The voltage-gated potassium channel Kv1.5 plays important roles in atrial repolarization and regulation of vascular tone. In the present study, we investigated the effects of mechanical stretch on Kv1.5 channels. We induced mechanical stretch by centrifuging or culturing Kv1.5-expressing HEK 293 cells and neonatal rat ventricular myocytes in low osmolarity (LO) medium, and then recorded Kv1.5 current (IKv1.5) in a normal, isotonic solution. We observed that mechanical stretch increased IKv1.5, and this increase required the intact long, proline-rich extracellular S1-S2 linker of the Kv1.5 channel. The LO-induced IKv1.5 increase also required an intact intracellular N-terminus, which contains the binding motif for endogenous Src tyrosine kinase that constitutively inhibits IKv1.5 Disrupting the Src-binding motif of Kv1.5 through N-terminal truncation or mutagenesis abolished the mechanical stretch-mediated increase in IKv1.5 Our results further showed that the extracellular S1-S2 linker of Kv1.5 communicates with the intracellular N-terminus. While the S1-S2 linker of WT Kv1.5 could be cleaved by extracellularly applied proteinase K (PK), an N-terminal truncation up to amino acid residue 209 altered the conformation of the S1-S2 linker and made it no longer susceptible to PK-mediated cleavage. In summary, the findings of our study indicate that the S1-S2 linker of Kv1.5 represents a mechanosensor that regulates the activity of this channel. By targeting the S1-S2 linker, mechanical stretch may induce a change in the N-terminal conformation of Kv1.5 that relieves Src-mediated tonic channel inhibition and results in an increase in IKv1.5.

中文翻译：

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机械拉伸通过S1-S2接头与通道N端之间的相互作用增加Kv1.5电流。

电压门控钾通道Kv1.5在心房复极和调节血管张力中起重要作用。在本研究中，我们研究了机械拉伸对Kv1.5通道的影响。我们通过在低渗透压（LO）培养基中离心或培养表达Kv1.5的HEK 293细胞和新生大鼠心室肌细胞来诱导机械拉伸，然后在正常的等渗溶液中记录Kv1.5电流（IKv1.5）。我们观察到机械拉伸增加了IKv1.5，而这种增加需要完整长的，富含脯氨酸的Kv1.5通道胞外S1-S2接头。LO诱导的IKv1.5的增加还需要完整的细胞内N端，其包含内源性Src酪氨酸激酶的结合基序，该结合基序可抑制IKv1.5，破坏Kv1的Src结合基序。通过N-末端截短或诱变的图5消除了IKv1.5的机械拉伸介导的增加。我们的结果进一步表明，Kv1.5的胞外S1-S2接头与胞内N末端连通。虽然WT Kv1.5的S1-S2接头可被胞外施加的蛋白酶K（PK）裂解，但N端截短至氨基酸残基209却改变了S1-S2接头的构象，使其不再易感PK介导的裂解。总而言之，我们研究的结果表明，Kv1.5的S1-S2接头代表了一种调节该通道活性的机械传感器。通过靶向S1-S2接头，机械拉伸可以诱导Kv1.5的N末端构象发生变化，从而缓解Src介导的强直通道抑制作用，并导致IKv1.5升高。