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In fura-2-loaded ECV304 cells ionomycin elicited a saturable biphasic change in intracellular Ca2+ concentration ([Ca2+]i),where the initial phase represented mobilization of intracellular stores and the sustained component represented Ca2+ influx. To examine whether ionomycin could stimulate influx via a store-dependent mechanism. Mn2+ entry was monitored by the quenching of fura-2 fluorescence: influx was enhanced even after ionomycin wash-out,provided that internal stores were not refilled with Ca2+. Moreover,the maximal rate of histamine-stimulated Mn2+ entry was unaffected by ionomycin,suggesting a common route of entry. The Ca(2+)-entry blocker SK&F 96365 inhibited both the ionomycin-induced Mn2+ entry and the sustained [Ca2+]i response to the ionophore (leaving the initial peak [Ca2+]i response unaffected). In other experiments,although addition of ionomycin further increased the plateau phase induced by 100 microM histamine,the increase was completely abolished by pretreatment with the store Ca(2+)-ATPase inhibitor cyclopiazonic acid (CPA). Furthermore,in store-depleted cells,re-addition of 1 mM extracellular Ca2+ (in the presence of CPA plus histamine) led to a rapid rise in [Ca2+]i,dependent on Ca2+ influx,with kinetics that were not enhanced by ionomycin. These data suggest that ionomycin acts primarily at the level of the internal Ca2+ stores,so that,at the concentrations used here (textless or = 1 microM),it increases Ca2+ (and Mn2+) influx via activation of endogenous entry pathways and not by plasmalemmal translocation. View Publication

The immunosuppressant,rapamycin,inhibits cell growth by interfering with the function of a novel kinase,termed mammalian target of rapamycin (mTOR). The putative catalytic domain of mTOR is similar to those of mammalian and yeast phosphatidylinositol (PI) 3-kinases. This study demonstrates that mTOR is a component of a cytokine-triggered protein kinase cascade leading to the phosphorylation of the eukaryotic initiation factor-4E (eIF-4E) binding protein,PHAS-1,in activated T lymphocytes. This event promotes G1 phase progression by stimulating eIF-4E-dependent translation initiation. A mutant YAC-1 T lymphoma cell line,which was selected for resistance to the growth-inhibitory action of rapamycin,was correspondingly resistant to the suppressive effect of this drug on PHAS-1 phosphorylation. In contrast,the PI 3-kinase inhibitor,wortmannin,reduced the phosphorylation of PHAS-1 in both rapamycin-sensitive and -resistant T cells. At similar drug concentrations (0.1-1 microM),wortmannin irreversibly inhibited the serine-specific autokinase activity of mTOR. The autokinase activity of mTOR was also sensitive to the structurally distinct PI 3-kinase inhibitor,LY294002,at concentrations (1-30 microM) nearly identical to those required for inhibition of the lipid kinase activity of the mammalian p85-p110 heterodimer. These studies indicate that the signaling functions of mTOR,and potentially those of other high molecular weight PI 3-kinase homologs,are directly affected by cellular treatment with wortmannin or LY294002. View Publication

Little is known about how neural stem cells are formed initially during development. We investigated whether a default mechanism of neural specification could regulate acquisition of neural stem cell identity directly from embryonic stem (ES) cells. ES cells cultured in defined,low-density conditions readily acquire a neural identity. We characterize a novel primitive neural stem cell as a component of neural lineage specification that is negatively regulated by TGFbeta-related signaling. Primitive neural stem cells have distinct growth factor requirements,express neural precursor markers,generate neurons and glia in vitro,and have neural and non-neural lineage potential in vivo. These results are consistent with a default mechanism for neural fate specification and support a model whereby definitive neural stem cell formation is preceded by a primitive neural stem cell stage during neural lineage commitment. View Publication

