gC1q-R/p32, a C1q-binding protein, is a receptor for the InlB invasion protein of Listeria monocytogenes

AUTOR(ES)

Braun, Laurence

FONTE

Oxford University Press

RESUMO

InlB is a Listeria monocytogenes protein that promotes entry of the bacterium into mammalian cells by stimulating tyrosine phosphorylation of the adaptor proteins Gab1, Cbl and Shc, and activation of phosphatidyl– inositol (PI) 3-kinase. Using affinity chromatography and enzyme-linked immunosorbent assay, we demonstrate a direct interaction between InlB and the mammalian protein gC1q–R, the receptor of the globular part of the complement component C1q. Soluble C1q or anti-gC1q–R antibodies impair InlB-mediated entry. Transient transfection of GPC16 cells, which are non-permissive to InlB-mediated entry, with a plasmid-expressing human gC1q–R promotes entry of InlB-coated beads. Furthermore, several experiments indicate that membrane recruitment and activation of PI 3-kinase involve an InlB–gC1q–R interaction and that gC1q–R associates with Gab1 upon stimulation of Vero cells with InlB. Thus, gC1q–R constitutes a cellular receptor involved in InlB-mediated activation of PI 3-kinase and tyrosine phosphorylation of the adaptor protein Gab1. After E–cadherin, the receptor for internalin, gC1q–R is the second identified mammalian receptor promoting entry of L.monocytogenes into mammalian cells.

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