and NOV; these encode secretory growth regulatory proteins with distinct functions in cell proliferation, migration, adhesion, and survival. We found that CYR61, CTGF, and NOV were expressed throughout the human central nervous system. Stimulation of mAChRs induced CYR61 expression in primary neurons and rat brain where CYR61 mRNA was detected in cortical layers V and VI and in thalamic nuclei. In contrast, CTGF and NOV expression was not altered by mAChRs neither in neuronal tissue culture nor rat brain. Receptor subtype analyses demonstrated that m1 and m3 mAChR subtypes strongly induced CYR61 expression, whereas m2 and m4 mAChRs had only subtle effects. Increased CYR61 expression was coupled to mAChRs by both protein kinase C and elevations of intracellular Ca(2+). Our results establish that CYR61 expression in mammalian brain is under the control of cholinergic neurotransmission; it may thus be involved in cholinergic regulation of synaptic plasticity.

Nov gene encodes adhesion factor for vascular smooth muscle cells and is dynamically regulated in response to vascular injury

Nephroblastoma overexpressed (NOV) is a member of the CCN family (connective tissue growth factor, CYR61, and NOV) of proteins that are involved in regulating the proliferation, differentiation, and adhesion of a variety of cell types. We have examined the expression of the NOV: gene and NOV protein by vascular smooth muscle cells (VSMCs), in vitro and in vivo, and the effects of recombinant NOV on VSMCs. Rat aortic VSMCs were found to express NOV: mRNA and NOV protein in vitro and in vivo. NOV: expression in adult rat tissues was very high in the aorta and was detected only weakly in the brain and lung by Northern analysis (relative levels 33:3:1). During postnatal development (3 days to 12 weeks), the expression of NOV: was correlated with markers of the differentiated smooth muscle cell phenotype (smooth muscle myosin heavy chain and SM22 alpha). In the rat carotid artery balloon injury model, NOV: was detectable by in situ hybridization and was downregulated in the media of the injured artery compared with the uninjured artery at 7 and 14 days after injury. Expression in the developing intima was barely detectable at 7 days after injury except for strong expression at the luminal surface. At 14 days after injury, NOV: expression was substantially increased throughout the intima. In vitro studies of the function of NOV protein showed that it promoted VSMC adhesion via a mechanism that was divalent cation and Arg-Gly-Asp independent but that it did not modulate VSMC proliferation or phenotype. The strong expression and dynamic regulation of NOV: in the arterial wall, together with its ability to promote VSMC adhesion, suggest that it may be involved in homeostasis and repair.

The immediate early gene product hCYR61 localizes to the secretory pathway in human osteoblasts

The human cysteine-rich protein 61 (hCYR61) belongs to the growing CCN (CYR61/CTGF/NOV) family of immediate early genes, which modulate cell growth and differentiation. hCYR61 is regulated by 1alpha, 25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) and growth factors in fetal human osteoblasts (hFOB cells). The murine homologue CYR61 was characterized as an extracellular matrix-associated protein that modulates basic fibroblast growth factor signaling, angiogenesis, and binds to integrin alpha(v)beta(3). Here we report the intracellular localization of the human CYR61 gene product by overexpressing fusion proteins with green fluorescent protein (GFP) in primary osteoblasts and the hFOB cell line. Full-length hCYR61-GFP localizes to the Golgi apparatus and cytoplasmatic granules, indicating targeting to the secretory pathway. Secretion of hCYR61 from osteoblasts is verified by Western blot detection from cellular supernatants. A truncated hCYR61-GFP fusion protein containing only the 34 N-terminal amino acids of hCYR61 also localizes to the Golgi apparatus mainly in the perinuclear region, which suggests that the N-terminus of hCYR61 is sufficient to target the protein to the secretory pathway. In summary, our results present the first evidence that human CYR61 localizes to the secretory pathway in primary osteoblasts and hFOB cells, and that it is secreted from these cells. The N-terminal 34 amino acids of hCYR61 provide a sufficient Golgi targeting sequence. Together with the immediate early regulation of hCYR61 mRNA by 1,25-(OH)(2)D(3), this suggests that hCYR61 might function as an extracellular signaling molecule in human bone.

