Faculty Bibliography

The retinol/retinol-binding protein/transthyretin complex, that carries and delivers hydrophobic retinol molecules to target cells, is assembled in the hepatocyte endoplasmic reticulum. In this paper, we review data related to events that lead to the formation of this complex, including transthyretin oligomerization and retinol-binding protein secretion. Our studies on transthyretin oligomerization have demonstrated that cleavage of signal peptide and the environment of endoplasmic reticulum influence transthyretin oligomerization. In vitro, mutated transthyretin without signal sequence fails to form dimers, while wild-type transthyretin is translocated into the microsomes where it forms dimers and small amounts of tetramers. In vivo, tetramers were detected in HepG2 cells but not in transfected Cos cells, suggesting that tissue-specific factors affect tetramer stability. In vitamin A deficiency, retinol-binding protein secretion is blocked and the protein accumulates in the endoplasmic reticulum, from where it is promptly released after retinol repletion. We use MMH cells to identify factors involved in complex formation, retention and secretion, the crucial steps to understand the molecular mechanisms underlying vitamin A homeostasis. In parallel, studies on vitamin A transport in fish are in progress; retinol-binding protein and transthyretin have already been characterized in different fish species.

The zebrafish zisp gene encodes a putative transmembrane protein with a DHHC zinc finger motif. At the segmentation period zisp is expressed in the adaxial cells and the somites in a striping pattern. The zisp transcripts are localized to the posterior parts within the individual somites. In fused somites mutants, zisp is expressed throughout the somitic mesoderm. These expression patterns are similar to those of myoD. In addition to the somitic expression, the zisp expression was observed in lens cells at the late segmentation period and the early pharyngula period.

The zebrafish zisp gene encodes a putative transmembrane protein with a DHHC zinc finger motif. At the segmentation period zisp is expressed in the adaxial cells and the somites in a striping pattern. The zisp transcripts are localized to the posterior parts within the individual somites. In fused somites mutants, zisp is expressed throughout the somitic mesoderm. These expression patterns are similar to those of myoD. In addition to the somitic expression, the zisp expression was observed in lens cells at the late segmentation period and the early pharyngula period.

There is increasing evidence that G-protein-coupled receptors cross-talk with growth factor receptor-mediated signal transduction in a variety of cell types. We have investigated mechanisms by which the activation of beta-adrenergic receptors, classically GTP-binding proteins coupled receptors, influence the migration of cultured human keratinocytes. We found that iso-proterenol, a beta-adrenergic receptor-selective agonist, inhibited cell migration stimulated by either epidermal growth factor, or extracellular Ca2+ in a concentration-dependent manner. This was prevented by pretreatment of the cells with the beta-adrenergic receptor-selective antagonist timolol. Interestingly, isoproterenol, at a concentration of 1 nm, did not measurably increase intracellular cyclic adenosine monophosphate concentrations yet inhibited cell migration by 50%. To test further if isoproterenol's actions were mediated via activation of adenylyl cyclase, two inhibitors of its activity, 2'5'-dideoxyadenosine and SQ22536, were used. Both compounds significantly diminished iso-proterenol-induced increases in intracellular cyclic adenosine monophosphate concentrations but did not attenuate isoproterenol-induced inhibition of cell migration. Also, forskolin (1 microm) markedly increased intracellular cyclic adenosine monophosphate concentrations but did not significantly inhibit cell migration. As mitogen-activated protein kinases are known to signal growth factor-stimulated cell migration, we examined whether beta-adrenergic receptor-mediated inhibition of keratinocyte migration might occur via inactivation of mitogen-activated protein kinases. We found that isoproterenol inhibited phosphorylation of extracellular signal-regulated kinase mitogen-activated protein kinase in a concentration-dependent manner but had no effect on the phosphorylation of the stress mitogen-activated protein kinases c-jun N-terminal kinase and stress-activated protein kinase-2. Neither forskolin nor a membrane permeable cyclic adenosine monophosphate analog inhibited phosphorylation of any of these mitogen-activated protein kinases. These findings suggest that beta-adrenergic receptor-induced inhibition of keratinocyte migration is mediated through inhibition of the extracellular signal-regulated kinase mitogen-activated protein kinase signaling in a cyclic adenosine monophosphate-independent manner

