In epidermis, it has been suggested, intercellular communication through gap junctions is important in coordinating cell behavior. The connexins, may facilitate selective assembly or permeability of gap junctions, influencing the distribution of metabolites between cells. Using immunohistochemistry, we have compared the distribution of connexins 26 and 43 with that of proliferating cells (Ki67 labeling) in normal epidermis, hyperplastic epidermis (tape-stripped epidermis, psoriatic lesions, and viral warts), and vaginal and buccal epithelia. Connexin 43 was abundant in spinous layers of all epidermal specimens and in vaginal and buccal epithelia. Connexin 26 was absent from the interfollicular and interductal epidermis of normal hair-bearing skin, and nonlesional psoriatic epidermis but present at very low levels in plantar epidermis. Connexin 26 was prominent in lesional psoriatic epidermis and viral warts and in vaginal and buccal epithelia. In three independent experiments connexin 26 appeared in a patchy intercellular distribution in the basal epidermis within 24 h of tape stripping, proceeding to more extensive distribution in basal and suprabasal layers by 48 h. The increase in connexin 26 preceded that in cell proliferation. In vaginal epithelium, buccal epithelium, and viral warts connexin 26 was restricted mainly to suprabasal, nonproliferating cells. In psoriatic lesional epidermis connexin 26 was also located mainly in suprabasal, nonproliferating cells. Connexin 26 was present in a patchy distribution in the basal layer of psoriatic lesional epidermis, but double labeling for connexin 26 and Ki67 showed that many connexin 26 positive basal cells were nonproliferative, suggesting that connexin 26 may be related to differentiation rather than to proliferation. These observations would be consistent with a role for connexin 26 containing gap junctions during both early and later stages of keratinocyte differentiation in hyperplastic epidermis and in vaginal and buccal epithelia.

Glutathione S-transferases (GSTs) from the phi (GSTF) and tau (GSTU) classes are unique to plants and play important roles in stress tolerance and secondary metabolism as well as catalyzing the detoxification of herbicides in crops and weeds. We have cloned and functionally characterized a group of GSTUs from wheat treated with fenchlorazole-ethyl, a herbicide safener. One of these enzymes, TaGSTU4-4, was highly active in conjugating the chemically distinct wheat herbicides fenoxaprop and dimethenamid. The structure of TaGSTU4-4 has been determined at 2.2 A resolution in complex with S-hexylglutathione. This enzyme is the first tau class GST structure to be determined and most closely resembles the omega class GSTs, but without the unique N-terminal extension or active site cysteine. The X-ray structure identifies key amino acid residues in the hydrophobic binding site and provides insights into the substrate specificity of these enzymes.

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