, 2004), and generated an OPHN1 mutant, OPHN1GAP (R409Q) that abolishes its Rho-GAP activity (Nadif Kasri Apoptosis Compound Library supplier et al., 2009; see Figure 3A). This mutant failed to rescue the OPHN1 RNAi-evoked defects in structural and functional maturation of glutamatergic synapses (Nadif Kasri et al., 2009). With regards to OPHN1 and Homer 1b/c, we demonstrated that these proteins physically interact and colocalize in dendritic spines (Govek et al., 2004; Figure S4A); the importance of this association remained however unknown. Introduction of mutations in the consensus Homer binding motif located in the N terminus of OPHN1 disrupted its interaction

with Homer 1b/c (OPHN1Hom; Figures 3A and 3B) (Govek et al., 2004). As an additional tool to acutely disrupt this interaction, we designed a peptide consisting of an OPHN1

sequence that contains the Homer ligand domain (pep-OPHN1Hom; Figure 3C). The peptide was made cell permeable by addition of the human immunodeficiency virus-type 1 Tat sequence. We found that this peptide disrupts the OPHN1-Homer 1b/c interaction (Figure 3C), whereas a control peptide containing three amino acid substitutions in the binding motif did not (pep-contHom, Figure 3C). Notably, pep-OPHN1Hom did not disrupt GSI-IX research buy the association between Homer 1b/c and dynamin-3, nor between Homer 1b/c and mGluR5 (Figures S4B and S4C). A third class of proteins we found to associate with OPHN1 are members of the endophilin MYO10 A family, which include endophilin A1, A2, and A3 (Kjaerulff et al., 2011). In previous studies, we and others demonstrated a direct interaction between OPHN1 and endophilin A1 (Endo1) (Khelfaoui et al., 2009 and Nakano-Kobayashi

et al., 2009), which is predominantly expressed in presynaptic nerve terminals, and showed that this interaction is critical for OPHN1′s presynaptic function in synaptic vesicle retrieval (Nakano-Kobayashi et al., 2009). The endophilin A2 (Endo2) and endophilin A3 (Endo3) proteins, on the other hand, are enriched in postsynaptic compartments and have been implicated in the regulation of AMPAR endocytosis in hippocampal neurons (Chowdhury et al., 2006). Given that all three family members are highly conserved, containing an N-terminal N-BAR (Bin/Amphiphysin/Rvs) domain and a C-terminal SH3 domain (Kjaerulff et al., 2011), we tested whether OPHN1 also interacts with Endo2 and 3. We found that this is indeed the case (Figures 3D and 3E and Figures S5A and S5B), and that the interaction is mediated via binding of the third proline rich domain (PRD3) of OPHN1 to the SH3 domain of Endo2/3 (Figure 3D and Figure S5B, data not shown). Moreover, coimmunoprecipitation experiments revealed that treatment of hippocampal slices with DHPG leads to increased binding of OPHN1 to Endo2/3, which, notably, is protein synthesis dependent (Figure 3E).