DAPK1 Promotes Extrasynaptic GluN2B Phosphorylation and Striatal Spine Instability in the YAC128 Mouse Model of Huntington Disease

Abstract

Huntington disease (HD) is a devastating neurodegenerative disorder caused by a CAG repeat expansion in the huntingtin gene. Disrupted cortico-striatal transmission is an early event that contributes to neuronal spine and synapse dysfunction primarily in striatal medium spiny neurons, the most vulnerable cell type in the disease, but also in neurons of other brain regions including the cortex. Although striatal and cortical neurons eventually degenerate, these synaptic and circuit changes may underlie some of the earliest motor, cognitive, and psychiatric symptoms. Moreover, synaptic dysfunction and spine loss are hypothesized to be therapeutically reversible before neuronal death occurs, and restoration of normal synaptic function may delay neurodegeneration. One of the earliest synaptic alterations to occur in HD mouse models is enhanced striatal extrasynaptic NMDA receptor expression and activity. This activity is mediated primarily through GluN2B subunitcontaining receptors and is associated with increased activation of cell death pathways, inhibition of survival signaling, and greater susceptibility to excitotoxicity. Abbreviations: AHA, azidohomoalanine; AP5, amino-5-phosphonovaleric acid; a competitive NMDA receptor antagonist; BACHD, Transgenic mouse model of Huntington disease containing the full-length human mutant huntingtin gene with 97 mixed CAA-CAG repeats; BDNF, brain-derived neurotrophic factor; C6R, Transgenic mouse model expressing full-length human mutant huntingtin bearing a point mutation at the D586 caspase cleavage site; CaMKII, calcium/calmodulindependent protein kinase II; CB, cerebellum; CK2, casein kinase 2; COS-7, fibroblast-like cell line derived from monkey kidney tissue; CREB, cAMP response element-binding protein; CS, cortico-striatal; CTX, cortex; cortical; DAPK1, death-associated protein kinase 1; DARPP32, dopamine-and cAMP-regulated neuronal phosphoprotein; DIV, day-in vitro; DKI, DAPK1 inhibitor; also referred to as TC

Roles of N-Methyl-D-Aspartate Receptors (NMDARs) in Epilepsy

“…Meanwhile, DAPK1 interacts with NMDAR involved in glutamate-induced neurological events during sudden physiopathologic conditions in the brain (DeGregorio-Rocasolano et al, 2020). Inhibition of DAPK1 results in the phosphorylation and surface normalization of GluN2B expression outside the synapse (Schmidt et al, 2020).…”

Non-Cell Autonomous and Epigenetic Mechanisms of Huntington’s Disease

“…NMDAR is composed of three types of subunits (GluN1, GluN2A-D, and GluN3A-B), where NMDAR that contains GluN2A or GluN2B control synaptic dynamics [59]. Particularly, GluN2B-type NMDARs are phosphorylated by death-associated protein kinase to serve as toxic receptors [60].…”

Rescue of aberrant huntingtin palmitoylation ameliorates mutant huntingtin-induced toxicity

“…Cortical and striatal tissues attached were dissected in ice-cold HBSS, gently dissociated with a P1000 pipette (×2-3 times) and briefly spun. Tissues were digested in 0.05% trypsin-EDTA for 8 min at 37°C until addition of 10% FBS in neurobasal (NB) medium, as previously described (Schmidt et al, 2020). Cells were centrifuged, further dissociated by mechanical trituration in NB medium (supplemented with B27, GlutaMAX, penicillin and streptomycin) and DNase (0.08 mg/mL).…”