The disruption of adherens junctions is associated with a decrease of E-cadherin phosphorylation by protein kinase CK2.

M. Serres (1) , O. Filhol (1) , H. Lickert (1) , C. Grangeasse (1) , Em Chambaz (1) , J. Stappert (1) , C. Vincent (1) , D. Schmitt (1)

1 IBCP - Institut de biologie et chimie des protéines [Lyon]

The down-regulation of E-cadherin is a common event in carcinogenesis. Phosphorylation/dephosphorylation is one posttranscriptional process which may regulate intercellular junctions. Here we show that in okadaic acid-treated keratinocytes, E-cadherin expression is shifted from the membrane to the cytoplasm, preventing cells from forming aggregates. These changes of E-cadherin localization and function are associated with a decrease in its phosphorylation state. The decrease in E-cadherin phosphorylation was essentially detected in okadaic acid-treated cell lysates isolated from 0.5% Triton-soluble fraction and not in the Triton-insoluble fraction linked to the cytoskeleton, suggesting a role of E-cadherin phosphorylation in cell-cell interactions. E-cadherin was markedly phosphorylated by CK2, either the purified recombinant enzyme or the endogenous enzyme. Using specific CK2 inhibitors such as heparin and 5, 6-dichloro-1-beta-d-ribofuranosylbenzimidazole, endogenous CK2 was confirmed as the main enzyme phosphorylating E-cadherin. The decrease in E-cadherin phosphorylation by endogenous CK2 was not restored by the addition of purified CK2, confirming that it is not due to a defect in CK2 expression or to its reduced activity, but rather to the incapacity of CK2 to phosphorylate E-cadherin. The co-immunoprecipitation and colocalization of E-cadherin and CK2 suggests that CK2 may play a critical role in the maintenance of epidermis cohesion.The down-regulation of E-cadherin is a common event in carcinogenesis. Phosphorylation/dephosphorylation is one posttranscriptional process which may regulate intercellular junctions. Here we show that in okadaic acid-treated keratinocytes, E-cadherin expression is shifted from the membrane to the cytoplasm, preventing cells from forming aggregates. These changes of E-cadherin localization and function are associated with a decrease in its phosphorylation state. The decrease in E-cadherin phosphorylation was essentially detected in okadaic acid-treated cell lysates isolated from 0.5% Triton-soluble fraction and not in the Triton-insoluble fraction linked to the cytoskeleton, suggesting a role of E-cadherin phosphorylation in cell-cell interactions. E-cadherin was markedly phosphorylated by CK2, either the purified recombinant enzyme or the endogenous enzyme. Using specific CK2 inhibitors such as heparin and 5, 6-dichloro-1-beta-d-ribofuranosylbenzimidazole, endogenous CK2 was confirmed as the main enzyme phosphorylating E-cadherin. The decrease in E-cadherin phosphorylation by endogenous CK2 was not restored by the addition of purified CK2, confirming that it is not due to a defect in CK2 expression or to its reduced activity, but rather to the incapacity of CK2 to phosphorylate E-cadherin. The co-immunoprecipitation and colocalization of E-cadherin and CK2 suggests that CK2 may play a critical role in the maintenance of epidermis cohesion.

Domaines: Biochimie, Biologie Moléculaire

M. Serres, O. Filhol, H. Lickert, C. Grangeasse, Em Chambaz, et al.. The disruption of adherens junctions is associated with a decrease of E-cadherin phosphorylation by protein kinase CK2.. Exp Cell Res, 2000, 257, pp.255-264. ⟨hal-00314355⟩