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The mucosal lymphocyte integrin αE(CD103)β7 is thought to be important for intraepithelial lymphocyte (IEL) localization or function. We cloned the murine integrin gene encoding αE, localized it to chromosome 11, and generated integrin αE-deficient mice. In αE−/− mice, intestinal and vaginal IEL numbers were reduced, consistent with the known binding of αEβ7 to E-cadherin expressed on epithelial cells. However, it was surprising that lamina propria T lymphocyte numbers were diminished, as E-cadherin is not expressed in the lamina propria. In contrast, peribronchial, intrapulmonary, Peyer’s patch, and splenic T lymphocyte numbers were not reduced in αE-deficient mice. Thus, αEβ7 was important for generating or maintaining the gut and vaginal T lymphocytes located diffusely within the epithelium or lamina propria but not for generating the gut-associated organized lymphoid tissues. Finally, the impact of αE deficiency upon intestinal IEL numbers was greater at 3–4 wk of life than in younger animals, and affected the TCR αβ+ CD8+ T cells more than the γδ T cells or the TCR αβ+ CD4+CD8− population. These findings suggest that αEβ7 is involved in the expansion/recruitment of TCR αβ+ CD8+ IEL following microbial colonization. Integrin αE-deficient mice will provide an important tool for studying the role of αEβ7 and of αEβ7-expressing mucosal T lymphocytes in vivo.

The membrane-bound component of the cerebral protein carboxylmethylation system, consisting of the membrane-bound enzyme protein carboxylmethyltransferase II (PCMT) and of selected membrane-bound methyl accepting proteins (MAP), is described. The cellular localization of this membrane-bound protein carboxylmethylation system is shown to include, in addition to nerve cell bodies and purified synaptosomes, astrocytes and oligodendroglia. The membrane-bound nature of the protein carboxylmethylation system was investigated and these studies revealed a tight association which exposure to several detergents could only partially solubilize. The membrane-bound PCMT could be shown to undergo activation after treatment with Na-deoxycholate and CHAPs, while after its detergent-induced solubilization PCMT activation was observed after Na-deoxycholate, Nonidet P-40 and Lubrol-P(X). Solubilization of the carboxylmethylation system in CHAPS appeared to be more effective at 0 degrees C than at 25 degrees C or 37 degrees C. Detergent treatment was shown to be deleterious to the MAPs as PCMT substrates, particularly when the exposure was extended to more than 1 h. These observations prompted exposure of the brain membranes and of their Lubrol-P(X) and Nonidet P-40 extracts to NH(4)OH, treatment which promotes the conversion of protein asparagine residues to atypical l-isoaspartate residues, recently shown (in synthetic peptides) to be the single most effective residue recognized for carboxylmethylation by PCMT. We found up to a 400% enhancement of the carboxylmethylation of solubilized membrane MAPs by the equally solubilized PCMT (which resisted the alkaline treatment virtually unscathed) after 90 min at 37 degrees C in 0.05 M NH(4)OH. However, when brain membrane Lubrol-P(x) extracts were first subjected to bis(I,I-trifluoroacetoxy)-iodobenzene, a reagent which converts the carboxyamide group of protein-bound asparagine to the corresponding primary amine, the amount of MAPs susceptible to be acted upon by 0.05 M NH(4)OH became greatly reduced. Finally, acidic slab gel electrophoresis of membrane-bound MAPs, carboxyl-[(3)H]-methylated by the membrane-bound PCMT, revealed the presence of about 12 radioactive protein bands, ranging in MW from under 20 KDa to about 90 KDa.