We report a case of febrile ulceronecrotic Mucha-Habermann disease (FUMHD) in a 21-year-old man. This disease is a severe form of pityriasis lichenoides et varioliformis acuta (PLEVA) and is characterized by the sudden onset of diffuse ulcerations associated with high fever and systemic symptoms. It is sometimes lethal especially in elderly patients. In the present case, intense generalized maculopapular erythematous plaques with central necrosis developed progressively in association with a high fever. Initial treatment with systemic betamethasone had been unsuccessful and the skin lesions, which covered about 50% of the body surface, became severely ulcerated. Although the development of new lesions had ceased spontaneously, widespread ulceration of the skin remained. Debridement of the necrotic skin and skin grafting using cultured epidermal autografts and meshed allografts of cadaver skin led to prompt reepithelization.

The molecular chaperone HSP90 regulates stability and function of multiple protein kinases. The HSP90-binding drug geldanamycin interferes with this activity and promotes proteasome-dependent degradation of most HSP90 client proteins. Geldanamycin also binds to GRP94, the HSP90 paralog located in the endoplasmic reticulum (ER). Because two of three ER stress sensors are transmembrane kinases, namely IRE1alpha and PERK, we investigated whether HSP90 is necessary for the stability and function of these proteins. We found that HSP90 associates with the cytoplasmic domains of both kinases. Both geldanamycin and the HSP90-specific inhibitor, 514, led to the dissociation of HSP90 from the kinases and a concomitant turnover of newly synthesized and existing pools of these proteins, demonstrating that the continued association of HSP90 with the kinases was required to maintain their stability. Further, the previously reported ability of geldanamycin to stimulate ER stress-dependent transcription apparently depends on its interaction with GRP94, not HSP90, since geldanamycin but not 514 led to up-regulation of BiP. However, this effect is eventually superseded by HSP90-dependent destabilization of unfolded protein response signaling. These data establish a role for HSP90 in the cellular transcriptional response to ER stress and demonstrate that chaperone systems on both sides of the ER membrane serve to integrate this signal transduction cascade

Regulatory T cells (also referred to as suppressor T cells) are important components of the homeostasis of the immune system, as impaired regulatory T cell activity can cause autoimmune diseases and atopy. It is now clear that the phrase 'regulatory T cells' encompasses more than one cell type. For instance, CD4(+)CD25(+) regulatory T cells have received attention due to their immunosuppressive properties in vitro and in vivo, but in several instances it has been shown that CD4(+)CD25(-) T cell populations also contain potent regulatory activity. Recent progress in the field of regulatory T cells includes the discovery of the role of two tumor necrosis factor receptor (TNFR) family members (GITR and TRANCE-R/RANK) in Treg biology, the improved understanding of the role of co-stimulatory molecules and cytokines IL-10 and IL-2 in the induction and function of Tregs, and the generation of CD25(+) and CD25(-) regulatory T cells in vivo through high-avidity T cell receptor interactions

Lipids, in addition to being structural components of cell membranes, can act as signaling molecules. Bioactive lipids, such as sphingosine 1-phosphate (S1P) and lysophosphatidic acid (LPA), may act intracellularly as second messengers or be secreted and act as intercellular signaling molecules. Such molecules can affect a variety of cellular processes including apoptosis, proliferation, differentiation and motility. To investigate possible sources of bioactive lipids during development we have searched the Drosophila genome for homologs of genes involved in mammalian S1P and LPA metabolism. Here we report the developmental expression of 31 such genes by in situ hybridization to Drosophila embryos. Most show expression in specific tissues, with expression in the gut and nervous system being recurring patterns

Lipids, in addition to being structural components of cell membranes, can act as signaling molecules. Bioactive lipids, such as sphingosine 1-phosphate (S1P) and lysophosphatidic acid (LPA), may act intracellularly as second messengers or be secreted and act as intercellular signaling molecules. Such molecules can affect a variety of cellular processes including apoptosis, proliferation, differentiation and motility. To investigate possible sources of bioactive lipids during development we have searched the Drosophila genome for homologs of genes involved in mammalian S1P and LPA metabolism. Here we report the developmental expression of 31 such genes by in situ hybridization to Drosophila embryos. Most show expression in specific tissues, with expression in the gut and nervous system being recurring patterns