Regulation of hyperpolarization-activated HCN channel gating and cAMP modulation due to interactions of COOH terminus and core transmembrane regions.
Regulation of hyperpolarization-activated HCN channel gating and cAMP modulation due to interactions of COOH terminus and core transmembrane regions.
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DOI：
10.1085/jgp.118.3.237
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发表时间：
2001-09
期刊：
影响因子：
--
通讯作者：
Siegelbaum SA
中科院分区：
文献类型：
--
作者：
Wang J;Chen S;Siegelbaum SA
超极化激活阳离子 (HCN) 通道家族的成员产生 HCN 电流 (Ih)，该电流受 cAMP 直接调节，有助于心脏和大脑的起搏活动。四种不同的 HCN 亚型表现出不同的生物物理特性。在非洲爪蟾卵母细胞的无细胞斑块中，HCN2 通道的稳态激活曲线比 HCN1 通道的超极化程度高 20 mV。尽管 cAMP 与 COOH 末端环核苷酸结合结构域 (CNBD) 的结合显着将 HCN2 的激活曲线移动 17 mV 至更正电位，但 HCN1 的响应则不太明显（移动 4 mV）。先前的缺失突变体研究表明，CNBD 在没有 cAMP 的情况下抑制超极化门控； cAMP 的结合通过解除这种抑制而将门控转变为更正的电压。 HCN1 和 HCN2 之间基础门控和 cAMP 反应性的差异被认为是由于与 HCN1 相比，HCN2 中 CNBD 的抑制作用更大。在这里，我们使用 HCN1 和 HCN2 之间的一系列嵌合体，其中我们交换 NH2 末端、跨膜结构域或 COOH 末端的不同结构域，以进一步研究 cAMP 调节作用的分子基础以及两个通道功能特性的差异。 HCN1 和 HCN2 之间 cAMP 调节的差异局限于两个通道 COOH 末端的序列差异。令人惊讶的是，HCN1 和 HCN2 之间 CNBD 的交换对基础门控几乎没有影响，并且对 cAMP 调节只有适度的影响。相反，cAMP 调节的差异取决于 CNBD 和 C 接头之间的相互作用，C 接头是一个保守的 80 个氨基酸区域，将最后一个 (S6) 跨膜片段连接到 CNBD。基础门控的差异取决于核心跨膜结构域和 COOH 末端。这些数据是在先前关于缺失突变体的数据的背景下得出的，表明 CNBD 对基础门控的抑制作用取决于其与通道的 C 连接子和核心跨膜结构域的相互作用。 cAMP 结合能够解除这种抑制的程度取决于 C-接头和 CNBD 之间的相互作用。
Members of the hyperpolarization-activated cation (HCN) channel family generate HCN currents (Ih) that are directly regulated by cAMP and contribute to pacemaking activity in heart and brain. The four different HCN isoforms show distinct biophysical properties. In cell-free patches from Xenopus oocytes, the steady-state activation curve of HCN2 channels is 20 mV more hyperpolarized compared with HCN1. Whereas the binding of cAMP to a COOH-terminal cyclic nucleotide binding domain (CNBD) markedly shifts the activation curve of HCN2 by 17 mV to more positive potentials, the response of HCN1 is much less pronounced (4 mV shift). A previous deletion mutant study suggested that the CNBD inhibits hyperpolarization-gating in the absence of cAMP; the binding of cAMP shifts gating to more positive voltages by relieving this inhibition. The differences in basal gating and cAMP responsiveness between HCN1 and HCN2 were proposed to result from a greater inhibitory effect of the CNBD in HCN2 compared with HCN1. Here, we use a series of chimeras between HCN1 and HCN2, in which we exchange the NH2 terminus, the transmembrane domain, or distinct domains of the COOH terminus, to investigate further the molecular bases for the modulatory action of cAMP and for the differences in the functional properties of the two channels. Differences in cAMP regulation between HCN1 and HCN2 are localized to sequence differences within the COOH terminus of the two channels. Surprisingly, exchange of the CNBDs between HCN1 and HCN2 has little effect on basal gating and has only a modest one on cAMP modulation. Rather, differences in cAMP modulation depend on the interaction between the CNBD and the C-linker, a conserved 80–amino acid region that connects the last (S6) transmembrane segment to the CNBD. Differences in basal gating depend on both the core transmembrane domain and the COOH terminus. These data, taken in the context of the previous data on deletion mutants, suggest that the inhibitory effect of the CNBD on basal gating depends on its interactions with both the C-linker and core transmembrane domain of the channel. The extent to which cAMP binding is able to relieve this inhibition is dependent on the interaction between the C-linker and the CNBD.
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影响因子：
16.2
作者：
GOULDING, EH;NGAI, J;CHESS, A
通讯作者：
CHESS, A
影响因子：
3.8
作者：
Paoletti, P;Young, EC;Siegelbaum, SA
通讯作者：
Siegelbaum, SA
影响因子：
64.8
作者：
Wainger, BJ;DeGennaro, M;Tibbs, GR
通讯作者：
Tibbs, GR
影响因子：
56.9
作者：
Varnum, MD;Zagotta, WN
通讯作者：
Zagotta, WN
DOI：
10.1073/pnas.94.26.14815
发表时间：
1997-12-23
影响因子：
11.1
作者：
Santoro, B;Grant, SGN;Kandel, ER
通讯作者：
Kandel, ER