Temporal expression of the chondrogenic and angiogenic growth factor CYR61 during fracture repair

The repair of a fractured bone is a complex biological event that essentially recapitulates embryonic development and requires the activity of a number of different cell types undergoing proliferation, migration, adhesion, and differentiation, while at the same time expressing a host of different genes. To identify such genes, we employed differential display and compared messenger RNA (mRNA) populations isolated from postfracture (PF) day 5 calluses to those of intact rat femurs. One such gene in which expression was up-regulated at PF day 5 is identified as CYR61, a member of the CCN family of secreted regulatory proteins. CYR61 is a growth factor that stimulates chondrogenesis and angiogenesis. We show that its mRNA expression during fracture repair is regulated temporally, with elevated levels seen as early as PF day 3 and day 5, rising dramatically at PF day 7 and day 10, and finally declining at PF day 14 and day 21. At the highest peak of expression (PF day 7 and day 10, which correlates with chondrogenesis), CYR61 mRNA levels are approximately 10-fold higher than those detected in intact femurs. Similarly, high protein levels are detected throughout the reparative phase of the callus, particularly in fibrous tissue and periosteum, and in proliferating chondrocytes, osteoblasts, and immature osteocytes. The secreted form of CYR61 also was detected within the newly made osteoid. No labeling was detected in hypertrophic chondrocytes or in mature cortical osteocytes. These results suggest that CYR61 plays a significant role in cartilage and bone formation and may serve as an important regulator of fracture healing.

The insulin-like growth factor-binding protein (IGFBP) superfamily

Over the last decade, the concept of an IGFBP family has been well accepted, based on structural similarities and on functional abilities to bind IGFs with high affinities. The existence of other potential IGFBPs was left open. The discovery of proteins with N-terminal domains bearing striking structural similarities to the N terminus of the IGFBPs, and with reduced, but demonstrable, affinity for IGFs, raised the question of whether these proteins were "new" IGFBPs (22, 23, 217). The N-terminal domain had been uniquely associated with the IGFBPs and has long been considered to be critical for IGF binding. No other function has been confirmed for this domain to date. Thus, the presence of this important IGFBP domain in the N terminus of other proteins must be considered significant. Although these other proteins appear capable of binding IGF, their relatively low affinity and the fact that their major biological actions are likely to not directly involve the IGF peptides suggest that they probably should not be classified within the IGFBP family as provisionally proposed (22, 23). The conservation of this single domain, so critical to high-affinity binding of IGF by the six IGFBPs, in all of the IGFBP-rPs, as well, speaks to its biological importance. Historically, and perhaps, functionally, this has led to the designation of an "IGFBP superfamily". The classification and nomenclature for the IGFBP superfamily, are, of course, arbitrary; what is ultimately relevant is the underlying biology, much of which still remains to be deciphered. The nomenclature for the IGFBP related proteins was derived from a consensus of researchers working in the IGFBP field (52). Obviously, a more general consensus on nomenclature, involving all groups working on each IGFBP-rP, has yet to be reached. Further understanding of the biological functions of each protein should help resolve the nomenclature dilemma. For the present, redesignating these proteins IGFBP-rPs simplifies the multiple names already associated with each IGFBP related protein, and reinforces the concept of a relationship with the IGFBPs. Beyond the N-terminal domain, there is a lack of structural similarity between the IGFBP-rPs and IGFBPs. The C-terminal domains do share similarities to other internal domains found in numerous other proteins. For example, the similarity of the IGFBP C terminus to the thyroglobulin type-I domain shows that the IGFBPs are also structurally related to numerous other proteins carrying the same domain (87). Interestingly, the functions of the different C-terminal domains in members of the IGFBP superfamily include interactions with the cell surface or ECM, suggesting that, even if they share little sequence similarities, the C-terminal domains may be functionally related. The evolutionary conservation of the N-terminal domain and functional studies support the notion that IGFBPs and IGFBP-rPs together form an IGFBP superfamily. A superfamily delineates between closely related (classified as a family) and distantly related proteins. The IGFBP superfamily is therefore composed of distantly related families. The modular nature of the constituents of the IGFBP superfamily, particularly their preservation of an highly conserved N-terminal domain, seems best explained by the process of exon shuffling of an ancestral gene encoding this domain. Over the course of evolution, some members evolved into high-affinity IGF binders and others into low-affinity IGF binders, thereby conferring on the IGFBP superfamily the ability to influence cell growth by both IGF-dependent and IGF-independent means (Fig. 10). A final word, from Stephen Jay Gould (218): "But classifications are not passive ordering devices in a world objectively divided into obvious categories. Taxonomies are human decisions imposed upon nature--theories about the causes of nature's order. The chronicle of historical changes in classification provides our finest insight into conceptual revolutions

