Microtubule binding by CRIPT and its potential role in the synaptic clustering of PSD-95.

CRIPT is a postsynaptic protein that binds selectively to the third PDZ domain (PDZ3) of PSD-95. Here we show that CRIPT also binds directly to microtubules, thereby linking PSD-95 to the microtubule cytoskeleton. Disrupting the CRIPT-PSD-95 interaction in cultured hippocampal neurons with a PDZ3-specific peptide prevented the association of PSD-95 with microtubules and inhibited the synaptic clustering of PSD-95, chapsyn-110/PSD-93 and GKAP (a PSD-95-binding protein). However, the number of synapses and the synaptic clustering of NMDA receptors were unaffected, suggesting that PSD-95-family proteins are not essential for the maintenance of synapses and the synaptic localization of NMDA receptors.