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  • Cell & Developmental Biology  (8,958)
  • FLUID MECHANICS AND HEAT TRANSFER  (3,549)
  • 1995-1999  (2,753)
  • 1990-1994  (9,754)
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  • 1
    Electronic Resource
    Electronic Resource
    1,2-dioctanoylglycerol accelerates or retards mitotlc progression in Tradescantia stamen hair cells as a function of the time of its addition (1990)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 16 (1990), S. 190-203 
    Details
    ISSN: 0886-1544
    Keywords: mitosis ; calcium ; diacylglycerol ; protein kinase C ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have treated living, intact stamen hair cells from the spiderwort plant, Tra-descantia virginiana, with 0.5 μg/ml or 60 μg/ml 1,2-dioctanoylglycerol, a potent and permeant activator of protein kinase C, and have observed the rates of progression of mitosis from prophase through anaphase. We have found that in addition to the concentration used, the time of initial treatment with 1,2-di-octanoylglycerol defines the response by the cells. The cells rapidly undergo nuclear envelope breakdown when this diglyceride is added in very late prophase, 0 to ∼8 min prior to the time of normal nuclear envelope breakdown. Anaphase onset occurs 28 min after nuclear envelope breakdown, rather than after the 33 min interval observed in untreated cells. Rapid progression through metaphase is also observed if cells are treated with 0.5 μg/ml 1,2-dioctanoylglycerol during prometaphase, up to 15 min after nuclear envelope breakdown. The addition of 0.5 μg/ml 1,2-dioctan oylglycerol in late metaphase, ∼26 min after nuclear envelope breakdown, results in sister chromatid separation slightly ahead of its normal time, 33 min after nuclear envelope breakdown, and in precocious cell plate vesicle aggregation, 3-5 min earlier than that observed in untreated cells. Treatment of cells with 60 μg/ml of 1,2-dioctanoylglycerol at any point during the interval from 0 to ∼5 min prior to nuclear envelope breakdown results in precocious entry into anaphase. If cells are treated with either 0.5 μg/ml or 60 μg/ml 1,2-dioctanoylglycerol earlier than 20 min before nuclear envelope breakdown, they do not enter mitosis, but instead revert to interphase without dividing. When 1,2-dioctanoylglycerol is added atother times during mitosis, the rate of subsequent mitotic progression is dramatically slowed; the cells require 〉55 min to progress from nuclear envelope breakdown to anaphase onset, though once in anaphase, the cells progress onward to cytokinesis at normal rates. Treatments of cells with 1,3-dioctanoylglycerol at any point during prophase, prometaphase, or metaphase are without effect on the rate of subsequent mitotic progression. The shifts in response by cells treated at specific times with 1,2-dioctanoylglycerol during mid- and late metaphase may be indicative of the existence of one or more regulatory switch points (i.e., checkpoints) just prior to anaphase onset.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970160306
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  • 2
    Electronic Resource
    Electronic Resource
    1,25(OH)2D3-dependent regulation of calbindin-D28k mRNA requires ongoing protein synthesis in chick duodenal organ culture (1995)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 58 (1995), S. 315-327 
    Details
    ISSN: 0730-2312
    Keywords: calbindin-D28k ; 1,25-dihydroxyvitamin D3 ; messenger RNA ; organ culture ; polymerase chain reaction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Organ culture of 19-day-old chick embryo duodena was utilized to evaluate the mechanism of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3)-dependent calbindin-D28k (CaBP) expression. Duodenal CaBP and 1,25(OH)2D3 receptor (VDR) expression were assessed by Western blot analysis, while CaBP and VDR mRNA levels were determined by Northen blot analysis. In untreated duodena, both VDR protein and mRNA were present, while CaBP protein and mRNA were undetectable. Treatment of cultured duodena with 25 nM 1,25(OH)2D3 resulted in detectable CaBP mRNA after 4 h which continued to increase during a 24 h time period. Under these conditions, localization of [3H-1β]1α,25(OH)2D3 in duodenal chromatin is rapid (≤ 30 min). Thus, the delayed accumulation of detectable CaBP mRNA cannot be explained by slow nuclear binding of 1,25(OH)2D3. The inclusion of 1.6 μM actinomycin D in the organ culture partially inhibited the 1,25(OH)2D3-regulated increase in CaBP mRNA, which implies