Steric volume exclusion sets soluble protein concentrations in photoreceptor sensory cilia
Steric volume exclusion sets soluble protein concentrations in photoreceptor sensory cilia
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DOI：
10.1073/pnas.1115109109
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发表时间：
2012-01-03
影响因子：
11.1
通讯作者：
Calvert, Peter D.
中科院分区：
文献类型：
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作者：
Najafi, Mehdi;Maza, Nycole A.;Calvert, Peter D.
蛋白质通过多种机制分离成离散的亚细胞区室，包括马达蛋白转运、局部结合和扩散屏障。这种细胞功能的物理分离部分地作为通过允许调节局部蛋白质浓度来控制区室活性的机制。在这项研究中，我们探讨了可溶性蛋白质的大小如何影响进入视网膜光感受器外节信号室的有限空间，并发现了一个惊人的陡峭的关系。我们发现，绿色荧光蛋白单体，二聚体，和三聚体转基因表达的青蛙棒中存在于外段在1.8-，2.9-和6.8倍的丰度低，相对于细胞体，比小的可溶性荧光标记，钙黄绿素。基于分子进入聚合物网的螺旋力学模型的理论分析表明，这些观察结果可以用占据外段盘膜之间高度受限空间的分子的空间位阻来解释。这一机制可能回答了一个长期存在的问题，即可溶性调节蛋白，arrestin，是如何有效地从暗适应杆和锥的外节排除。一般来说，我们的研究结果表明，一种替代模式的控制蛋白质访问细胞域的基础上动态的，大小依赖的分区，不需要扩散障碍，主动运输，或大量的固定结合位点。
Proteins segregate into discrete subcellular compartments via a variety of mechanisms, including motor protein transport, local binding, and diffusion barriers. This physical separation of cell functions serves, in part, as a mechanism for controlling compartment activity by allowing regulation of local protein concentrations. In this study we explored how soluble protein size impacts access to the confined space within the retinal photoreceptor outer segment signaling compartment and discovered a strikingly steep relationship. We find that GFP monomers, dimers, and trimers expressed transgenically in frog rods are present in the outer segment at 1.8-, 2.9-, and 6.8-fold lower abundances, relative to the cell body, than the small soluble fluorescent marker, calcein. Theoretical analysis, based on statistical-mechanical models of molecular access to polymer meshes, shows that these observations can be explained by the steric hindrance of molecules occupying the highly constrained spaces between outer segment disc membranes. This mechanism may answer a long-standing question of how the soluble regulatory protein, arrestin, is effectively excluded from the outer segments of dark-adapted rods and cones. Generally, our results suggest an alternate mode for the control of protein access to cell domains based on dynamic, size-dependent compartmental partitioning that does not require diffusion barriers, active transport, or large numbers of immobile binding sites.