Iida J, Meijne A M, Oegema T R, Yednock T A, Kovach N L, Furcht L T, McCarthy J B
Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, Minnesota 55455, USA.
J Biol Chem. 1998 Mar 6;273(10):5955-62. doi: 10.1074/jbc.273.10.5955.
We have previously reported that alpha4beta1 (but not alpha5beta1) integrin-mediated melanoma cell adhesion is inhibited by removal of cell surface chondroitin sulfate glycosaminoglycan (CSGAG), suggesting that melanoma chondroitin sulfate proteoglycan plays a role in modulating the adhesive function of alpha4beta1 integrin. In the current study, we demonstrated that alpha4beta1 integrin binds to CSGAG. We have identified a peptide from within alpha4 integrin termed SG1 (KKEKDIMKKTI) that binds to cell surface melanoma chondroitin sulfate proteoglycan, indicating that SG1 represents a CSGAG binding site within the alpha4 integrin subunit. Soluble SG1 inhibits alpha4beta1 integrin-mediated human melanoma cell adhesion to CS1. Polyclonal antibody generated against the peptide inhibits melanoma cell adhesion to CS1, and the inhibition is reversed by Mn2+ and an activating monoclonal antibody anti-beta1 (8A2). Additionally, pretreatment of cells with anti-SG1 IgG inhibits the expression of the monoclonal antibody 15/7 epitope in the presence of soluble CS1 peptide, suggesting that anti-SG1 IgG prevents ligand binding by alpha4beta1 integrin. These results demonstrate that alpha4beta1 integrin interacts directly with CSGAG through SG1 site, and that this site can affect the ligand binding properties of the integrin.
我们之前报道过，去除细胞表面硫酸软骨素糖胺聚糖（CSGAG）可抑制α4β1（而非α5β1）整合素介导的黑色素瘤细胞黏附，这表明黑色素瘤硫酸软骨素蛋白聚糖在调节α4β1整合素的黏附功能中发挥作用。在当前研究中，我们证明α4β1整合素与CSGAG结合。我们从α4整合素中鉴定出一段名为SG1（KKEKDIMKKTI）的肽段，它能与细胞表面黑色素瘤硫酸软骨素蛋白聚糖结合，这表明SG1代表α4整合素亚基内的一个CSGAG结合位点。可溶性SG1可抑制α4β1整合素介导的人黑色素瘤细胞与CS1的黏附。针对该肽段产生的多克隆抗体可抑制黑色素瘤细胞与CS1的黏附，且Mn2+和一种抗β1激活单克隆抗体（8A2）可逆转这种抑制作用。此外，用抗SG1 IgG预处理细胞可在可溶性CS1肽存在的情况下抑制单克隆抗体15/7表位的表达，这表明抗SG1 IgG可阻止α4β1整合素与配体结合。这些结果表明，α4β1整合素通过SG1位点直接与CSGAG相互作用，且该位点可影响整合素的配体结合特性。
