Lin T H, Yurochko A, Kornberg L, Morris J, Walker J J, Haskill S, Juliano R L
Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill 27599.
J Cell Biol. 1994 Sep;126(6):1585-93. doi: 10.1083/jcb.126.6.1585.
Integrin-mediated cell adhesion, or cross-linking of integrins using antibodies, often results in the enhanced tyrosine phosphorylation of certain intracellular proteins, suggesting that integrins may play a role in signal transduction processes. In fibroblasts, platelets, and carcinoma cells, a novel tyrosine kinase termed pp125FAK has been implicated in integrin-mediated tyrosine phosphorylation. In some cell types, integrin ligation or cell adhesion has also been shown to result in the increased expression of certain genes. Although it seems reasonable to hypothesize that integrin-mediated tyrosine phosphorylation and integrin-mediated gene induction are related, until now, there has been no direct evidence supporting this hypothesis. In the current report, we explore the relationship between integrin-mediated tyrosine phosphorylation and gene induction in human monocytes. We demonstrate that monocyte adherence to tissue culture dishes or to extracellular matrix proteins is followed by a rapid and profound increase in tyrosine phosphorylation, with the predominant phosphorylated component being a protein of 76 kD (pp76). Tyrosine phosphorylation of pp76 and other monocyte proteins can also be triggered by incubation of monocytes with antibodies to the integrin beta 1 subunit, or by F(ab')2 fragments of such antibodies, but not by F(ab) fragments. The ligation of beta 1 integrins with antibodies or F(ab')2 fragments also induces the expression of immediate-early (IE) genes such as IL-1 beta. When adhering monocytes are treated with the tyrosine kinase inhibitors genistein or herbimycin, both phosphorylation of pp76 and induction of IL-1 beta message are blocked in a dose-dependent fashion. Similarly, treatment with genistein or herbimycin can block tyrosine phosphorylation of pp76 and IL-1 beta message induction mediated by ligation of beta 1 integrin with antibodies. These observations suggest that protein tyrosine phosphorylation is an important aspect of integrin-mediated IE gene induction in monocytes. The cytoplasmic tyrosine kinase pp125FAK, although important in integrin signaling in other cell types, seems not to play a role in monocytes because this protein could not be detected in these cells.
整合素介导的细胞黏附，或者使用抗体对整合素进行交联，常常会导致某些细胞内蛋白质的酪氨酸磷酸化增强，这表明整合素可能在信号转导过程中发挥作用。在成纤维细胞、血小板和癌细胞中，一种名为pp125FAK的新型酪氨酸激酶与整合素介导的酪氨酸磷酸化有关。在某些细胞类型中，整合素连接或细胞黏附也已被证明会导致某些基因的表达增加。尽管假设整合素介导的酪氨酸磷酸化与整合素介导的基因诱导相关似乎是合理的，但到目前为止，尚无直接证据支持这一假设。在本报告中，我们探讨了人单核细胞中整合素介导的酪氨酸磷酸化与基因诱导之间的关系。我们证明，单核细胞黏附于组织培养皿或细胞外基质蛋白后，酪氨酸磷酸化会迅速且显著增加，主要的磷酸化成分是一种76kD的蛋白质（pp76）。用抗整合素β1亚基的抗体孵育单核细胞，或者用此类抗体的F(ab')2片段处理，也能触发pp76和其他单核细胞蛋白的酪氨酸磷酸化，但F(ab)片段则不能。用抗体或F(ab')2片段连接β1整合素也会诱导白细胞介素-1β等早期即刻（IE）基因的表达。当黏附的单核细胞用酪氨酸激酶抑制剂染料木黄酮或除莠霉素处理时，pp76的磷酸化和白细胞介素-1β信使核糖核酸的诱导均以剂量依赖的方式被阻断。同样，用染料木黄酮或除莠霉素处理可阻断由抗体连接β1整合素介导的pp76的酪氨酸磷酸化和白细胞介素-1β信使核糖核酸的诱导。这些观察结果表明，蛋白质酪氨酸磷酸化是单核细胞中整合素介导的IE基因诱导的一个重要方面。细胞质酪氨酸激酶pp125FAK虽然在其他细胞类型的整合素信号传导中很重要，但在单核细胞中似乎不起作用，因为在这些细胞中无法检测到这种蛋白质。
