http://www.biomedcentral.com/bmccellbiol/ The editor's pick of recent articles published by BMC Cell Biology 2012-03-19T00:00:00Z Background: A cholesterol-palmitoyl interaction has been reported to occur in the dimeric interface of the β2-adrenergic receptor crystal structure. We sought to investigate whether a similar phenomenon could be observed with μ-opioid receptor (OPRM1), and if so, to assess the role of cholesterol in this class of G protein-coupled receptor (GPCR) signaling. Results: C3.55(170) was determined to be the palmitoylation site of OPRM1. Mutation of this Cys to Ala did not affect the binding of agonists, but attenuated receptor signaling and decreased cholesterol associated with the receptor signaling complex. In addition, both attenuation of receptor palmitoylation (by mutation of C3.55[170] to Ala) and inhibition of cholesterol synthesis (by treating the cells with simvastatin, a HMG-CoA reductase inhibitor) impaired receptor signaling, possibly by decreasing receptor homodimerization and Gαi2 coupling; this was demonstrated by co-immunoprecipitation, immunofluorescence colocalization and fluorescence resonance energy transfer (FRET) analyses. A computational model of the OPRM1 homodimer structure indicated that a specific cholesterol-palmitoyl interaction can facilitate OPRM1 homodimerization at the TMH4-TMH4 interface. Conclusions: We demonstrate that C3.55(170) is the palmitoylation site of OPRM1 and identify a cholesterol-palmitoyl interaction in the OPRM1 complex. Our findings suggest that this interaction contributes to OPRM1 signaling by facilitating receptor homodimerization and G protein coupling. This conclusion is supported by computational modeling of the OPRM1 homodimer. http://www.biomedcentral.com/1471-2121/13/6 Hui Zheng Elizabeth A Pearsall Dow P Hurst Yuhan Zhang Ji Chu Yali Zhou Patricia H Reggio Horace H Loh Ping-Yee Law BMC Cell Biology 2012, 13:6 2012-03-19T00:00:00Z 10.1186/1471-2121-13-6 Role of palmitoylation in OPRM1 signaling The presence of a palmitoylation site on the μ-opioid receptor (OPRM1) and a cholesterol-palmitoyl interaction in the receptor complex may contribute to OPRM1 signaling by facilitating homodimerization and G protein coupling. /content/figures/1471-2121-13-6-toc.gif BMC Cell Biology 1471-2121 13 6 2012-03-19T00:00:00Z XML Background: Transforming growth factor-beta 1 (TGF-β1) has been implicated in hyperoxia-induced cell death and impaired alveolarization in the developing lung. In addition, the c-JunNH2-terminal kinase (JNK) pathway has been shown to have a role for TGF-β1-mediated effects. We hypothesized that the JNK pathway is an important regulator of hyperoxia-induced pulmonary responses in the developing murine lung. Results: We used cultured human lung epithelial cells, fetal rat lung fibroblasts and a neonatal TGF-β1 transgenic mouse model. We demonstrate that hyperoxia inhibits cell proliferation, activates cell death mediators and causes cell death, and promotes myofibroblast transdifferentiation, in a dose-dependent manner. Except for fibroblast proliferation, the effects were mediated via the JNK pathway. In addition, since we observed increased expression of TGF-β1 by epithelial cells on exposure to hyperoxia, we used a TGF-β1 transgenic mouse model to determine the role of JNK activation in TGF-β1 induced effects on lung development and on exposure to hyperoxia. We noted that, in this model, inhibition of JNK signaling significantly improved the spontaneously impaired alveolarization in room air and decreased mortality on exposure to hyperoxia. Conclusions: When viewed in combination, these studies demonstrate that hyperoxia-induced cell death, myofibroblast transdifferentiation, TGF-β1- and hyperoxia-mediated pulmonary responses are mediated, at least in part, via signaling through the JNK pathway. http://www.biomedcentral.com/1471-2121/12/54 Zhang Li Rayman Choo-Wing Huanxing Sun Angara Sureshbabu Reiko Sakurai Virender K Rehan Vineet Bhandari BMC Cell Biology 2011, 12:54 2011-12-15T00:00:00Z 10.1186/1471-2121-12-54 JNK pathway mediates hyperoxia lung responses The c-JunNH2-terminal kinase (JNK) signaling pathway mediates, at least in part, hyperoxia-induced cell death, myofibroblast transdifferentiation and TGF-β1-mediated pulmonary injury, and may regulate these responses in the developing murine lung. /content/figures/1471-2121-12-54-toc.gif BMC Cell Biology 1471-2121 12 54 2011-12-15T00:00:00Z XML Background: Embryonic stem cells (ESCs) can proliferate endlessly and are able to differentiate into all cell lineages that make up the adult organism. Under particular in vitro culture conditions, ESCs can be expanded and induced to differentiate into cardiomyocytes in stirred suspension bioreactors (SSBs). However, in using these systems we must be cognizant of the mechanical forces acting upon the cells. The effect of mechanical forces and shear stress on ESC pluripotency and differentiation has yet to be clarified. The purpose of this study was to investigate the impact of the suspension culture environment on ESC pluripotency during cardiomyocyte differentiation. Results: Murine D3-MHC-neor ESCs formed embyroid bodies (EBs) and differentiated into cardiomyocytes over 25 days in static culture and suspension bioreactors. G418 (Geneticin) was used in both systems from day 10 to enrich for cardiomyocytes by eliminating non-resistant, undifferentiated cells. Treatment of EBs with 1 mM ascorbic acid and 0.5% dimethyl sulfoxide from day 3 markedly increased the number of beating EBs, which displayed spontaneous and cadenced contractile beating on day 11 in the bioreactor. Our results showed that the bioreactor differentiated cells displayed the characteristics of fully functional cardiomyocytes. Remarkably, however, our results demonstrated that the bioreactor differentiated ESCs retained their ability to express pluripotency markers, to form ESC-like colonies, and to generate teratomas upon transplantation, whereas the cells differentiated in adherent culture lost these characteristics. Conclusions: This study demonstrates that although cardiomyocyte differentiation can be achieved in stirred suspension bioreactors, the addition of medium enhancers is not adequate to force complete differentiation as fluid shear forces appear to maintain a subpopulation of cells in a transient pluripotent state. The development of successful ESC differentiation protocols within suspension bioreactors demands a more complete understanding of the impacts of shear forces on the regulation of pluripotency and differentiation in pluripotent stem cells. http://www.biomedcentral.com/1471-2121/12/53 Mehdi Shafa Roman Krawetz Yuan Zhang Jerome B Rattner Anna Godollei Henry J Duff Derrick E Rancourt BMC Cell Biology 2011, 12:53 2011-12-14T00:00:00Z 10.1186/1471-2121-12-53 Cardiomyocyte differentiation in bioreactors Cardiomyocyte differentiation can be achieved in suspension bioreactors but the addition of medium enhancers isn?t adequate to force complete differentiation as fluid shear forces may maintain a subpopulation of cells in a transient pluripotent state. /content/figures/1471-2121-12-53-toc.gif BMC Cell Biology 1471-2121 12 53 2011-12-14T00:00:00Z XML