Neural Cell Adhesion Molecule 2 (NCAM2)-Induced c-Src-Dependent Propagation of Submembrane Ca2+ Spikes Along Dendrites Inhibits Synapse Maturation

Abstract

The neural cell adhesion molecule 2 (NCAM2) is encoded by a gene on chromosome 21 in humans. NCAM2 accumulates in synapses, but its role in regulation of synapse formation remains poorly understood. We demonstrate that an increase in NCAM2 levels results in increased instability of dendritic protrusions and reduced conversion of protrusions to dendritic spines in mouse cortical neurons. NCAM2 overexpression induces an increase in the frequency of submembrane Ca2+ spikes localized in individual dendritic protrusions and promotes propagation of submembrane Ca2+ spikes over segments of dendrites or the whole dendritic tree. NCAM2-dependent submembrane Ca2+ spikes are L-type voltage-gated Ca2+ channel-dependent, and their propagation but not initiation depends on the c-Src protein tyrosine kinase. Inhibition of initiation or propagation of NCAM2-dependent submembrane Ca2+ spikes reduces the NCAM2-dependent instability of dendritic protrusions. Synaptic boutons formed on dendrites of neurons with elevated NCAM2 expression are enriched in the protein marker of immature synapses GAP43, and the number of boutons with mature activity-dependent synaptic vesicle recycling is reduced. Our results indicate that synapse maturation is inhibited in NCAM2-overexpressing neurons and suggest that changes in NCAM2 levels and altered submembrane Ca2+ dynamics can cause defects in synapse maturation in Down syndrome and other brain disorders associated with abnormal NCAM2 expression.

Whole genome analyses reveal significant convergence in obsessive-compulsive disorder between humans and dogs

“…Intriguingly, the thin spines are generally accepted as learning spines due to their greater potential for strengthening [76]. Hence, our results suggest that Ppp2r2b may selectively target immature spine structures and further affect synaptic plasticity in OCD pathogenesis, probably through a mechanism similar to that observed with the OCD risk gene NCAM2 [77], which is also detected in our population stratification and differentiation analysis. We also found that reduced expression of Adamtsl3 in neurons led to an increased density of mushroom spines, which are the most mature form of all spines and referred to as memory spines for their pivotal roles in long-term memory [76,78].…”

Erythrocytic α-synuclein contained in microvesicles regulates astrocytic glutamate homeostasis: a new perspective on Parkinson’s disease pathogenesis

“…Immunocytochemistry was performed as described previously [ 78 ]. Cells were fixed in 4% paraformaldehyde for 30 min at room temperature, washed 2 × 5 min with PBS, and blocked in 4% NGS, 1% BSA, and 0.4% Triton X-100 for 1 h at room temperature.…”

“…Tissue was rinsed twice in 70% ethanol, washed 3 × 10 min in TBS-T, and mounted with Vectashield with DAPI (Vector Laboratories, USA). Immunocytochemistry was performed as described previously [78]. Cells were fixed in 4% paraformaldehyde for 30 min at room temperature, washed 2 × 5 min with PBS, and blocked in 4% NGS, 1% BSA, and 0.4% Triton X-100 for 1 h at room temperature.…”

“…PL assays in cultured cells were performed as described previously [48,78] with modifications. Cultured astrocytes were treated with RBC-EVs at 37°C for 3 h. Then, cultured astrocytes were fixed in 4% formaldehyde in PBS, washed with PBS and blocked by incubating with blocking solution (5% donkey serum, 2% BSA and 0.1 Triton x-100 in PBS) for 1 h. Primary antibodies against the intracellular domain of EAAT2 and α-syn were applied to the cells in 0.1% BSA in blocking solution overnight at 4°C.…”

Trafficking and Activity of Glutamate and GABA Receptors: Regulation by Cell Adhesion Molecules

“…Correspondingly, knockdown of these CAMs results in reductions in the number of synapses in cultured neurons (Chih and others 2005; De Wit and others 2009). Finally, aside from their structural function in synapse formation and maintenance, CAMs are also capable of promoting intracellular signaling by interacting with cell surface receptors (Cavallaro and Dejana 2011; Dityatev and others 2004; Kiselyov and others 2003; Niethammer and others 2002), or by organizing signaling complexes at synapses via direct or indirect associations with cytosolic enzymes such as kinases (Dalva and others 2007; Sheng and others 2018; Sytnyk and others 2006).…”