In humans, TASL (TLR adaptor interacting with SLC15A4 on the lysosome) is encoded by CXorf21 that is associated with systemic lupus erythematosus [1]. It is an immune adaptor that is required for recruitment and activation of IRF5 by TLR7, TLR8 and TLR9, in mechanistic analogy to IRF3 and its three adaptors STING, MAVS and TRIF. TASL interacts with the endolysosomal transporter SLC15A4 forming the SLC15A4-TASL complex, which is required for endolysosomal TLR signalling. TASL contains a pLxIS motif that is important for its function [2].

1: Lysosomal pH Is Regulated in a Sex Dependent Manner in Immune Cells Expressing CXorf21. Harris VM, Harley ITW, Kurien BT, Koelsch KA, Scofield RH; Front Immunol. 2019;10:578. PMID:31001245

2: TASL is the SLC15A4-associated adaptor for IRF5 activation by TLR7-9. Heinz LX, Lee J, Kapoor U, Kartnig F, Sedlyarov V, Papakostas K, Cesar-Razquin A, Essletzbichler P, Goldmann U, Stefanovic A, Bigenzahn JW, Scorzoni S, Pizzagalli MD, Bensimon A, Muller AC, King FJ, Li J, Girardi E, Mbow ML, Whitehurst CE, Rebsamen M, Superti-Furga G; Nature. 2020;581:316-322. PMID:32433612