Tight junctions and the experimental modifications of lipid content
Tight junctions and the experimental modifications of lipid content
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DOI：
10.1007/s002329900393
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发表时间：
1998-07-01
影响因子：
2.4
通讯作者：
Cereijido, M
中科院分区：
文献类型：
--
作者：
Calderón, V;Lázaro, A;Cereijido, M
紧密连接（TJ）是由链组成的细胞与细胞的接触，其在冷冻断裂复制品上表现为P面上的脊和E面上的互补沟。关于这些链是否由膜结合蛋白或脂质胶束组成的证据和意见有所不同。在本工作中，我们使用一种新的方法改变Madin-Darby犬肾单层的脂质组成，同时研究（i）它们的跨上皮电阻，一个取决于TJ密封程度的参数;（ii）4kD荧光葡聚糖（J（DEX））的顶侧至基底侧通量，其反映了细胞间隙的渗透性;（iii）TJ限制膜脂质从顶侧向基底侧扩散的能力;和（iv）内源性和转染的occludin的分布模式，occludin是目前已知形成TJ一部分的唯一膜蛋白。我们表明，改变磷脂，鞘脂，胆固醇和脂肪酸的含量的总组合物，不改变TER也不链的结构。有趣的是，富含亚油酸使J（DEX）增加了631%。这种增加并没有反映在TER的减少，这一事实表明，连接股不作为简单的电阻元件，但可能包含移动的易位机制。
Tight junctions (TJs) are cell-to-cell contacts made of strands, which appear as ridges on P faces and complementary furrows on E faces on freeze fracture replicas. Evidences and opinions on whether these strands are composed of either membrane-bound proteins or lipid micelles are somewhat varied. In the present work we alter the lipid composition of Madin-Darby canine kidney monolayers using a novel approach, while studying (i) their transepithelial electrical resistance, a parameter that depends on the degree of sealing of the TJs; (ii) the apical-to-basolateral flux of 4 kD fluorescent dextran (J(DEX)), that reflects the permeability of the intercellular spaces; (iii) the ability of TJs to restrict apical-to-basolateral diffusion of membrane lipids; and (iv) the pattern of distribution of endogenous and transfected occludin, the sole membrane protein presently known to form part of the TJs. We show that changing the total composition of phospholipids, sphingolipids, cholesterol and the content of fatty acids, does not alter TER nor the structure of the strands. Interestingly, enrichment with linoleic acid increases the J(DEX) by 631%. The fact that this increase is not reflected in a decrease of TER, suggests that junctional strands do not act as simple resistive elements but may contain mobile translocating mechanisms.