Although butein (3,4,2',4'-tetrahydroxychalcone) is known to exhibit anti-inflammatory,anti-cancer,and anti-fibrogenic activities,very little is known about its mechanism of action. Because numerous effects modulated by butein can be linked to interference with the NF-kappaB pathway,we investigated in detail the effect of this chalcone on NF-kappaB activity. As examined by DNA binding,we found that butein suppressed tumor necrosis factor (TNF)-induced NF-kappaB activation in a dose- and time-dependent manner; suppressed the NF-kappaB activation induced by various inflammatory agents and carcinogens; and inhibited the NF-kappaB reporter activity induced by TNFR1,TRADD,TRAF2,NIK,TAK1/TAB1,and IKK-beta. We also found that butein blocked the phosphorylation and degradation of IkappaBalpha by inhibiting IkappaBalpha kinase (IKK) activation. We found the inactivation of IKK by butein was direct and involved cysteine residue 179. This correlated with the suppression of phosphorylation and the nuclear translocation of p65. In this study,butein also inhibited the expression of the NF-kappaB-regulated gene products involved in anti-apoptosis (IAP2,Bcl-2,and Bcl-xL),proliferation (cyclin D1 and c-Myc),and invasion (COX-2 and MMP-9). Suppression of these gene products correlated with enhancement of the apoptosis induced by TNF and chemotherapeutic agents; and inhibition of cytokine-induced cellular invasion. Overall,our results indicated that antitumor and anti-inflammatory activities previously assigned to butein may be mediated in part through the direct inhibition of IKK,leading to the suppression of the NF-kappaB activation pathway. View Publication

Patterning of bioactive enzymes with subcellular resolution is achieved by dispensing droplets of dextran (DEX) onto polyethylene glycol (PEG)-covered cells though a glass capillary needle connected to a pneumatic pump. This technique is applied to purify colonies of induced pluripotent stem cells (iPSCs) from mouse embryonic fibroblast (MEF) feeder cultures and inefficiently induced iPSC colonies by selectively dissociating the iPSCs with proteases. View Publication

A defined xeno-free system for patient-specific iPSC derivation and differentiation is required for translation to clinical applications. However,standard somatic cell reprogramming protocols rely on using MEFs and xenogeneic medium,imposing a significant obstacle to clinical translation. Here,we describe a well-defined culture system based on xeno-free media and LN521 substrate which supported i) efficient reprogramming of normal or diseased skin fibroblasts from human of different ages into hiPSCs with a 15-30 fold increase in efficiency over conventional viral vector-based method; ii) long-term self-renewal of hiPSCs; and iii) direct hiPSC lineage-specific differentiation. Using an excisable polycistronic vector and optimized culture conditions,we achieved up to 0.15%-0.3% reprogramming efficiencies. Subsequently,transgene-free hiPSCs were obtained by Cre-mediated excision of the reprogramming factors. The derived iPSCs maintained long-term self-renewal,normal karyotype and pluripotency,as demonstrated by the expression of stem cell markers and ability to form derivatives of three germ layers both in vitro and in vivo. Importantly,we demonstrated that Parkinson's patient transgene-free iPSCs derived using the same system could be directed towards differentiation into dopaminergic neurons under xeno-free culture conditions. Our approach provides a safe and robust platform for the generation of patient-specific iPSCs and derivatives for clinical and translational applications. textcopyright 2013 Elsevier Ltd. View Publication

Autologous feeder cells have been developed by various methods to minimize the presence of xenogenic entities in human embryonic stem cell (hESC) cultures. However,there was no systematic comparison of supportive effects of the feeder cells on hESC growth,nor comparison to the supportive effects of various feeder-free culture systems and standard mouse feeder cells. In this study,we aimed to compare the supportive abilities of autologous feeders derived either directly from H9 hESCs (H9 dF) or from outgrowth of embryoid body predifferentiated in suspension from H9 hESCs (H9 ebF). Mouse feeder system and matrigel-mTeSR1 feeder-free system were used as controls. H9 ebF was found to secrete more basic fibroblast growth factor in the conditioned medium than H9 dF did. The undifferentiated state of H9 hESCs was sustained more stably on H9 ebF than on H9 dF,and the differentiation potential of H9 hESCs on H9 ebF was higher than on H9 dF. We concluded that H9 ebF was an optimal autologous feeder to maintain the long-term undifferentiated state of hESCs in our current culture system. This study helps to standardize the autologous culture of hESCs. It also suggests a more definite direction for future development of xeno-free culture system for hESCs. View Publication