Carnosine uptake in rat choroid plexus primary cell cultures and choroid plexus whole tissue from PEPT2 null mice.
Carnosine uptake in rat choroid plexus primary cell cultures and choroid plexus whole tissue from PEPT2 null mice.
复制标题
大鼠脉络丛原代细胞培养物和来自 PEPT2 缺失小鼠的脉络丛全组织中的肌肽摄取。
DOI：
10.1111/j.1471-4159.2004.02333.x
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
Smith,DavidE
中科院分区：
文献类型：
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作者：
Teuscher,NathanS;Shen,Hong;Shu,Cathaleen;Xiang,Jianming;Keep,RichardF;Smith,DavidE
PEPT2具有功能活性，定位于大鼠脉络丛上皮细胞的顶膜。然而，关于内源性神经肽在脉络丛中的转运机制，以及PEPT2在这一过程中的作用，目前还知之甚少。在本研究中，我们研究了原代培养的大鼠脉络丛细胞和野生型(PEPT2+/+)和空白(PEPT2-/-)小鼠脉络丛整体组织对肌肽的摄取动力学。我们的结果表明，肌肽优先从细胞单层的顶端摄取，而不是基侧膜，基侧外流是有限的。肌肽跨上皮流量与细胞旁扩散流量无明显差别。肌肽的顶端摄取是一个高亲和力(Km= 34 μm)、低容量(Vmax= 73 /mg蛋白/分钟)的过程，与PEPT2的摄取过程一致。非饱和成分很小(Kd= 0.063 μL/mg蛋白质/分钟)，在线性条件下，仅占总吸收的3%。对转基因小鼠的研究清楚地表明，PEPT2负责脉络丛整个组织90%以上的肌肽摄取。这些发现阐明了PEPT2在调节血-脑脊液界面神经肽稳态方面的独特作用。
PEPT2 is functionally active and localized to the apical membrane of rat choroid plexus epithelial cells. However, little is known about the transport mechanisms of endogenous neuropeptides in choroid plexus, and the role of PEPT2 in this process. In the present study, we examined the uptake kinetics of carnosine in rat choroid plexus primary cell cultures and choroid plexus whole tissue from wild‐type (PEPT2+/+) and null (PEPT2–/–) mice. Our results indicate that carnosine is preferentially taken up from the apical as opposed to basolateral membrane of cell monolayers, and that basolateral efflux in limited. Transepithelial flux of carnosine was not distinguishable from that of paracellular diffusion. The apical uptake of carnosine was characterized by a high affinity (Km= 34 μm), low capacity (Vmax= 73 pmol/mg protein/min) process, consistent with that of PEPT2. The non‐saturable component was small (Kd= 0.063 μL/mg protein/min) and, under linear conditions, was only 3% of the total uptake. Studies in transgenic mice clearly demonstrated that PEPT2 was responsible for over 90% of carnosine's uptake in choroid plexus whole tissue. These findings elucidate the unique role of PEPT2 in regulating neuropeptide homeostasis at the blood–cerebrospinal fluid interface.