Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

After isoprenylation, the Ras proteins and other CAAX proteins undergo two additional enzymatic modifications-endoproteolytic release of the last three amino acids of the protein by the protease Rce1 and methylation of the carboxyl-terminal isoprenylcysteine by the methyltransferase Icmt. This postisoprenylation processing is thought to be important for the association of Ras proteins with membranes. Blocking postisoprenylation processing, by inhibiting Rce1, has been suggested as a potential approach for retarding cell growth and blocking cellular transformation. The objective of this study was to develop a cell culture system for addressing these issues. We generated mice with a conditional Rce1 allele (Rce1(flox)) and produced Rce1(flox/flox) fibroblasts. Cre-mediated excision of Rce1 (thereby producing Rce1(Delta/Delta) fibroblasts) eliminated Ras endoproteolytic processing and methylation and caused a partial mislocalization of truncated K-Ras and H-Ras fusion proteins within cells. Rce1(Delta/Delta) fibroblasts grew more slowly than Rce1(flox/flox) fibroblasts. The excision of Rce1 also reduced Ras-induced transformation, as judged by the growth of colonies in soft agar. The excision of Rce1 from a Rce1(flox/flox) skin carcinoma cell line also significantly retarded the growth of cells, and this effect was exaggerated by cotreatment of the cells with a farnesyltransferase inhibitor. These studies support the idea that interference with postisoprenylation processing retards cell growth, limits Ras-induced transformation, and sensitizes tumor cells to a farnesyltransferase inhibitor.
Mol Cell Biol 2002 Jan
PMID:Absence of the CAAX endoprotease Rce1: effects on cell growth and transformation. 1173 32

Estrogen and its catechol metabolites from both the circulation and synthesized within the breast are important in the pathogenesis of breast cancer. Blocking estrogen's effects on the breast with selective estrogen receptor modulators (SERMS) is an ongoing strategy. Thus, tamoxifen and raloxifene reduce risk as monotherapy. Aromatase (estrogen synthetase) inhibitors are a logical alternative to SERMS. To date, SERMS have demonstrated reduction only in estrogen-progesterone receptor positive cancers without reduction in receptor negative tumors. By inhibiting the parent estrogens and their catechol metabolites, true prevention of cancer initiation might occur and reduction not only in the receptor positive but also negative tumors might result. Ongoing adjuvant breast cancer trials are exploring aromatase inhibitors as alternatives to tamoxifen, or in sequence or in combination with tamoxifen. Relative efficacies including reduction in contralateral breast cancer, toxicities and end-organ effects and impact on quality of life, are being explored. Data from these trials will help to guide future chemoprevention strategies. Proof of principal trials in 'high risk' cohorts such as premalignant breast lesions, dense screening mammograms, high plasma estradiol levels or increased bone density are already ongoing. Issues such as dose, schedule, therapeutic index and mono versus combination therapy are important to define.
J Steroid Biochem Mol Biol 2001 Dec
PMID:Chemoprevention with aromatase inhibitors--trial strategies. 1185 Feb 18

We examined the biogenesis of the von Hippel-Lindau (VHL) tumor suppressor protein (pVHL) in vitro and in vivo. pVHL formed a complex with the cytosolic chaperonin containing TCP-1 (CCT or TRiC) en route to assembly with elongin B/C and the subsequent formation of the VCB-Cul2 ubiquitin ligase. Blocking the interaction of pVHL with elongin B/C resulted in accumulation of pVHL within the CCT complex. pVHL present in purified VHL-CCT complexes, when added to rabbit reticulocyte lysate, proceeded to form VCB and VCB-Cul2. Thus, CCT likely functions, at least in part, by retaining VHL chains pending the availability of elongin B/C for final folding and/or assembly. Tumor-associated mutations within exon II of the VHL syndrome had diverse effects upon the stability and/or function of pVHL-containing complexes. First, a pVHL mutant lacking the entire region encoded by exon II did not bind to CCT and yet could still assemble into complexes with elongin B/C and elongin B/C-Cul2. Second, a number of tumor-derived missense mutations in exon II did not decrease CCT binding, and most had no detectable effect upon VCB-Cul2 assembly. Many exon II mutants, however, were found to be defective in the binding to and subsequent ubiquitination of hypoxia-inducible factor 1alpha (HIF-1alpha), a substrate of the VCB-Cul2 ubiquitin ligase. We conclude that the selection pressure to mutate VHL exon II during tumorigenesis does not relate to loss of CCT binding but may reflect quantitative or qualitative defects in HIF binding and/or in pVHL-dependent ubiquitin ligase activity.
Mol Cell Biol 2002 Mar
PMID:Diverse effects of mutations in exon II of the von Hippel-Lindau (VHL) tumor suppressor gene on the interaction of pVHL with the cytosolic chaperonin and pVHL-dependent ubiquitin ligase activity. 1186 71

