A 21-kDa sarface protein of Mycobacterium leprae binds peripheral nerve laminin-2 and mediates Schwann cell invasion

摘要

Nerve damage is the hallmark of rium 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 #alpha#2 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 #alpha#2 laminins as a probe, a major 28-kDa protein in the M. leprae cell wall fraction that binds #alpha# 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 mi- croscopy on intact M. teprae with mAbs against recombinant (r) ML-LBP21 revealed that the protein is surface exposed. rML- LBP21 avidly bound to #alpha#2 laminins, the rG domain of the laminin-#alpha#2 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 #alpha#2 laminins. Taken together, the present data suggest that ML-LBP21 may function as