總結(jié) |
Voltage-gated K+ channels are involved in maintaining membrane potential and regulating cell volume. They are also important for determining the cellular response to the external stimulus of neurotransmitters and neuro-peptides1. Their diverse functions include regulating neurotransmitter release, heart rate, insulin secretion, neuronal excitability, epithelial electrolyte transport, smooth muscle contraction, and cell volume.Voltage-gated K+ channels are transmembrane proteins consisting of four α-subunits arranged in radially symmetric fashion around a central aqueous pore. Each α-subunit consists of six transmembrane segments (S1–S6) with cytoplasmic NH2- and COOH-termini 2. In mammals, a large family of genes encodes α-subunits: KV1 (homologous to Drosophila Shaker), KV2 (Shab), KV3 (Shaw), KV4 (Shal), KV5, KV6, and KV8 3.New electrically silent α subunits have recently been cloned which constitute three new subfamilies: KV5.1, KV6.1, and KV8.1. These α subunits, although cannot generate K+ channel activity by themselves, can modulate in a specific way the function of KV2.1 and KV2.2 subunits. They inhibit the KV2.1 and KV2.2 channels when expressed at high concentrations4.KV5.1 is expressed in heart, skeletal muscle, brain, kidney, and pancreas. A recent study revealed the expression of KV5.1 in isolated urinary bladder smooth muscle (UBSM) myocytes5.
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