Perni Stefano, Beam Kurt
Department of Physiology and Biophysics, Anschutz Medical Campus, University of Colorado, Aurora, United States.
Elife. 2021 Mar 26;10:e64249. doi: 10.7554/eLife.64249.
Junctions between the endoplasmic reticulum and plasma membrane that are induced by the neuronal junctophilins are of demonstrated importance, but their molecular architecture is still poorly understood and challenging to address in neurons. This is due to the small size of the junctions and the multiple isoforms of candidate junctional proteins in different brain areas. Using colocalization of tagged proteins expressed in tsA201 cells, and electrophysiology, we compared the interactions of JPH3 and JPH4 with different calcium channels. We found that JPH3 and JPH4 caused junctional accumulation of all the tested high-voltage-activated Ca isoforms, but not a low-voltage-activated Ca. Also, JPH3 and JPH4 noticeably modify Ca2.1 and Ca2.2 inactivation rate. RyR3 moderately colocalized at junctions with JPH4, whereas RyR1 and RyR2 did not. By contrast, RyR1 and RyR3 strongly colocalized with JPH3, and RyR2 moderately. Likely contributing to this difference, JPH3 binds to cytoplasmic domain constructs of RyR1 and RyR3, but not of RyR2.
由神经元连接亲环蛋白诱导形成的内质网与质膜之间的连接已被证明具有重要意义，但其分子结构仍知之甚少，且在神经元中研究颇具挑战性。这是由于这些连接的尺寸较小，以及不同脑区中候选连接蛋白存在多种亚型。利用在tsA201细胞中表达的标记蛋白的共定位以及电生理学方法，我们比较了JPH3和JPH4与不同钙通道的相互作用。我们发现，JPH3和JPH4会导致所有测试的高电压激活型钙亚型在连接处聚集，但不会使低电压激活型钙亚型聚集。此外，JPH3和JPH4会显著改变Ca2.1和Ca2.2的失活速率。RyR3与JPH4在连接处有中度共定位，而RyR1和RyR2则没有。相比之下，RyR1和RyR3与JPH3有强烈共定位，RyR2与JPH3有中度共定位。JPH3与RyR1和RyR3的胞质结构域构建体结合，但不与RyR2的胞质结构域构建体结合，这可能是造成这种差异的原因。
