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Neurons express multiple types of voltage-gated calcium (Ca2+) channels. Two subtypes of neuronal L-type Ca2+ channels are encoded by Cav1.2 and Cav1.3 pore-forming subunits. Both Cav1.2 and Cav.3 subunits contain class I PDZ (postsynaptic density-95/Discs large/zona occludens-1) domain-binding consensus at their C termini. In yeast two-hybrid screen of rat brain cDNA library with the C-terminal bait of Cav1.3a (long C-terminal splice variant) L-type Ca2+ channel subunit, we isolated multiple clones of postsynaptic adaptor protein Shank. We demonstrated a specific association of Cav1.3a C termini, but not of Cav1.2 C termini, with Shank PDZ domain in vitro. We further demonstrated that the proline-rich region present in C termini of Cav1.3a subunit binds to Shank Src homology 3 domain. We established that Cav1.3a and Shank localized to postsynaptic locations in cultured rat hippocampal neurons. By expressing epitope-tagged recombinant Cav1.3 subunits in rat hippocampal neuronal cultures, we demonstrated that the presence of Shank-binding motifs in Cav1.3a sequence is both necessary and sufficient for synaptic clustering of Cav1.3 L-type Ca2+ channels. In experiments with dominant-negative peptides and dihydropyridine-resistant Cav1.3a mutants, we demonstrated an importance of Shank-binding motif in Cav1.3a sequence for phosphorylated cAMP response element-binding protein (pCREB) signaling in cultured hippocampal neurons. Our results directly link Cav1.3 neuronal L-type Ca2+ channels to macromolecular signaling complex formed by Shank and other modular adaptor proteins at postsynaptic density and provide novel information about the role played by Cav1.3 L-type Ca2+ channels in pCREB signaling. [ABSTRACT FROM AUTHOR]