The present study demonstrates a novel stimulatory effect of a cannabinoid agonist on calcium channels. DALN (1 nM) potentiated 45Ca(2+)-uptake by N18TG2 neuroblastoma cells, an effect that was abolished by the specific CB1 receptor antagonist SR141716A. The stimulation of 45Ca(2+)-uptake by DALN was resistant to pertussis toxin (PTX), suggesting that Gi/Go GTP-binding proteins did not mediate this effect. Furthermore, PTX unmasked a stimulatory effect of a high concentration of DALN (1 microM), which by itself failed to stimulate calcium uptake in naive cells. The stimulatory effect of DALN on calcium entry to the cells was blocked by nicardipine but not by omega-conotoxin GVIA, indicating the entry of calcium through L-type voltage-dependent calcium channels. Blocking cAMP-dependent protein kinase (PKA) by H-89 completely eliminated the elevation in calcium uptake, while blocking protein kinase C (PKC) by chelerythrine and calphostine-C only partially attenuated the stimulation. Blocking calmodulin by W-7 revealed a similar partial inhibition of the stimulatory effect of DALN. Hence, we suggest a cannabinoid-specific, PTX-insensitive, stimulatory effect on L-type voltage-dependent calcium channels, which is mediated by PKA and modulated by PKC and calmodulin.
Brain Res Mol Brain Res 2002 May 30
PMID:The cannabinoid agonist DALN positively modulates L-type voltage-dependent calcium-channels in N18TG2 neuroblastoma cells. 1200 36

The ubiquitin-proteasome pathway regulates the turnover of many transcription factors, including steroid hormone receptors such as the estrogen receptor and progesterone receptor. For these receptors, proteasome inhibition interferes with steroid-mediated transcription. We show here that proteasome inhibition with MG132 results in increased accumulation of the glucocorticoid receptor (GR), confirming that it is likewise a substrate for the ubiquitin-proteasome degradative pathway. Using the mouse mammary tumor virus (MMTV) promoter integrated into tissue culture cells, we found that proteasome inhibition synergistically increases GR-mediated transactivation. This increased activation was observed in a number of cell lines and on various MMTV templates, either as transiently transfected reporters or stably integrated into chromatin. These observations suggest that the increase in GR-mediated transcription due to proteasome inhibition may occur downstream of the initial chromatin remodeling step. In support of this concept, the increase in transcription did not correlate with an increase in chromatin remodeling, as measured by restriction enzyme hypersensitivity, or transcription factor loading, as exemplified by nuclear factor 1. To investigate the relationship between GR turnover, transcription, and subnuclear trafficking, we examined the effect of proteasome inhibition on the mobility of the GR within the nucleus and association of the GR with the nuclear matrix. Blocking GR turnover reduced the mobility of the GR within the nucleus, and this correlated with increased association of the receptor with the nuclear matrix. As a result of proteasome inhibition, GR mobility within the nucleus was reduced while its association with the nuclear matrix was increased. Thus, while altered nuclear mobility of steroid receptors may be a common feature of proteasome inhibition, GR is unique in its enhanced transactivation activity that results when proteasome function is compromised. Proteasomes may therefore impact steroid receptor action at multiple levels and exert distinct effects on individual receptor types.
Mol Cell Biol 2002 Jun
PMID:Proteasomal inhibition enhances glucocorticoid receptor transactivation and alters its subnuclear trafficking. 1202 25

