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The molecular mechanisms of interferon-alpha (IFN-α)-mediated cell growth inhibition are incompletely understood. Here, we have analysed how IFN-α interferes with the interleukin-3 (IL-3)-stimulated cell cycle progression by Ba/F3 cells. The antiproliferative cytokine caused a delay in cell cycle progression, which correlated with a diminished activation of the cyclin-dependent kinases 2 and 4 in IL-3-stimulated cells. While IFN-α did not affect the expression of p27Kip1 and p21Waf1, it efficiently inhibited the IL-3-induced expression of D-type cyclin and cyclin E proteins. No IL-3-antagonistic effects of the IFN, however, were observed at the mRNA level of cyclin expression. Furthermore, IFN-α suppressed the IL-3-induced release of E2F transcription factors from the retinoblastoma protein (pRb) and enhanced pRb-mediated transcriptional repression. The growth factor-antagonistic action of IFN-α correlated with a strong stimulation of protein kinase R expression, suggesting that inhibition of protein synthesis plays a pivotal role in IFN-α-mediated inhibition of cell cycle progression. [Copyright &y& Elsevier]

Bone morphogenetic proteins (BMPs) and transforming growth factor-β (TGFβ) are potent regulators of osteoblast differentiation and proliferation, processes that are crucial in bone remodeling. BMPs and TGFβ act in concert with other local factors and hormones, among them 1,25(OH)2-vitamin D3 and insulin. Here we show that BMP7 inhibits 1,25(OH)2-vitamin D3-induced differentiation of human osteoblasts, whereas TGFβ1 stimulates it, as assessed by assays for alkaline phosphatase (ALP) induction, matrix mineralization, and morphology changes. BMP7 or TGFβ1 alone affects the differentiation of human osteoblasts. Similar results were obtained in assays for ALP induction using conditionally immortalized human osteoblasts (hFOB) and primary osteoblasts obtained from trabecular bone of the femoral head after hip replacement surgery. BMP7 stimulation led to a decrease of 1,25(OH)2-vitamin D3-induced binding of nuclear proteins to a vitamin D response element, as shown by electrophoretic mobility shift assay. Our results suggest that 1,25(OH)2-vitamin D3 modulates in opposite ways the effects of BMP7 and TGFβ1 on osteoblast differentiation. [Copyright &y& Elsevier]

Galectin-1 (gal-1) a member of the mammalian β-galactoside-binding proteins recognizes preferentially Galβ1–4GlcNAc sequences of oligosaccharides associated with several cell surface glycoconjugates. In the present work, gal-1 has been identified to be a ligand for the CD3-complex as well as for CD2 as detected by affinity chromatography of Jurkat T-cell lysates on gal-1 agarose and by binding of the biotinylated lectin to CD3 and CD2 immunoprecipitates on blots. In CD45+ Jurkat E6.1 cells, the lectin stimulates a sustained increase in the intracytoplasmic calcium concentration ([Ca2+]i) consisting of both the release of calcium from intracellular stores and the calcium influx from the extracellular space. This effect of gal-1 on [Ca2+]iis completely inhibited by lactose at 10 mM and was absent in CD45– Jurkat J45.01 cells. Preincubation of Jurkat E6.1 cells with cholera toxin or with the protein tyrosine kinase inhibitor herbimycin A reduced the gal-1 induced calcium response whereas the increase in [Ca2+]i stimulated by CD2 or CD3 monoclonal antibodies (mAbs) was completely inhibited. Depolarization of E6.1 cells in a high-potassium buffer, a standard method to activate voltage-operated calcium channels, was without effect on [Ca2+]i. Membrane depolarization with gramicidin or by a high-potassium buffer was without effects on the lectin-mediated calcium release from intracellular stores but inhibited the gal-1 induced receptor-operated calcium influx. In Jurkat E6.1 cells the lectin stimulates the transient generation of inositol-1,4,5-trisphosphate and the tyrosine phosphorylation of phospholipase Cγ1. The results suggest that the ligation of CD2 and CD3 by gal-1 induces early events in T-cell activation comparable with that elicited by CD2 or CD3 mAbs. [ABSTRACT FROM PUBLISHER]

Bone morphogenetic proteins (BMPs) and transforming growth factor-beta (TGFbeta) are potent regulators of osteoblast differentiation and proliferation, processes that are crucial in bone remodeling. BMPs and TGFbeta act in concert with other local factors and hormones, among them 1,25(OH)2-vitamin D3 and insulin. Here we show that BMP7 inhibits 1,25(OH)2-vitamin D3-induced differentiation of human osteoblasts, whereas TGFbeta1 stimulates it, as assessed by assays for alkaline phosphatase (ALP) induction, matrix mineralization, and morphology changes. BMP7 or TGFbeta1 alone affects the differentiation of human osteoblasts. Similar results were obtained in assays for ALP induction using conditionally immortalized human osteoblasts (hFOB) and primary osteoblasts obtained from trabecular bone of the femoral head after hip replacement surgery. BMP7 stimulation led to a decrease of 1,25(OH)2-vitamin D3-induced binding of nuclear proteins to a vitamin D response element, as shown by electrophoretic mobility shift assay. Our results suggest that 1,25(OH)2-vitamin D3 modulates in opposite ways the effects of BMP7 and TGFbeta1 on osteoblast differentiation., (Copyright 2002 Elsevier Science (USA).)