small conductance calcium-activated potassium channel activity

Definition

Target type: molecularfunction

Enables the transmembrane transfer of potassium by a channel with a unit conductance of 2 to 20 picoSiemens that opens in response to stimulus by internal calcium ions. Small conductance calcium-activated potassium channels are more sensitive to calcium than are large conductance calcium-activated potassium channels. Transport by a channel involves catalysis of facilitated diffusion of a solute (by an energy-independent process) involving passage through a transmembrane aqueous pore or channel, without evidence for a carrier-mediated mechanism. [GOC:mtg_transport, OMIM:602754]

Small conductance calcium-activated potassium channels (SK channels) are a family of potassium channels that are activated by intracellular calcium ions. These channels are characterized by their small conductance and their sensitivity to a variety of pharmacological agents. SK channels play a crucial role in regulating neuronal excitability, synaptic transmission, and muscle contraction.

SK channels are tetrameric proteins, each subunit consisting of six transmembrane domains (S1-S6). The pore-forming region of the channel is located between the S5 and S6 transmembrane domains. The N-terminus of the channel protein is located intracellularly, and the C-terminus is located extracellularly.

The opening of SK channels is triggered by an increase in intracellular calcium concentration. Calcium ions bind to a specific site on the intracellular domain of the channel protein, causing a conformational change that opens the pore. The opening of the channel allows potassium ions to flow out of the cell, hyperpolarizing the membrane potential.

SK channels are expressed in a wide variety of tissues, including the brain, heart, smooth muscle, and endocrine glands. They are particularly abundant in neurons, where they play a crucial role in regulating neuronal excitability and synaptic transmission.

**Molecular function of SK channels:**

* **Regulation of neuronal excitability:** SK channels contribute to the regulation of neuronal excitability by mediating a calcium-dependent afterhyperpolarization (AHP) following an action potential. This AHP helps to repolarize the membrane potential, preventing repetitive firing and contributing to the precise timing of neuronal activity.
* **Synaptic transmission:** SK channels play a role in regulating synaptic transmission by modulating the release of neurotransmitters. They can influence the duration and amplitude of synaptic currents, contributing to the integration of synaptic inputs and the plasticity of neural circuits.
* **Muscle contraction:** SK channels are involved in regulating muscle contraction, particularly in smooth muscle. They contribute to the relaxation of smooth muscle by hyperpolarizing the membrane potential and reducing calcium influx.
* **Other physiological processes:** SK channels have been implicated in a variety of other physiological processes, including the regulation of hormone secretion, the control of cell growth and differentiation, and the modulation of inflammatory responses.

**Pharmacological modulation of SK channels:**

SK channels are targets for a variety of pharmacological agents. These agents can either activate or inhibit the channel, depending on their structure and mechanism of action.

* **Activators:** Some pharmacological agents can activate SK channels, enhancing their potassium conductance. This can lead to hyperpolarization of the membrane potential and a reduction in neuronal excitability.
* **Inhibitors:** Other pharmacological agents can inhibit SK channels, reducing their potassium conductance. This can lead to depolarization of the membrane potential and an increase in neuronal excitability.

The pharmacological modulation of SK channels has therapeutic potential for a variety of disorders, including epilepsy, Parkinson's disease, and pain.

In summary, SK channels are essential for regulating neuronal excitability, synaptic transmission, and muscle contraction. Their molecular function is mediated by calcium-dependent activation and their activity is regulated by a variety of pharmacological agents. The pharmacological modulation of SK channels offers therapeutic potential for a range of neurological and muscular disorders.'
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Proteins (4)

Compounds (8)