Novel aspects of the insulin-like growth factor binding proteins

The insulin-like growth factors (IGFs), IGF binding proteins (IGFBPs), and IGFBP proteases regulate somatic growth and cellular proliferation both in vivo and in vitro. IGFs are potent mitogens whose actions are determined by the availability of free IGFs to interact with IGF receptors. IGFBPs comprise a family of six proteins that bind IGFs with high affinity and specificity and thereby regulate IGF-dependent actions. IGFBPs have also recently emerged as IGF-independent regulators of cell growth. Several IGFBP association proteins have been discovered recently which can affect IGFBP action. Cleavage of IGFBPs by specific proteases modulates levels of free IGFs and IGFBPs and thereby their actions. IGFBP-related proteins (IGFBP-rPs) are an emerging group of proteins which bind IGFs with low affinity and also play important roles in cell growth and differentiation. The IGFBPs appear to have emerging roles in the mechanisms underlying human cancer. The GH-IGF-IGFBP axis is complex and powerful. Future research on its physiology promises exciting insights into cell biology as well as advancements in the treatment of a wide range of disease states including cancer, diabetes, vascular disease, asthma, and growth disorders.

Nephroblastoma overexpressed gene (NOV) codes for a growth factor that induces protein tyrosine phosphorylation

NOV (nephroblastoma overexpressed gene) is a member of the CCN (connective tissue growth factor [CTGF], Cyr61/Cef10, NOV) family of proteins. These proteins are cysteine-rich and are noted for having growth-regulatory functions. We have isolated the rat NOV gene, and the DNA sequence shares 90% identity with the mouse and 80% identity with the human sequences. The rat NOV gene was expressed in all rat tissues examined, including brain, lung, heart, kidney, liver, spleen, thymus and skeletal muscle. Higher levels of rat NOV mRNA were seen in the brain, lung and skeletal muscle compared to the other tissues. Examination of NOV expression in various human cell lines revealed that NOV was expressed in U87, 293, T98G, SK-N-MC and Hs683 but not in HepG2, HL60, THP1 and Jurkat. The human NOV gene was transfected into 293 cells and the expressed protein purified. When 3T3 fibroblasts were treated with this recombinant NOV protein, a dose-dependent increase in proliferation was observed. Analysis of tyrosine-phosphorylated proteins revealed that when 3T3 cells were treated with NOV, a 221 kDa protein was phosphorylated. These data suggest that NOV can act as a growth factor for some cells and binds to a specific receptor that leads to the phosphorylation of a 221 kDa protein.

Identification and cloning of a connective tissue growth factor-like cDNA from human osteoblasts encoding a novel regulator of osteoblast functions

We have identified and cloned a novel connective tissue growth factor-like (CTGF-L) cDNA from primary human osteoblast cells encoding a 250-amino acid single chain polypeptide. Murine CTGF-L cDNA, encoding a polypeptide of 251 amino acids, was obtained from a murine lung cDNA library. CTGF-L protein bears significant identity ( approximately 60%) to the CCN (CTGF, Cef10/Cyr61, Nov) family of proteins. CTGF-L is composed of three distinct domains, an insulin-like growth factor binding domain, a von Willebrand Factor type C motif, and a thrombospondin type I repeat. However, unlike CTGF, CTGF-L lacks the C-terminal domain implicated in dimerization and heparin binding. CTGF-L mRNA ( approximately 1.3 kilobases) is expressed in primary human osteoblasts, fibroblasts, ovary, testes, and heart, and a approximately 26-kDa protein is secreted from primary human osteoblasts and fibroblasts. In situ hybridization indicates high expression in osteoblasts forming bone, discrete alkaline phosphatase positive bone marrow cells, and chondrocytes. Specific binding of 125I-labeled insulin-like growth factors to CTGF-L was demonstrated by ligand Western blotting and cross-linking experiments. Recombinant human CTGF-L promotes the adhesion of osteoblast cells and inhibits the binding of fibrinogen to integrin receptors. In addition, recombinant human CTGF-L inhibits osteocalcin production in rat osteoblast-like Ros 17/2.8 cells. Taken together, these results suggest that CTGF-L may play an important role in modulating bone turnover.

