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Lindquist JN, Phan VT, Riquelme E, Mukherjee K, Farías O, Gupta A, Raja M, Rai R, Uppal H, Protter AA. Abstract B30: Talazoparib efficacy is enhanced by noncytotoxic doses of temozolomide-mediated DNA damage in prostate cancer cell lines. Mol Cancer Res 2017. [DOI: 10.1158/1557-3125.dnarepair16-b30] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Purpose: To investigate the effects of talazoparib alone and in combination with temozolomide (TMZ) on prostate cancer cells
Introduction: Talazoparib is a potent, orally bioavailable, small molecule inhibitor of PARP (poly-ADP ribose polymerase) enzyme activity that also traps PARP protein onto DNA at sites of DNA damage; both activities result in cancer cell death (Murai et al. Mol Cancer Ther. 2014;13:433-43). Talazoparib is currently under investigation for clinical activity in patients who have locally advanced and/or metastatic breast cancer with germline BRCA mutations (EMBRACA; Clinical Trials.gov; NCT01945775). In the current nonclinical study, talazoparib demonstrated potent antitumor effects on androgen receptor (AR)-positive prostate cancer cells expressing both full length AR (LNCaP cells) as well as the androgen-independent splice variant, AR-V7 (22RV1 cells), when used either as a single agent or in combination with low, noncytotoxic concentrations of TMZ, a DNA alkylating therapeutic.
Methods: Viability of prostate cancer cells (LNCaP and 22RV1 cells) after 7 days of treatment was measured by Cell Titer Glo (Promega) after treatment with vehicle, talazoparib, TMZ or a combination of the two. DNA damage was determined by immunofluorescence against gH2AX (EMD Millipore), and the amount of PARP trapped on DNA, determined by Western Blot analysis of chromatin probed with antibodies specific for PARP. Cellular homeostasis was determined by flow cytometry analysis for cell cycle stage, and apoptosis indicated by Annexin V staining (BD Pharmingen) or caspase activation with Caspase Glo (Promega) assays. Nucleotide adducts, N7 methyl-2'-deoxyguanosine (N7-MedG) and O6-Methyl-2'-deoxyguanosine (O6-MedG), from 1-, 2- and 4-hour TMZ-treated calf thymus DNA and genomic DNA from LNCaP cells treated with TMZ were detected after DNA hydrolysis and quantitated by LC-mass spectrometry in multiple reaction monitoring mode.
Results: Talazoparib treatment resulted in a concentration-dependent inhibition of cell viability in LNCaP (AR wildtype) and 22RV1 (AR-V7) cells. Talazoparib's antitumor effects were greatly enhanced when combined with noncytotoxic TMZ concentrations. In a cell-free study using calf thymus DNA, TMZ generated both N7-MedG and O6-MedG DNA adducts, with the N7-MedG being more abundant than the O6-MedG. Analysis of DNA from LNCaP cells treated with TMZ generated detectable N7-MedG DNA adducts. Low, noncytotoxic concentrations of TMZ potentiated the effects of talazoparib on prostate cancer cell viability independent of AR variant status. Treatment with talazoparib alone and in combination with TMZ was associated with increased gH2AX staining (DNA damage) and enhanced PARP-DNA trapping complexes. The combination treatment also induced an increase in apoptotic cells at early time points.
Conclusion: Talazoparib is cytotoxic to prostate cancer cells as a single agent in nonclinical cell based models. Herein, we demonstrate that combining noncytotoxic doses of TMZ with talazoparib improves efficacy in killing of LNCaP and 22RV1 cells. The increased efficacy corresponds with increased DNA-damage and increased trapped PARP-DNA complexes. Low, noncytotoxic doses of TMZ are shown to generate DNA damage sites in vitro and in treated LNCaP cells, providing a mechanistic basis for the combination effect of talazoparib and TMZ. Together, these nonclinical data provide scientific rationale for a clinical trial strategy of combining talazoparib with low, noncytotoxic doses of TMZ to enhance efficacy in prostate cancer.
