CYR61 Regulates BMP-2-dependent Osteoblast Differentiation through the αvβ3 Integrin/Integrin-linked Kinase/ERK Pathway

Abstract

Osteoporosis is one of the most common bone pathologies. A number of novel molecules have been reported to increase bone formation including cysteine-rich protein 61 (CYR61), a ligand of integrin receptor, but mechanisms remain unclear. It is known that bone morphogenetic proteins (BMPs), especially BMP-2, are crucial regulators of osteogenesis. However, the interaction between CYR61 and BMP-2 is unclear. We found that CYR61 significantly increases proliferation and osteoblastic differentiation in MC3T3-E1 osteoblasts and primary cultured osteoblasts. CYR61 enhances mRNA and protein expression of BMP-2 in a time-and dose-dependent manner. Moreover, CYR61-mediated proliferation and osteoblastic differentiation are significantly decreased by knockdown of BMP-2 expression or inhibition of BMP-2 activity. In this study we found integrin ␣ v ␤ 3 is critical for CYR61-mediated BMP-2 expression and osteoblastic differentiation. We also found that integrin-linked kinase, which is downstream of the ␣ v ␤ 3 receptor, is involved in CYR61-induced BMP-2 expression and subsequent osteoblastic differentiation through an ERK-dependent pathway. Taken together, our results show that CYR61 up-regulates BMP-2 mRNA and protein expression, resulting in enhanced cell proliferation and osteoblastic differentiation through activation of the ␣ v ␤ 3 integrin/integrin-linked kinase/ ERK signaling pathway.Bone is a mineralized tissue that underlies multiple mechanical and metabolic functions of the skeleton (1). Bone functions include maintaining blood calcium levels, providing mechanical support to soft tissues and serving as levers for muscle action, supporting hematopoiesis, and housing the brain and spinal cord (2). Formation and maintenance of bone tissue are regulated in a sophisticated fashion by boneforming osteoblasts and bone-resorbing osteoclasts (3). Development and differentiation of these two cell types are under tight regulation by a number of endogenous substances such as hormones, growth factors, and cytokines (4). These factors are individually secreted through endocrine, paracrine/autocrine, and neurocrine systems, with subsequent interaction essential to the delicate balance between bone-forming and -resorbing cells in the marrow microenvironment. An imbalance between the two cell types leads to pathogenesis of certain bone diseases including osteopetrosis and osteoporosis (5, 6).Osteoporosis is the most common human metabolic bone disorder characterized by progressive and age-dependent bone loss and increasing bone fracture risk. It is an important public health issue in postmenopausal women; if untreated, more than half of white women will experience fractures during their lifetime. Between 30 and 50% of women and 15-30% of men will suffer a fracture related to osteoporosis in their lifetime (7). Fractures increase morbidity and mortality and impose a financial burden on the community (8). A most compelling therapeutic need for osteoporosis at the present time is a drug that will substantially increase bone formation...

Role of Integrin-Linked Kinase in Multi-drug Resistance of Human Gastric Carcinoma SGC7901/DDP Cells

“…Additionally, as mentioned previously, AKT was a linker between ILK and NF-κB. Early reports showed that ILK could regulate the ERK pathway as well, but until the recent study, the interaction manner were still not quite clear (Su et al, 2010). The WB results showed that the phosphorylation of AKT and ERK were attenuated by ILK silencing ( Figure 6A).…”

Cyr61, a Matricellular Protein, Is Needed for Dendritic Arborization of Hippocampal Neurons

“…Cyr61 was shown to activate small GTPase Rac1 in prostate cancer cells (55), which is a widely accepted activator of dendritic growth (3,56,57). Cyr61 can also act upstream of PI3K-mTOR and ERK signaling pathways (58,59), raising the intriguing possibility that the initial activation of cyr61 expression downstream of these kinases is an early step in a positive feedback loop that potentiates their progrowth effects and coordinates the actions of these kinases with remodeling of the extracellular matrix.…”

Osteoblast-released Matrix Vesicles, Regulation of Activity and Composition by Sulfated and Non-sulfated Glycosaminoglycans

“…However, the following five proteins were identified as being significantly regulated in the presence of HA or CS1: (i) CCN1 and THBS2 were up-regulated in the presence of CS1 (FC ϭ 0.8 and 0.6 compared with the untreated control). As discussed earlier, both proteins are involved in cell adhesion and, moreover, osteoblast differentiation either directly by increasing the BMP synthesis (62) or indirectly by the activation of TGF-␤ (54). (ii) POSTN, the Pentraxin-related protein 3 (PTX3), and the FTH1 were significantly down-regulated in the presence of HA (FC ϭ Ϫ0.9, Ϫ1.3, and Ϫ1.6 compared with the untreated control).…”

“…Moreover, in comparative analysis to CS1, the growth factor CCN2 was identified to be up-regulated by sHA1 (FC ϭ 2.6). Both CCN family members were shown to induce the osteoblastogenesis (62)(63)(64).…”