Gene therapy represents an attractive approach for the treatment of eye diseases such as glaucoma. Ocular administration of viral vectors produces localized retinal gene expression with reduced risks of side effects reported with systemic administration of viral vectors. Recombinant adeno-associated viral (AAV) vectors have proven effective in producing long-term retinal gene expression, due to stable integration of DNA into the genome and lack of host immune response to the virus. Recently developed AAV constructs using the chicken beta-actin (CBA) promoter drive highly efficient transgene expression in retinal ganglion cells (RGCs), photoreceptors, and pigment epithelium. Rats were given unilateral intravitreal injections of AAV-CBA vector coding for human baculoviral IAP repeat-containing protein-4 (BIRC4), a potent caspase inhibitor. Ocular hypertension was induced in the same eye by sclerosis of aqueous humor outflow channels. After chronic exposure to elevated intraocular pressure, we performed optic nerve axon counts to determine the neuroprotective effects of retinal BIRC4 expression, and compared axon survival with vector and balanced salt solution control groups. Gene therapy delivering BIRC4 significantly promoted optic nerve axon survival in a chronic ocular hypertensive model of rat glaucoma. Blocking RGC apoptosis with caspase inhibitors represents a promising approach for treatment of human glaucoma.
Mol Ther 2002 Jun
PMID:Baculoviral IAP repeat-containing-4 protects optic nerve axons in a rat glaucoma model. 1202 63

Integrins represent the primary mechanism of cell-extracellular matrix interactions and control cell morphology, proliferation, and differentiation. We have previously shown that substrate-dependent modulation of adsorbed fibronectin (Fn) conformation alters alpha5beta1 integrin binding to Fn and directs C2C12 myoblast proliferation and differentiation (Mol. Biol. Cell 10 (1999) 785). The model substrates used in these experiments were bacteriological (untreated) polystyrene (B), tissue culture polystyrene (T), and type-I collagen-coated T (C). In the present study, we examined MC3T3-EI osteoblast-like cell differentiation on Fn-coated B, T, and C substrates. Immunofluorescence staining revealed substrate-dependent differences in integrin alpha5beta1 binding and clustering into focal adhesions (C > T > B), consistent with our previous integrin binding analysis. Alkaline phosphatase activity and matrix mineralization showed substrate-dependent differences (C > T > B, p < 0.05). Similar trends were observed for alkaline phosphatase, osteocalcin, and bone sialoprotein gene expression. Blocking experiments with antibodies directed against Fn completely inhibited matrix mineralization on Fn-coated C, indicating that Fn is critical to expression of the osteoblastic phenotype on this extracellular matrix component. These substrate-dependent differences in osteoblast differentiation correlated with differences in alpha5beta1 binding, suggesting that these differences arise from substrate modulation of integrin-matrix interactions. Substrate-dependent modulation of cell function may provide a versatile mechanism to control cell responses in numerous biomedical applications.
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PMID:Enhanced expression of the osteoblastic phenotype on substrates that modulate fibronectin conformation and integrin receptor binding. 1203

