Sheth Parimal, Seth Ankur, Atkinson Katherine J, Gheyi Tarun, Kale Gautam, Giorgianni Francesco, Desiderio Dominic M, Li Chunying, Naren Anjaparavanda, Rao Radhakrishna
Department of Physiology, University of Tennessee Health Science Center, University of Memphis, Memphis, TN 38163, USA.
Biochem J. 2007 Mar 1;402(2):291-300. doi: 10.1042/BJ20060665.
Interactions between E-cadherin, beta-catenin and PTP1B (protein tyrosine phosphatase 1B) are crucial for the organization of AJs (adherens junctions) and epithelial cell-cell adhesion. In the present study, the effect of acetaldehyde on the AJs and on the interactions between E-cadherin, beta-catenin and PTP1B was determined in Caco-2 cell monolayers. Treatment of cell monolayers with acetaldehyde induced redistribution of E-cadherin and beta-catenin from the intercellular junctions by a tyrosine phosphorylation-dependent mechanism. The PTPase activity associated with E-cadherin and beta-catenin was significantly reduced and the interaction of PTP1B with E-cadherin and beta-catenin was attenuated by acetaldehyde. Acetaldehyde treatment resulted in phosphorylation of beta-catenin on tyrosine residues, and abolished the interaction of beta-catenin with E-cadherin by a tyrosine kinase-dependent mechanism. Protein binding studies showed that the treatment of cells with acetaldehyde reduced the binding of beta-catenin to the C-terminal region of E-cadherin. Pairwise binding studies using purified proteins indicated that the direct interaction between E-cadherin and beta-catenin was reduced by tyrosine phosphorylation of beta-catenin, but was unaffected by tyrosine phosphorylation of E-cadherin-C. Treatment of cells with acetaldehyde also reduced the binding of E-cadherin to GST (glutathione S-transferase)-PTP1B. The pairwise binding study showed that GST-E-cadherin-C binds to recombinant PTP1B, but this binding was significantly reduced by tyrosine phosphorylation of E-cadherin. Acetaldehyde increased the phosphorylation of beta-catenin on Tyr-331, Tyr-333, Tyr-654 and Tyr-670. These results show that acetaldehyde induces disruption of interactions between E-cadherin, beta-catenin and PTP1B by a phosphorylation-dependent mechanism.
E-钙黏蛋白、β-连环蛋白和蛋白酪氨酸磷酸酶1B（PTP1B）之间的相互作用对于黏附连接（AJs）的组织和上皮细胞间黏附至关重要。在本研究中，在Caco-2细胞单层中测定了乙醛对AJs以及E-钙黏蛋白、β-连环蛋白和PTP1B之间相互作用的影响。用乙醛处理细胞单层通过酪氨酸磷酸化依赖性机制诱导E-钙黏蛋白和β-连环蛋白从细胞间连接重新分布。与E-钙黏蛋白和β-连环蛋白相关的蛋白酪氨酸磷酸酶活性显著降低，并且乙醛减弱了PTP1B与E-钙黏蛋白和β-连环蛋白的相互作用。乙醛处理导致β-连环蛋白酪氨酸残基磷酸化，并通过酪氨酸激酶依赖性机制消除了β-连环蛋白与E-钙黏蛋白的相互作用。蛋白质结合研究表明，用乙醛处理细胞会降低β-连环蛋白与E-钙黏蛋白C末端区域的结合。使用纯化蛋白的成对结合研究表明，β-连环蛋白的酪氨酸磷酸化会降低E-钙黏蛋白和β-连环蛋白之间的直接相互作用，但不受E-钙黏蛋白-C酪氨酸磷酸化的影响。用乙醛处理细胞也会降低E-钙黏蛋白与谷胱甘肽S-转移酶（GST）-PTP1B的结合。成对结合研究表明，GST-E-钙黏蛋白-C与重组PTP1B结合，但E-钙黏蛋白的酪氨酸磷酸化会显著降低这种结合。乙醛增加了β-连环蛋白在Tyr-331、Tyr-333、Tyr-654和Tyr-670位点的磷酸化。这些结果表明，乙醛通过磷酸化依赖性机制诱导E-钙黏蛋白、β-连环蛋白和PTP1B之间相互作用的破坏。
