The integrin αEβ7 is expressed on intestinal intraepithelial T lymphocytes and CD8+ T lymphocytes in inflammatory lesions near epithelial cells. Adhesion between αEβ7+ T and epithelial cells is mediated by the adhesive interaction of αEβ7 and E-cadherin; this interaction plays a key role in the damage of target epithelia. To explore the structure-function relationship of the heterophilic adhesive interaction between E-cadherin and αEβ7, we performed cell aggregation assays using L cells transfected with an extracellular domain-deletion mutant of E-cadherin. In homophilic adhesion assays, L cells transfected with wild-type or a domain 5-deficient mutant formed aggregates, whereas transfectants with domain 1-, 2-, 3-, or 4-deficient mutants did not. These results indicate that not only domain 1, but domains 2, 3, and 4 are involved in homophilic adhesion. When αEβ7+ K562 cells were incubated with L cells expressing the wild type, 23% of the resulting cell aggregates consisted of αEβ7+ K562 cells. In contrast, the binding of αEβ7+ K562 cells to L cells expressing a domain 5-deficient mutant was significantly decreased, with αEβ7+ K562 cells accounting for only 4% of the cell aggregates, while homophilic adhesion was completely preserved. These results suggest that domain 5 is involved in heterophilic adhesion with αEβ7, but not in homophilic adhesion, leading to the hypothesis that the fifth domain of E-cadherin may play a critical role in the regulation of heterophilic adhesion to αEβ7 and may be a potential target for treatments altering the adhesion of αEβ7+ T cells to epithelial cells in inflammatory epithelial diseases.

We have reported that the TCRζ mRNA with alternatively spliced 3′ UTR (ζ mRNA/as-3′-untranslated region (UTR)) and ζ mRNA lacking exon 7 (ζ mRNA/exon 7−) observed in systemic lupus erythematosus patient T cells can lead to down-regulation of both ζ and TCR/CD3 complexes. To determine whether these T cells expressing decreased ζ exhibit differential transcription patterns, we transfected retrovirus vectors containing wild-type ζ cDNA, ζ cDNA/as-3′ UTR, and ζ cDNA/exon 7− into murine T cell hybridoma MA5.8 cells which lack ζ expression to construct the MA5.8 mutants WT, AS3′ UTR, and EX7−, respectively. FACS analyses demonstrated reduced cell surface expression of ζ and TCR/CD3 complexes on the AS3′ UTR mutant and the EX7− mutant in comparison to that on the WT mutant. Total RNA was collected after stimulating the MA5.8 mutants with anti-CD3 Ab. Reverse-transcribed cDNA was applied to the mouse cDNA microarray containing 8691 genes, and the results were confirmed by real-time PCR. The results showed that 36 genes encoding cytokines and chemokines, including IL-2, IL-15, IL-18, and TGF-β2, were down-regulated in both the AS3′ UTR mutant and the EX7− mutant. Another 16 genes were up-regulated in both, and included genes associated with membranous proteins and cell damage granules, including the genes encoding poliovirus receptor-related 2, syndecan-1, and granzyme A. Increased protein expression of these genes was confirmed by Western blot and FACS analyses. Identification of these responsive genes in T cells in which the ζ and TCR/CD3 complexes were down-regulated may help to better understand the pathogenesis of systemic lupus erythematosus.