Interaction of the brain‐specific protein p42 IP4 /centaurin‐α1 with the peptidase nardilysin is regulated by the cognate ligands of p42 IP4 , PtdIns(3,4,5)P 3 and Ins(1,3,4,5)P 4 , with stereospecificity

The brain‐specific protein p42 IP4 , also called centaurin‐α1, specifically binds phosphatidylinositol 3,4,5‐trisphosphate [PtdIns(3,4,5)P 3 ] and inositol 1,3,4,5‐tetrakisphosphate [Ins(1,3,4,5)P 4 ]. 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)P 4 and the lipid diC8PtdIns(3,4,5)P 3 negatively modulates the interaction between the two proteins. d ‐Ins(1,3,4,5)P 4 and diC8PtdIns(3,4,5)P 3 suppress the interaction with virtually identical concentration dependencies. This inhibition is highly ligand specific. The enantiomer l ‐Ins(1,3,4,5)P 4 is not effective. Similarly, the phosphoinositides diC8PtdIns(3,4)P 2 , diC8PtdIns(3,5)P 2 and diC8PtdIns(4,5)P 2 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)P 4 , but not with inositol 1,4,5‐trisphosphate [Ins(1,4,5)P 3 ]. 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.