The Golgi-Associated PDZ Domain Protein Gopc/PIST Is Required for Synaptic Targeting of mGluR5

In neuronal cells, many membrane receptors interact via their intracellular, C-terminal tails with PSD-95/discs large/ZO-1 (PDZ) domain proteins. Some PDZ proteins act as scaffold proteins. In addition, there are a few PDZ proteins such as Gopc which bind to receptors during intracellular transport. Gopc is localized at the trans-Golgi network (TGN) and binds to a variety of receptors, many of which are eventually targeted to postsynaptic sites. We have analyzed the role of Gopc by knockdown in primary cultured neurons and by generating a conditional Gopc knockout (KO) mouse line. In neurons, targeting of neuroligin 1 (Nlgn1) and metabotropic glutamate receptor 5 (mGlu5) to the plasma membrane was impaired upon depletion of Gopc, whereas NMDA receptors were not affected. In the hippocampus and cortex of Gopc KO animals, expression levels of Gopc-associated receptors were not altered, while their subcellular localization was disturbed. The targeting of mGlu5 to the postsynaptic density was reduced, coinciding with alterations in mGluR-dependent synaptic plasticity and deficiencies in a contextual fear conditioning paradigm. Our data imply Gopc in the correct subcellular sorting of its associated mGlu5 receptor in vivo.