The receptor binding mechanism of mouse sPLA2 group IIE.

Secreted phospholipase A2s (sPLA2s) participate in physiological function by their enzyme and receptor binding activity. Muscle-type phospholipase A2 receptor (M-type PLA2R) is the sPLA2 binding protein with the highest affinity so far, and also inhibits the enzyme activity of sPLA2. There is species specificity and pH dependence for the binding of M-type PLA2R to sPLA2. Mouse sPLA2 Group IIE (mGIIE) has been verified to have a high affinity for mouse M-type PLA2R (M-type mPLA2R) at the nanomolar scale. For further exploration of the receptor binding mechanism of GIIE, in this study, we use Alphafold Multimer to generate complex models of mGIIE with the M-type mPLA2R ectodomain, wild-type CTLD5 domain of mPLA2R, and three CTLD5 mutants, respectively. mPLA2R-mGIIE models exhibit heterogeneous extended mPLA2R conformations with uncovered sPLA2-binding surface of CTLD5 domain. Complexed models of mGIIE with wild-type and mutated mCTLD5 further confirm that helix α1 of mCTLD5, especially essential residues F838 and W842, interact with the substrate pocket of mGIIE and thus inhibit its enzyme activity. Peptides from helix α1 of mCTLD5 are verified to inhibit the enzymatic activity of mGIIE. This AI-guided research would substantially accelerate our understanding of the functional study of GIIE, and provide the lead-peptide for the further inhibitor design of sPLA2.