scholarly journals Epidermal growth factor increases the level of the cyclin-dependent kinase (CDK) inhibitor p21/CIP1 (CDK-interacting protein 1) in A431 cells by increasing the half-lives of the p21/CIP1 transcript and the p21/CIP1 protein

1999 ◽  
Vol 337 (3) ◽  
pp. 599-606 ◽  
Author(s):  
Lene E. JOHANNESSEN ◽  
Sigrun L. KNARDAL ◽  
Inger Helene MADSHUS
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Half Life ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Cyclin Dependent Kinase ◽  
A431 Cells ◽  
Interacting Protein ◽  
Prolonged Incubation ◽  
Epidermal Growth

DNA synthesis was inhibited in A431 cells by epidermal growth factor (EGF) in a p21/CIP1-dependent manner [where CIP1 is cyclin-dependent kinase (CDK)-interacting protein 1]. When 1 or 10 nM EGF was added, the level of p21/CIP1 was increased to the same extent, and the protein level peaked after approx. 5 h of incubation. The increase in p21/CIP1 mRNA upon addition of EGF was rapid, and was enhanced in the presence of cycloheximide. The half-life of p21/CIP1 mRNA in EGF-treated A431 cells was increased approx. 2-fold; this is in contrast with the case in MCF-7 cells with normal p53, in which the half-life of p21/CIP1 mRNA was not increased upon addition of EGF. This increased stability accounts for most of the increase in mRNA levels observed in A431 cells during short incubation periods. Additionally, upon prolonged incubation of A431 cells with EGF, the half-life of the protein was also increased compared with that in untreated cells and in cells treated with EGF for short time periods. Nuclear run-on assays demonstrated only marginal stimulation of transcription by 10 or 1 nM EGF, or by 10 ng/ml tumour necrosis factor α. Our results indicate that the most important mechanisms by which EGF increases p21/CIP1 protein levels in A431 cells are post-transcriptional and post-translational stabilization.

scholarly journals Expression of the v-crk oncogene product in PC12 cells results in rapid differentiation by both nerve growth factor- and epidermal growth factor-dependent pathways.

1994 ◽  
Vol 14 (3) ◽  
pp. 1964-1971 ◽  
Author(s):  
B L Hempstead ◽  
R B Birge ◽  
J E Fajardo ◽  
R Glassman ◽  
D Mahadeo ◽  
...  
Keyword(s):  
Nerve Growth Factor ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Fusion Protein ◽  
Pc12 Cells ◽  
Dependent Manner ◽  
Egf Receptors ◽  
A431 Cells ◽  
Nerve Growth ◽  
Epidermal Growth

The transforming gene of the avian sarcoma virus CT10 encodes a fusion protein (p47gag-crk or v-Crk) containing viral Gag sequences fused to cellular sequences consisting primarily of Src homology regions 2 and 3 (SH2 and SH3 sequences). Here we report a novel function of v-Crk in the mammalian pheochromocytoma cell line, PC12, whereby stable expression of v-Crk induces accelerated differentiation, as assessed by induction of neurites following nerve growth factor (NGF) or basic fibroblast growth factor (bFGF) treatment compared with the effect in native PC12 cells. Surprisingly, however, these cells also develop extensive neurite processes after epidermal growth factor (EGF) stimulation, an event which is not observed in native PC12 cells. Following EGF or NGF stimulation of the v-CrkPC12 cells, the v-Crk protein itself became tyrosine phosphorylated within 1 min. Moreover, in A431 cells or TrkA-PC12 cells, which overexpress EGF receptors and TrkA, respectively, a GST-CrkSH2 fusion protein was indeed capable of binding these receptors in a phosphotyrosine-dependent manner, suggesting that v-Crk can directly couple to receptor tyrosine kinase pathways in PC12 cells. In transformed fibroblasts, v-Crk binds to specific tyrosine-phosphorylated proteins of p130 and paxillin. Both of these proteins are also complexed to v-Crk in PC12 cells, as evidenced by their coprecipitation with v-Crk in detergent lysates, suggesting that common effector pathways may occur in both cell types. However, whereas PC12 cellular differentiation can occur solely by overexpression of the v-Src or oncogenic Ras proteins, that induced by v-Crk requires a growth factor stimulatory signal, possibility in a two-step process.

Regulation of steady-state follistatin mRNA levels in rat granulosa cells in vitro

1992 ◽  
Vol 9 (2) ◽  
pp. 147-156 ◽  
Author(s):  
U. Michel ◽  
J. W. McMaster ◽  
J. K. Findlay
Keyword(s):  
Steady State ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Cell Cultures ◽  
Granulosa Cells ◽  
Internal Standard ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Epidermal Growth

