KCNN2 (Potassium Calcium-Activated Channel Subfamily N Member 2), also known as SK2 (Small-Conductance Calcium-Activated Potassium Channel 2), encodes a neuronal small-conductance calcium-activated potassium channel with critical roles in synaptic plasticity, learning, and memory. SK2 channels are particularly enriched in hippocampal CA1 pyramidal neurons where they regulate dendritic integration and synaptic transmission.
KCNN2 is located on chromosome 5q22.1 and encodes the SK2 channel protein. The gene is catalogued as NCBI Gene ID 3777 and OMIM 609922. Unlike KCNN1, SK2 channels are primarily localized to dendritic compartments where they shape synaptic integration and plasticity.
| Property |
Value |
| Gene Symbol |
KCNN2 |
| Full Name |
Potassium Calcium-Activated Channel Subfamily N Member 2 |
| Aliases |
SK2, KCa2.2, hSK2 |
| Chromosomal Location |
5q22.1 |
| NCBI Gene ID |
3777 |
| OMIM |
609922 |
| Ensembl ID |
ENSG00000162610 |
| UniProt ID |
Q9H5Y2 |
¶ Protein Structure and Function
KCNN2 encodes the SK2 subunit of small-conductance calcium-activated potassium channels:
- Six transmembrane domains (S1-S6) with pore loop
- Calmodulin-binding domain in C-terminus for calcium sensitivity
- Dendritic targeting motifs for subcellular localization
- Homotetrameric assembly forming functional channels
SK2 channels are uniquely positioned to regulate synaptic plasticity through their dendritic localization.
- Dendritic integration: Regulate synaptic integration in dendritic spines
- Synaptic plasticity: Critical for long-term potentiation (LTP) and depression (LTD)
- Learning and memory: SK2 plasticity underlies hippocampal-dependent learning
- Place cell function: Regulate hippocampal place cell firing stability
- Emotion regulation: SK2 channels in amygdala affect fear and anxiety
KCNN2 shows region-specific expression:
- Hippocampus: CA1 pyramidal neuron dendrites, especially in stratum radiatum
- Cortex: Layer 2/3 and layer 5 pyramidal neuron dendrites
- Cerebellum: Molecular layer interneurons
- Thalamus: Dendrites of thalamocortical relay neurons
- Olfactory bulb: Mitral and tufted cells
Expression data is available from the Allen Human Brain Atlas.
SK2 channels are critically involved in AD pathophysiology:
- Synaptic dysfunction: Aβ oligomers downregulate SK2 expression in hippocampal neurons
- Memory deficits: SK2 channel dysfunction contributes to hippocampal-dependent memory impairment
- Dendritic spine loss: SK2 alterations contribute to spine morphological deficits
- Therapeutic potential: SK2 activators improve synaptic function in AD models
- Striatal plasticity: SK2 channels regulate long-term depression in striatal medium spiny neurons
- Motor learning: SK2 dysfunction may contribute to motor learning deficits
- Dyskinesias: Altered SK2 expression in basal ganglia in levodopa-induced dyskinesias
- Motor neuron dysfunction: SK2 channel downregulation in ALS motor neurons
- Hyperexcitability: Loss of SK2 contributes to motor neuron hyperexcitability
- Cortical involvement: Cortical motor neuron SK2 alterations in ALS
- Seizure genesis: SK2 dysregulation contributes to hippocampal hyperexcitability
- Temporal lobe epilepsy: Reduced SK2 expression in epileptic hippocampus
- Therapeutic potential: SK2 modulators reduce seizure severity
- Stroke: SK2 channels in ischemic penumbra determine neuronal survival
- Autism spectrum disorders: SK2 gene variants associated with ASD
- Intellectual disability: KCNN2 mutations cause neurodevelopmental disorders
- Migraine: SK2 channels in cortical neurons involved in cortical spreading depression
SK2 channels are promising therapeutic targets:
- Cognitive enhancement: SK2 activators improve hippocampal-dependent memory
- Anti-epileptic drugs: SK2 modulators reduce seizure frequency
- Neuroprotection: SK2 activation reduces ischemic brain damage
- Psychiatric disorders: SK2-targeting compounds for anxiety and depression
KCNN2 interacts with several key proteins:
- Calmodulin: Calcium sensor for channel activation
- NMDA receptors: Major calcium source for SK2 activation at synapses
- AMPA receptors: Co-localization in dendritic spines
- SAP97: Scaffolding protein for dendritic targeting
- Cav2.1 channels: P/Q-type calcium channels providing calcium for SK2
- KO mice: KCNN2-/- mice show enhanced LTP and improved spatial memory
- Transgenic mice: Conditional KO mice for temporal-specific deletion
- Pharmacological tools: Specific activators (NS309, chlorzoxazone), blockers (apamin)
- AAV vectors: For region-specific SK2 overexpression or knockdown
KCNN2 encodes the SK2 small-conductance calcium-activated potassium channel, essential for dendritic synaptic integration, plasticity, and hippocampal-dependent learning. SK2 dysfunction contributes to Alzheimer's disease, Parkinson's disease, ALS, epilepsy, and neurodevelopmental disorders. SK2 channel modulators represent promising therapeutic strategies for cognitive enhancement and neuroprotection.