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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 62 (1994), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Incubation of rat brainstem slices with [3H]- mevalonate ([3H]MVA) in the presence of lovastatin resulted in the incorporation of label into three groups of myelin-associated proteins with molecular masses of 47, 21–27, and 8 kDa, as revealed on sodium dodecyl sulfate- polyacrylamide rod gel electrophoresis. Although the gel patterns of [3H]MVA-derived prenylated proteins were similar, the relative level of 3H incorporated into each protein species differed between myelin and the brainstem homogenate. Immunoprecipitation studies identified the 47-kDa prenylated protein as a 2′-3′-cyclic nucleotide phospho- diesterase, whereas the 8-kDa protein proved to be the γ subunit of membrane-associated guanine nucleotide regulatory protein. The 3H-labeled 21–27-kDa group in myelin corresponds to the molecular mass of the extensive Ras- like family of monomeric GTP-binding proteins known to be prenylated in other tissues. Increase in lovastatin concentration resulted in reduced levels of [3H]MVA-labeled species in myelin and concomitantly increased levels in the cytosol. A cold MVA chase restored to normality the appearance of [3H]MVA-labeled proteins in myelin. Furthermore, a high lovastatin concentration in the brainstem slice incubation mixture altered the appearance of newly synthesized nonprenylated myelin proteins, including proteolipid protein and the 17-kDa subspecies of myelin basic protein. Because other myelin proteins were unaffected by the high lovastatin concentration, restricting the availability of MVA in myelin-forming cells may selectively alter processes required for myelinogenesis. Although the molecular basis for the” different MVA requirements in myelin- forming cells remains undefined, it may involve an alteration in the biological activity of certain proteins that require prenylation to be functionally active, and that are responsible for promoting insertion of specific proteins into the myelin membrane.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0843
    Keywords: Key words Protein farnesylation inhibitor ; Human prostate tumors ; Efficacy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: These studies sought to evaluate the antitumor properties of an inhibitor of ras functionality, L-744,832, which acts at the level of its associated protein farnesyltransferase. Methods: Studies were carried out to measure the effects of L-744,832 alone and in combination with paclitaxel (PTXL) against TSU-PR1, DU-145 and PC-3 human prostate tumors xenografted to NCR-nu1 (AT) mice. Tumor-bearing mice were treated on a schedule of daily for 5 days ×2 or 3 with the MTD of L-744,832 and every 3–4 days ×4 with the MTD of PTXL starting 3–5 days after tumor implantation. Tumor volume in millimeters (4/3πr3) was measured 3–5 days after cessation of treatment and the increase in tumor volume in treated and control groups compared. Statistical analysis was carried out by the Chi-squared test. Results: L-744,832 at its MTD markedly inhibited the growth of all three tumors (T/C for increase in tumor mass varied from 11% to 15% and inhibition of growth had a rapid onset (within 1–2 days) and was independent of ras gene status. Estimated tumor doubling times were 8–12-fold greater in treated animals than in control animals. Treatment with L-744,832 for as long as 3 weeks had no untoward effects on the mice as determined by gross examination or necropsy. Administration of L-744,832 with this same dose and schedule potentiated the growth-inhibitory effect of PTXL at its MTD and induced some regression of TSU-PR1 with no obvious deleterious effects on the mice. Conclusions: L-744,832 could be safely administered over a protracted period of time to mice at doses which were markedly inhibitory to the growth of three human prostate tumor xenografts and in combination with PTXL was also well tolerated and brought about some regression of the TSU-PR1 tumor. Overall, these results suggest that L-744,832 could be clinically useful for long-term treatment of early-stage prostate cancer in patients and as an adjunct to cytotoxic therapy for late stages of this disease.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-7217
    Keywords: oncogenes ; mitogenic signal transduction ; cancer chemotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The oncoprotein encoded by mutantras genes is initially synthesized as a cytoplasmic precursor which requires posttranslational processing to attain biological activity; farnesylation of the cysteine residue present in the CaaX motif located at the carboxy-terminus of all Ras proteins is the critical modification. Once farnesylated and further modified, the mature Ras protein is inserted into the cell's plasma membrane where it participates in the signal transduction pathways that control cell growth and differentiation. The farnesylation reaction that modifies Ras and other cellular proteins having an appropriate CaaX motif is catalyzed by a housekeeping enzyme termed farnesyl-protein transferase (FPTase). Inhibitors of this enzyme have been prepared by several laboratories in an effort to identify compounds that would block Ras-induced cell transformation and thereby function as Ras-specific anticancer agents. A variety of natural products and synthetic organic compounds were found to block farnesylation of Ras proteinsin vitro. Some of these compounds exhibit antiproliferative activity in cell culture, block the morphological alterations associated with Ras-transformation, and can block the growth of Ras-transformed cell lines in tumor colony-forming assays. By contrast, these compounds do not affect the growth or morphology of cells transformed by the Raf or Mos oncoproteins, which do not require farnesylation to achieve biological activity. The efficacy and lack of toxicity observed with FPTase inhibitors in an animal tumor model suggest that specific FPTase inhibitors may be useful for the treatment of some types of cancer.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Breast cancer research and treatment 47 (1998), S. 235-253 
    ISSN: 1573-7217
    Keywords: insulin-like growth factors (IGFs) ; IGF-I receptor ; insulin receptor ; regulation ; signal transduction ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Insulin-like growth factors I and II (IGF-I, IGF-II) were originally identified as potent mitogens and as the mediators of growth hormone action. Besides being mitogenic, however, these polypeptide growth factors play a crucial role in cell survival, and contribute to transformation and to maintenance of the malignant phenotype. Here we will discuss signaling by the IGFs, focusing specifically on the structure and function of the IGF-I receptor and the domains of this receptor responsible for distinct IGF functions: mitogenesis, transformation, and protection from apoptosis. We will also compare the structural domains of the related but functionally distinct receptor for insulin.
    Type of Medium: Electronic Resource
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