Model of TEP1 convertase formation.
In steady state hemolymph a pool of TEP1-F is processed by an unknown protease to generate TEP1cut, which interacts and circulates with the LRIM1/APL1C complex. Recognition of microbial surfaces leads to deposition of LRIM1/APL1C and TEP1cut and subsequent recruitment of SPCLIP1. An unknown catalytically active protease is then recruited generating the mature TEP1 convertase, which processes TEP1-F causing it to rapidly interact with nearby surfaces. Steady state processing of TEP1-F and that performed by the TEP1 convertase are distinct, as only the latter requires SPCLIP1. Formation of the TEP1 convertase is required for phagocytosis, lysis, or CLIPA8 cleavage by an unknown protease and subsequent activation of the melanization cascade.