Castillo Karen, Contreras Gustavo F, Pupo Amaury, Torres Yolima P, Neely Alan, González Carlos, Latorre Ramon
Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2366103, Chile; and.
Departmento de Nutricion y Bioquimica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogota DC 110111, Colombia.
Proc Natl Acad Sci U S A. 2015 Apr 14;112(15):4809-14. doi: 10.1073/pnas.1504378112. Epub 2015 Mar 30.
Being activated by depolarizing voltages and increases in cytoplasmic Ca(2+), voltage- and calcium-activated potassium (BK) channels and their modulatory β-subunits are able to dampen or stop excitatory stimuli in a wide range of cellular types, including both neuronal and nonneuronal tissues. Minimal alterations in BK channel function may contribute to the pathophysiology of several diseases, including hypertension, asthma, cancer, epilepsy, and diabetes. Several gating processes, allosterically coupled to each other, control BK channel activity and are potential targets for regulation by auxiliary β-subunits that are expressed together with the α (BK)-subunit in almost every tissue type where they are found. By measuring gating currents in BK channels coexpressed with chimeras between β1 and β3 or β2 auxiliary subunits, we were able to identify that the cytoplasmic regions of β1 are responsible for the modulation of the voltage sensors. In addition, we narrowed down the structural determinants to the N terminus of β1, which contains two lysine residues (i.e., K3 and K4), which upon substitution virtually abolished the effects of β1 on charge movement. The mechanism by which K3 and K4 stabilize the voltage sensor is not electrostatic but specific, and the α (BK)-residues involved remain to be identified. This is the first report, to our knowledge, where the regulatory effects of the β1-subunit have been clearly assigned to a particular segment, with two pivotal amino acids being responsible for this modulation.
电压和钙激活钾（BK）通道及其调节性β亚基可被去极化电压和细胞质Ca(2+)增加所激活，能够抑制或终止多种细胞类型（包括神经元和非神经元组织）中的兴奋性刺激。BK通道功能的微小改变可能导致包括高血压、哮喘、癌症、癫痫和糖尿病在内的多种疾病的病理生理过程。几种门控过程彼此变构偶联，控制BK通道活性，并且是几乎在其发现的每种组织类型中与α（BK）亚基一起表达的辅助β亚基进行调节的潜在靶点。通过测量与β1和β3或β2辅助亚基之间的嵌合体共表达的BK通道中的门控电流，我们能够确定β1的细胞质区域负责电压传感器的调节。此外，我们将结构决定因素缩小到β1的N末端，其包含两个赖氨酸残基（即K3和K4），替换后几乎消除了β1对电荷移动的影响。K3和K4稳定电压传感器的机制不是静电作用而是特异性的，涉及的α（BK）残基仍有待确定。据我们所知，这是第一份将β1亚基的调节作用明确归因于特定片段的报告，其中两个关键氨基酸负责这种调节。
