Wnt-5a/Frizzled9 Receptor Signaling through the Gαo-Gβγ Complex Regulates Dendritic Spine Formation

Abstract

Wnt ligands play crucial roles in the development and regulation of synapse structure and function. Specifically, Wnt-5a acts as a secreted growth factor that regulates dendritic spine formation in rodent hippocampal neurons, resulting in postsynaptic development that promotes the clustering of the PSD-95 (postsynaptic density protein 95). Here, we focused on the early events occurring after the interaction between Wnt-5a and its Frizzled receptor at the neuronal cell surface. Additionally, we studied the role of heterotrimeric G proteins in Wnt-5a-dependent synaptic development. We report that FZD9 (Frizzled9), a Wnt receptor related to Williams syndrome, is localized in the postsynaptic region, where it interacts with Wnt-5a. Functionally, FZD9 is required for the Wnt-5a-mediated increase in dendritic spine density. FZD9 forms a precoupled complex with G␣ o under basal conditions that dissociates after Wnt-5a stimulation. Accordingly, we found that G protein inhibition abrogates the Wnt-5a-dependent pathway in hippocampal neurons. In particular, the activation of G␣ o appears to be a key factor controlling the Wnt-5a-induced dendritic spine density. In addition, we found that G␤␥ is required for the Wnt-5a-mediated increase in cytosolic calcium levels and spinogenesis. Our findings reveal that FZD9 and heterotrimeric G proteins regulate Wnt-5a signaling and dendritic spines in cultured hippocampal neurons.The Wnt family proteins are secreted growth factors that regulate developmental processes, such as cell fate and polarity and general cell maintenance events, by modulating homeostasis and the cell cycle (1, 2). Furthermore, Wnt signaling controls various steps in the differentiation of the central nervous system (3-5), including axon guidance, dendrite development, synapse formation and plasticity (6, 7). Certain Wnt ligands, such as Wnt-7a and Wnt-3a, regulate the development and activity of the pre-and postsynaptic regions of glutamatergic synapses (8 -10). Similarly, previous results have shown that Wnt-5a regulates the synaptic structure and function by inducing the clustering of PSD-95 through the activation of the c-Jun N-terminal kinase (JNK) (11) and modulates glutamate receptors through nitric oxide production (12). Additionally, Wnt-5a promotes the de novo formation of dendritic spines in hippocampal neurons (13) through the non-canonical Wnt/Ca 2ϩ pathway.The Frizzled (FZD) 2 family has 10 members in vertebrates and represents unconventional G protein-coupled receptors (GPCRs) (14). FZD proteins have been identified as Wnt receptors, and they can mediate the signaling triggered by several Wnt ligands. Wnt-5a activity has been linked to several FZDs receptors and other co-receptors in different model systems (15-18). However, the FZD receptor mediating Wnt-5a signaling and spine formation in hippocampal neurons has not yet been identified.Several signaling cascades can be triggered upon Wnt binding to a FZD receptor, including canonical (i.e. ␤-catenin-dependent) and non-canonical pathways (19). Co...

Wnt5a is essential for hippocampal dendritic maintenance and spatial learning and memory in adult mice

“…S1 F-J). These results show that Wnt5a is dispensable for establishing dendritic arbors and for spine formation in CA1 pyramidal neurons in vivo, contrary to published reports that Wnt5a promotes neuronal morphogenesis in cultured hippocampal neurons (15,18,19,32).…”

“…Ror2 is abundantly expressed in mature CA1 dendrites, promotes dendritic activation of noncanonical Wnt signaling and, notably, is necessary for Wnt5a-mediated potentiation of NMDAR currents in acute hippocampal slices (82). Ror2 may function in coordination with Frizzled receptors; in particular, Frizzled-9 is localized to postsynaptic sites in hippocampal neurons, binds Wnt5a via its cysteine-rich domain in biochemical analyses, and the Frizzled-9 cysteine-rich domain is required for Wnt5a-mediated changes in spine densities in cultured hippocampal neurons (32).…”

Wnt5a promotes differentiation and development of adult-born neurons in the hippocampus by noncanonical Wnt signaling

“…Wnt5a is known to induce noncanonical Wnt/JNK and Wnt/Ca 2+ signaling pathways in cultured neurons . Moreover, Wnt5a was shown to induce AP‐1 signaling and phosphorylation of JNK downstream target c‐Jun in differentiating AHPs .…”

“…Wnt5a mRNA is enriched in the dentate gyrus and the CA1 region of adult mice, and the Wnt5a protein is highly expressed in the adult hippocampus . In cultured hippocampal neurons, Wnt5a regulates developmental axon and dendrite outgrowth, synapse formation, and dendritic spine formation . In the adult hippocampus, Wnt5a is required in CA1 neurons to maintain dendritic architecture, and for hippocampal plasticity and spatial learning and memory .…”

Activation of Wnt Signaling in Cortical Neurons Enhances Glucose Utilization through Glycolysis

“…The activity of the Wnt signaling pathway is essential for the development and function of central synapses that modulate several process, such as adult hippocampal neurogenesis, the establishment of synapses, neuronal firing activity, neuronal plasticity, nerve transmission, dendritic spine formation, and mitochondrial dynamics (2,(35)(36)(37)(38)(39). The deregulation of Wnt activity by loss or gain of function has been associated with the progression of various diseases, including cancer, diabetes mellitus type II, fibrosis, and AD (6,30,40,41).…”