Cytoskeletal tension actively sustains the migratory T cell synaptic contact

Abstract

When migratory T cells encounter antigen presenting cells (APCs), they arrest and form radially symmetric, stable intercellular junctions termed immunological synapses which facilitate exchange of crucial biochemical information and are critical for T cell immunity. While the cellular processes underlying synapse formation have been well-characterized, those that maintain the symmetry, and thereby the stability of the synapse remain unknown. Here we identify an antigen-triggered mechanism that actively promotes T cell synapse symmetry by generating cytoskeletal tension in the plane of the synapse through focal nucleation of actin via Wiskott -Aldrich syndrome Protein (WASP), and contraction of the resultant actin filaments by myosin II. Following T cell activation, WASP is degraded, leading to cytoskeletal rearrangement and tension decay, which result in synapse breaking.Thus, our study identifies and characterizes a mechanical program within otherwise highly motile T cells that sustains the symmetry and stability of the T cell-APC synaptic contact.

WASP facilitates tumor mechanosensitivity in T lymphocytes

“…2A-B) The similarity in WASP-/-and WASPΔC CTL phenotypes indicated that WASP's nucleation-promoting factor (NPF) activity is essential for its support of TCR activation and CTL cytotoxicity. To further test whether the mechanical stresses are compromised in WASP-/-CTL synapses, we utilized the lymphocyte form of P130Cas (CasL), phosphorylated at Tyr-249, as endogenous mechanotransduction sensor 30 . P130 Cas as well as CasL localize to filamentous actin and show higher phosphorylation at Tyr-249 in response to elevated local cytoskeletal stresses 30,45,49 .…”

“…To further test whether the mechanical stresses are compromised in WASP-/-CTL synapses, we utilized the lymphocyte form of P130Cas (CasL), phosphorylated at Tyr-249, as endogenous mechanotransduction sensor 30 . P130 Cas as well as CasL localize to filamentous actin and show higher phosphorylation at Tyr-249 in response to elevated local cytoskeletal stresses 30,45,49 . Indeed, phospho-Tyr-249-CasL (pCasL) was reduced in the synapses formed between B16 and WASP-/-CTL and could be significantly rescued by the expression of full-length WASP protein.…”

“…Such an effect of forces on the density of the branched actin network has been reported previously 54 . In addition, actin foci are dynamic structures that undergo formation, growth, and dissipation within a few seconds 30 . It is therefore possible that the membrane receptors at the actin foci site experience transitions in micro-and nano-scale forces during different phases of the foci lifetime, enabling mechanotransduction.…”

“…On day 5, the CTLs were harvested and used for experiments. For both synapse and cytotoxicity assays, B16 cells were incubated with 100ng/ml of IFNγ overnight, pulsed with 10µM GP100 peptide (25)(26)(27)(28)(29)(30)(31)(32)(33); EGSRNQDWL; Anaspec AS-64752) for 1h, washed and utilized for the experiments.…”

“…In addition, whether the target cell cytoskeleton is also involved in lymphocyte mechanosensing is not known. This is a crucial knowledge gap, since cortical cytoskeletal processes would be the primary modulators of target cell stiffness 29 and would thereby regulate lymphocyte immune response 2,7,14,22,[30][31][32][33][34] .…”