Biology subjects

Poncer, J. C.

Publications and source records attributed to Poncer, J. C..

5 recordsLinked to original sources

bioRxiv2026

Differential isoform-specific control of KCC2 function in developing cortical neurons

The K-Cl cotransporter KCC2 is essential for fast synaptic inhibition in the mature brain. It is encoded by a single gene and expressed as two isoforms: KCC2a and KCC2b, which differ in their N-terminal domains. While KCC2b is predominant, the function of the weakly expressed KCC2a isoform remains unclear. Here, we reveal that KCC2a is a potent, bidirectional regulator of KCC2b membrane stability and function in cortical neurons. In immature neurons, where WNK-SPAK kinase activity is high, KCC2a promotes SPAK-dependent phosphorylation of KCC2b at Thr1007, which likely contributes to hindering its membrane expression and function. Conversely, in mature neurons with low basal WNK-SPAK activity, KCC2a promotes KCC2b expression, clustering, and function. At this stage, although accounting for less than 5% of total KCC2 mRNA, KCC2a is enriched in dendrites and within KCC2 clusters, where it prevents clathrin-mediated KCC2b endocytosis, as well as polyubiquitination and proteasomal degradation. Thus, KCC2a acts as a developmental switch that first inhibits KCC2b during early development and then ensures its membrane stability to support effective synaptic inhibition in the adult brain.

neuroscience↗

bioRxiv2023

Enhancing KCC2 function reduces interictal activity and prevents seizures in mesial temporal lobe epilepsy

The neuronal K/Cl cotransporter KCC2 regulates the transmembrane chloride gradient, which controls the efficacy of GABAergic signaling. In mesial temporal lobe epilepsy (mTLE) and other neurological disorders, reduced KCC2 expression or function can result in depolarizing GABA signaling, which is thought to contribute to pathological activity and seizures. Therefore, restoring chloride homeostasis represents a promising therapeutic strategy. We investigated the mechanisms and antiseizure effects of two small molecules, prochlorperazine (PCPZ) and CLP-257, that have been identified as potential KCC2 enhancers. We found that both compounds enhance KCC2 function and clustering in cortical neurons while reducing its membrane diffusion, without altering canonical regulatory phosphorylation. CLP-257 also selectively increased extrasynaptic, but not synaptic, GABAA receptor-mediated currents. Using in vitro recordings from resected brain tissue of patients with drug-resistant mTLE and in vivo recordings from a mouse model, we show that PCPZ and CLP-257 (or its prodrug CLP-290) effectively suppressed spontaneous epileptiform activity in both models. These findings reveal that PCPZ and CLP-257 act as genuine KCC2 enhancers and provide experimental evidence of the therapeutic potential of such compounds for treating drug-resistant mTLE. Significance statementA major challenge in treating epilepsy is the high percentage of patients with drug-resistant forms, like mesial temporal lobe epilepsy (mTLE). This study investigates a therapeutic strategy by targeting the neuronal KCC2 transporter, which is often dysfunctional in epilepsy. Our findings identify two compounds, prochlorperazine and CLP-257, that enhance KCC2 function by promoting its clustering on the cell membrane, a previously uncharacterized mechanism. Importantly, these compounds effectively reduce spontaneous epileptiform activity in human brain tissue from mTLE patients and significantly reduce seizure frequency in a mouse model. This work provides a critical proof-of-concept for activating KCC2 as a viable therapeutic approach for drug-resistant epilepsy.

neuroscience↗

bioRxiv2022

Silencing KCC2 in mouse dorsal hippocampus compromises spatial and contextual memory

Delayed upregulation of the neuronal chloride extruder KCC2 underlies the progressive shift in GABA signaling polarity during development. Conversely, KCC2 downregulation is observed in a variety of neurological and psychiatric disorders often associated with cognitive impairment. Reduced KCC2 expression and function in mature networks may disrupt GABA signaling and promote anomalous network activities underlying these disorders. However, the causal link between KCC2 downregulation, altered brain rhythmogenesis and cognitive function remains elusive. Here, by combining behavioral exploration with in vivo electrophysiology we assessed the impact of chronic KCC2 silencing in mouse dorsal hippocampus and showed it compromises both spatial and contextual memory. This was associated with altered hippocampal rhythmogenesis and neuronal hyperexcitability, with increased CA1 pyramidal cell burst firing during non-REM sleep. Reducing neuronal excitability with terbinafine, a specific Task-3 leak potassium channel activator, occluded the impairment of contextual memory upon KCC2 silencing. Our results establish a causal relationship between KCC2 expression and cognitive performance and suggest that impaired rhythmopathies and neuronal hyperexcitability are central to the deficits caused by KCC2 silencing in the adult mouse brain.

