Campanero M R, Arroyo A G, Pulido R, Ursa A, de Matías M S, Sánchez-Mateos P, Kassner P D, Chan B M, Hemler M E, Corbí A L
Sección de Immunología, Hospital de la Princesa, Madrid, Spain.
Eur J Immunol. 1992 Dec;22(12):3111-9. doi: 10.1002/eji.1830221213.
Whereas all of the integrins in the VLA protein subfamily are involved in cell-extracellular matrix interactions, only VLA-4 (through the alpha 4 subunit) has been implicated in the triggering of intercellular adhesion. Here we describe that the VLA protein beta 1 subunit (CD29) is also involved in the induction of homotypic cell aggregation. We have obtained three novel anti-beta 1 monoclonal antibodies (mAb) with the ability to induce cell aggregation on different leukocyte cell types. These mAb recognize an antigenic site on the common beta 1 chain of VLA proteins which is topographically and/or functionally distinct from other epitopes previously defined by several prototype anti-beta 1 mAb. Induction of cell aggregation by anti-beta 1 mAb is epitope specific, isotype and Fc independent, and displays kinetics similar to alpha 4-mediated aggregation. This cell aggregation requires an intact cellular metabolism, the presence of divalent cations in the extracellular medium, and the integrity of the cytoskeleton. We also have found that the Na+/H+ antiporter may be essential for this process. For Ramos cells, which bear only the VLA alpha 4/beta 1 heterodimer, intercellular adhesion induced through the VLA-beta 1 chain could be selectively inhibited by other anti-beta 1 mAb as well as by anti-alpha 4 mAb. Interestingly, anti-beta 1 mAb which induced strong aggregation of VLA-alpha 2- or VLA-alpha 4-transfected K562 cells, had minimal effect on the alpha 2- alpha 4- alpha 5+ K562 cell line. Furthermore, the beta 1-mediated induction of cell aggregation on alpha 2-K562- and alpha 4-K562-transfected cells was blocked by preincubation with either anti-alpha 2 or anti-alpha 4 mAb, respectively, as well as by other anti-beta 1 mAb. Interestingly, parental K562 cells were able to interact with both alpha 2- and alpha 4-transfected K562 cells, thus suggesting that counter-receptors for both integrins (VLA-2 and VLA-4) might exist on these cells. Together these results provide strong evidence supporting the involvement of alpha 2/beta 1 and alpha 4/beta 1 heterodimers in intercellular interactions and underline the pivotal role of the common beta 1 chain of VLA proteins in the integrin-mediated induction of cell aggregation.
鉴于VLA蛋白亚家族中的所有整合素都参与细胞与细胞外基质的相互作用，但只有VLA - 4（通过α4亚基）与细胞间黏附的触发有关。在此我们描述VLA蛋白β1亚基（CD29）也参与同型细胞聚集的诱导。我们获得了三种新型抗β1单克隆抗体（mAb），它们能够在不同白细胞类型上诱导细胞聚集。这些mAb识别VLA蛋白共同β1链上的一个抗原位点，该位点在拓扑结构和/或功能上与先前几种原型抗β1 mAb所定义的其他表位不同。抗β1 mAb诱导细胞聚集具有表位特异性，与抗体类型和Fc无关，并且显示出与α4介导的聚集相似的动力学。这种细胞聚集需要完整的细胞代谢、细胞外培养基中存在二价阳离子以及细胞骨架的完整性。我们还发现Na + /H + 反向转运体可能对这一过程至关重要。对于仅携带VLAα4/β1异二聚体的Ramos细胞，通过VLA - β1链诱导的细胞间黏附可被其他抗β1 mAb以及抗α4 mAb选择性抑制。有趣的是，能诱导VLA - α2或VLA - α4转染的K562细胞强烈聚集的抗β1 mAb，对α2 - α4 - α5 + K562细胞系的影响极小。此外，β1介导的α2 - K562和α4 - K562转染细胞上的细胞聚集分别被用抗α2或抗α4 mAb预孵育以及其他抗β1 mAb所阻断。有趣的是，亲本K562细胞能够与α2和α4转染的K562细胞相互作用，因此表明这些细胞上可能存在两种整合素（VLA - 2和VLA - 4）的反受体。这些结果共同提供了强有力的证据，支持α2/β1和α4/β1异二聚体参与细胞间相互作用，并强调了VLA蛋白共同β1链在整合素介导的细胞聚集诱导中的关键作用。
