Biomedical subjects

Lore Florin

Publications and source records attributed to Lore Florin.

8 recordsLinked to original sources

PubMed2006

JunB is required for endothelial cell morphogenesis by regulating core-binding factor beta.

The molecular mechanism triggering the organization of endothelial cells (ECs) in multicellular tubules is mechanistically still poorly understood. We demonstrate that cell-autonomous endothelial functions of the AP-1 subunit JunB are required for proper endothelial morphogenesis both in vivo in mouse embryos with endothelial-specific ablation of JunB and in in vitro angiogenesis models. By cDNA microarray analysis, we identified core-binding factor beta (CBFbeta), which together with the Runx proteins forms the heterodimeric core-binding transcription complex CBF, as a novel JunB target gene. In line with our findings, expression of the CBF target MMP-13 was impaired in JunB-deficient ECs. Reintroduction of CBFbeta into JunB-deficient ECs rescued the tube formation defect and MMP-13 expression, indicating an important role for CBFbeta in EC morphogenesis.

Animals↗

PubMed2006

Cutting edge: the AP-1 subunit JunB determines NK cell-mediated target cell killing by regulation of the NKG2D-ligand RAE-1epsilon.

The activating receptor NKG2D and its ligands RAE-1 play an important role in the NK, gammadelta+, and CD8+ T cell-mediated immune response to tumors. Expression levels of RAE-1 on target cells have to be tightly controlled to allow immune cell activation against tumors but to avoid destruction of healthy tissues. In this study, we report that cell surface expression of RAE-1epsilon is greatly enhanced on cells lacking JunB, a subunit of the transcription complex AP-1. Furthermore, tissue-specific junB knockout mice respond to 12-O-tetradecanoyl-phorbol-13-acetate, a potent AP-1 activator, with markedly increased and sustained epidermal RAE-1epsilon expression. Accordingly, junB-deficient cells are efficiently killed via NKG2D by NK cells and induce IFN-gamma production. Our data indicate that the transcription factor AP-1, which is involved in tumorigenesis and cellular stress responses, regulates RAE-1epsilon. Thus, up-regulated RAE-1epsilon expression due to low levels of JunB could alert immune cells to tumors and stressed cells.

Animals↗

PubMed2006

Delayed wound healing and epidermal hyperproliferation in mice lacking JunB in the skin.

The cutaneous response to injury and stress comprises a temporary change in the balance between epidermal proliferation and differentiation as well as an activation of the immune system. Soluble factors play an important role in the regulation of these complex processes by coordinating the intercellular communication between keratinocytes, fibroblasts, and inflammatory cells. In this study, we demonstrate that JunB, a member of the activator protein-1 transcription factor family, is an important regulator of cytokine expression and thus critically involved in the cutaneous response to injury and stress. Mice lacking JunB in the skin develop normally, indicating that JunB is neither required for cutaneous organogenesis, nor homeostasis. However, upon wounding and treatment with the phorbol ester 12-O-decanoyl-phorbol-13-acetate, JunB-deficiency in the skin likewise resulted in pronounced epidermal hyperproliferation, disturbed differentiation, and prolonged inflammation. Furthermore, delayed tissue remodelling was observed during wound healing. These phenotypic skin abnormalities were associated with JunB-dependent alterations in expression levels and kinetics of important mediators of wound repair, such as granulocyte macrophage colony-stimulating factor, growth-regulated protein-1, macrophage inflammatory protein-2, and lipocalin-2 in both the dermal and epidermal compartment of the skin, and a reduced ability of wound contraction of mutant dermal fibroblasts in vitro.

Animals↗

PubMed2005

Psoriasis-like skin disease and arthritis caused by inducible epidermal deletion of Jun proteins.

Psoriasis is a frequent, inflammatory disease of skin and joints with considerable morbidity. Here we report that in psoriatic lesions, epidermal keratinocytes have decreased expression of JunB, a gene localized in the psoriasis susceptibility region PSORS6. Likewise, inducible epidermal deletion of JunB and its functional companion c-Jun in adult mice leads (within two weeks) to a phenotype resembling the histological and molecular hallmarks of psoriasis, including arthritic lesions. In contrast to the skin phenotype, the development of arthritic lesions requires T and B cells and signalling through tumour necrosis factor receptor 1 (TNFR1). Prior to the disease onset, two chemotactic proteins (S100A8 and S100A9) previously mapped to the psoriasis susceptibility region PSORS4, are strongly induced in mutant keratinocytes in vivo and in vitro. We propose that the abrogation of JunB/activator protein 1 (AP-1) in keratinocytes triggers chemokine/cytokine expression, which recruits neutrophils and macrophages to the epidermis thereby contributing to the phenotypic changes observed in psoriasis. Thus, these data support the hypothesis that epidermal alterations are sufficient to initiate both skin lesions and arthritis in psoriasis.

Aging↗

PubMed2005

Increased keratinocyte proliferation by JUN-dependent expression of PTN and SDF-1 in fibroblasts.

