CDB15:0001408 SPP1 — ITGAV
Experimentally validated in Human; Orthology-inferred in Mouse, Rat, Zebrafish, Chicken, Macaque, Pig, Dog, Cow, Chimp, Horse, Marmoset, Sheep
Title
Journal:; Year Published:
Abstract
Substrate specificity of alpha(v)beta(3) integrin-mediated cell migration and phosphatidylinositol 3-kinase/AKT pathway activation.
The Journal of biological chemistry, 2000; PubMed, Homo sapiens SPP1 — Homo sapiens ITGAV
ABSTRACT: The alpha(v)beta(3) integrin has been shown to bind several ligands, including osteopontin and vitronectin. Its role in modulating cell migration and downstream signaling pathways in response to specific extracellular matrix ligands has been investigated in this study. Highly invasive prostate cancer PC3 cells that constitutively express alpha(v)beta(3) adhere and migrate on osteopontin and vitronectin in an alpha(v)beta(3)-dependent manner. However, exogenous expression of alpha(v)beta(3) in noninvasive prostate cancer LNCaP (beta(3)-LNCaP) cells mediates adhesion and migration on vitronectin but not on osteopontin. Activation of alpha(v)beta(3) by epidermal growth factor stimulation is required to mediate adhesion to osteopontin but is not sufficient to support migration on this substrate. We show that alpha(v)beta(3)-mediated cell migration requires activation of the phosphatidylinositol 3-kinase (PI 3-kinase)/protein kinase B (PKB/AKT) pathway since wortmannin, a PI 3-kinase inhibitor, prevents PC3 cell migration on both osteopontin and vitronectin; furthermore, alpha(v)beta(3) engagement by osteopontin and vitronectin activates the PI 3-kinase/AKT pathway. Migration of beta(3)-LNCaP cells on vitronectin also occurs through activation of the PI 3-kinase pathway; however, AKT phosphorylation is not increased upon engagement by osteopontin. Furthermore, phosphorylation of focal adhesion kinase (FAK), known to support cell migration in beta(3)-LNCaP cells, is detected on both substrates. Thus, in PC3 cells, alpha(v)beta(3) mediates cell migration and PI 3-kinase/AKT pathway activation on vitronectin and osteopontin; in beta(3)-LNCaP cells, alpha(v)beta(3) mediates cell migration and PI 3-kinase/AKT pathway activation on vitronectin, whereas adhesion to osteopontin does not support alpha(v)beta(3)-mediated cell migration and PI 3-kinase/AKT pathway activation. We conclude therefore that alpha(v)beta(3) exists in multiple functional states that can bind either selectively vitronectin or both vitronectin and osteopontin and that can differentially activate cell migration and intracellular signaling pathways in a ligand-specific manner.
Distinct structural requirements for binding of the integrins alphavbeta6, alphavbeta3, alphavbeta5, alpha5beta1 and alpha9beta1 to osteopontin.
Matrix biology : journal of the International Society for Matrix Biology, 2005; PubMed, Homo sapiens SPP1 — Homo sapiens ITGAV
ABSTRACT: The extracellular matrix protein, osteopontin, is a ligand for several members of the integrin family, including alpha5beta1, alphavbeta3, alphavbeta5 and alpha9beta1. Osteopontin is a substrate for a number of extracellular proteases, including thrombin and the metalloproteases MMP-3 and MMP-7, which cleave osteopontin at sites close to or within the mapped integrin binding sites. Using affinity chromatography and cell adhesion assays, we now identify the integrin alphavbeta6 as an additional osteopontin receptor. Utilizing a series of recombinant forms of osteopontin, we compared the structural requirements for alphavbeta6 binding with those for the 4 other osteopontin-binding integrins. Like alpha5beta1, alphavbeta3 and alphavbeta5 (but not alpha9beta1), alphavbeta6 binds to the RGD site in osteopontin, since RGD peptide or mutation of this site to RAA completely inhibits alphavbeta6-mediated cell adhesion. For both alpha9beta1 and alpha5beta1, the N-terminal fragment generated by thrombin cleavage is a much better ligand than full length osteopontin, whereas thrombin-cleavage does not appear to be required for optimal adhesion to alphavbeta3, alphavbeta5 or alphavbeta6. A recombinant fragment predicted to be generated by MMP cleavage no longer supported alpha5beta1 or alpha9beta1-mediated adhesion, but adhesion mediated by alphavbeta5 or alphavbeta6 was unaffected. Finally, adhesion of alphavbeta5 or alphavbeta6 was inhibited by mutation of two aspartic acid residues upstream of the RGD site, whereas adhesion mediated by alphavbeta3, alpha5beta1 or alpha9beta1 was unaffected by these mutations. These results suggest that the hierarchy of integrin interactions with osteopontin can undergo complex regulation at least in part through the action of extracellular proteases.
A biochemical characterization of the binding of osteopontin to integrins alpha v beta 1 and alpha v beta 5.
The Journal of biological chemistry, 1995; PubMed, Homo sapiens SPP1 — Homo sapiens ITGAV
ABSTRACT: Osteopontin (OPN) is an extracellular matrix protein that binds to integrin alpha v beta 3. Here we demonstrate that two other integrins, alpha v beta 1 and alpha v beta 5, are also receptors for OPN. Human embryonic kidney 293 cells adhere to human recombinant osteopontin (glutathione S-transferase-osteopontin; GST-OPN) using integrin alpha v beta 1. When the 293 cells are transfected with the beta 5 subunit, they can also adhere to GST-OPN using integrin alpha v beta 5. Divalent cations regulate the binding of GST-OPN to both alpha v beta 1 and alpha v beta 5. Mg2+ and Mn2+ support the binding of GST-OPN to these integrins but Ca2+ does not. The highest affinity is observed in Mn2+. In the presence of this ion, the affinity of GST-OPN for alpha v beta 1 is 18 nM and the affinity for alpha v beta 5 is 48 nM. The antibody 8A2, which is an agonist for beta 1, promotes the adhesion of 293 cells to GST-OPN even when Ca2+ is present. This observation suggests that cellular events could modulate the affinity of alpha v beta 1 for OPN. Collectively, these findings prove that integrins alpha v beta 1, alpha v beta 3, and alpha v beta 5 have similar affinity for OPN. Therefore, all three integrins must be considered when evaluating the biological affects of OPN.