Identification of genes regulated by muscarinic acetylcholine receptors: application of an improved and statistically comprehensive mRNA differential display technique

In order to identify genes that are regulated by muscarinic acetylcholine receptors, we developed an mRNA differential display technique (DD) approach. By increasing redundancy and by evaluating optimised reagents and conditions for reverse transcription of total RNA, PCR and separation of PCR products, we generated a DD protocol that yields highly consistent results. A set of 64 distinct random primers was specifically designed in order to approach a statistically comprehensive analysis of all mRNA species in a defined cell population. This modified DD protocol was applied to total RNA of HEK293 cells stably expressing muscarinic m1 acetylcholine receptors and cells stimulated with the receptor agonist carbachol were compared to identical but non-stimulated cells. In 81 of 192 possible PCR experiments, 38 differential bands were identified. Sequence analysis followed by northern blot analyses confirmed differentially expressed genes in 19 of 23 bands analysed. These represented 10 distinct immediate-early genes that were up-regulated by m1AChR activation: Egr-1, Egr-2, Egr-3, NGFi-B, ETR101, c- jun, jun -D, Gos-3 and hcyr61, as well as the unknown gene Gig-2. These data show that this improved DD protocol can be readily applied to reliably identify differentially expressed genes.

Insulin-like growth factor binding proteins: a proposed superfamily

The conventional concept is that the insulin-like growth factor binding proteins (IGFBPs) are cysteine-rich proteins, with conserved N- and C-domains, that are capable of binding insulin-like growth factors (IGFs) with high affinity. This dogma was recently challenged by the discovery of a group of cysteine-rich proteins that share important structural similarities with the IGFBPs, but have demonstrably lower affinity for IGFs. It is therefore proposed that these IGFBP-related proteins (IGFBP-rPs) and the IGFBPs constitute an IGFBP superfamily. We speculate that the IGFBP superfamily is derived from an ancestral gene/protein that was critically involved in the regulation of cell growth and was capable of binding IGF peptides. Over the course of evolution, some members (IGFBPs) evolved into high-affinity IGF binders and others (IGFBP-rPs) into low-affinity IGF binders, thereby conferring on the IGFBP superfamily the ability to influence cell growth by both IGF-dependent and IGF-independent means.

Expression of the extracellular matrix signaling molecule Cyr61 is downregulated in prostate cancer

BACKGROUND

Prostate cancer (CaP) is one of the most common neoplasms in the USA and Europe. We used differential display PCR (DD-PCR) to identify genes related to the development of prostate cancer.

METHODS

The RNA of 4 patients with untreated CaP was analyzed for differentially expressed genes. Using DD-PCR, we identified a downregulated cDNA-fragment in these prostate cancer cells. This fragment (N7) was cloned and further analyzed by CMRT-PCR, Northern-blot analysis, and in situ hybridization.

RESULTS

Sequence analysis revealed that N7 is identical to the 3'-untranslated region of the recently described immediate early gene Cyr61. Comparative multiplex RT-PCR with sequence specific primers showed that Cyr61 is downregulated in the tumor tissue of 7 out of 13 patients. By in situ hybridization we could demonstrate that the expression of Cyr61 is restricted to the epithelium of the prostate. Immunohistochemical analysis showed that Cyr61 protein could be found in the epithelium of normal prostatic tissue, whereas prostate cancer tissue showed a marked decrease of Cyr61 protein expression.