ABSTRACT The regulation of steady-state follistatin mRNA levels by different pituitary hormones and peptide factors was examined in granulosa cell cultures derived from diethylstilboestrol-treated immature rats. Cytosolic RNA from cell cultures was prepared by lysis and equal amounts of RNA from all samples were analysed with a solution—hybridization assay using a 32P-labelled antisense probe corresponding to a part of exon 5 together with a part of the 5′ end of exon 6 of the rat follistatin gene. In addition, a specific 35S-labelled probe for cyclophilin was used as an internal standard. The results show that 5 μg FSH/1 for 24 to 72 h stimulated steady-state follistatin mRNA levels, reaching levels 18·5-fold higher than controls. LH (0·2-100 μg/l) had only minor effects on follistatin mRNA levels in FSH-primed granulosa cells and prolactin, GH and IGF-I did not show any significant effects. Activin raised basal as well as FSH-stimulated steady-state follistatin mRNA levels up to ten- and twofold above controls respectively, whereas epidermal growth factor was found to inhibit FSH-stimulated follistatin mRNA levels in a dose-dependent manner. It is concluded that follistatin mRNA levels in granulosa cells are regulated by FSH rather than LH, and that the stimulation by FSH can be inhibited by epidermal growth factor but enhanced by activin. Activin alone was also capable of stimulating follistatin mRNA.

Transcriptional down-regulation by epidermal growth factor of TRH receptor mRNA in rat pituitary cells

1995 ◽  
Vol 15 (1) ◽  
pp. 73-79 ◽  
Author(s):  
T Monden ◽  
M Yamada ◽  
S Konaka ◽  
T Satoh ◽  
H Ezawa ◽  
...  
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Mrna Level ◽  
Pituitary Cells ◽  
Mrna Levels ◽  
Dependent Manner ◽  
R Gene ◽  
Binding Studies ◽  
Epidermal Growth ◽  
Rat Pituitary Cells

ABSTRACT To gain insight into the mechanism underlying the epidermal growth factor (EGF)-induced changes in responsiveness to TRH and in the numbers of TRH receptors (TRH-Rs) in the pituitary, we investigated the transcriptional regulation by EGF of the TRH-R gene in GH4C1 cells. Northern blot analyses and binding studies revealed that EGF reduced both TRH binding and TRH-R mRNA levels in a dose- and time-dependent manner, while no significant changes were observed in β-actin mRNA levels. Addition of actinomycin D caused an acute increase in the basal TRH-R mRNA level, and the rate of decrease of the TRH-R mRNA was identical in control and EGF-treated groups, suggesting that the stability of the TRH-R mRNA was not significantly affected in EGF-treated cells. Incubation with cycloheximide also induced an increase in the basal TRH-R mRNA level and completely reversed the EGF-induced reduction of TRH-R mRNA levels. Furthermore, a nuclear run-on assay demonstrated that the rate of transcription of the TRH-R gene was significantly inhibited in cells treated with EGF. We conclude that (1) EGF decreases the expression of the TRH-R mRNA largely by reducing its rate of transcription, and this action requires the synthesis of new proteins, and (2) inhibitors of protein and RNA synthesis cause a significant increase in the basal TRH-R mRNA level, suggesting that there may be a short-lived protein suppressing the TRH-R mRNA level in the pituitary.

Expression of the v-crk oncogene product in PC12 cells results in rapid differentiation by both nerve growth factor- and epidermal growth factor-dependent pathways

1994 ◽  
Vol 14 (3) ◽  
pp. 1964-1971
Author(s):  
B L Hempstead ◽  
R B Birge ◽  
J E Fajardo ◽  
R Glassman ◽  
D Mahadeo ◽  
...  
Keyword(s):  
Nerve Growth Factor ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Fusion Protein ◽  
Pc12 Cells ◽  
Dependent Manner ◽  
Egf Receptors ◽  
A431 Cells ◽  
Nerve Growth ◽  
Epidermal Growth

The transforming gene of the avian sarcoma virus CT10 encodes a fusion protein (p47gag-crk or v-Crk) containing viral Gag sequences fused to cellular sequences consisting primarily of Src homology regions 2 and 3 (SH2 and SH3 sequences). Here we report a novel function of v-Crk in the mammalian pheochromocytoma cell line, PC12, whereby stable expression of v-Crk induces accelerated differentiation, as assessed by induction of neurites following nerve growth factor (NGF) or basic fibroblast growth factor (bFGF) treatment compared with the effect in native PC12 cells. Surprisingly, however, these cells also develop extensive neurite processes after epidermal growth factor (EGF) stimulation, an event which is not observed in native PC12 cells. Following EGF or NGF stimulation of the v-CrkPC12 cells, the v-Crk protein itself became tyrosine phosphorylated within 1 min. Moreover, in A431 cells or TrkA-PC12 cells, which overexpress EGF receptors and TrkA, respectively, a GST-CrkSH2 fusion protein was indeed capable of binding these receptors in a phosphotyrosine-dependent manner, suggesting that v-Crk can directly couple to receptor tyrosine kinase pathways in PC12 cells. In transformed fibroblasts, v-Crk binds to specific tyrosine-phosphorylated proteins of p130 and paxillin. Both of these proteins are also complexed to v-Crk in PC12 cells, as evidenced by their coprecipitation with v-Crk in detergent lysates, suggesting that common effector pathways may occur in both cell types. However, whereas PC12 cellular differentiation can occur solely by overexpression of the v-Src or oncogenic Ras proteins, that induced by v-Crk requires a growth factor stimulatory signal, possibility in a two-step process.

Sign in / Sign up

Export Citation Format

Share Document