Staphylococcal Superantigens Use LAMA2 as a Coreceptor To Activate T Cells.

Canonical Ag-dependent TCR signaling relies on activation of the src-family tyrosine kinase LCK. However， staphylococcal superantigens can trigger TCR signaling by activating an alternative pathway that is independent of LCK and utilizes a Gα11-containing G protein-coupled receptor (GPCR) leading to PLCβ activation. The molecules linking the superantigen to GPCR signaling are unknown. Using the ligand-receptor capture technology LRC-TriCEPS， we identified LAMA2， the α2 subunit of the extracellular matrix protein laminin， as the coreceptor for staphylococcal superantigens. Complementary binding assays (ELISA， pull-downs， and surface plasmon resonance) provided direct evidence of the interaction between staphylococcal enterotoxin E and LAMA2. Through its G4 domain， LAMA2 mediated the LCK-independent T cell activation by these toxins. Such a coreceptor role of LAMA2 involved a GPCR of the calcium-sensing receptor type because the selective antagonist NPS 2143 inhibited superantigen-induced T cell activation in vitro and delayed the effects of toxic shock syndrome in vivo. Collectively， our data identify LAMA2 as a target of antagonists of staphylococcal superantigens to treat toxic shock syndrome.