CONCLUSIONS

Cyr61 is a member of the emerging family of extracellular signaling proteins and enhances the effect of bFGF. The changed pattern of expression Cyr61 might therefore contribute to the altered interactions between epithelial and stromal cells in prostate carcinoma.

The human analog of murine cystein rich protein 61 [correction of 16] is a 1alpha,25-dihydroxyvitamin D3 responsive immediate early gene in human fetal osteoblasts: regulation by cytokines, growth factors, and serum

1Alpha,25-dihydroxyvitamin D3 (1,25-(OH)2D3) is a potent mediator of differentiation and maintenance of specific functions of osteoblasts. To detect novel targets for 1,25-(OH)2D3 action, we applied differential display PCR to human fetal osteoblast-like cells and identified the human analog of murine cystein rich protein 61 (hCYR61) as a 1,25-(OH)2D3-responsive immediate early gene in differentiated fetal osteoblast-like cells. The murine gene CYR61 is important for cell-cell and cell-matrix interactions, and it belongs to an emerging gene family of cysteine-rich proteins. hCYR61 messenger RNA (mRNA) steady-state levels were stimulated 11-fold by 10 nM 1,25-(OH)2D3 by 1 h and declined to control levels by 4 h. This transient stimulation of hCYR61 mRNA was not inhibited by cycloheximide but was prevented by actinomycin D, indicating that the 1,25-(OH)2D3 effect involves transcriptional events and does not require de novo protein synthesis. hCYR61 mRNA stability was not influenced by 1,25(OH)2D3, whereas cycloheximide treatment stabilized hCYR61 mRNA. FCS, as well as growth factors and cytokines such as basic fibroblast growth factor, epidermal growth factor, tumor necrosis factor alpha, and interleukin-1, strongly elevated hCYR61 mRNA steady-state levels within 1 h. hCYR61 mRNA was expressed also in primary human osteoblasts and osteosarcoma cell lines. Using a commercial tissue blot, hCYR61 mRNA was only observed in skeletal muscle. The fast and transient response of hCYR 61 to 1,25-(OH)2D3, serum, growth factors, and cytokines suggests an important role of hCYR61 for osteoblast function and differentiation.

Chromosomal mapping and expression of the human cyr61 gene in tumour cells from the nervous system

AIMS

To characterise the human cyr61 gene (cyr61H) and determine its chromosomal locality. To compare expression of cyr61H in human tumour cell lines with that of two other structurally related genes, novH (nephroblastoma overexpressed gene) and CTGF (connective tissue growth factor), that are likely to play a role in the control of cell proliferation and differentiation.

METHODS

To isolate the human cyr61 gene, placental genomic and HeLa cDNA libraries were screened with murine cyr61 cDNA. The nucleotide sequence of the complete cyr61H cDNA was established. Both Southern blotting of a panel of somatic cell hybrids and in situ hybridisation on chromosomes were performed to map the cyr61H gene. Expression of cyr61H, novH, CTGF, and novH was analysed by northern blotting in both human neuroblastomas and glioblastoma cell lines.

RESULTS

Genomic and cDNA clones encompassing the cyr61H gene were isolated and characterised. Comparison of mouse and human cyr61 sequences indicated that their genomic organisation is highly conserved. Alignment of coding sequences highlighted the conservation of cyr61 regions that might be critical for its biological function. The data showed that the cyr61H gene is assigned to chromosome 1p22.3 and that different levels of cyr61H, CTGF, and novH mRNA have been detected in several human tumour cell lines derived from the nervous system.

CONCLUSIONS

The human cyr61 gene belongs to an emerging family of genes including CTGF/fisp12 and nov. The murine cyr61 encodes an extracellular cysteine rich protein that exhibits chemotactic activity, promotes attachment and spreading of cells, and potentiates the mitogenic effect of growth factors. Assignment of the cyr61H gene to chromosome 1p22.3 will allow studies to determine whether human pathologies derived from the nervous system or from other tissues are associated with chromosomal abnormalities involving this region. Although the coding regions of cyr61H, CTGF, and novH are highly homologous, a growing body of evidence suggests that expression of these genes is regulated differentially, and that a balance between expression of these genes might represent a key element in determining the stage of differentiation and/or the malignant potential of tumour cells.