T-cell receptor triggering requires inactivation of Lim kinase-1 by Slingshot-1 phosphatase

Actin dynamics control early T cell receptor signalling during T cell activation. However, the precise regulation of initial actin rearrangements is not completely understood. Here, we have investigated the regulatory role of the phosphatase Slingshot-1 (SSH1) in this process. Our data show that SSH1 rapidly polarises to nascent cognate synaptic contacts and later relocalises to peripheral F-actin networks organised at the mature synapses. Knockdown of SSH1 expression by CRISPR/Cas9-mediated genome editing or small interfering RNA revealed a regulatory role for SSH1 in CD3ε conformational change, allowing Nck binding and proper downstream signalling and immunological synapse organisation. TCR triggering induced the SSH1-mediated activation of actin dynamics through a mechanism mediated by Limk1 inactivation. These data suggest that during early TCR activation, SSH1 is required for early F-actin rearrangements that mediate initial conformational changes of the TCR, integrin organisation and proximal signalling events for proper synapse organisation.