Citation Format: Jeffrey N. Lindquist, Vernon T. Phan, Eduardo Riquelme, Kakoli Mukherjee, Olivia Farías, Ashu Gupta, Mohd Raja, Roopa Rai, Hirdesh Uppal, Andrew A. Protter. Talazoparib efficacy is enhanced by noncytotoxic doses of temozolomide-mediated DNA damage in prostate cancer cell lines [abstract]. In: Proceedings of the AACR Special Conference on DNA Repair: Tumor Development and Therapeutic Response; 2016 Nov 2-5; Montreal, QC, Canada. Philadelphia (PA): AACR; Mol Cancer Res 2017;15(4_Suppl):Abstract nr B30.
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Affiliation(s)
| | | | | | | | | | - Ashu Gupta
- 3Integral BioScience Pvt. Ltd., Noida Uttar Pradesh, India
| | - Mohd Raja
- 3Integral BioScience Pvt. Ltd., Noida Uttar Pradesh, India
| | - Roopa Rai
- 1Medivation, Inc., San Francisco, CA,
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Ramachandran SA, Jadhavar PS, Singh MP, Sharma A, Bagle GN, Quinn KP, Wong PY, Protter AA, Rai R, Pham SM, Lindquist JN. Discovery of pyrazolopyrimidine derivatives as novel inhibitors of ataxia telangiectasia and rad3 related protein (ATR). Bioorg Med Chem Lett 2017; 27:750-754. [DOI: 10.1016/j.bmcl.2017.01.045] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 01/13/2017] [Indexed: 12/20/2022]
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Jadhavar PS, Ramachandran SA, Riquelme E, Gupta A, Quinn KP, Shivakumar D, Ray S, Zende D, Nayak AK, Miglani SK, Sathe BD, Raja M, Farias O, Alfaro I, Belmar S, Guerrero J, Bernales S, Chakravarty S, Hung DT, Lindquist JN, Rai R. Targeting prostate cancer with compounds possessing dual activity as androgen receptor antagonists and HDAC6 inhibitors. Bioorg Med Chem Lett 2016; 26:5222-5228. [PMID: 27717544 DOI: 10.1016/j.bmcl.2016.09.058] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Revised: 09/22/2016] [Accepted: 09/23/2016] [Indexed: 01/19/2023]
Abstract
While enzalutamide and abiraterone are approved for treatment of metastatic castration-resistant prostate cancer (mCRPC), approximately 20-40% of patients have no response to these agents. It has been stipulated that the lack of response and the development of secondary resistance to these drugs may be due to the presence of AR splice variants. HDAC6 has a role in regulating the androgen receptor (AR) by modulating heat shock protein 90 (Hsp90) acetylation, which controls the nuclear localization and activation of the AR in androgen-dependent and independent scenarios. With dual-acting AR-HDAC6 inhibitors it should be possible to target patients who don't respond to enzalutamide. Herein, we describe the design, synthesis and biological evaluation of dual-acting compounds which target AR and are also specific towards HDAC6. Our efforts led to compound 10 which was found to have potent dual activity (HDAC6 IC50=0.0356μM and AR binding IC50=<0.03μM). Compound 10 was further evaluated for antagonist and other cell-based activities, in vitro stability and pharmacokinetics.
