The Protease Inhibitor, MG132, Blocks Maturation of the Amyloid Precursor Protein Swedish Mutant Preventing Cleavage by β-Secretase

Steinhilb, Michelle Leigh; Turner, R. Scott; Gaut, James R.

doi:10.1074/jbc.m008793200

Cited by 69 publications

(69 citation statements)

References 32 publications

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“…7B, right panel), suggesting that proteasomes are not involved in formation of the 60-kDa FKHR. These findings are similar to the proteasemediated cleavage of ␤-secretase that is sensitive to MG132 but resistant to lactacystin (50). Thus, a mechanism other than proteasome degradation appears to underlie the proteolysis of the FKHR protein.…”

Section: Fig 3 Effect Of Androgens On the Transcriptional Activatiosupporting

confidence: 70%

Androgens Negatively Regulate Forkhead Transcription Factor FKHR (FOXO1) through a Proteolytic Mechanism in Prostate Cancer Cells

Huang

Muddiman

Tindall

2004

Journal of Biological Chemistry

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The ability of androgens to inhibit apoptosis in both normal and malignant prostatic cells has been well documented. However, the underlying mechanisms are understood poorly. Here we demonstrated that forkhead transcription factor FKHR (FOXO1)-induced death of LNCaP cells was blocked by a synthetic androgen R1881. Androgen treatment also resulted in a reduction in transcriptional activity of FKHR in these cells. Moreover, treatment of LNCaP cells with R1881 led to a decrease in the intact FKHR protein (70 kDa) and an increase in a faster migrating protein band (60 kDa). Androgen-enhanced appearance of the 60-kDa protein was diminished specifically by lysosomal acidic cysteine protease inhibitors. Mass spectrometry analyses of the purified FLAG-tagged 70-and 60-kDa proteins demonstrated that the 60-kDa species is a FKHR protein product that lacks about 120 amino acid residues of the C-terminal end. Mutagenesis of the basic amino acid Arg 537 in the protease cleavage region, as suggested by mass spectrometry, abrogated both the androgen-induced accumulation of the 60-kDa product and decrease in cell death induced by FKHR, suggesting that the residue Arg 537 is a potential protease cleavage site. Finally, ectopic expression of the first 537 amino acids of FKHR produced an inhibitory effect on transcriptional activity of the intact protein. Together, these results suggest that androgens induce increased activity of an acidic cysteine protease, which in turn cleaves FKHR. This provides a mechanism by which androgens protect prostate cancer cells from the killing effect of FKHR.Androgens are critical for proliferation and apoptosis in both normal and malignant prostatic epithelial cell (1). Orchitectomy results in extensive apoptosis and involution of the rat ventral prostate and human prostate cancer xenografts (2-4). Regression of prostatic tumors in patients following androgen ablation therapy is associated with apoptotic death in malignant prostatic epithelium (5, 6). These findings suggest that androgens function as antiapoptotic factors in both normal and malignant prostatic cells.The tumor suppressor gene PTEN (phosphatase and tensin homolog deleted on chromosome ten; also known as MMAC1/ TEP1) is mutated frequently in a variety of tumors including prostate, brain, and endometrium (7-9). Although the overall prevalence of PTEN mutations in primary prostate cancer is low relative to other tumors (10), the gene product is lost frequently in advanced prostate tumors (11, 12). Inactivation of PTEN through different mechanisms such as deletion, methylation, or protein degradation has been implicated in progression of a number of tumors (7,8,(13)(14)(15)(16)(17). Heterozygous disruption results in hyperplasia of the prostate, skin, and colon. Prostate-specific homozygous deletion of PTEN alleles in mice results in metastatic prostate cancer (18). PTEN acts as a tumor suppressor protein primarily via its phosphatidylinositol phosphatase activity, which antagonizes the phosphatidylinositol 3-kinase/Akt pathway (19,20)....

