To gain insight into the molecular mechanisms underlying cutaneous wound repair, we performed a large scale screen to identify novel injury-regulated genes. Here we show a strong up-regulation of the RNA and protein levels of the two Ca 2؉ -binding proteins S100A8 and S100A9 in the hyperthickened epidermis of acute murine and human wounds and of human ulcers. Furthermore, both genes were expressed by inflammatory cells in the wound. The increased expression of S100A8 and S100A9 in wound keratinocytes is most likely related to the activated state of the keratinocytes and not secondary to the inflammation of the skin, since we also found up-regulation of S100A8 and S100A9 in the epidermis of activin-overexpressing mice, which develop a hyperproliferative and abnormally differentiated epidermis in the absence of inflammation. Furthermore, S100A8 and S100A9 expression was found to be associated with partially differentiated keratinocytes in vitro. Using confocal microscopy, both proteins were shown to be at least partially associated with the keratin cytoskeleton. In addition, cultured keratinocytes efficiently secreted the S100A8/A9 dimer. These results together with previously published data suggest that S100A8 and S100A9 are novel players in wound repair, where they might be involved in the reorganization of the keratin cytoskeleton in the wounded epidermis, in the chemoattraction of inflammatory cells, and/or in the defense against microorganisms.After cutaneous injury, a series of biological events takes place that aims at the reconstruction of the damaged skin. Among them are the migration, proliferation, and differentiation of inflammatory, epithelial, and mesenchymal cells. These cells exert specific functions in a temporally and spatially coordinated manner such as the removal of irreversibly destructed tissue, the deposition of new extracellular matrix, and the reestablishment of the cutaneous barrier (1, 2). These processes are well described at the histological level, but little is known about their molecular basis.To gain insight into the molecular mechanisms that underlie the repair process, we performed a large scale subtractive hybridization screen to systematically identify genes that are differentially expressed in injured compared with normal skin. To minimize the risk of detecting differences in gene expression levels due to changes in cellular composition rather than to transcriptional regulation, we compared normal skin with early (24 h) wounds, because only minor changes in cell type composition occur during the initial wound healing period.One of the cDNA clones that we obtained encodes the murine S100A8 protein (also known as calgranulin A, MRP8, leukocyte protein L1, or cytokine CP-10). S100 proteins are intracellular Ca 2ϩ -binding and Ca 2ϩ -modulated proteins that form antiparallel noncovalently linked dimers in solution and play a role in various Ca 2ϩ -mediated cellular functions including cell growth and differentiation, energy metabolism, cytoskeletalmembrane interactions; some of th...

Photoautotrophic suspension-culture cells of Chenopodium rubrum that were shifted to mixotrophic growth by adding glucose were used as model system to investigate the influence of the source-sink transition in higher plants on the expression and enzyme activities of intracellular and extracellular invertases. The complete cDNA coding for an extracellular invertase was cloned and sequenced from C. rubrum, and its identity has been proven by heterologous expression in Saccbaromyces cerevisiae. The higher activity of extracellular invertase after preincubation in the presente of glucose was paralleled by an increased expression of the corresponding gene. The induction by glucose could be mimicked by the nonmetabolizable glucose analog 6-deoxyglucose. Both enzyme activity and mRNA leve1 of extracellular invertase showed a sink-tissue-specific distribution in plants. The activity of neutra1 and acidic intracellular invertases were not affected by preincubation of autotrophic tissue cultures with sugars, nor did they show a tissuespecific distribution in plants. The data suggest that apoplastic invertase not only has an important function in phloem unloading and carbohydrate partitioning between source and sink tissues but may also have a role in establishing metabolic sinks.

The fibroblast growth factor-binding protein (FGF-BP) binds and activates FGF-1 and FGF-2, thereby contributing to tumor angiogenesis. In this study, we identified novel binding partners of FGF-BP, and we provide evidence for a role of this protein in epithelial repair processes. We show that expression of FGF-BP increases after injury to murine and human skin, in particular in keratinocytes. This upregulation is most likely achieved by major keratinocyte mitogens present at the wound site.Most importantly, we demonstrate that FGF-BP interacts with FGF-7, FGF-10, and with the recently identified FGF-22, and enhances the activity of low concentrations of ligand. Due to the important functions of FGF-7 and FGF-10 for repair of injured epithelia, our findings suggest that upregulation of FGF-BP expression after injury stimulates FGF activity at the wound site, thus enhancing the process of epithelial repair.

No abstract

Integrins of the ␤7 subfamily, ␣4␤7 and ␣E␤7, contribute to lymphocyte homing and to the development of protective or autoreactive immune responses at mucosal sites. The ␤ subunits of integrins are considered important for regulation of stimulated cell adhesion and adhesion-dependent signal transduction. Using a yeast interaction trap screen, a human WD repeat protein, termed WAIT-1, was isolated that interacts with the integrin ␤7 cytoplasmic tail and is homologous to mouse EED and Drosophila ESC proteins. WAIT-1 also binds to the cytoplasmic domains of ␣4 and ␣E but not to those of integrin ␤1, ␤2, and ␣L subunits. Association of WAIT-1 and ␤7-integrin was confirmed by coprecipitation from transiently transfected 293 cells. The binding site for WAIT-1 was mapped to a short membrane-proximal region of the ␤7 cytoplasmic tail with Tyr-735 being of critical importance. Northern blot analysis revealed multiple WAIT-1-related transcripts with differential expression in circulating leukocytes, tissue-resident cells of diverse origin, and lymphoid malignancies. These results suggest that WAIT-1, together with the recently identified RACK1, may define a novel subfamily of WD repeat proteins that interact with distinct subsets of integrin cytoplasmic tails and may act as specific regulators of integrin function.Expression of ␤7-integrins, ␣4␤7 and ␣E␤7, is largely confined to leukocytes. Although ␣4␤7-integrin is homogeneously expressed on natural killer cells, eosinophils, and naive T and B cells, its distribution on effector/memory T and B cells is restricted to a subset of gut-homing lymphocytes (1-6). Peripheral blood monocytes do not express ␤7-integrins, but ␣4␤7 and ␣E␤7 are up-regulated upon stimulation of macrophage differentiation with phorbol ester or interferon-␥ (7). Recent studies have indicated that, in addition, ␣4␤7-integrin is induced on endothelial cells after treatment with proinflammatory mediators such as tumor necrosis factor (8). In contrast to ␣4␤7, expression of the ␣E␤7-integrin is confined to a subset of gutassociated T lymphocytes and dendritic cells (4,6,9).␤7-Integrins are considered important for the development and function of gut-associated lymphoid tissues. Interaction of ␣4␤7 with MAdCAM-1 allows for tissue-specific migration of circulating lymphocytes into the lamina propria and Peyer's patches of the gut (10, 11), whereas ␣E␤7 may retain intraepithelial lymphocytes within the gut epithelium through binding of E-cadherin on epithelial cells (12,13). Lack of ␤7-integrins severely impairs the development of the gut immune system, as Peyer's patches are absent or hypoplastic, and fewer intraepithelial lymphocytes are detected in ␤7-integrin-deficient mice (14). Moreover, gut-homing ␣4␤7 ϩ CD4 T cells specifically harbor cellular memory for intestinal antigens, suggesting that ␣4␤7 helps to target and segregate intestinal versus systemic immune responses (15).Integrins of the ␤7 family are involved in the development and/or progression of diseases such as colitis (16,17), diabetic insul...