neuroscience↗

bioRxiv2019

Cation-chloride cotransporters and the polarity of GABA signaling in mouse hippocampal parvalbumin interneurons

Transmembrane chloride gradients govern the efficacy and polarity of GABA signaling in neurons and are usually maintained by the activity of cation chloride cotransporters, such as KCC2 and NKCC1. Whereas their role is well established in cortical principal neurons, it remains poorly documented in GABAergic interneurons. We used complementary electrophysiological approaches to compare the effects of GABAAR activation in adult mouse hippocampal parvalbumin interneurons (PV INs) and pyramidal cells (PCs). Loose cell attached, tight-seal and gramicidin-perforated patch recordings all show GABAAR-mediated transmission is slightly depolarizing and yet inhibitory in both PV INs and PCs. Focal GABA uncaging in whole-cell recordings reveal that KCC2 and NKCC1 are functional in both PV INs and PCs but differentially contribute to transmembrane chloride gradients in their soma and dendrites. Blocking KCC2 function depolarizes the reversal potential of GABAAR-mediated currents in PV INs and PCs, often beyond firing threshold, showing KCC2 is essential to maintain the inhibitory effect of GABAARs. Finally, we show that repetitive 10 Hz activation of GABAARs in both PV INs and PCs leads to a progressive decline of the postsynaptic response independently of the ion flux direction or KCC2 function. This suggests intraneuronal chloride buildup may not predominantly contribute to activity-dependent plasticity of GABAergic synapses in this frequency range. Altogether our data demonstrate similar mechanisms of chloride regulation in mouse hippocampal PV INs and PCs and suggest KCC2 downregulation in the pathology may affect the valence of GABA signaling in both cell types.\n\nKey point summaryO_LICation-chloride cotransporters (CCCs) play a critical role in controlling the efficacy and polarity of GABAA receptor (GABAAR)-mediated transmission in the brain, yet their expression and function in GABAergic interneurons has been overlooked.\nC_LIO_LIWe compared the polarity of GABA signaling and the function of CCCs in mouse hippocampal pyramidal neurons and parvalbumin-expressing interneurons.\nC_LIO_LIUnder resting conditions, GABAAR activation was mostly depolarizing and yet inhibitory in both cell types. KCC2 blockade further depolarized the reversal potential of GABAAR-mediated currents often above action potential threshold.\nC_LIO_LIHowever, during repetitive GABAAR activation, the postsynaptic response declined independently of the ion flux direction or KCC2 function, suggesting intracellular chloride buildup is not responsible for this form of plasticity.\nC_LIO_LIOur data demonstrate similar mechanisms of chloride regulation in mouse hippocampal pyramidal neurons and parvalbumin interneurons.\nC_LI

neuroscience↗

bioRxiv2018

KCC2 regulates neuronal excitability and hippocampal activity via interaction with Task-3 channels

The K+/Cl- co-transporter KCC2 (SLC12A5) regulates neuronal transmembrane chloride gradients and thereby controls GABA signaling in the brain. KCC2 downregulation is observed in several neurological and psychiatric disorders including epilepsy, neuropathic pain and autism spectrum disorders. Paradoxical, excitatory GABA signaling is usually assumed to contribute to abnormal network activity underlying the pathology. We tested this hypothesis and explored the functional impact of chronic KCC2 downregulation in the rat dentate gyrus. Although the reversal potential of GABAA receptor currents was depolarized in KCC2 knockdown neurons, this shift was fully compensated by depolarization of their resting membrane potential. This effect was due to downregulation of Task-3 leak potassium channels that we show require KCC2 for membrane trafficking. Increased neuronal excitability upon KCC2 suppression altered dentate gyrus rhythmogenesis that could be normalized by chemogenetic hyperpolarization. Our data reveal KCC2 downregulation engages complex synaptic and cellular alterations beyond GABA signaling that concur to perturb network activity, thus offering novel targets for therapeutic intervention.

neuroscience↗