Shimoji Y, Ng V, Matsumura K, Fischetti V A, Rambukkana A
Laboratory of Bacterial Pathogenesis and Immunology, The Rockefeller University, New York, NY 10021, USA.
Proc Natl Acad Sci U S A. 1999 Aug 17;96(17):9857-62. doi: 10.1073/pnas.96.17.9857.
Nerve damage is the hallmark of Mycobacterium leprae infection, which results from M. leprae invasion of the Schwann cell of the peripheral nervous system. We have recently shown that the laminin-2 isoform, specially the G domain of laminin alpha2 chain, on the Schwann cell-axon unit serves as an initial neural target for M. leprae. However, M. leprae surface molecules that mediate bacterial invasion of peripheral nerves are entirely unknown. By using human alpha2 laminins as a probe, a major 28-kDa protein in the M. leprae cell wall fraction that binds alpha2 laminins was identified. After N-terminal amino acid sequence analysis, PCR-based strategy was used to clone the gene that encodes this protein. Deduced amino acid sequence of this M. leprae laminin-binding protein predicts a 21-kDa molecule (ML-LBP21), which is smaller than the observed molecular size in SDS/PAGE. Immunofluorescence and immunoelectron microscopy on intact M. leprae with mAbs against recombinant (r) ML-LBP21 revealed that the protein is surface exposed. rML-LBP21 avidly bound to alpha2 laminins, the rG domain of the laminin-alpha2 chain, and the native peripheral nerve laminin-2. The role of ML-LBP21 in Schwann cell adhesion and invasion was investigated by using fluorescent polystyrene beads coated with rML-LBP21. Although beads coated with rML-LBP21 alone specifically adhered to and were ingested by primary Schwann cells, these functions were significantly enhanced when beads were preincubated with exogenous alpha2 laminins. Taken together, the present data suggest that ML-LBP21 may function as a critical surface adhesin that facilitates the entry of M. leprae into Schwann cells.
神经损伤是麻风分枝杆菌感染的标志，这是由麻风分枝杆菌侵入外周神经系统的施万细胞所致。我们最近发现，施万细胞 - 轴突单元上的层粘连蛋白 -2 异构体，特别是层粘连蛋白α2 链的 G 结构域，是麻风分枝杆菌的初始神经靶点。然而，介导细菌侵入外周神经的麻风分枝杆菌表面分子却完全未知。通过使用人α2 层粘连蛋白作为探针，在麻风分枝杆菌细胞壁组分中鉴定出一种与α2 层粘连蛋白结合的主要 28 kDa 蛋白。经过 N 端氨基酸序列分析后，采用基于 PCR 的策略克隆编码该蛋白的基因。该麻风分枝杆菌层粘连蛋白结合蛋白的推导氨基酸序列预测为一个 21 kDa 的分子（ML-LBP21），其在 SDS/PAGE 中观察到的分子大小要小。用抗重组（r）ML-LBP21 的单克隆抗体对完整的麻风分枝杆菌进行免疫荧光和免疫电子显微镜观察，结果显示该蛋白暴露于表面。rML-LBP21 能强烈结合α2 层粘连蛋白、层粘连蛋白α2 链的 rG 结构域以及天然外周神经层粘连蛋白 -2。通过使用包被有 rML-LBP21 的荧光聚苯乙烯珠来研究 ML-LBP21 在施万细胞黏附和侵入中的作用。尽管单独包被有 rML-LBP21 的珠子能特异性黏附并被原代施万细胞摄取，但当珠子与外源性α2 层粘连蛋白预孵育时，这些功能会显著增强。综上所述，目前的数据表明 ML-LBP21 可能作为一种关键的表面黏附素，促进麻风分枝杆菌进入施万细胞。
