Controlled aggregation of ferritin to modulate MRI relaxivity
Controlled aggregation of ferritin to modulate MRI relaxivity
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DOI：
10.1529/biophysj.107.116145
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发表时间：
2008-07-01
影响因子：
3.4
通讯作者：
Koretsky, Alan P.
中科院分区：
文献类型：
--
作者：
Bennett, Kevin M.;Shapiro, Erik M.;Koretsky, Alan P.
铁蛋白是在哺乳动物细胞中以不同浓度表达的铁储存蛋白。铁蛋白的核心中的三价铁的沉积使其成为磁共振成像造影剂，并且铁蛋白最近被提议作为用于磁共振成像的基因表达报告蛋白。迄今为止，铁蛋白已在体内过表达，并已与转铁蛋白受体共表达，以增加细胞中的铁负荷。然而，铁蛋白在典型的磁场强度下具有相对低的T-2弛豫率（R-2接近1 mM（-1）s（-1）），因此需要高水平的表达来检测。调节超顺磁性剂的横向弛豫率的一种方法是使其聚集，从而操纵水扩散通过的磁场梯度。在这项工作中，它是通过计算机模拟和体外证明，铁蛋白的聚集可以改变弛豫。研究了骨料粒径和骨料内扰动间距对R-2的影响。计算机模拟表明，对于水扩散速率的典型范围，用于增加R-2的聚集体中的铁蛋白分子的最佳间距为100-200 nm。与未交联的铁蛋白对照相比，铁蛋白在12埃间距下的化学交联导致R-2增加70%。为了以潜在的生物学相关方式调节铁蛋白聚集，将铁蛋白附着于肌动蛋白并在体外聚合。与未聚合的铁蛋白-G-肌动蛋白相比，铁蛋白-F-肌动蛋白的聚合引起R-2增加20%。通过将铁蛋白在肌动蛋白上间隔得更远，R-2值增加了另外10%。哀叹。通过与细胞骨架元件结合来调节铁蛋白聚集可能是制备用于磁共振成像的功能性报告基因的有用策略。
Ferritin is an iron storage protein expressed in varying concentrations in mammalian cells. The deposition of ferric iron in the core of ferritin makes it a magnetic resonance imaging contrast agent, and ferritin has recently been proposed as a gene expression reporter protein for magnetic resonance imaging. To date, ferritin has been overexpressed in vivo and has been coexpressed with transferrin receptor to increase iron loading in cells. However, ferritin has a relatively low T-2 relaxivity (R-2 approximate to 1 mM(-1) s(-1)) at typical magnetic field strengths and so requires high levels of expression to be detected. One way to modulate the transverse relaxivity of a superparamagnetic agent is to cause it to aggregate, thereby manipulating the magnetic field gradients through which water diffuses. In this work, it is demonstrated by computer simulation and in vitro that aggregation of ferritin can alter relaxivity. The effects of aggregate size and intraaggregate perturber spacing on R-2 are studied. Computer modeling indicates that the optimal spacing of the ferritin molecules in aggregate for increasing R-2 is 100-200 nm for a typical range of water diffusion rates. Chemical cross-linking of ferritin at 12 angstrom spacing led to a 70% increase in R-2 compared to uncross-linked ferritin controls. To modulate ferritin aggregation in a potentially biologically relevant manner, ferritin was attached to actin and polymerized in vitro. The polymerization of ferritin-F-actin caused a 20% increase in R-2 compared to unpolymerized ferritin-G-actin. The R-2-value was increased by another 10% by spacing the ferritin farther apart on the actin. laments. The modulation of ferritin aggregation by binding to cytoskeletal elements may be a useful strategy to make a functional reporter gene for magnetic resonance imaging.