We postulate that intercellular adhesion molecule-1 (ICAM-1) on type I alveolar epithelial cells (AEC) facilitates phagocytic activity of alveolar macrophages (AM) in the alveolus. When wild-type and ICAM-1-deficient mice were inoculated intratracheally with FITC-labeled microspheres, AM phagocytosis of beads (after 1 and 4 h) was significantly reduced in ICAM-1-/- mice compared with controls. To focus on ICAM-1-mediated interactions specifically involving AM and AEC, rat AM were placed in culture with rat AEC treated with neutralizing anti-ICAM-1 F(ab')(2) fragments. Blocking ICAM-1 significantly decreased the AM phagocytosis of beads. Planar chemotaxis of AM over the surface of AEC was also significantly impaired by neutralization of AEC ICAM-1. ICAM-1 in rat AEC is associated with the actin cytoskeleton. Planar chemotaxis of AM was also significantly reduced by pretreatment of the AEC monolayer with cytochalasin B to disrupt the actin cytoskeleton. These studies indicate that ICAM-1 on the AEC surface promotes mobility of AM in the alveolus and is critically important for the efficient phagocytosis of particulates by AM.
Am J Physiol Lung Cell Mol Physiol 2002 Jul
PMID:ICAM-1 facilitates alveolar macrophage phagocytic activity through effects on migration over the AEC surface. 1206 May 75

The aim of this study was to determine the effects of glutathione (GSH) on trachea smooth muscle tension in view of previously reported interactions between GSH and nitric oxide (NO) (Gaston B. Biochim Biophys Acta 1411: 323-333, 1999; Kelm M. Biochim Biophys Acta 1411: 273-289, 1999; and Kharitonov VG, Sundquist AR, and Sharma VS. J Biol Chem 270: 28158-28164, 1995) and the high (millimolar) concentrations of GSH in trachea epithelium (Rahman I, Li XY, Donaldson K, Harrison DJ, and MacNee W. Am J Physiol Lung Cell Mol Physiol 269: L285-L292, 1995). GSH and other thiols (1.0-10 mM) dose dependently decreased the tension in isolated guinea pig tracheas. Relaxations by GSH were paralleled with sevenfold increased nitrite levels (P < 0.05) in the tracheal effluent, suggesting an interaction between GSH and NO. However, preincubation with a NO scavenger did not reduce the relaxations by GSH or its NO adduct, S-nitrosoglutathione (GSNO). Inhibition of guanylyl cyclase inhibited the relaxations induced by GSNO, but not by GSH. Blocking potassium channels, however, completely abolished the relaxing effects of GSH (P < 0.05). Preincubation of tracheas with GSH significantly (P < 0.05) suppressed hyperreactivity to histamine as caused by removal of tracheal epithelium. These data indicate that GSH plays a role in maintaining tracheal tone. The mechanism is probably an antioxidative action of GSH itself rather than an action of NO or GSNO.
Am J Physiol Lung Cell Mol Physiol 2002 Aug
PMID:Glutathione and other low-molecular-weight thiols relax guinea pig trachea ex vivo: interactions with nitric oxide? 1211 2

Oxytocin (OT) is a neurohypophysial hormone with unclear physiological functions in the male. Several previous studies indicated that OT might have a role in the ejaculatory process, stimulating sperm release from the epididymal storage. In this study we investigated on the presence and function of OT receptor (OTR) in rabbit and human epididymis. By using RT-PCR, Western and binding studies, we found that OTR gene and protein is expressed in the human epididymis and stimulates in vitro contractility. The immunolocalization of OTR suggests that the receptor is not only present in the smooth muscle cells of the human epididymis but also in the epithelial compartment. Experiments performed in rabbit epididymal epithelial (rEE) cells in culture indicate that OT induces the release of an other potent stimulator of epididymal contractility, endothelin-1 (ET-1), Blocking the ET(A) subtype of the ET-1 receptors, by using a specific antagonist (BQ-123), partially counteracts the contractile effect of OT, suggesting positive interactions between the two peptides in regulating epididymal contractility. Finally, to investigate whether an acute OT administration increases sperm release also in humans, we treated oligozoospermic patients with an intravenous bolus of OT (2.5 IU), just before sperm collection. In a small, single blind study, we found that OT almost doubled sperm retrieval when compared with vehicle administration. Our results indicate that OT might have physiological functions also in the male, controlling epididymal motility and sperm progression through the male genital tract.
Mol Cell Endocrinol 2002 Jul 31
PMID:Identification, localization and functional activity of oxytocin receptors in epididymis. 1216 Oct 7


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