Differential expression of Rab3 isoforms in high- and low-secreting mast cell lines

Consequences of Rab GTPase dysfunction in genetic or acquired human diseases

Rab GTPases are important regulators of intracellular membrane trafficking in eukaryotes. Both activating and inactivating mutations in Rab genes have been identified and implicated in human diseases ranging from neurological disorders to cancer. In addition, altered Rab expression is often associated with disease prognosis. As such, the study of diseases associated with Rabs or Rab-interacting proteins has shed light on the important role of intracellular membrane trafficking in disease etiology. In this review, we cover recent advances in the field with an emphasis on cellular mechanisms.

Consequences of Rab GTPase dysfunction in genetic or acquired human diseases

Rab GTPases are important regulators of intracellular membrane trafficking in eukaryotes. Both activating and inactivating mutations in Rab genes have been identified and implicated in human diseases ranging from neurological disorders to cancer. In addition, altered Rab expression is often associated with disease prognosis. As such, the study of diseases associated with Rabs or Rab-interacting proteins has shed light on the important role of intracellular membrane trafficking in disease etiology. In this review, we cover recent advances in the field with an emphasis on cellular mechanisms.

Anti-inflammatory and anti-allergic effects of Agrimonia pilosa Ledeb extract on murine cell lines and OVA-induced airway inflammation

ETHNOPHARMACOLOGICAL EVIDENCE

Agrimonia pilosa Ledeb (Rosaceae, AP) has long been used as a traditional medicine in Korea and other Asian countries to treat various diseases.

AIM OF THE STUDY

In the present study, the anti-inflammatory and anti-allergic effects of AP extract in in vitro cell lines and in vivo mouse model of inflammation and the molecular mechanisms involved were reported.

MATERIALS AND METHODS

Using Raw 264.7 murine macrophages the effects of methanol extract of AP in lipopolysaccharide (LPS)-induced production of inflammatory mediators were measured. Further IgE-DNP-induced interleukin (IL)-4 production and degranulation in RBL-2H3 rat basophilic cell lines was also estimated. To investigate the anti-asthmatic effect of AP in vivo, airway inflammation in ovalbumin (OVA)-induced mouse model was used.

RESULTS

AP attenuated the production of inflammatory mediators such as NO, PGE(2) and pro-inflammatory cytokines in LPS-induced Raw 264.7 cells. Further, AP inhibited IL-4 production and degranulation in IgE-DNP-induced RBL-2H3 cells. Furthermore, AP attenuated the infiltration of immune cells into lung, cytokines production in broncho-alveolar lavage fluid (BALF) and airway-hyperresponsiveness (AHR) on OVA-induced mouse model of inflammation.

CONCLUSION

Our results showed that AP attenuated the activation of macrophages, basophils, and inhibited the OVA-induced airway inflammation. The molecular mechanisms leading to AP's potent anti-inflammatory and anti-allergic effects might be through regulation of TRIF-dependent and Syk-PLCγ/AKT signaling pathways, suggesting that AP may provide a valuable therapeutic strategy in treating various inflammatory diseases including asthma.

Synthesis and incorporation into cyclic peptides of tolan amino acids and their hydrogenated congeners: construction of an array of A-B-loop mimetics of the Cε3 domain of human IgE

The disruption of the human immunolobulin E-high affinity receptor I (IgE-FcεRI) protein-protein interaction (PPI) is a validated strategy for the development of anti asthma therapeutics. Here, we describe the synthesis of an array of conformationally constrained cyclic peptides based on an epitope of the A-B loop within the Cε3 domain of IgE. The peptides contain various tolan (i.e., 1,2-biarylethyne) amino acids and their fully and partially hydrogenated congeners as conformational constraints. Modest antagonist activity (IC(50) ∼660 μM) is displayed by the peptide containing a 2,2'-tolan, which is the one predicted by molecular modeling to best mimic the conformation of the native A-B loop epitope in IgE.

Rab18 inhibits secretory activity in neuroendocrine cells by interacting with secretory granules

Rab proteins comprise a complex family of small GTPases involved in the regulation of intracellular membrane trafficking and reorganization. In this study, we identified Rab18 as a new inhibitory player of the secretory pathway in neuroendocrine cells. In adrenal chromaffin PC12 cells and pituitary AtT20 cells, Rab18 is located at the cytosol but associates with a subpopulation of secretory granules after stimulation of the regulated secretory pathway, strongly suggesting that induction of secretion provokes Rab18 activation and recruitment to these organelles. In support of this, a dominant-inactive Rab18 mutant was found to distribute diffusely in the cytosol, whereas a dominant-active Rab18 mutant was predominantly associated to secretory granules. Furthermore, interaction of Rab18 with secretory granules was associated to an inhibition in the secretory activity of PC12 and AtT20 cells in response to stimulatory challenges. Association of Rab18 with secretory granules was also observed by immunoelectron microscopy in normal, non-tumoral endocrine cells (pituitary melanotropes), wherein Rab18 protein content is inversely correlated to the level of secretory activity of cells. Taken together, these findings suggest that, in neuroendocrine cells, Rab18 acts as a negative regulator of secretory activity, likely by impairing secretory granule transport.

Intracellular formation of collagen microfibrils in granulation tissue

It is important to determine the biosynthesis process of collagen fibers to elucidate the mechanism by which granulation tissue is induced after injury. The purpose of this study is to investigate whether collagen microfibrils can be formed not only outside but also inside a cell. Fibroblast-like cells in granulation tissue resulting from incision and ligation were examined. The cells possessed vesicles containing collagen microfibrils. The vesicles were present in connection with Golgi apparatus or the rough endoplasmic reticulum. Furthermore, the vesicles were exhibited to be secretory granules with the secretory granule marker Rab3A. The fibroblast-like cells were also indicated to be myofibroblasts, using conventional transmission electron microscopy and immunoelectron microscopy for the myofibroblast marker alpha smooth muscle actin. In conclusion, it was demonstrated that collagen microfibrils could be formed in the cell in the case of collagen fiber overproduction.

Solid-phase synthesis of an A-B loop mimetic of the Cepsilon3 domain of human IgE: macrocyclization by Sonogashira coupling

The solid-phase synthesis of a cyclic peptide containing the 21-residue epitope found in the A-B loop of the Cepsilon3 domain of human immunoglobulin E has been carried out. The key macrocyclization step to form the 65-membered ring is achieved in approximately 15% yield via an "on-resin" Sonogashira coupling reaction which concomitantly installs a diphenylacetylene amino acid conformational constraint within the loop.

Protein mapping in rat basophilic leukaemia cells

This review discusses some of our recent studies on rat basophilic leukaemia (RBL) cells, a model cell line for mast cell function. Our interest in these cells is a consequence of the role played by mast cells in the allergic response. Thus far we have described the identification of several spots, and their pI/M(r) co-ordinates. Here we describe how we can further decipher the mast cell proteome using a variety of staining/immuno-blotting procedures. We demonstrate the sensitivity of staining procedures and immuno-blotting using an anti-phosphotyrosine antibody. Our aim is to contribute to the ever-expanding two-dimensional gel and phosphoprotein databases currently available.