The mechanism how Pretubulysin-induced microtubule disassembly improves T cell search efficiency
To clean tissue from tumorigenic and infected cells, cytotoxic T lymphocytes (CTLs) must navigate confined environments in vivo, locate the infected cells and eliminate them. Impaired CTL migration towards the tumor can limit the efficacy of immunotherapy. Microtubules (MTs) have emerged as promising targets, because destabilizing MTs enhances T-cell migration and subsequent killing, yet the underlying mechanisms are poorly understood. Here, we use pretubulysin, a potent MT depolymerizer, to uncover how MT dynamics regulate CTL motility. Complete MT disassembly markedly increased CTL infiltration and migration in 3D matrices. To investigate how altered migration affects target elimination, we employed a persistent random-walk model parameterized solely with experimental motility data. The model shows that the increase in speed and persistence induced by pretubulysin explains enhanced search efficiency increasing the encounter rate of CTLs with target cells. The simulations also predict how these gains in search efficiency scale with tissue thickness and CTL density. Mechanistically, MT depolymerization in activated CTLs triggers localized actomyosin accumulation at the uropod. This enhances rear contraction forces and promotes faster, more persistent migration and efficient search. Our findings clarify how MT dynamics influence CTL ability to eliminate targets in 3D environments and highlights the potential of MT-targeting agents such as pretubulysin to optimize T cell-based immunotherapies.