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- Botling, Johan, et al.
(författare)
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Vitamin D3 and retinoic acid induced monocytic differentiation : Interactions between the endogenous vitamin D3, retinoic acid and retinoid X receptors in U-937 cells
- 1996
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Ingår i: Cell growth & differentiation. - 1044-9523. ; 7:9, s. 1239-49
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Tidskriftsartikel (refereegranskat)abstract
- Retinoic acid (RA) and 1,25 alpha-dihydroxycholecalciferol (VitD3) are potent regulators of hematopoletic differentiation. Yet, little is known as to how the RA and VitD3 receptor network operates in hematopoietic cells, and whether receptor interactions can explain the interplay between the RA- and VitD3-signaling pathways during differentiation. Therefore, we analyzed the expression, DNA binding, and transcriptional activity of the endogenous RA and VitD3 receptors [retinoic acid receptors (RARs), retinoid X receptors (RXRs), and VitD3 receptor (VDR)] in the U-937 cell line, in which RA and VitD3 induce distinct monocytic differentiation pathways. VitD3 induction resulted in the formation of VDR/RXR DNA-binding complexes on both VitD3 response elements and RA response elements (RAREs). However, transcriptional activation was only observed from a VitD3 response element-driven reporter construct. Several DNA-binding complexes were detected on RAREs in undifferentiated cells. Stimulation by RA resulted in increased RAR beta/RXR DNA binding, activated RARE-dependent transcription, and increased expression of RAR-beta. Concomitant stimulation by VitD3 inhibited the RA-stimulated formation of RAR beta/RXR heterodimers, favoring VDR/RXR binding to the RARE. Also, VitD3 inhibited the expression of CD23 and CD49f, characteristic markers of retinoid-induced U-937 cell differentiation. In contrast, neither the RA-stimulated, RARE-mediated transcription nor the induced RAR-beta expression was suppressed by VitD3, suggesting that VitD3 selectively inhibited the retinoid-induced differentiation program but not the RARE-mediated signal. These results demonstrate a complex role for VitD3 in modifying the retinoid differentiation pathway and may have implications for differentiation-inducing therapy of hematopoietic tumors.
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| 2. |
- Fagerström, Sofia, et al.
(författare)
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Protein kinase C-epsilon is implicated in neurite outgrowth in differentiating human neuroblastoma cells
- 1996
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Ingår i: Cell growth & differentiation. - : American Association of Cancer Research. - 1044-9523. ; 7:6, s. 775-785
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Tidskriftsartikel (refereegranskat)abstract
- A combination of basic fibroblast growth factor (bFGF) and insulin-like growth factor-I (IGF-I) or 16 nM 12-O-tetradecanoylphorbol-13-acetate (TPA) and serum induces human SH-SY5Y neuroblastoma cells to undergo differentiation and acquire a neuronal phenotype. Nerve growth factor (NGF) added to SH-SY5Y cells stably transfected with the NGF-receptor TRK-A (SH-SY5Y/trk) induces a similar differentiated phenotype. SH-SY5Y cells express protein kinase C (PKC)-alpha, PKC-beta I, PKC-epsilon, and PKC-zeta protein, and phorbol ester- or growth factor-induced differentiation results in a sustained activation of PKC. The specific PKC inhibitor GF 109203X blocked TPA- and bFGF-IGF-I-induced neurite outgrowth in wild-type SH-SY5Y cells and NGF-induced neurite outgrowth in SH-SY5Y/trk cells. When added to differentiated cells, GF 109203X caused rapid retraction of growth cone filopodia. In TPA- and bFGF-IGF-I-treated cells, addition of GF 109203X also blocked induced expression of growth associated protein-43 and neuropeptide tyrosine while the increase in expression of these two genes was only slightly affected by the inhibitor in NGF-treated SH-SY5Y/trk cells. Thus, a portion of the NGF-induced phenotypic changes appears not to be mediated via PKC-dependent signaling. A high concentration of TPA (1.6 microM) down regulated PKC-alpha and PKC-beta I almost completely and PKC-epsilon partially in wild-type SH-SY5Y and SH-SY5Y/trk cells. Cells with down-regulated PKC-alpha and PKC-beta I after 1.6 microM TPA treatment still differentiated with growth factors. In these cells, the PKC-epsilon level was restored, and the PKC-epsilon protein was enriched in the growth cones. The 1.6 microM TPA-induced down-regulation of PKC-epsilon was counteracted by bFGF and NGF but not by platelet-derived growth factor or IGF-I. These data indicate that PKC activity is vital for neurite formation, and that the cells can differentiate under conditions when PKC-alpha and PKC-beta I are extensively down regulated. The close correlation between differentiation and presence of PKC-epsilon protein suggests an important function for this isoform during this process.
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