Tang J, Lin Y, Zhang Z, Tikunova S, Birnbaumer L, Zhu M X
Neurobiotechnology Center, Department of Neuroscience, Ohio State University, Columbus, Ohio 43210, USA.
J Biol Chem. 2001 Jun 15;276(24):21303-10. doi: 10.1074/jbc.M102316200. Epub 2001 Apr 4.
Homologues of Drosophila Trp (transient receptor potential) form plasma membrane channels that mediate Ca(2+) entry following the activation of phospholipase C by cell surface receptors. Among the seven Trp homologous found in mammals, Trp3 has been shown to interact with and respond to IP(3) receptors (IP(3)Rs) for activation. Here we show that Trp4 and other Trp proteins also interact with IP(3)Rs. The IP(3)R-binding domain also interacts with calmodulin (CaM) in a Ca(2+)-dependent manner with affinities ranging from 10 nm for Trp2 to 290 nm for Trp6. In addition, other binding sites for CaM and IP(3)Rs are present in the alpha but not the beta isoform of Trp4. In the presence of Ca(2+), the Trp-IP(3)R interaction is inhibited by CaM. However, a synthetic peptide representing a Trp-binding domain of IP(3)Rs inhibited the binding of CaM to Trp3, -6, and -7 more effectively than that to Trp1, -2, -4, and -5. In inside-out membrane patches, Trp4 is activated strongly by calmidazolium, an antagonist of CaM, and a high (50 microm) but not a low (5 microm) concentration of the Trp-binding peptide of the IP(3)R. Our data support the view that both CaM and IP(3)Rs play important roles in controlling the gating of Trp-based channels. However, the sensitivity and responses to CaM and IP(3)Rs differ for each Trp.
果蝇瞬时受体电位（Trp）的同源物形成质膜通道，该通道在细胞表面受体激活磷脂酶C后介导钙离子内流。在哺乳动物中发现的7种Trp同源物中，Trp3已被证明可与IP3受体（IP3Rs）相互作用并对其激活作出反应。在此我们表明，Trp4和其他Trp蛋白也与IP3Rs相互作用。IP3R结合结构域还以钙依赖的方式与钙调蛋白（CaM）相互作用，亲和力范围从Trp2的10 nM到Trp6的290 nM。此外，Trp4的α亚型而非β亚型中存在其他CaM和IP3Rs结合位点。在钙离子存在的情况下，Trp与IP3R的相互作用被CaM抑制。然而，一种代表IP3Rs的Trp结合结构域的合成肽抑制CaM与Trp3、-6和-7结合的效果比其与Trp1、-2、-4和-5结合的效果更显著。在内外膜片钳实验中，CaM拮抗剂平静咪唑和高浓度（50 μM）而非低浓度（5 μM）的IP3R的Trp结合肽可强烈激活Trp4。我们的数据支持以下观点：CaM和IP3Rs在控制基于Trp的通道门控方面均发挥重要作用。然而，每种Trp对CaM和IP3Rs的敏感性和反应各不相同。
