Immediate-early protein playing a role in various cellular processes including proliferation, adhesion, migration, differentiation and survival. Acts by binding to integrins or membrane receptors such as NOTCH1. Essential regulator of hematopoietic stem and progenitor cell function. Inhibits myogenic differentiation through the activation of Notch-signaling pathway. Inhibits vascular smooth muscle cells proliferation by increasing expression of cell-cycle regulators such as CDKN2B or CDKN1A independently of TGFB1 signaling. Ligand of integrins ITGAV:ITGB3 and ITGA5:ITGB1, acts directly upon endothelial cells to stimulate pro-angiogenic activities and induces angiogenesis. In endothelial cells, supports cell adhesion, induces directed cell migration (chemotaxis) and promotes cell survival. Also plays a role in cutaneous wound healing acting as integrin receptor ligand. Supports skin fibroblast adhesion through ITGA5:ITGB1 and ITGA6:ITGB1 and induces fibroblast chemotaxis through ITGAV:ITGB5. Seems to enhance bFGF-induced DNA synthesis in fibroblasts (By similarity). Involved in bone regeneration as a negative regulator (PubMed:23653360). Enhances the articular chondrocytic phenotype, whereas it repressed the one representing endochondral ossification (By similarity). Impairs pancreatic beta-cell function, inhibits beta-cell proliferation and insulin secretion (PubMed:23705021). Plays a role as negative regulator of endothelial pro-inflammatory activation reducing monocyte adhesion, its anti-inflammatory effects occur secondary to the inhibition of NF-kappaB signaling pathway (By similarity). Contributes to the control and coordination of inflammatory processes in atherosclerosis (PubMed:24722330). Attenuates inflammatory pain through regulation of IL1B- and TNF-induced MMP9, MMP2 and CCL2 expression. Inhibits MMP9 expression through ITGB1 engagement (By similarity). Interacts with FBLN1. Interacts (via CTCK domain) with NOTCH1 (via the EGF-like repeat region). Interacts with GJA1/CX43. Interacts with ITGA5:ITGB1, ITGAV:ITGB3 and ITGAV:ITGB5. Interacts with ZDHHC22; the interaction may lead to CCN3 palmitoylation (PubMed:29287726). Localizes at the gap junction in presence of GJA1. Expressed in large vessels including the ascending aorta, carotid arteries, and the thoracic aorta, in medium-sized vessels such as coronary arteries and small pulmonary veins and also in small vessels. In addition, also found to be present in the heart (at protein level) (PubMed:21063504). Expressed in astrocytes (at protein level) (PubMed:15213231). Detected in brain, bone, lung and muscle tissues (PubMed:20139355, PubMed:23653360). Expressed in skin, expression highly increases 5 days post-wounding, peaking on the 7th day to decline after 9 days (PubMed:15611078). Expressed in pancreatic ducts and beta-cell islets (PubMed:23705021). Up-regulated in the early phase of bone regeneration. Expression is reduced in atherosclerosis progression. May be palmitoylated on Cys-241, which is important for extracellular secretion. Mutants develop normally but have enhanced arterial neointimal hyperplasia in response to injury (PubMed:20139355). Animals show an accelerated bone regeneration comparing to in wild-type mice (PubMed:24722330). Belongs to the CCN family.