Medical Research Council-Laboratory of Molecular Biology, Cambridge, UK.
PLoS Genet. 2011 Mar;7(3):e1001341. doi: 10.1371/journal.pgen.1001341. Epub 2011 Mar 17.
Genome sequence comparisons have highlighted many novel gene families that are conserved across animal phyla but whose biological function is unknown. Here, we functionally characterize a member of one such family, the macoilins. Macoilins are characterized by several highly conserved predicted transmembrane domains towards the N-terminus and by coiled-coil regions C-terminally. They are found throughout Eumetazoa but not in other organisms. Mutants for the single Caenorhabditis elegans macoilin, maco-1, exhibit a constellation of behavioral phenotypes, including defects in aggregation, O₂ responses, and swimming. MACO-1 protein is expressed broadly and specifically in the nervous system and localizes to the rough endoplasmic reticulum; it is excluded from dendrites and axons. Apart from subtle synapse defects, nervous system development appears wild-type in maco-1 mutants. However, maco-1 animals are resistant to the cholinesterase inhibitor aldicarb and sensitive to levamisole, suggesting pre-synaptic defects. Using in vivo imaging, we show that macoilin is required to evoke Ca²(+) transients, at least in some neurons: in maco-1 mutants the O₂-sensing neuron PQR is unable to generate a Ca²(+) response to a rise in O₂. By genetically disrupting neurotransmission, we show that pre-synaptic input is not necessary for PQR to respond to O₂, indicating that the response is mediated by cell-intrinsic sensory transduction and amplification. Disrupting the sodium leak channels NCA-1/NCA-2, or the N-,P/Q,R-type voltage-gated Ca²(+) channels, also fails to disrupt Ca²(+) responses in the PQR cell body to O₂ stimuli. By contrast, mutations in egl-19, which encodes the only Caenorhabditis elegans L-type voltage-gated Ca²(+) channel α1 subunit, recapitulate the Ca²(+) response defect we see in maco-1 mutants, although we do not see defects in localization of EGL-19. Together, our data suggest that macoilin acts in the ER to regulate assembly or traffic of ion channels or ion channel regulators.
基因组序列比较突出了许多在动物门之间保守的新基因家族，但它们的生物学功能尚不清楚。在这里，我们对这样一个家族的一个成员进行了功能表征，该成员称为 macoilin。Macoilin 的特点是在 N 端有几个高度保守的预测跨膜结构域，在 C 端有卷曲螺旋区。它们存在于真后生动物中，但不存在于其他生物体中。秀丽隐杆线虫中单个 macoilin 的突变体 maco-1 表现出一系列行为表型，包括聚集缺陷、O₂ 反应和游泳缺陷。MACO-1 蛋白广泛而特异性地在神经系统中表达，并定位于粗面内质网；它不位于树突和轴突中。除了细微的突触缺陷外，神经系统发育在 maco-1 突变体中看起来是野生型的。然而，maco-1 动物对乙酰胆碱酯酶抑制剂 aldicarb 具有抗性，对左旋咪唑敏感，表明存在突触前缺陷。通过体内成像，我们表明 macoilin 是产生 Ca²(+)瞬变所必需的，至少在某些神经元中是这样：在 maco-1 突变体中，O₂ 感应神经元 PQR 无法对 O₂ 升高产生 Ca²(+)反应。通过遗传干扰神经传递，我们表明 PQR 对 O₂ 的反应不需要突触前输入，表明该反应是由细胞内固有感觉转导和放大介导的。破坏钠离子泄漏通道 NCA-1/NCA-2 或 N-、P/Q、R 型电压门控 Ca²(+)通道也不能破坏 PQR 细胞体对 O₂ 刺激的 Ca²(+)反应。相比之下，在编码唯一的秀丽隐杆线虫 L 型电压门控 Ca²(+)通道 α1 亚基的 egl-19 中发生突变，可重现我们在 maco-1 突变体中看到的 Ca²(+)反应缺陷，尽管我们没有看到 EGL-19 的定位缺陷。总之，我们的数据表明，macoilin 在 ER 中作用于调节离子通道或离子通道调节剂的组装或运输。
