Interaction of the brain‐specific protein p42IP4/centaurin‐α1 with the peptidase nardilysin is regulated by the cognate ligands of p42IP4, PtdIns(3,4,5)P3 and Ins(1,3,4,5)P4, with stereospecificity

Abstract

The brain-specific protein p42^IP4, also called centaurin-α1, specifically binds phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P₃] and inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P₄]. Here, we investigate the interaction of p42^IP4/centaurin-α1 with nardilysin (NRDc), a member of the M16 family of zinc metalloendopeptidases. Members of this peptidase family exhibit enzymatic activity and also act as receptors for other proteins. We found that p42^IP4/centaurin-α1 binds specifically to NRDc from rat brain. We further detected that centaurin-α2, a protein that is highly homologuous to p42^IP4/centaurin-α1 and expressed ubiquitously, also binds to NRDc. In vivo interaction was demonstrated by co-immunoprecipitation of p42^IP4/centaurin-α1 with NRDc from rat brain. The acidic domain of NRDc (NRDc-AD), which does not participate in catalysis, is sufficient for the protein interaction with p42^IP4. Interestingly, preincubation of p42^IP4 with its cognate ligands d-Ins(1,3,4,5)P₄ and the lipid diC8PtdIns(3,4,5)P₃ negatively modulates the interaction between the two proteins. d-Ins(1,3,4,5)P₄ and diC8PtdIns(3,4,5)P₃ suppress the interaction with virtually identical concentration dependencies. This inhibition is highly ligand specific. The enantiomer l-Ins(1,3,4,5)P₄ is not effective. Similarly, the phosphoinositides diC8PtdIns(3,4)P₂, diC8PtdIns(3,5)P₂ and diC8PtdIns(4,5)P₂ all have no influence on the interaction. Further experiments revealed that endogenous p42^IP4 from rat brain binds to glutathione-S-transferase (GST)-NRDc-AD. The proteins dissociate from each other when incubated with d-Ins(1,3,4,5)P₄, but not with inositol 1,4,5-trisphosphate [Ins(1,4,5)P₃]. In summary, we demonstrate that p42^IP4 binds to NRDc via the NRDc-AD, and that this interaction is controlled by the cognate cellular ligands of p42^IP4/centaurin-α1. Thus, specific ligands of p42^IP4 can modulate the recruitment of proteins, which are docked to p42^IP4, to specific cellular compartments.