that there is a transcriptional component involved in the increased CaBP mRNA levels. Similarly, quantitative polymerase chain reaction studies allowed the detection of CaBP pre-mRNA and mRNA sequences 1 h after hormone treatment, suggesting that CaBP gene transcription is initiated rapidly. Treatment of cultures with 36 μM cycloheximide 1 h prior to 1,25(OH)2D3 addition resulted in superinduction of VDR mRNA levels but sharply reduced CaBP steady-state mRNA levels. This dramatic reduction in CaBP mRNA reveals that 1,25(OH)2D3-mediated CaBP expression is dependent on ongoing protein synthesis. Thus, we propose that a labile auxiliary protein or other cofactor, which may or may not be 1,25(OH)2D3-dependent, is necessary for 1,25(OH)2D3-mediated CaBP gene transcription in chick duodena.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240580306
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  • 3
    Electronic Resource
    Electronic Resource
    1,25-dihydroxy vitamin D3 and 12-O-tetradecanoyl phorbol-13-acetate synergistically induce monocytic cell differentiation: FOS and RB expression (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 156 (1993), S. 198-203 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: 1,25-dihydroxy vitamin D3 and 12-O-tetradecanoyl phorbol-13-acetate (TPA) interact synergistically to induce monocytic differentiation of U937 histiocytic lymphoma cells. Addition of TPA causes an otherwise ineffective dose of 1,25-dihydroxy vitamin D3 to induce differentiation. The induced differentiation depends on the simultaneous (vs. sequential) presence of both agents. The kinetics of induced differentiation are consistent with a G1 specific cellular response to initiate the metabolic cascade culminating in cell differentiation. The induced differentiation occurs with down-regulation of c-fos protein and an accompanying up-regulation of RB protein expression, consistent with a possible need for up-regulated RB expression to maintain a given differentiated phenotype and suppress transcriptional activators that might typically be associated with proliferation. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041560126
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  • 4
    Electronic Resource
    Electronic Resource
    1,25-dihydroxy-vitamin-D3 enhances antiproliferative effect and transcription of TGF-β1 on human keratinocytes in culture (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 151 (1992), S. 579-587 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Both TGF-β and 1,25-dihydroxy-vitamin-D3 (1,25(OH)2D3) have been reported to decrease the proliferation of normal human keratinocytes. The effect and expression of TGF-β in keratinocytes treated with 1,25(OH)2D3 was investigated. Human keratinocytes were grown in the presence of various concentrations of TGF-β and/or 1,25(OH)2D3 prior to enumeration. TGF-β, alone, has a half maximal dose of inhibition (ED50) of approximately 750 pg/ml after seven days in culture in Keratinocyte Growth Medium (KGM®; Clonetics) supplemented with 1.5 mM calcium. When 1,25(OH)2D3 (10-7M) was also added to cultures with various concentrations of TGF-β, the ED50 shifted an average of 2-fold less. The presence of TGF-β (10 pg/ml) augmented the potency of 1,25(OH)2D3 by at least 10-fold. In keratinocyte cultures, the antiproliferative effect of the two compounds together is synergistic. In keratinocytes grown for 1 week in the presence of 1,25(OH)2D3 at 10-6M, the TGF-β1 message increased approximately 5-fold. An increase is detected within 2 hours of exposure to 1,25(OH)2D3. There was only a 50% increase in the levels of TGF-β2 and no detection of TGF-β3. When keratinocyte cultures were treated with 1,25(OH)2D3 and neutralizing antibodies to TGF-β, the induced-antiproliferative activity was blocked by more than 50%. The keratinocytes produced more active than latent TGF-β after growth with high doses of 1,25(OH)2D3. © 1992 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041510318
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  • 5
    Electronic Resource
    Electronic Resource
    1,25-Dihydroxycholecalciferol modulates 3H-Thymidine Incorporation in FRTL5 Cells (1992)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 49 (1992), S. 304-309 
    Details
    ISSN: 0730-2312