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Affiliation(s)
- Pradeep S Jadhavar
- Integral BioSciences Pvt. Ltd, C-64, Hosiery Complex Phase II Extension, Noida, Uttar Pradesh 201306, India
| | - Sreekanth A Ramachandran
- Integral BioSciences Pvt. Ltd, C-64, Hosiery Complex Phase II Extension, Noida, Uttar Pradesh 201306, India
| | - Eduardo Riquelme
- Fundación Ciencia y Vida, Avenida Zañartu 1482, Ñuñoa, Santiago 7780272, Chile
| | - Ashu Gupta
- Integral BioSciences Pvt. Ltd, C-64, Hosiery Complex Phase II Extension, Noida, Uttar Pradesh 201306, India
| | - Kevin P Quinn
- Medivation, 525 Market Street, 36th Floor, San Francisco, CA 94105, USA
| | | | | | - Dnyaneshwar Zende
- Integral BioSciences Pvt. Ltd, C-64, Hosiery Complex Phase II Extension, Noida, Uttar Pradesh 201306, India
| | - Anjan K Nayak
- Integral BioSciences Pvt. Ltd, C-64, Hosiery Complex Phase II Extension, Noida, Uttar Pradesh 201306, India
| | - Sandeep K Miglani
- Integral BioSciences Pvt. Ltd, C-64, Hosiery Complex Phase II Extension, Noida, Uttar Pradesh 201306, India
| | - Balaji D Sathe
- Integral BioSciences Pvt. Ltd, C-64, Hosiery Complex Phase II Extension, Noida, Uttar Pradesh 201306, India
| | - Mohd Raja
- Integral BioSciences Pvt. Ltd, C-64, Hosiery Complex Phase II Extension, Noida, Uttar Pradesh 201306, India
| | - Olivia Farias
- Fundación Ciencia y Vida, Avenida Zañartu 1482, Ñuñoa, Santiago 7780272, Chile
| | - Ivan Alfaro
- Fundación Ciencia y Vida, Avenida Zañartu 1482, Ñuñoa, Santiago 7780272, Chile
| | - Sebastián Belmar
- Fundación Ciencia y Vida, Avenida Zañartu 1482, Ñuñoa, Santiago 7780272, Chile
| | - Javier Guerrero
- Fundación Ciencia y Vida, Avenida Zañartu 1482, Ñuñoa, Santiago 7780272, Chile
| | | | | | - David T Hung
- Medivation, 525 Market Street, 36th Floor, San Francisco, CA 94105, USA
| | | | - Roopa Rai
- Medivation, 525 Market Street, 36th Floor, San Francisco, CA 94105, USA.
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Acevedo LM, Lindquist JN, Walsh BM, Sia P, Cimadamore F, Chen C, Denzel M, Pernia CD, Ranscht B, Terskikh A, Snyder EY, Cheresh DA. hESC Differentiation toward an Autonomic Neuronal Cell Fate Depends on Distinct Cues from the Co-Patterning Vasculature. Stem Cell Reports 2015; 4:1075-88. [PMID: 26004631 PMCID: PMC4471822 DOI: 10.1016/j.stemcr.2015.04.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 04/22/2015] [Accepted: 04/25/2015] [Indexed: 11/23/2022] Open
Abstract
To gain insight into the cellular and molecular cues that promote neurovascular co-patterning at the earliest stages of human embryogenesis, we developed a human embryonic stem cell model to mimic the developing epiblast. Contact of ectoderm-derived neural cells with mesoderm-derived vasculature is initiated via the neural crest (NC), not the neural tube (NT). Neurovascular co-patterning then ensues with specification of NC toward an autonomic fate requiring vascular endothelial cell (EC)-secreted nitric oxide (NO) and direct contact with vascular smooth muscle cells (VSMCs) via T-cadherin-mediated homotypic interactions. Once a neurovascular template has been established, NT-derived central neurons then align themselves with the vasculature. Our findings reveal that, in early human development, the autonomic nervous system forms in response to distinct molecular cues from VSMCs and ECs, providing a model for how other developing lineages might coordinate their co-patterning. Neural crest (NC) cells drive neurovascular co-patterning, as modeled by hESC Autonomic differentiation of NC cells depends on contact with perivascular cells This requires endothelial-derived NO and T-cadherin-mediated interaction with VSMCs
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Affiliation(s)
