, 2004), while the ZDHHC8 gene lies in a region of chromosome 22 repeatedly implicated in schizophrenia ( Mukai et al., 2004 and Chen et al., 2004). Palmitoylation of neuronal proteins by DHHC5/8 is, therefore, likely essential for normal neuronal function Sorafenib datasheet and may be impaired in disease states. However, little is known regarding the direct neuronal substrates of DHHC5/8. Here, we identify a specific splice form of the multi-PDZ domain containing protein GRIP1b as a novel neuronal substrate for DHHC5/8. Palmitoylated

GRIP1b, which is targeted to trafficking endosomes, serves as a specific link between endosomes and microtubule motors. This localization places palmitoylated GRIP1b in a perfect position to mediate activity-dependent AMPA-R trafficking, a role we recently revealed for GRIP1. Indeed, palmitoylation enhances GRIP1b’s ability to accelerate AMPA-R recycling. Strikingly, binding, palmitoylation, and dendritic targeting of GRIP1b by DHHC5 all require a novel PDZ ligand-dependent recognition mechanism. These findings not only identify a neuronal DHHC5/8 substrate, but also define additional mechanisms

controlling palmitoylation specificity. DHHC5 and DHHC8 are closely related but differ markedly in structure from all other PATs because they possess greatly extended C-terminal tails (Fukata et al., 2004 and Ohno et al., 2006). We hypothesized SB431542 that these tails might provide clues to the possible specific roles and targets of DHHC5/8. In particular, we noticed that both tails end with a motif that is predicted to bind to PDZ domain-containing proteins (Kim and Sheng, 2004 and Feng and Zhang, 2009). PDZ domain proteins

are heavily implicated in many aspects of neuronal regulation but are especially known to control the targeting and trafficking of glutamate receptors (Kornau et al., 1995, Dong et al., 1997, Srivastava et al., 1998, Steinberg et al., 2006, Daw et al., 2000, Osten et al., 2000, Wyszynski et al., 2002, Terashima et al., 2008 and Hanley, 2008). We, therefore, hypothesized that DHHC5/8 might use their C-terminal motif to bind specific next PDZ domain proteins and potentially to recognize them as substrates for palmitoylation. The DHHC5 and DHHC8 C termini are identical and conform to a type II PDZ ligand (EISV; Figure 1A; Songyang et al., 1997). As a first step to address the possibility that DHHC5/8 use this C-terminal motif to bind specific substrates, we performed a yeast two-hybrid screen of a rat hippocampal cDNA library using a C-terminal bait that included the shared DHHC5/8 PDZ ligand. Of 8 × 106 clones screened, four “hits” encoded an identical central region (PDZ domains 4–6: “GRIP1-456”) of the multi-PDZ domain adaptor protein GRIP1 (Dong et al., 1997).