    Keywords: thyroid follicular cells ; cell proliferation ; cAMP ; protein kinase C ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: 1,25-dihydroxycholecalciferol (1,25(OH)2D3) possesses proliferation and differentiation modulating effects in many cell types in vitro. We studied the effect of 1,25(OH)2D3 on 3H-thymidine incorporation in FRTL5 cells, a cultured rat thyroid follicular cell line. 1,25(OH)2D3 alone at 10-11 and 10-9 M exerted no effect on 3H-thymidine incorporation. However, at 10-7 M, 1,25(OH)2D3 slightly enhanced 3H-thymidine incorporation. In the presence of 5% calf serum, 1,25(OH)2D3 increased 3H-thymidine incorporation induced by calf serum in a dose-dependent manner. 1,25(OH)2D3 also enhanced 3H-thymidine incorporation induced by PMA, an extrinsic stimulator of protein kinase C, without directly affecting PMA-induced protein kinase C translocation. In contrast to the stimulatory effects of 1,25(OH)2D3 on the calf serum and PMA-induced 3H-thymidine incorporation, 1,25(OH)2D3 inhibited the increase in 3H-thymidine incorporation induced by TSH in a dose-dependent manner. This effect of 1,25(OH)2D3 on TSH-induced 3H-thymidine incorporation may be, in part, due to post-cAMP pathways since 1,25(OH)2D3 also inhibited the increase in 3H-thymidine incorporation induced by Bu2cAMP without affecting the TSH-induced increase in cAMP. The stimulatory effect of insulin on 3H-thymidine incorporation, a cAMP-independent process, was also inhibited by 1,25(OH)2D3. We conclude that 1,25(OH)2D3 affects 3H-thymidine incorporation in FRTL5 cells raising the possibility of a physiologic role for 1,25(OH)2D3 in the growth and function of thyroid follicular cells.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240490314
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  • 6
    Electronic Resource
    Electronic Resource
    1,25-dihydroxyvitamin D3 and macrophage colony-stimulating factor-1 synergistically phosphorylate talin (1993)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 53 (1993), S. 145-155 
    Details
    ISSN: 0730-2312
    Keywords: CSF-1 ; talin ; macrophages ; phosphorylation ; vitamin D ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Macrophage colony stimulating factor (CSF-1) and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) are potent inducers of macrophage differentiation. Both appear to modulate protein phosphorylation, at least in part, through protein kinase C (PKC) raising the question as to whether they concurrently impact on macrophage-like cells. In this regard, we utilized the CSF-1 dependent murine macrophage-like line BAC 1.25F5. CSF-1 treatment of these cells for 30 min leads to particular phosphorylation of a 165 kDa protein, the putative CSF-1 receptor, and a 210 kDa moiety. 1,25(OH)2D3 exposure for 24 h prior to addition of CSF-1 enhances phosphorylation of the 165 kDa species and, especially, the 210 kDa protein. Phosphorylation of the latter protein is 1,25(OH)2D3 dose- and time-dependent and the molecule is specifically immunoprecipitated with a rabbit polyclonal anti-talin antibody. Experiments with okadaic acid show that the enhanced phosphorylation of talin does not result from serine phosphatase inhibition. CSF-1 and 1,25(OH)2D3, alone or in combination, do not increase talin protein expression. The tyrosine kinase inhibitor, genestein, blocks 1,25(OH)2D3/CSF-1 induced phosphorylation of the putative CSF-1 receptor but has no effect on talin phosphorylation which occurs exclusively on serine. In contrast to genestein, staurosporin, an inhibitor of PKC, inhibits phosphorylation of talin. Moreover, exposure of 1,25(OH)2D3 pretreated cells to phorbol 12-myristate 13-acetate (PMA) in place of CSF-1 also prompts talin phosphorylation. Finally, 1,25(OH)2D3 enhances 3[H]PDBu binding, indicating that the steroid increases PMA receptor capacity. Thus, CSF-1 and 1,25(OH)2D3 act synergistically via PKC to phosphorylate talin, a cytoskeletal-associated protein.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240530207
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  • 7
    Electronic Resource
    Electronic Resource
    1,25-Dihydroxyvitamin D3 increases type 1 interleukin-1 receptor expression in a murine T cell line (1993)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 52 (1993), S. 159-170 
    Details
    ISSN: 0730-2312