- Lisette M Acevedo
- Moores Cancer Center, University of California, San Diego, La Jolla, CA, 92093, USA; Sanford Burnham Medical Research Institute, La Jolla, CA 92037, USA; Department of Pathology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Jeffrey N Lindquist
- Moores Cancer Center, University of California, San Diego, La Jolla, CA, 92093, USA; Sanford Burnham Medical Research Institute, La Jolla, CA 92037, USA
| | - Breda M Walsh
- Moores Cancer Center, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Peik Sia
- Moores Cancer Center, University of California, San Diego, La Jolla, CA, 92093, USA
| | | | - Connie Chen
- Sanford Burnham Medical Research Institute, La Jolla, CA 92037, USA
| | - Martin Denzel
- Sanford Burnham Medical Research Institute, La Jolla, CA 92037, USA
| | - Cameron D Pernia
- Sanford Burnham Medical Research Institute, La Jolla, CA 92037, USA; Sanford Consortium for Regenerative Medicine, La Jolla, CA 92037, USA
| | - Barbara Ranscht
- Sanford Burnham Medical Research Institute, La Jolla, CA 92037, USA
| | - Alexey Terskikh
- Sanford Burnham Medical Research Institute, La Jolla, CA 92037, USA
| | - Evan Y Snyder
- Sanford Burnham Medical Research Institute, La Jolla, CA 92037, USA; Sanford Consortium for Regenerative Medicine, La Jolla, CA 92037, USA; Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA.
| | - David A Cheresh
- Moores Cancer Center, University of California, San Diego, La Jolla, CA, 92093, USA; Sanford Consortium for Regenerative Medicine, La Jolla, CA 92037, USA; Department of Pathology, University of California, San Diego, La Jolla, CA 92093, USA.
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Abstract
The formation of the multicellular vascular system is critical to the growth, development, and viability of an organism, and many embryonic lethal mouse knockouts are due to vascular defects. Unfortunately, the complex nature, and many cell types involved in vasculogenesis and angiogenesis has stymied in vitro models of vascular formation. This unit describes a system that allows human embryonic stem cells to differentiate and spontaneously form vascular networks via both vasculogenesis and angiogenesis in the context of the three germ layers.
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Lindquist JN, Snyder EY, Cheresh DA. Vascular Dependence of Neuronal Fate Determination. FASEB J 2008. [DOI: 10.1096/fasebj.22.2_supplement.608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Evan Y Snyder
- Stem Cells and Neuroscience ResearchThe Burnham Institute for Medical ResearchLa JollaCA
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Abstract
In the developing myocardium, vascular endothelial growth factor (VEGF)-dependent neovascularization occurs by division of existing vessels, a process that persists for several weeks following birth. During this remodeling phase, mRNA expression of beta3 integrin in the heart decreases significantly as vessel maturation progresses. However, in male mice lacking beta3, coronary capillaries fail to mature and continue to exhibit irregular endothelial thickness, endothelial protrusions into the lumen, and expanded cytoplasmic vacuoles. Surprisingly, this phenotype was not seen in female beta3-null mice. Enhanced VEGF signaling contributes to the beta3-null phenotype, because these vessels can be normalized by inhibitors of VEGF or Flk-1. Moreover, intravenous injection of VEGF induces a similar angiogenic phenotype in hearts of adult wild-type mice. These findings show a clear vascular phenotype in the hearts of mice lacking beta3 and suggest this integrin plays a critical role in coronary vascular development and the vascular response to VEGF.
