KCNA2
Domain
The cytoplasmic N-terminus is important for tetramerization. Interactions between the different subunits modulate the gating characteristics (By similarity). Besides, the cytoplasmic N-terminal domain mediates interaction with RHOA and thus is required for RHOA-mediated endocytosis (By similarity).
The transmembrane segment S4 functions as a voltage-sensor and is characterized by a series of positively charged amino acids at every third position. Channel opening and closing is effected by a conformation change that affects the position and orientation of the voltage-sensor paddle formed by S3 and S4 within the membrane. A transmembrane electric field that is positive inside would push the positively charged S4 segment outwards, thereby opening the pore, while a field that is negative inside would pull the S4 segment inwards and close the pore. Changes in the position and orientation of S4 are then transmitted to the activation gate formed by the inner helix bundle via the S4-S5 linker region.
Function
Voltage-gated potassium channel that mediates transmembrane potassium transport in excitable membranes, primarily in the brain and the central nervous system, but also in the cardiovascular system. Prevents aberrant action potential firing and regulates neuronal output. Forms tetrameric potassium-selective channels through which potassium ions pass in accordance with their electrochemical gradient. The channel alternates between opened and closed conformations in response to the voltage difference across the membrane (PubMed:11211111, PubMed:19912772, PubMed:23769686, PubMed:8495559). Can form functional homotetrameric channels and heterotetrameric channels that contain variable proportions of KCNA1, KCNA2, KCNA4, KCNA5, KCNA6, KCNA7, and possibly other family members as well; channel properties depend on the type of alpha subunits that are part of the channel (PubMed:20220134, PubMed:8495559). Channel properties are modulated by cytoplasmic beta subunits that regulate the subcellular location of the alpha subunits and promote rapid inactivation of delayed rectifier potassium channels. In vivo, membranes probably contain a mixture of heteromeric potassium channel complexes, making it difficult to assign currents observed in intact tissues to any particular potassium channel family member. Homotetrameric KCNA2 forms a delayed-rectifier potassium channel that opens in response to membrane depolarization, followed by slow spontaneous channel closure (PubMed:19912772, PubMed:23769686). In contrast, a heteromultimer formed by KCNA2 and KCNA4 shows rapid inactivation (PubMed:8495559). Regulates neuronal excitability and plays a role as pacemaker in the regulation of neuronal action potentials (By similarity). KCNA2-containing channels play a presynaptic role and prevent hyperexcitability and aberrant action potential firing (By similarity). Response to toxins that are selective for KCNA2-containing potassium channels suggests that in Purkinje cells, dendritic subthreshold KCNA2-containing potassium channels prevent random spontaneous calcium spikes, suppressing dendritic hyperexcitability without hindering the generation of somatic action potentials, and thereby play an important role in motor coordination (By similarity). Plays a role in the induction of long-term potentiation of neuron excitability in the CA3 layer of the hippocampus (By similarity). May function as down-stream effector for G protein-coupled receptors and inhibit GABAergic inputs to basolateral amygdala neurons (By similarity). May contribute to the regulation of neurotransmitter release, such as gamma-aminobutyric acid (GABA) (By similarity). Contributes to the regulation of the axonal release of the neurotransmitter dopamine (By similarity). Reduced KCNA2 expression plays a role in the perception of neuropathic pain after peripheral nerve injury, but not acute pain (By similarity). Plays a role in the regulation of the time spent in non-rapid eye movement (NREM) sleep (By similarity).
Involvement in disease
Developmental and epileptic encephalopathy 32
DEE32
A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE32 inheritance is autosomal dominant.
None
The disease is caused by variants affecting the gene represented in this entry.
Nizon-Isidor syndrome
NIZIDS
An autosomal dominant neurodevelopmental disorder characterized by intellectual disability, global developmental delay, speech impairment, and behavioral abnormalities including autism spectrum disorder and aggressive behavior. Other features include a thin corpus callosum, and mild facial dysmorphism. Disease onset is in infancy or early childhood.
None
The disease is caused by variants affecting the gene represented in this entry.
Post-translational modifications
Phosphorylated on tyrosine residues; phosphorylation increases in response to ischemia (By similarity). Phosphorylated on tyrosine residues by activated PTK2B/PYK2 (By similarity). Phosphorylation on tyrosine residues suppresses ion channel activity (By similarity). Phosphorylated on tyrosine residues in response to CHRM1 activation; this abolishes interaction with CTTN. This is probably due to endocytosis of the phosphorylated channel subunits (By similarity). Phosphorylated on serine residues in response to increased cAMP levels; phosphorylation is apparently not catalyzed by PKA (By similarity).
N-glycosylated, with complex, sialylated N-glycans.
Sequence Similarities
Belongs to the potassium channel family. A (Shaker) (TC 1.A.1.2) subfamily. Kv1.2/KCNA2 sub-subfamily.
Tissue Specificity
Detected in brain cortex (PubMed:16473933). Detected in peroneal nerve in the juxtaparanodal regions of the node of Ranvier; expression is decreased in patients with diabetes mellitus that suffer from axonal neuropathy (PubMed:22649228). Detected in paranodal and juxtanodal zones in myelinated spinal cord (at protein level) (PubMed:11086297).
Cellular localization
- Cell membrane
- Multi-pass membrane protein
- Membrane
- Cell projection
- Axon
- Synapse
- Endoplasmic reticulum membrane
- Cell projection
- Lamellipodium membrane
- Synapse
- Synaptosome
- Presynaptic cell membrane
- Cell projection
- Dendrite
- Cell junction
- Paranodal septate junction
- KCNA2 by itself is detected both at the endoplasmic reticulum and at the cell membrane. Coexpression with KCNA4 or with beta subunits promotes expression at the cell membrane. Coexpression with KCNA1 inhibits cell surface expression. In myelinated peripheral axons, clustered in the juxtaparadonal region and at an internodal line located along the mesaxon and below the Schmidt-Lanterman incisures (By similarity).
Alternative names
Potassium voltage-gated channel subfamily A member 2, NGK1, Voltage-gated K(+) channel HuKIV, Voltage-gated potassium channel HBK5, Voltage-gated potassium channel subunit Kv1.2, KCNA2