脂肪酸转运蛋白 (FATP) 家族：超长链酰基辅酶 A 合成酶还是溶质载体？,Journal of Molecular Neuroscience

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脂肪酸转运蛋白 (FATP) 家族：超长链酰基辅酶 A 合成酶还是溶质载体？
Journal of Molecular Neuroscience ( IF 2.8 ) Pub Date : 2007-09-01 , DOI: 10.1007/s12031-007-0038-z
Zhenzhen Jia ₁ , Zhengtong Pei , Dony Maiguel , Cicely J Toomer , Paul A Watkins

Affiliation

细胞脂肪酸通常来自细胞外环境的摄取，并且在较小程度上来自从头合成。细胞外脂肪酸必须穿过质膜，然后被激活为 CoA 硫酯以进行后续代谢。摄取和代谢都是快速过程，关于脂肪酸跨质膜脂质双层的转运是通过扩散进行还是需要转运蛋白，存在相当大的争议。一组提议用于转运脂肪酸的蛋白质是六成员脂肪酸转运蛋白 (FATP) 家族。这些蛋白质之所以如此命名是因为当过度表达时，宿主细胞表现出更高的放射性或荧光脂肪酸的增加率。然而，这个家族的一个成员，FATP2，与具有极长链酰基辅酶 A 合成酶 (ACSVL) 活性的酶相同。这种酶（ACSVL1 或 FATP2）是使用经典的蛋白质纯化技术分离的。事实上，六人 ACSVL 蛋白家族与六人 FATP 家族相同。我们和其他人已经确定所有六种蛋白质都具有酰基辅酶 A 合成酶活性。它们是否参与物理易位过程，或通过捕获通过扩散进入细胞的脂肪酸作为 CoA 衍生物促进运输仍有待确定。为了表征 ACSVL 的生物学功能，我们正在研究过度表达的蛋白质和内源性蛋白质的特性。我们观察到，对于许多 ACSVL，过表达蛋白的亚细胞定位与内源蛋白的亚细胞定位不同。使用 RNA 干扰 (siRNA)，我们敲低了 Neuro2a 细胞中 FATP4（提议名称：ACSVL5）的表达。当 FATP4 耗尽时，长链 (C16:0) 和极长链脂肪酸 (C24:0) 的激活都会降低。尽管酶活性降低，但当 FATP4 耗尽时，[14C]C16:0 的初始摄取率并未受到影响。相比之下，过表达 FATP4 的 COS-1 细胞显示出增强的 [14C]C16:0 摄取。在常规细胞培养条件下，内源性 (Neuro2a) 和过表达 (COS-1) FATP4 均未定位于质膜，而是在细胞内膜隔室中发现。我们得出结论，在所研究的细胞系中，内源性 FATP4 没有将 FA 转运穿过质膜的功能。当 FATP4 耗尽时，长链 (C16:0) 和极长链脂肪酸 (C24:0) 的激活都会降低。尽管酶活性降低，但当 FATP4 耗尽时，[14C]C16:0 的初始摄取率并未受到影响。相比之下，过表达 FATP4 的 COS-1 细胞显示出增强的 [14C]C16:0 摄取。在常规细胞培养条件下，内源性 (Neuro2a) 和过表达 (COS-1) FATP4 均未定位于质膜，而是在细胞内膜隔室中发现。我们得出结论，在所研究的细胞系中，内源性 FATP4 没有将 FA 转运穿过质膜的功能。当 FATP4 耗尽时，长链 (C16:0) 和极长链脂肪酸 (C24:0) 的激活都会降低。尽管酶活性降低，但当 FATP4 耗尽时，[14C]C16:0 的初始摄取率并未受到影响。相比之下，过表达 FATP4 的 COS-1 细胞显示出增强的 [14C]C16:0 摄取。在常规细胞培养条件下，内源性 (Neuro2a) 和过表达 (COS-1) FATP4 均未定位于质膜，而是在细胞内膜隔室中发现。我们得出结论，在所研究的细胞系中，内源性 FATP4 没有将 FA 转运穿过质膜的功能。过表达 FATP4 的 COS-1 细胞显示出增强的 [14C]C16:0 摄取。在常规细胞培养条件下，内源性 (Neuro2a) 和过表达 (COS-1) FATP4 均未定位于质膜，而是在细胞内膜隔室中发现。我们得出结论，在所研究的细胞系中，内源性 FATP4 没有将 FA 转运穿过质膜的功能。过表达 FATP4 的 COS-1 细胞显示出增强的 [14C]C16:0 摄取。在常规细胞培养条件下，内源性 (Neuro2a) 和过表达 (COS-1) FATP4 均未定位于质膜，而是在细胞内膜隔室中发现。我们得出结论，在所研究的细胞系中，内源性 FATP4 没有将 FA 转运穿过质膜的功能。

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The fatty acid transport protein (FATP) family: very long chain acyl-CoA synthetases or solute carriers?

Cellular fatty acids typically derive from uptake from the extracellular milieu and, to a lesser extent, de novo synthesis. Extracellular fatty acids must traverse the plasma membrane, after which they are activated to their CoA thioesters for subsequent metabolism. Both uptake and metabolism are rapid processes, and there has been considerable debate as to whether transport of fatty acids across the lipid bilayer of the plasma membrane proceeds by diffusion or requires transport proteins. One group of proteins proposed to translocate fatty acids is the six-member Fatty Acid Transport Protein (FATP) family. These proteins were designated as such because when overexpressed, host cells exhibited higher rates of accretion of radioactive or fluorescent fatty acids. However, one member of this family, FATP2, is identical to an enzyme with very long-chain acyl-CoA synthetase (ACSVL) activity. This enzyme (ACSVL1 or FATP2), was isolated using classical protein purification techniques. In fact, the six-member ACSVL protein family is identical to the six-member FATP family. We and others have established that all six proteins have acyl-CoA synthetase activity. It remains to be established whether they participate in the physical translocation process, or facilitate transport by trapping, as CoA derivatives, fatty acids that enter cells by diffusion. To characterize the biological functions of the ACSVLs, we are investigating the properties of the overexpressed proteins and the endogenous proteins. We observed that for many ACSVLs, the subcellular location of the overexpressed protein differs from that of the endogenous protein. Using RNA interference (siRNA), we knocked down expression of FATP4 (proposed name: ACSVL5) in Neuro2a cells. Activation of both long-chain (C16:0) and very long-chain fatty acids (C24:0) was decreased when FATP4 was depleted. Despite decreased enzyme activity, initial rates of uptake of [14C]C16:0 were not affected when FATP4 was depleted. In contrast, COS-1 cells overexpressing FATP4 showed enhanced [14C]C16:0 uptake. Neither endogenous (Neuro2a) nor overexpressed (COS-1) FATP4 was localized to plasma membrane under routine cell culture conditions, but rather were found in intracellular membrane compartments. We conclude that, in the cell lines studied, endogenous FATP4 does not function to translocate FA across the plasma membrane.

更新日期：2019-11-01

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