In skin, fibroblasts of the connective tissue play a decisive role in epidermal homeostasis and repair by contributing to the regulation of keratinocyte proliferation and differentiation. The AP-1 transcription factor subunit JUN plays a crucial role in this mesenchymal-epithelial interplay by regulating the expression of two critical paracrine-acting cytokines, keratinocyte growth factor (KGF) and granulocyte-macrophage colony-stimulating factor (GM-CSF). We have performed gene expression profiling of wild-type and Jun(-/-) mouse embryonic fibroblasts to identify additional players involved in this complex network, and have found pleiotrophin (PTN) and the stromal cell-derived factor 1 (SDF-1) as novel JUN-regulated factors. Both cytokines are expressed by dermal fibroblasts in vivo, as shown by semi-quantitative RT-PCR and in situ hybridization on murine skin sections. Using a heterologous feeder layer co-culture system, we demonstrated that PTN and SDF-1 exert a mitogenic effect on primary human keratinocytes. Moreover, SDF-1-induced keratinocyte proliferation could be specifically inhibited by neutralizing antibodies against SDF-1 or its receptor, CXCR4. Consistent with its role in promoting keratinocyte growth, PTN was upregulated during cutaneous wound healing in vivo. Interestingly, co-cultivation with keratinocytes stimulated PTN expression but repressed SDF-1 production in fibroblasts, demonstrating the complexity of the paracrine regulatory cytokine networks that control skin homeostasis and regeneration.

Animals↗

PubMed2004

Identification of novel AP-1 target genes in fibroblasts regulated during cutaneous wound healing.

Mesenchymal-epithelial interactions are increasingly considered to be of vital importance for epithelial homeostasis and regeneration. In skin, the transcription factor AP-1 was shown to be critically involved in the communication between keratinocytes and dermal fibroblasts. After skin injury, the release of IL-1 from keratinocytes induces the activity of the AP-1 subunits c-Jun and JunB in fibroblasts leading to a global change in gene expression. To identify AP-1 target genes in fibroblasts, which are involved in the process of cutaneous repair, we performed gene expression profiling of wild-type, c-jun- and junB-deficient fibroblasts in response to IL-1, mimicking the initial phase of wound healing. Using a 15K cDNA collection, over 1000 genes were found to be Jun-dependent and additional 300 clones showed IL-1 responsiveness. Combinatorial evaluation allowed for the dissection of the specific contribution of either AP-1 subunit to gene regulation. Besides previously identified genes that are involved in cutaneous repair, we have identified novel genes regulated during wound healing in vivo and showed their expression by fibroblasts on wound sections. The identification of novel Jun target genes should provide a basis for understanding the molecular mechanisms underlying mesenchymal-epithelial interactions and the critical contribution of AP-1 to tissue homeostasis and repair.

Animals↗

PubMed2004

Cre recombinase-mediated gene targeting of mesenchymal cells.

Loss-of-function approaches by the Cre/loxP technology have provided powerful tools for functional analyses of genes of interest expressed preferentially in a particular tissue. Here we describe the generation of transgenic mouse lines expressing Cre recombinase under the control of the promoter/enhancer unit of the gene for the alpha2 chain of collagen type I (Col1alpha2). As an expression vector, we used a P1-derived artificial chromosome (PAC), which harbors approximately 100 kb carrying the col1alpha2 gene. The improved coding sequence of the Cre recombinase was introduced to replace the first exon of col1alpha2. Cre expression was determined by immunohistochemistry and Cre-mediated onset of beta-galactosidase expression in ROSA26R-Cre reporter mice. In four analyzed transgenic lines, Cre recombinase was efficiently expressed during embryogenesis and in adult animals in cells of mesenchymal origin, such as dermal fibroblasts, mesenchymal cells of blood vessel walls, and cells in fibrous connective tissues surrounding internal organs.

Animals↗

PubMedDate not supplied

The K252a derivatives, inhibitors for the PAK/MLK kinase family selectively block the growth of RAS transformants.

BACKGROUND: Oncogenic RAS mutants such as v-Ha-RAS activate members of Rac/CDC42-dependent kinases (PAKs) and appear to contribute to the development of more than 30% of all human cancers. PAK1 activation is essential for oncogenic RAS transformation, and several chemical compounds that inhibit Tyr kinases essential for the RAS-induced activation of PAK1 strongly suppress RAS transformation either in cell culture or in vivo (nude mice). Although we have developed a cell-permeable PAK-specific peptide inhibitor called WR-PA18, so far no chemical (metabolically stable) compound has been developed that directly inhibits PAK1 in a highly selective manner. Thus, we have explored such a PAK1 inhibitor(s) among synthetic derivatives of an adenosine triphosphate antagonist. RESULTS: From the naturally occurring adenosine triphosphate antagonist K252a, we have developed two bulky derivatives, called CEP-1347 and KT D606 (a K252a dimer), which selectively inhibit PAKs or mixed-lineage kinases both in vitro and in cell culture and convert v-Ha-RAS-transformed NIH 3T3 cells to flat fibroblasts similar to the parental normal cells. Furthermore, these two K252a analogues suppress the proliferation of v-Ha-RAS transformants, but not the normal cells. CONCLUSION: These bulky adenosine triphosphate antagonists derived from K252a or related indolocarbazole compounds such as staurosporine would be potentially useful for the treatment of RAS/ PAK1-induced cancers, once their anti-PAK1 activity is significantly potentiated by a few additional chemical modifications at the sugar ring suggested in this paper.

3T3 Cells↗