Yin/Yang expression of CCN family members: Transforming growth factor beta 1, via ALK5/FAK/MEK, induces CCN1 and CCN2, yet suppresses CCN3, expression in human dermal fibroblasts

Abstract

The role of the microenvironment in driving connective tissue disease is being increasingly appreciated. Matricellular proteins of the CCN family are signaling modifiers that are secreted by cells into the extracellular matrix microenvironment where they have profound, context-dependent effects on organ development, homeostasis and disease. Indeed, CCN proteins are emergent targets for therapeutic intervention. Recent evidence suggests that, in vivo, CCN3 has effects opposing CCN2. Moreover, when CCN3 expression is high, CCN2 expression is low. That is, they appear to be regulated in a yin/yang fashion, leading to the hypothesis that the CCN2:CCN3 ratio is important to control tissue homeostasis. To begin to test the hypothesis that alterations in CCN2:CCN3 expression might be important in skin biology in vivo, we evaluated the relative ex vivo effects of the profibrotic protein TGFbeta1 on dermal fibroblasts on protein and RNA expression of CCN3 and CCN2, as well as the related protein CCN1. We also used signal transduction inhibitors to begin to identify the signal transduction pathways controlling the ability of fibroblasts to respond to TGFbeta1. As anticipated, CCN1 and CCN2 protein and mRNA were induced by TGFbeta1 in human dermal fibroblasts. This induction was blocked by TAK1, FAK, YAP1 and MEK inhibition. Conversely, TGFbeta1 suppressed CCN3 mRNA expression in a fashion insensitive to FAK, MEK, TAK1 or YAP1 inhibition. Unexpectedly, CCN3 protein was not detected in human dermal fibroblasts basally. These data suggest that, in dermal fibroblasts, the profibrotic protein TGFbeta1 has a divergent effect on CCN3 relative to CCN2 and CCN1, both at the mRNA and protein level. Given that the major source in skin in vivo of CCN proteins are fibroblasts, our data are consistent that alterations in CCN2/CCN1: CCN3 ratios in response to profibrotic agents such as TGFbeta1 may play a role in connective tissue pathologies including fibrosis.

Calreticulin exploits TGF‐β for extracellular matrix induction engineering a tissue regenerative process

“…5,9,[37][38][39][40][41][42] Similarly, cutaneous wound remodeling is a dynamic process that usually leads to fibrosis/scarring involving TGF-β signaling with downstream focal adhesion kinase (FAK) activation and/or increasing Connective Tissue Growth Factor (CCN2). 43,44 The three mammalian isoforms of TGF-β share 67%-80% amino acid homology and signal through two major receptors, TGF-β RII (TβRII) and TGF-βRI (TβRI). 45,46 Extracellular matrix induction characterizing the fibrotic response occurs mainly through TGF-β canonical signaling involving the binding of TGF-β ligand to TβRII, autophosphorylation and subsequent phosphorylation and dimerization with TβRI, which phosphorylates Smad2/3 transcription factors for downstream target gene activation; PI3K, ERK, and p38MAPK are also intermediate signaling mediators that respond to TGF-β.…”

“…The cytokine Transforming growth factor‐β (TGF‐β) is a key protein responsible for the fibrotic response in nearly every organ in which pathologies such as nephropathies and lung disease culminate in severe fibrosis causing loss of organ function 5,9,37‐42 . Similarly, cutaneous wound remodeling is a dynamic process that usually leads to fibrosis/scarring involving TGF‐β signaling with downstream focal adhesion kinase (FAK) activation and/or increasing Connective Tissue Growth Factor (CCN2) 43,44 . The three mammalian isoforms of TGF‐β share 67%‐80% amino acid homology and signal through two major receptors, TGF‐β RII (TβRII) and TGF‐βRI (TβRI) 45,46 .…”

Endogenous CCN family member WISP1 inhibits trauma-induced heterotopic ossification

“…In previous studies with genetic deletion of CCN family member proteins, other CCN family members can play a compensatory role (48). For example, overexpression of Ccn3 in murine embryonic skin fibroblastderived NIH3T3 cells results in a significant decrease in expression of Ccn2 and Ccn4, suggesting the compensatory nature of these CCN family member proteins in organ fibrosis (49,50). As a second potential limitation, global knockout of Wisp1 not only affects mesenchymal cells, but likely has secondary effects on inflammatory cell types, such as macrophages and T lymphocytes (51).…”

CCN2 (Cellular Communication Network factor 2) in the bone marrow microenvironment, normal and malignant hematopoiesis

“…CCN2 is just one representative of the family of closely related CCN genes, which also includes CCN1 (Cysteine rich 61/Cyr61), CCN3 (Nephroblastoma overexpressed/NOV), CCN4 (Wnt-inducible-secreted protein (WISP)-1), CCN5 (WISP-2) and CCN6 (WISP-3) (Brigstock et al 1997 ; Perbal 2018 ).The CCN family members can work in concert to orchestrate a multitude of biological processes in similar but also partly opposite ways (Peidl et al 2019 ; Perbal 2018 ; Riser et al 2009 , 2010 ). Therefore, the CCN family genes should ideally be studied together rather than separate.…”

“…The CCN proteins act as central mediators of mechanotransduction and play important roles in, amongst others, angiogenesis, inflammation, connective tissue deposition, and a broad range of pathological processes including fibrosis and cancer (Chaqour 2020 ; Leask 2020 ). The proteins of the CCN family might play as a team and ideally should be assessed together rather than individually (Peidl et al 2019 ; Perbal 2018 ; Riser et al 2009 , 2010 ), but for most of them, little is known about their possible involvement in hematopoiesis and the BM microenvironment. Since CCN2 is by far the most studied CCN protein in this field, it will therefore be the focus of this review, and the more limited available knowledge on the other CCN proteins is included at the end.…”