['The synaptic protein PSD-95/SAP90 interacts with ion channels such as the N-methyl-D-aspartate-receptor (NMDA-R) via its PDZ domain, and is involved in their clustering. Moreover, it interacts with signalling molecules and plays an important role in coupling NMDA-R to pathways that control synaptic plasticity and learning.', 'We report that PSD-95 interacts with the adenomatous polyposis coli (APC) tumour suppressor protein via its PDZ domain. Furthermore, we found that PSD-95, NMDA-R and APC are contained in the same complex in vivo. PSD-95-NMDA-R-APC association was found to require two cysteine residues conserved in the amino-terminus of PSD-95 that are known to be critical for its multimerization.'] Is the colorectal tumour suppressor APC present in the NMDA-receptor-PSD-95 complex in the brain?