Dersch P, Isberg R R
Department of Molecular Biology and Microbiology, Tufts University School of Medicine and Howard Hughes Medical Institute, 136 Harrison Avenue, Boston, MA 02111, USA.
EMBO J. 1999 Mar 1;18(5):1199-213. doi: 10.1093/emboj/18.5.1199.
Invasin allows efficient entry into mammalian cells by Yersinia pseudotuberculosis. It has been shown that the C-terminal 192 amino acids of invasin are essential for binding of beta1 integrin receptors and subsequent uptake. By analyzing the internalization of latex beads coated with invasin derivatives, an additional domain of invasin was shown to be required for efficient bacterial internalization. A monomeric derivative encompassing the C-terminal 197 amino acids was inefficient at promoting entry of latex beads, whereas dimerization of this derivative by antibody significantly increased uptake. By using the DNA-binding domain of lambda repressor as a reporter for invasin self-interaction, we have demonstrated that a region of the invasin protein located N-terminal to the cell adhesion domain of invasin is able to self-associate. Chemical cross-linking studies of purified and surface-exposed invasin proteins, and the dominant-interfering effect of a non-functional invasin derivative are consistent with the presence of a self-association domain that is located within the region of invasin that enhances bacterial uptake. We conclude that interaction of homomultimeric invasin with multiple integrins establishes tight adherence and receptor clustering, thus providing a signal for internalization.
侵袭素可使假结核耶尔森菌高效进入哺乳动物细胞。研究表明，侵袭素的C末端192个氨基酸对于β1整合素受体的结合及随后的摄取至关重要。通过分析包被有侵袭素衍生物的乳胶珠的内化过程，发现侵袭素的一个额外结构域对于细菌的高效内化是必需的。包含C末端197个氨基酸的单体衍生物在促进乳胶珠进入方面效率低下，而通过抗体使该衍生物二聚化则显著增加了摄取。通过使用λ阻遏物的DNA结合结构域作为侵袭素自身相互作用的报告分子，我们证明了侵袭素蛋白中位于侵袭素细胞黏附结构域N末端的一个区域能够自我缔合。对纯化的和表面暴露的侵袭素蛋白进行的化学交联研究，以及无功能侵袭素衍生物的显性干扰效应，均与存在一个位于侵袭素中增强细菌摄取的区域内的自我缔合结构域相一致。我们得出结论，同源多聚体侵袭素与多种整合素的相互作用建立了紧密黏附并使受体聚集，从而为内化提供信号。
