Tamalin is a scaffold protein known to regulate membrane trafficking through its interaction with cytohesin-2/ARNO, guanine nucleotide exchange factor (GEF) on ADP-ribosylation factor (Arf) 1/6, and induces actin reorganization. However, the neuronal function of Tamalin is not well understood. Here, we report that Tamalin participates in neurite development through the association with exchange factor for Arf6 (EFA6A)/Arf6 signaling. In immature hippocampal neuron, Tamalin knockdown markedly reduced the dendritic outgrowth, the number of dendritic tips and the levels of filamentous actin (F-actin) and microtubule-associated protein 2 (MAP2) in dendrites. In addition, Tamalin colocalized with EFA6A and Arf6 in the dendritic shaft. Tamalin knockdown reduced the number, size, and intensity of endogenous EFA6A cluster, whereas overexpression of Tamalin showed opposite effects compared with those of knockdown. These results suggest that Tamalin is responsible for neuronal dendritic development via regulation of EFA6A/Arf6-mediated cytoskeleton dynamics.

Variants of the SHANK3 gene, which encodes a core scaffold protein of the postsynaptic density of excitatory synapses, have been causally associated with numerous brain disorders. Shank3 proteins directly bind zinc ions through their C-terminal sterile α motif domain, which enhances the multimerization and synaptic localization of Shank3, to regulate excitatory synaptic strength. However, no studies have explored whether zinc affects the protein interactions of Shank3, which might contribute to the synaptic changes observed after zinc application. To examine this, we first purified Shank3 protein complexes from mouse brain synaptosomal lysates that were incubated with different concentrations of ZnCl2, and analyzed them with mass spectrometry. We used strict criteria to identify 71 proteins that specifically interacted with Shank3 when extra ZnCl2 was added to the lysate. To characterize the zinc-induced Shank3 interactome, we performed various bioinformatic analyses that revealed significant associations of the interactome with subcellular compartments, including mitochondria, and brain disorders, such as bipolar disorder and schizophrenia. Together, our results showing that zinc affected the Shank3 protein interactions of in vitro mouse synaptosomes provided an additional link between zinc and core synaptic proteins that have been implicated in multiple brain disorders.

In an attempt to isolate genes involved in the brain development using ordered differential display PCR, we cloned rgpr85 which encodes rat G-protein-coupled receptor with high degree of identity to the amine-like neurotransmitter receptors. This gene was found to be localized at rat chromosome 4q21. In situ hybridization demonstrated that rgpr85 was predominantly expressed in the developing brain and spinal cord. Hybridization signal was especially abundant within the embryonic cortical plates where postmitotic cortical neurons are localized. In the cerebral cortex, the expression of rgpr85 was gradually decreased postnatally and became undetectable by P18. However, weak but significant expression of rgpr85 was maintained in the adult hippocampal formation, olfactory bulb, and cerebellum. Interestingly, rgpr85 expression was transiently induced in the adult hippocampal formation, piriform cortex, and amygdaloid complex by kainic acid (KA) treatment. Thus, dynamic regulation of rgpr85 expression suggests an importance of rgpr85-mediated signaling in the development of cerebral cortex and in the KA-induced responses in the adult brain.