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Section: Fig 3 Effect Of Androgens On the Transcriptional Activatiosupporting

confidence: 70%

Androgens Negatively Regulate Forkhead Transcription Factor FKHR (FOXO1) through a Proteolytic Mechanism in Prostate Cancer Cells

Huang

Muddiman

Tindall

2004

Journal of Biological Chemistry

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“…3, strongly support the latter. The induction of cyclin E mRNA in response to UV irradiation was significantly greater than that observed in the presence of 40 lM MG132, a concentration that almost completely inhibits proteasome activity (25), as evaluated by the ratio UV/MG132 5 1.60, at 4 h and 1.94 at 8 h.…”

Section: E2f1 Protein Accumulation In Response To Uv Light Is the Resmentioning

confidence: 89%

E2F1 transcription is induced by genotoxic stress through ATM/ATR activation

et al. 2009

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SummaryE2F1, a member of the E2F family of transcription factors, plays a critical role in controlling both cell cycle progression and apoptotic cell death in response to DNA damage and oncogene activation. Following genotoxic stresses, E2F1 protein is stabilized by phosphorylation and acetylation driven to its accumulation. The aim of the present work was to examine whether the increase in E2F1 protein levels observed after DNA damage is only a reflection of an increase in E2F1 protein stability or is also the consequence of enhanced transcription of the E2F1 gene. The data presented here demonstrates that UV light and other genotoxics induce the transcription of E2F1 gene in an ATM/ATR dependent manner, which results in increasing E2F1 mRNA and protein levels. After genotoxic stress, transcription of cyclin E, an E2F1 target gene, was significantly induced. This induction was the result of two well-differentiated effects, one of them dependent on de novo protein synthesis and the other on the protein stabilization. Our results strongly support a transcriptional effect of DNA damaging agents on E2F1 expression. The results presented herein uncover a new mechanism involving E2F1 in response to genotoxic stress.

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“…In vivo metabolic labeling and pulse-chase experiments were performed as described (Steinhilb et al, 2001). After pulse or pulse-chase with 100 mCi [ 35 S]methionine (75 mCi/ml) (Amersham), the cells were lysed in IP buffer.…”

Section: Metabolic Labeling Pulse and Pulse-chasementioning

confidence: 99%

Akt negatively regulates translation of the ternary complex factor Elk-1

Figueroa

Vojtek

2003

Oncogene

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Cross-talk between signaling pathways plays an important role in regulation of cell growth, differentiation, survival, and death. Here, we show that Akt regulates the Elk-1 transcription factor, independent of its negative regulation of Raf kinases. Using a constitutively active Mek1 to bypass the regulation of Raf by Akt, we find that the Elk-1 and Sap1a proteins are dramatically decreased in the presence of activated Akt. Akt catalytic activity is required. Also, Mek-dependent activation of a TCF (Elk-1/Sap-1a)-dependent c-fos reporter is decreased by activated Akt. Neither the level of Elk-1 mRNA nor the stability of the Elk-1 protein is altered by activated Akt. Instead, the rate of incorporation of labeled methionine into Elk-1 protein is decreased in the presence of Akt. In addition, the level of the Elk-1 protein but not GFP is significantly decreased in the presence of activated Akt, when GFP is expressed from an IRES element in a bicistronic message with Elk-1. We conclude that Akt negatively regulates translation of the Elk-1 mRNA. A coding region determinant that maps within the first 279 nts of the Elk-1 message is necessary and sufficient for Akt-mediated regulation of Elk-1.

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The Protease Inhibitor, MG132, Blocks Maturation of the Amyloid Precursor Protein Swedish Mutant Preventing Cleavage by β-Secretase

Cited by 69 publications

References 32 publications

Androgens Negatively Regulate Forkhead Transcription Factor FKHR (FOXO1) through a Proteolytic Mechanism in Prostate Cancer Cells

Androgens Negatively Regulate Forkhead Transcription Factor FKHR (FOXO1) through a Proteolytic Mechanism in Prostate Cancer Cells

E2F1 transcription is induced by genotoxic stress through ATM/ATR activation

Akt negatively regulates translation of the ternary complex factor Elk-1

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