MALT1 Protease Activation Triggers Acute Disruption of Endothelial Barrier Integrity via CYLD Cleavage

Microvascular endothelial cells maintain a tight barrier to prevent passage of plasma and circulating immune cells into the extravascular tissue compartment, yet endothelial cells respond rapidly to vasoactive substances, including thrombin, allowing transient paracellular permeability. This response is a cornerstone of acute inflammation, but the mechanisms responsible are still incompletely understood. Here, we demonstrate that thrombin triggers MALT1 to proteolytically cleave cylindromatosis (CYLD). Fragmentation of CYLD results in microtubule disruption and a cascade of events leading to endothelial cell retraction and an acute permeability response. This finding reveals an unexpected role for the MALT1 protease, which previously has been viewed mostly as a driver of pro-inflammatory NF-κB signaling in lymphocytes. Thus, MALT1 not only promotes immune cell activation but also acutely regulates endothelial cell biology, actions that together facilitate tissue inflammation. Pharmacologic inhibition of MALT1 may therefore have synergistic impact by targeting multiple disparate steps in the overall inflammatory response. [Display omitted] •Thrombin induces MALT1 protease activity in endothelial cells•MALT1-dependent cleavage of CYLD initiates microtubule disruption•Blocking MALT1 protease activity or CYLD cleavage reduces endothelial permeability•Mice harboring catalytically inactive MALT1 are protected from pulmonary edema Klei et al. show that the MALT1 protease functions in cells outside the immune system and is activated in response to the GPCR agonist thrombin. In endothelial cells, MALT1 cleaves CYLD, triggering microtubule destabilization and paracellular permeability. Inhibiting MALT1 may represent an approach for controlling capillary leakage, edema, and inflammation.