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Mediated Stimulation (mediated + stimulation)
Selected AbstractsPhosphate and calcium are required for TGF,-mediated stimulation of ANK expression and function during chondrogenesisJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2010Paulina Oca The expression of ANK, a key player in biomineralization, is stimulated by treatment with TGF,. The purpose of this study was to determine whether TGF, stimulation of ANK expression during chondrogenesis was dependent upon the influx of calcium and phosphate into cells. Treatment of ATDC5 cells with TGF, increased ANK expression during all phases of chondrogenic differentiation, particularly at day 14 (proliferation) and day 32 (mineralizing hypertrophy) of culture. Phosphate uptake studies in the presence and absence of phosphonoformic acid (PFA), a competitive inhibitor of the type III Na+/Pi channels Pit-1 and Pit-2, indicated that the stimulation of ANK expression by TGF, required the influx of phosphate, specifically by the Pit-1 transporter, at all phases of differentiation. At hypertrophy, when alkaline phosphatase is highly expressed, inhibition of its activity with levamisole also abrogated the stimulatory effect of TGF, on ANK expression, further illustrating that Pi availability and uptake by the cells is necessary for stimulation of ANK expression in response to TGF,. Since previous studies of endochondral ossification in the growth plate have shown that L-type calcium channels are essential for chondrogenesis, we investigated their role in the TGF,-stimulated ANK response in ATDC5 cells. Treatment with nifedipine to inhibit calcium influx via the L-type channel Cav1.2 (,1C) inhibited the TGF, stimulated increase in ANK expression at all phases of chondrogenesis. Our findings indicate that TGF, stimulation of ANK expression is dependent upon the influx of phosphate and calcium into ATDC5 cells at all stages of differentiation. J. Cell. Physiol. 224: 540,548, 2010. © 2010 Wiley-Liss, Inc. [source] Histamine induces neural stem cell proliferation and neuronal differentiation by activation of distinct histamine receptorsJOURNAL OF NEUROCHEMISTRY, Issue 2 2008Anayansi Molina-Hernández Abstract Histamine has neurotransmitter/neuromodulator functions in the adult brain, but its role during CNS development has been elusive. We studied histamine effects on proliferation, cell death and differentiation of neuroepithelial stem cells from rat cerebral cortex in vitro. RT-PCR and Western blot experiments showed that proliferating and differentiated cells express histamine H1, H2 and H3 receptors. Treatments with histamine concentrations (100 nM,1 mM) caused significant increases in cell numbers without affecting Nestin expression. Cell proliferation was evaluated by BrdU incorporation; histamine caused a significant increase dependent on H2 receptor activation. Apoptotic cell death during proliferation was significantly decreased at all histamine concentrations, and cell death was promoted in a concentration-dependent manner by histamine in differentiated cells. Immunocytochemistry studies showed that histamine increased 3-fold the number of neurons after differentiation, mainly by activation of H1 receptor, and also significantly decreased the glial (astrocytic) cell proportion, when compared to control conditions. In summary, histamine increases cell number during proliferative conditions, and has a neuronal-differentiating action on neural stem cells, suggesting that the elevated histamine concentration reported during development might play a role in cerebrocortical neurogenesis, by activation of H2 receptors to promote proliferation of neural precursors, and favoring neuronal fate by H1 -mediated stimulation. [source] Dissection of a functional interaction between the DNA translocase, FtsK, and the XerD recombinaseMOLECULAR MICROBIOLOGY, Issue 6 2006James Yates Summary Successful bacterial circular chromosome segregation requires that any dimeric chromosomes, which arise by crossing over during homologous recombination, are converted to monomers. Resolution of dimers to monomers requires the action of the XerCD site-specific recombinase at dif in the chromosome replication terminus region. This reaction requires the DNA translocase, FtsKC, which activates dimer resolution by catalysing an ATP hydrolysis-dependent switch in the catalytic state of the nucleoprotein recombination complex. We show that a 62-amino-acid fragment of FtsKC interacts directly with the XerD C-terminus in order to stimulate the cleavage by XerD of BSN, a dif-DNA suicide substrate containing a nick in the ,bottom' strand. The resulting recombinase,DNA covalent complex can undergo strand exchange with intact duplex dif in the absence of ATP. FtsKC -mediated stimulation of BSN cleavage by XerD requires synaptic complex formation. Mutational impairment of the XerD,FtsKC interaction leads to reduction in the in vitro stimulation of BSN cleavage by XerD and a concomitant deficiency in the resolution of chromosomal dimers at dif in vivo, although other XerD functions are not affected. [source] RGS4 Controls Renal Blood Flow and Inhibits Cyclosporine-Mediated NephrotoxicityAMERICAN JOURNAL OF TRANSPLANTATION, Issue 2 2010A. Siedlecki Calcineurin inhibitors (CNI) are powerful immunomodulatory