Ion channels are channels on the cell membrane that can regulate and transport specific ions through the cell membrane. They are usually composed of protein molecules, and often several transmembrane protein subunits form an ion channel. It is an important basis for maintaining the information transmission of the body’s nervous system, the rhythmic beating of the heart, the secretion of hormones, and the contraction of muscles. According to the types of ions passing through ion channels, they can be divided into potassium ion channels, calcium ion channels, sodium ion channels, and so on.
Potassium ion channels enable potassium ions to pass through cell membranes quickly and selectively along an electrochemical gradient. They are the most widely distributed ion channels that exist in most cell types and are found in almost all organisms. In 1998, American scientist R. Mackinnon (R. Mackinnon, 1956-) used X-ray crystal diffraction for the first time to analyze the three-dimensional structure of the potassium ion channel of a species of Streptomyces. It consists of four identical subunits forming an inverted cone with a selective “filter” outside the wide end. This filter only matches the dehydrated potassium ions, and the sodium ions are too small to pass through. In the filter, two close potassium ions will repel each other. This repulsive force can overcome the strong interaction force between the ions and the protein, so that the potassium ions can quickly pass through the channel with high selectivity. Potassium ion channels are involved in regulating the secretion of hormones, such as regulating the release of insulin; potassium ion channels are also involved in maintaining the tension of blood vessels and regulating the action potential of myocardial cells. Its dysfunction may lead to arrhythmia. In recent years, researchers have used potassium channels as targets to develop drugs. For example, potassium channel blocker 4-aminopyridine has been studied for the treatment of multiple sclerosis, and potassium channel activators are very important antihypertensive and bronchodilator drugs.
Potassium ion channels enable potassium ions to pass through cell membranes quickly and selectively along an electrochemical gradient. They are the most widely distributed ion channels that exist in most cell types and are found in almost all organisms. In 1998, American scientist R. Mackinnon (R. Mackinnon, 1956-) used X-ray crystal diffraction for the first time to analyze the three-dimensional structure of the potassium ion channel of a species of Streptomyces. It consists of four identical subunits forming an inverted cone with a selective “filter” outside the wide end. This filter only matches the dehydrated potassium ions, and the sodium ions are too small to pass through. In the filter, two close potassium ions will repel each other. This repulsive force can overcome the strong interaction force between the ions and the protein, so that the potassium ions can quickly pass through the channel with high selectivity. Potassium ion channels are involved in regulating the secretion of hormones, such as regulating the release of insulin; potassium ion channels are also involved in maintaining the tension of blood vessels and regulating the action potential of myocardial cells. Its dysfunction may lead to arrhythmia. In recent years, researchers have used potassium channels as targets to develop drugs. For example, potassium channel blocker 4-aminopyridine has been studied for the treatment of multiple sclerosis, and potassium channel activators are very important antihypertensive and bronchodilator drugs.
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Calcium ion channel is a channel that selectively passes calcium ions. It is an oligomeric protein that is mainly involved in the release of neurotransmitters and the regulation of neuronal excitability. According to the kinetic characteristics of activation and inactivation, ion specificity and sensitivity to drugs and toxins, channels can be divided into L-type, P-type, N-type, R-type, T-type, etc., among which L-type and T-type exist In the cardiovascular and central nervous system, N-type, P-type, Q-type and R-type are mainly located in neurons. Calcium ion channel blockers are a kind of drugs that can block the flow of Ca2+ into cells and reduce the intracellular Ca2+ concentration, and have important clinical application value. For example, L-type calcium channel blockers can be used to treat hypertension. Because in most areas of our body, the process of depolarization is mediated by the influx of sodium ions, changing the permeability of calcium ions has little effect on the action potential. However, in many smooth muscle tissues, depolarization is mainly mediated by calcium ion influx. L-type calcium channel blockers selectively inhibit these action potentials in smooth muscle, resulting in vasodilation, thereby achieving high therapeutic levels. The purpose of blood pressure.
The sodium ion channel is a kind of hydrophilic pores on the membrane that allows a small amount of sodium ions to enter human cells along the electrochemical gradient, and its essence is an internal membrane protein. It is widely present in excitable cells. The main function of sodium ion channel opening is to depolarize cells and spread action potentials. When the cell is stimulated, the channel opens to form an action potential, which causes the membrane potential to rise rapidly and depolarize. Depolarization of membrane potential can cause the opening of potassium ion channels and calcium ion channels, thereby repolarizing the action potential. It can be seen that sodium ion channels play an important role in maintaining cell excitability and normal physiological functions. Like potassium channels and calcium channels, it is also the target of many drugs.
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