Contrasting effects of ERK on tight junction integrity in differentiated and under-differentiated Caco-2 cell monolayers.
Contrasting effects of ERK on tight junction integrity in differentiated and under-differentiated Caco-2 cell monolayers.
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DOI：
10.1042/bj20100249
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发表时间：
2011-01-01
期刊：
影响因子：
--
通讯作者：
Rao RK
中科院分区：
文献类型：
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作者：
Aggarwal S;Suzuki T;Taylor WL;Bhargava A;Rao RK
ERK（细胞外信号调节激酶）的激活导致一些上皮单层紧密连接的破坏，而它可以防止其他上皮紧密连接的破坏。造成ERK对紧密结完整性的这种不同影响的因素尚不清楚。本研究探讨了细胞分化状态对erk介导的Caco-2细胞单层紧密连接调控的影响。EGF（表皮生长因子）增强了h2o2诱导的未分化细胞单层紧密连接破坏，MEK [MAPK（丝裂原活化蛋白激酶）/ERK激酶]抑制剂U0126减弱了这种破坏。相比之下，EGF可以阻止h2o2诱导的分化细胞单层紧密连接的破坏，U0126也可以减弱这种破坏。敲低ERK1/2可增强未分化单层细胞紧密连接的完整性并加速紧密连接的组装，而在分化单层细胞中则相反。在未分化的细胞中，野生型和组成型活性MEK1的表达调控会破坏紧密连接，而显性阴性MEK1的表达增强了紧密连接的完整性，而在分化细胞中则记录了截然相反的反应。在分化的单层细胞中，EGF通过erk依赖机制阻止h2o2诱导的PP2A（蛋白磷酸酶2A）和PKCζ（蛋白激酶Cζ）与occludin的关联缺失，但在未分化的单层细胞中没有。活性ERK在未分化的单层细胞中主要分布在细胞内，而在已分化的单层细胞中主要分布在周结区。因此，ERK可能通过其亚细胞分布的差异以及调节PKCζ和PP2A与紧密连接蛋白结合的能力，在未分化和分化的上皮细胞中表现出对紧密连接完整性的不同影响。
ERK (extracellular-signal-regulated kinase) activation leads to disruption of tight junctions in some epithelial monolayers, whereas it prevents disruption of tight junctions in other epithelia. The factors responsible for such contrasting influences of ERK on tight junction integrity are unknown. The present study investigated the effect of the state of cell differentiation on ERK-mediated regulation of tight junctions in Caco-2 cell monolayers. EGF (epidermal growth factor) potentiated H2O2-induced tight junction disruption in under-differentiated cell monolayers, which was attenuated by the MEK [MAPK (mitogen-activated protein kinase)/ERK kinase] inhibitor U0126. In contrast, EGF prevented H2O2-induced disruption of tight junctions in differentiated cell monolayers, which was also attenuated by U0126. Knockdown of ERK1/2 enhanced tight junction integrity and accelerated assembly of tight junctions in under-differentiated cell monolayers, whereas it had the opposite effect in differentiated cell monolayers. Regulated expression of wild-type and constitutively active MEK1 disrupted tight junctions, and the expression of dominant-negative MEK1 enhanced tight junction integrity in under-differentiated cells, whereas contrasting responses were recorded in differentiated cells. EGF prevented both H2O2-induced association of PP2A (protein phosphatase 2A), and loss of association of PKCζ (protein kinase Cζ), with occludin by an ERK-dependent mechanism in differentiated cell monolayers, but not in under-differentiated cell monolayers. Active ERK was distributed in the intracellular compartment in under-differentiated cell monolayers, whereas it was localized mainly in the perijunctional region in differentiated cell monolayers. Thus ERK may exhibit its contrasting influences on tight junction integrity in under-differentiated and differentiated epithelial cells by virtue of differences in its subcellular distribution and ability to regulate the association of PKCζ and PP2A with tight junction proteins.