agents that produce marked renal dysfunction due in part to endothelin-1-mediated reductions in renal blood flow. Ligand-stimulated Gq protein signaling promotes the contraction of smooth muscle cells via phospholipase C,-mediated stimulation of cytosolic calcium release. RGS4 is a GTPase activating protein that promotes the deactivation of Gq and Gi family members. To investigate the role of G protein-mediated signaling in the pathogenesis of CNI-mediated renal injury, we used mice deficient for RGS4 (rgs4,/,). Compared to congenic wild type control animals, rgs4,/, mice were intolerant of the CNI, cyclosporine (CyA), rapidly developing fatal renal failure. Rgs4,/, mice exhibited markedly reduced renal blood flow after CyA treatment when compared to congenic wild type control mice as measured by magnetic resonance imaging (MRI). Hypoperfusion was reversed by coadministration of CyA with the endothelin antagonist, bosentan. The MAPK/ERK pathway was activated by cyclosporine administration and was inhibited by cotreatment with bosentan. These results show that endothelin-1-mediated Gq protein signaling plays a key role in the pathogenesis of vasoconstrictive renal injury and that RGS4 antagonizes the deleterious effects of excess endothelin receptor activation in the kidney. [source] Antagonists of ionotropic ,-aminobutyric acid receptors impair the NiCl2 -mediated stimulation of the electroretinogram b-wave amplitude from the isolated superfused vertebrate retinaACTA OPHTHALMOLOGICA, Issue 8 2009Siarhei A Siapich Abstract. Purpose:, NiCl2 (15 ,M) stimulates the electroretinogram (ERG) b-wave amplitude of vertebrate retina up to 1.5-fold through its blocking of E/R-type voltage-gated Ca2+ channels. Assuming that such an increase is mediated by blocking the release of the inhibitory neurotransmitter ,-aminobutyric acid (GABA) via ionotropic GABA receptors, we tested the effect of both GABA itself and GABA-receptor antagonists such as (,)bicuculline (1.51-fold increase) and (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA; 1.46-fold increase) on the b-wave amplitude. Methods:, Recording of the transretinal potentials from the isolated bovine retina. Results:, GABA (100 ,M) reduced the b-wave amplitude only when NiCl2 (15 ,M) was applied first. Each antagonist applied on its own stimulated the b-wave amplitude only partially: subsequent NiCl2 superfusion caused a small but additional increase, leading to a 1.69- and a 1.88-fold total increase of the amplitude by Ni2+ plus (,)bicuculline or Ni2+ plus TPMPA, respectively. Only the application of both antagonists in combination, before superfusing low NiCl2 (15 ,M), completely prevented subsequent stimulation by NiCl2 with a similar 1.90-fold total increase of b-wave amplitude. Those retina segments that did not respond to NiCl2 could not be stimulated by (,)bicuculline and vice versa. Conclusion:, The stimulatory effect of NiCl2 on the ERG b-wave amplitude is mainly, but not only, mediated by a NiCl2 -sensitive, Cav2.3-triggered GABA release acting through ionotropic GABA-A and GABA-C receptors. [source] Gq/11 and Gi/o activation profiles in CHO cells expressing human muscarinic acetylcholine receptors: dependence on agonist as well as receptor-subtypeBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2001Elizabeth C Akam Profiles of G protein activation have been assessed using a [35S]-GTP,S binding/immunoprecipitation strategy in Chinese hamster ovary cells expressing either M1, M2, M3 or M4 muscarinic acetylcholine (mACh) receptor subtypes, where expression levels of M1 and M3, or M2 and M4 receptors were approximately equal. Maximal [35S]-GTP,S binding to Gq/11, stimulated by M1/M3 receptors, or Gi1 , 3, stimulated by M2/M4 receptors occurred within approximately 2 min of agonist addition. The increases in Gq/11,-[35S]-GTP,S binding after M1 and M3 receptor stimulation differed substantially, with M1 receptors causing a 2 , 3 fold greater increase in [35S]-GTP,S binding and requiring 5 fold lower concentrations of methacholine to stimulate a half-maximal response. Comparison of M2 and M4 receptor-mediated Gi1 , 3,-[35S]-GTP,S binding also revealed differences, with M2 receptors causing a greater increase in Gi1 , 3, activation and requiring 10 fold lower concentrations of methacholine to stimulate a half-maximal response. Comparison of methacholine- and pilocarpine-mediated effects revealed that the latter partial agonist is more effective in activating Gi3, compared to Gi1/2, for both M2 and M4 receptors. More marked agonist/partial agonist differences were observed with respect to M1/M3 -mediated stimulations of Gq/11,- and Gi1 , 3,-[35S]-GTP,S binding. Whereas coupling to these G, subclasses decreased proportionately for M1 receptor stimulation by these agonists, pilocarpine possesses a greater intrinsic activity at M3 receptors for Gi, versus Gq/11, activation. These data demonstrate that mACh receptor subtype and the nature of the agonist used govern the repertoire of G proteins activated. They also provide insights into how the diversity of coupling can be pharmacologically exploited, and provide a basis for a better understanding of how multiple receptor subtypes can be differentially regulated. British Journal of Pharmacology (2001) 132, 950,958; doi:10.1038/sj.bjp.0703892 [source] | |||||||||||||