    Keywords: Northern analysis ; vitamin D receptor ; metabolite specificity ; immune regulation ; cellular proliferation ; MTT assay ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The biologically active metabolite of vitamin D3, 1,25 (OH)2 D3, exerts important immunoregulatory effects in addition to being a central mediator of calcium/phosphate metabolism. Utilizing an interleukin 1 responsive murine T cell line and 125I-interleukin 1α, we show that 1,25 (OH)2 D3 (5,50 nM) enhanced 125I-interleukin 1α binding up to almost 2-fold over control. This 1,25 (OH)2 D3 effect occurred in a dose-dependent manner and was detectable after 24 h but not before 7 h of culture. Scatchard analysis of 125I-interleukin 1α binding data demonstrated that 1,25 (OH)2 D3 enhanced interleukin 1 receptor number without a significant change in affinity. The biologically less potent metabolite of vitamin D3, 25 (OH) D3, also augmented 125I-interleukin 1α binding but at steroid levels 2-3 log orders greater than 1,25 (OH)2 D3. This observation, combined with the presence of high-affinity 3H-1,25 (OH)2 D3 receptors (88 sites/cell, K = 0.45 nM) in cytosolic extracts, strongly suggests that the nuclear vitamin D receptor mediates this steroid's effect on interleukin 1 receptor expression. Based on the capacity of an anti-type 1 interleukin 1 receptor monoclonal antibody (35F5) to block 1,25 (OH)2 D3-enhanced 125I-interleukin 1α binding, we conclude that this steroid augments type 1 interleukin 1 receptor expression. When combined with interleukin 1, a cytokine that also impacts MD10 interleukin 1 receptor expression, 1,25 (OH)2 D3 enhanced interleukin 1 receptor expression. Northern blots hybridized with a 32P-type 1 interleukin 1 receptor cDNA probe show that 1,25 (OH)2 D3 enhanced type 1 interleukin 1 receptor steady state mRNA levels. Functionally, 1,25 (OH)2 D3 pretreatment augmented the MD10 proliferative response to suboptimal levels of interleukin 1 (〈 100 fM interleukin 1α). These findings further support 1,25 (OH)2 D3's role as an immunoregulatory molecule and provides a possible mechanism by which this steroid could potentiate certain immune activities.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/jcb.240520208
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  • 8
    Electronic Resource
    Electronic Resource
    1,25-Dihydroxyvitamin D3 or dexamethasone modulate arachidonic acid uptake and distribution into glycerophospholipids by normal adult human osteoblast-like cells (1995)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 57 (1995), S. 599-609 
    Details
    ISSN: 0730-2312
    Keywords: 17β-estradiol ; phosphatidylinositol ; gas chromatography ; fatty acid metabolism ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The effects of treatment with the osteotropic steroids 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), 17β-estradiol, or dexamethasone on [1-14C]arachidonic acid (AA) uptake and distribution into glycerophospholipid classes by normal adult human osteoblast-like (hOB) cells were investigated. Total uptake of [1-14C]AA was decreased in cells treated with dexamethasone when assayed after a 24-, 48-, or 96-h exposure to the hormone. Specific radiolabel incorporation into phosphatidylcholine was reduced by a 48-h treatment with dexamethasone with a concurrent increase in the radiolabeling of phosphatidylethanolamine. However, these changes were transient, and by 96 h of dexamethasone treatment the distribution of the radiolabeled fatty acid had reequilibrated to resemble the pattern found for vehicle treated samples. Total uptake of [1-14C]AA was diminished by 96-h treatment with 1,25(OH)2D3 (79 ± 3% of control, P 〈 0.01); at that time point, a significant decrease in the proportional radiolabeling of the phosphatidylinositol pool was identified (92 ± 2% of control, P 〈 0.05). The 1,25(OH)2D3-dependent decrease in total uptake and in phosphatidylinositol incorporation of [1-14C]AA were found to be hormone dose dependent. Treatment with 24,25(OH)2D3 was without effect on either total [1-14C]AA uptake or the specific [1-14C]AA radiolabeling of the phosphatidylinositol pool. 1,25(OH)2D3 treatment decreased hOB cell uptake of [1-14C]oleic acid and decreased its proportional incorporation into the phosphatidylinositol pool. Gas chromatographic analyses revealed no 1,25(OH)2D3-dependent effects on total phosphatidylinositol lipid mass or on the mole percent of arachidonic acid within the phosphatidylinositol pool, leaving the mechanism of the effects of the secosteroid on hOB cell AA metabolism unexplained. 17β-Estradiol had no effects on the parameters of AA metabolism measured. As a consequence of their modulation of arachidonic acid uptake and its distribution into hOB cellular phospholipids, steroids might alter the biological effects of other hormones whose actions include the stimulated production of bioactive AA metabolites, such as prostaglandins or the various lipoxygenase products.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/jcb.240570404
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  • 9
