Lack of Pannexin 1 Alters Synaptic GluN2 Subunit Composition and Spatial Reversal Learning in Mice

Abstract

Long-term potentiation (LTP) and long-term depression (LTD) are two forms of synaptic plasticity that have been considered as the cellular substrate of memory formation. Although LTP has received considerable more attention, recent evidences indicate that LTD plays also important roles in the acquisition and storage of novel information in the brain. Pannexin 1 (Panx1) is a membrane protein that forms non-selective channels which have been shown to modulate the induction of hippocampal synaptic plasticity. Animals lacking Panx1 or blockade of Pannexin 1 channels precludes the induction of LTD and facilitates LTP. To evaluate if the absence of Panx1 also affects the acquisition of rapidly changing information we trained Panx1 knockout (KO) mice and wild type (WT) littermates in a visual and hidden version of the Morris water maze (MWM). We found that KO mice find the hidden platform similarly although slightly quicker than WT animals, nonetheless, when the hidden platform was located in the opposite quadrant (OQ) to the previous learned location, KO mice spent significantly more time in the previous quadrant than in the new location indicating that the absence of Panx1 affects the reversion of a previously acquired spatial memory. Consistently, we observed changes in the content of synaptic proteins critical to LTD, such as GluN2 subunits of N-methyl-D-aspartate receptors (NMDARs), which changed their contribution to synaptic plasticity in conditions of Panx1 ablation. Our findings give further support to the role of Panx1 channels on the modulation of synaptic plasticity induction, learning and memory processes.

Overlap in synaptic neurological condition susceptibility pathways and the neural pannexin 1 interactome revealed by bioinformatics analyses

“…This regulation of neurites and dendritic spines connects nicely with our earlier discovery of Panx1 proteinprotein interactions (PPIs) with dendritic spine regulating proteins, such as the actin-related protein (Arp) 2/3 complex components (Wicki-Stordeur and Swayne, 2013), and the microtubule-interacting protein collapsin-response mediator protein 2 (Crmp2) (Xu et al, 2018). A role for Panx1 in regulating neuronal development and connectivity is further supported by work revealing its role in hippocampal synaptic plasticity under naïve conditions (Ardiles et al, 2014;Gajardo et al, 2018;Prochnow et al, 2012), as well as recently reported connections to intellectual disability (Shao et al, 2016) and autism spectrum disorder (ASD) (Davis et al, 2012). Moreover, Panx1 has been implicated in synaptic dysfunction in ischemia (MacVicar and Thompson, 2010;Weilinger et al, 2016;Weilinger et al, 2013) and has been suggested to be involved in CNS dysfunction associated with Alzheimer disease (Orellana et al, 2011b) and Parkinson disease (Diaz et al, 2019).…”

Acute Pannexin 1 Blockade Mitigates Early Synaptic Plasticity Defects in a Mouse Model of Alzheimer’s Disease

“…Hippocampal slices were prepared as we previously reported (Ardiles et al, 2012;Gajardo et al, 2018). Briefly, mice were deeply anesthetized with isoflurane, brains quickly removed and hippocampus sectioned in slices of 350 µm in ice-cold dissection buffer using a vibroslicer (Leica VT1200S, Leica Microsystems, Nussloch, Germany).…”

“…Synaptosomes were extracted from hippocampus of 6 m.o. male mice as we previously described (Gajardo et al, 2018). Hippocampi were homogenized in ice-cold homogenization buffer [320 mM sucrose, 4 mM 4-(2-hydroxyethyl)-1piperazineethanesulfonic acid (HEPES), and 1 mM ethylene glycol-bis(β-aminoethyl ether)-N,N,N ,N -tetraacetic acid; EGTA), pH 7.4; protease and phosphatase inhibitor cocktails] using a Dounce tissue grinder.…”

Pannexin 1 Regulates Dendritic Protrusion Dynamics in Immature Cortical Neurons

“…PANX1 is broadly and highly expressed in the brain during early postnatal development (Ray et al, 2005;Vogt et al, 2005) and localized and enriched in synaptic compartments (Zoidl et al, 2007;Sanchez-Arias et al, 2019). Pharmacological and genetic disruption of PANX1 results in enhanced hippocampal LTP induction while precluding that of LTD (Prochnow et al, 2012;Ardiles et al, 2014;Gajardo et al, 2018). Given that PANX1interacting cytoskeletal regulators, collapsin response mediator protein 2 (CRMP2) and actinrelated protein 2/3 complex (ARP2/3), are known to control dendritic spine formation (Wicki-Stordeur and Swayne, 2013;Spence et al, 2016;Zhang et al, 2016;Xu et al, 2018), it was perhaps not surprising that Sanchez-Arias et al (2019) recently showed that Panx1 deletion led to the formation of larger cortical neuron network ensembles and that this was due, in part, to increased cortical neuron dendritic spine density.…”