Roles of heterotypic CCN2/CTGF-CCN3/NOV and homotypic CCN2-CCN2 interactions in expression of the differentiated phenotype of chondrocytes

To identify proteins that regulate CCN2 activity, we carried out GAL4-based yeast two-hybrid screening with a cDNA library derived from a chondrocytic cell line, HCS-2/8. CCN2/CTGF and CCN3/NOV polypeptides were picked up as CCN2-binding proteins, and CCN2CCN2 and CCN2CCN3 binding domains were identified. Direct binding between CCN2 and CCN3 was confirmed by coimmunoprecipitation in vitro and in vivo and surface plasmon resonance, and the calculated dissociation constants (Kd) were 1.17 x 10-9 m for CCN2 and CCN2, and 1.95 x 10-9 m for CCN2 and CCN3. Ectopically overexpressed green fluorescent proteinCCN2 and HaloCCN3 in COS7 cells colocalized, as determined by direct fluorescence analysis. We present evidence that CCN2CCN3 interactions modulated CCN2 activity such as enhancement of ACAN and col2a1 expression. Curiously, CCN2 enhanced, whereas CCN3 inhibited, the expression of aggrecan and col2a1 mRNA in HCS-2/8 cells, and combined treatment with CCN2 and CCN3 abolished the inhibitory effect of CCN3. These effects were neutralized with an antibody against the von Willebrand factor type C domain of CCN2 (11H3). This antibody diminished the binding between CCN2 and CCN2, but enhanced that between CCN3 and CCN2. Our results suggest that CCN2 could form homotypic and heterotypic dimers with CCN2 and CCN3, respectively. Strengthening the binding between CCN2 and CCN3 with the 11H3 antibody had an enhancing effect on aggrecan expression in chondrocytes, suggesting that CCN2 had an antagonizing effect by binding to CCN3

CCN2 as a Novel Molecule Supporting Energy Metabolism of Chondrocytes

CCN2/connective tissue growth factor (CTGF) is a unique molecule that promotes both chondrocytic differentiation and proliferation through its matricellular interaction with a number of extracellular biomolecules. This apparently contradictory functional property of CCN2 suggests its certain role in basic cellular activities such as energy metabolism, which is required for both proliferation and differentiation. Comparative metabolomic analysis of costal chondrocytes isolated from wild-type and Ccn2-null mice revealed overall impaired metabolism in the latter. Among the numerous metabolites analyzed, stable reduction in the intracellular level of ATP, GTP, CTP, or UTP was observed, indicating a profound role of CCN2 in energy metabolism. Particularly, the cellular level of ATP was decreased by more than 50% in the Ccn2-null chondrocytes. The addition of recombinant CCN2 (rCCN2) to cultured Ccn2-null chondrocytes partly redeemed the cellular ATP level attenuated by Ccn2 deletion. Next, in order to investigate the mechanistic background that mediates the reduction in ATP level in these Ccn2-null chondrocytes, we performed transcriptome analysis. As a result, several metabolism-associated genes were found to have been up-regulated or down-regulated in the mutant mice. Up-regulation of a number of ribosomal protein genes was observed upon Ccn2 deletion, whereas a few genes required for aerobic and anaerobic ATP production were down-regulated in the Ccn2-null chondrocytes. Among such genes, reduction in the expression of the enolase 1 gene was of particular note. These findings uncover a novel functional role of CCN2 as a metabolic supporter in the growth-plate chondrocytes, which is required for skeletogenesis in mammals

Matricellular CCN proteins

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Ten years later…

This year we’re coming upon the tenth anniversary of our biannual International Workshop on the CCN family of genes. It was during our very first meeting that the International CCN Society was conceived. This editorial provides us with the opportunity to briefly review how the need for a CCN meeting emerged and evolved, following the discovery of CTGF, CYR61, and NOV, the three founding members of the CCN family of proteins that in humans are known as as CCN1 (CTGF), CCN2 (CYR61), CCN3(NOV), CCN4(WISP1), CCN5 (WISP2) and CCN6 (WISP3)

Alternative splicing of CCN mRNAs …. it has been upon us

Variant CCN proteins have been identified over the past decade in several normal and pathological situations. The production of CCN truncated proteins have been reported in the case of CCN2(ctgf), CCN3(nov), CCN4(wisp-1) and CCN6(wisp-3). Furthermore, the natural CCN5 is known to miss the C-terminal domain that is present in all other members of the CCN family of proteins. In spite of compelling evidence that assign important biological activities to these truncated CCN variants, their potential regulatory functions have only recently begun to be widely accepted. The report of CCN1(cyr61) intron 3 retention in breast cancer cells now confirms that, in addition to well documented post-translational processing of full length CCN proteins, alternative splicing is to be regarded as another effective way to generate CCN variants. These observations add to a previous bulk of evidence that support the existence of alternative splicing for other CCN genes. It has become clearly evident that we need to recognize these mechanisms as a means to increase the biological diversity of CCN proteins

APC: the toll road to continued high quality communication

In this article we briefly review the reasons and advantages that underly our publisher's decision to introduce article-processing charges (APC) for manuscripts submitted to Cell Communication and Signaling. The charge is an attempt to develop a new business model for distributing biomedical information and has been accepted in a number of other journals. APCs will enable BioMed Central to continue to provide their excellent service and will help to establish our journal

pyr RNA binding to the Bacillus caldolyticus PyrR attenuation protein – characterization and regulation by uridine and guanosine nucleotides

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90317/1/FEBS_6227_sm_FigsS1-S5.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/90317/2/j.1742-4658.2007.06227.x.pd

NOV story: the way to CCN3

The principal aim of this historical review- the first in a new series- is to present the basic concepts that led to the discovery of NOV and to show how our ideas evolved regarding the role and functions of this new class of proteins. It should prove particularly useful to the new comers and to students who are engaged in this exciting field. It is also a good opportunity to acknowledge the input of those who participated in the development of this scientific endeavou