    Electronic Resource
    Electronic Resource
    1,25-dihydroxyvitamin D3 pretreatment limits prostaglandin biosynthesis by cytokine-stimulated adult human osteoblast-like cells (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 237-246 
    Details
    ISSN: 0730-2312
    Keywords: transforming growth factor-β ; tumor necrosis factor-α ; phospholipase A2 ; arachidonic acid ; AACOCF3 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The steroid derivative 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) is a regulator of bone biology, and there is evidence that 1,25(OH)2D3 modulates arachidonic acid metabolism in osteoblastic cell model systems and in bone organ cultures. In the present studies, 1,25(OH)2D3 decreased prostaglandin (PG) biosynthesis by normal adult human osteoblast-like (hOB) cell cultures by about 30%. The decrease was observed under basal incubation conditions, or in specimens stimulated by transforming growth factor-β1 (TGF-β) or by tumor necrosis factor-α (TNF). The inhibition of the TGF-β-stimulated PG production appeared to reflect a diminished efficiency of arachidonic acid conversion into PGs by the cells, while the efficiency of substrate utilization for PG biosynthesis was unaffected by 1,25(OH)2D3 pretreatment in the unstimulated samples, or in samples stimulated with TNF or with TNF plus TGF-β. Free arachidonic acid levels were decreased following 1,25(OH)2D3 pretreatment in the TNF stimulated samples. hOB cell phospholipase A2 activity was measured in subcellular fractions, and this activity was decreased by 20-25% in the 1,25(OH)2D3 pretreated samples. The addition of the selective inhibitor AACOCF3 to the phospholipase A2 assays provided evidence that it was the cytoplasmic isoform of the enzyme that was affected by the 1,25(OH)2D3 pretreatment of the hOB cells. Thus, 1,25(OH)2D3 regulation of hOB cell biology includes significant effects on arachidonic acid metabolism. In turn, this could influence the effects of other hormones and cytokines whose actions include the stimulated production of bioactive arachidonic acid metabolites. J. Cell. Biochem. 68:237-246, 1998. © 1998 Wiley-Liss, Inc.
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  • 10
    Electronic Resource
    Electronic Resource
    1,25-dihydroxyvitamin D3 regulates pp60c-src activity and expression of a pp60c-src activating phosphatase (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 67 (1997), S. 432-438 
    Details
    ISSN: 0730-2312
    Keywords: pp60c-src ; 1,25-dihydroxyvitamin D3 ; phosphatase ; c-src kinase ; tyrosine kinase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The nonreceptor tyrosine kinase, c-src, and the steroid hormone, 1,25-dihydroxyvitamin D3(1,25(OH)2D3), are essential to development of the osteoclast phenotype. On the other hand, functional relationships between the activities of c-src and 1,25(OH)2D3 are as yet unknown. To determine if 1,25(OH)2D3 modulates c-src in osteoclastogenesis, we tested the steroid's effect on avian marrow-derived osteoclast precursors. We find c-src mRNA and immunoprecipitable c-src protein (pp60c-src) unaltered by 72 h exposure of these cells to 1,25(OH)2D3 (10-11 to 10-9 M). Despite no quantitative change in pp60c-src, in vitro kinase assay of the immune complex reveals 1,25(OH)2D3 dose-dependently accelerates the catalytic activity of pp60c-src, enhancing its autophosphorylation and phosphorylation of exogenous substrate. This observation represents the first documentation, in nontransformed cells, of humoral induction of pp60c-src kinase. Consistent with the fact pp60c-src is activated by dephosphorylation of tyrosine 527 (Y527), the phosphotyrosine content of the pp60c-src immunoprecipitate, measured by immunoblot, is decreased by 1,25(OH)2D3. Alternatively, mRNA and protein levels of c-src kinase (CSK), which inactivates pp60c-src by phosphorylating Y527, are not altered by the steroid. In contrast, 1,25(OH)2D3 enhances mRNA and especially protein levels of avian protein tyrosine phosphatase λ (PTPλ), an enzyme specifically activating pp60c-src by dephosphorylating Y527 [Fang et al. (1994): J Biol Chem 269:20194-20200]. Thus, treatment of avian osteoclast precursors with 1,25(OH)2D3 accelerates the catalytic activity of pp60c-src independent of protein expression. Activation of the kinase may occur via the Y527 dephosphorylating enzyme PTP, expression of which, we show for the first time, is regulated. J. Cell. Biochem. 67:432-438, 1997. © 1997 Wiley-Liss, Inc.
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