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Affiliation(s)
- Sara M Weis
- Moores UCSD Cancer Center, University of California, San Diego, CA 92093-0803, USA
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Pettit SC, Lindquist JN, Kaplan AH, Swanstrom R. Processing sites in the human immunodeficiency virus type 1 (HIV-1) Gag-Pro-Pol precursor are cleaved by the viral protease at different rates. Retrovirology 2005; 2:66. [PMID: 16262906 PMCID: PMC1291402 DOI: 10.1186/1742-4690-2-66] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Accepted: 11/01/2005] [Indexed: 11/18/2022] Open
Abstract
We have examined the kinetics of processing of the HIV-1 Gag-Pro-Pol precursor in an in vitro assay with mature protease added in trans. The processing sites were cleaved at different rates to produce distinct intermediates. The initial cleavage occurred at the p2/NC site. Intermediate cleavages occurred at similar rates at the MA/CA and RT/IN sites, and to a lesser extent at sites upstream of RT. Late cleavages occurred at the sites flanking the protease (PR) domain, suggesting sequestering of these sites. We observed paired intermediates indicative of half- cleavage of RT/RH site, suggesting that the RT domain in Gag-Pro-Pol was in a dimeric form under these assay conditions. These results clarify our understanding of the processing kinetics of the Gag-Pro-Pol precursor and suggest regulated cleavage. Our results further suggest that early dimerization of the PR and RT domains may serve as a regulatory element to influence the kinetics of processing within the Pol domain.
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Affiliation(s)
- Steve C Pettit
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- The UNC Center for AIDS Research, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- 3805-103 Chimney Ridge Pl., Durham, NC, 27713, USA
| | - Jeffrey N Lindquist
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Pathology, Moores UCSD Cancer Center, 3855 Health Sciences Dr. #0803, La Jolla, CA 92093-0803, USA
| | - Andrew H Kaplan
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Ronald Swanstrom
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- The UNC Center for AIDS Research, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- CB7295, Rm 22-006 Lineberger Bldg, UNC Center For AIDS Research, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7295, USA
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Lindquist JN, Parsons CJ, Stefanovic B, Brenner DA. Regulation of alpha1(I) collagen messenger RNA decay by interactions with alphaCP at the 3'-untranslated region. J Biol Chem 2004; 279:23822-9. [PMID: 14973140 DOI: 10.1074/jbc.m314060200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Liver fibrosis is characterized by an increased deposition of extracellular matrix proteins, including collagen type I, by activated hepatic stellate cells (HSCs). Previous studies have shown that this increase is mediated primarily by a post-transcriptional mechanism. In particular, the RNA-binding protein alphaCP binds to the alpha1(I) collagen 3'-untranslated region (UTR) and stabilizes this RNA in activated, but not quiescent, HSCs. This study examines the role of alphaCP in the decay of transcripts containing the collagen 3'-UTR in extracts obtained from NIH fibroblasts and quiescent and activated HSCs. Using an in vitro decay system, alphaCP binding activity was competed out with the addition of wild type oligonucleotides, but not with mutant oligonucleotides. Competition of alphaCP binding activity increased the rate of decay of wild type transcripts containing the alphaCP 3'-UTR binding site, but not of transcripts containing a mutated binding site. Quiescent HSC extracts contain no alphaCP binding activity and have no difference in the rate of decay of transcripts with wild type and mutant binding sites for alphaCP. The addition of recombinant alphaCP was sufficient to increase the half-life of the wild type transcript, whereas that of the mutant transcript was minimally changed. In vitro decay assays performed with activated HSC extracts that contain alphaCP binding activity demonstrate a markedly reduced decay rate of wild type compared with mutant transcripts. In vivo small interfering RNA experiments targeting alphaCP showed a reduction of the binding activity of alphaCP and a concomitant reduction in intracellular levels of alpha1(I) collagen messenger RNA. In conclusion, this study demonstrates the direct role of alphaCP in the stabilization of alpha1(I) collagen messenger RNA by blocking RNA degradation in activated HSCs.
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Affiliation(s)
- Jeffrey N Lindquist
- Biochemistry and Biophysics and Medicine, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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Abstract
BACKGROUND & AIMS The mechanisms by which hepatitis C virus (HCV) induces liver fibrosis are unknown. Hepatocytes secrete HCV proteins, which may interact with hepatic stellate cells (HSCs). Our aims were to investigate whether HCV proteins induce fibrogenic effects on HSCs. METHODS & RESULTS Human-activated HSCs expressed messenger RNA (mRNA) for the putative HCV receptors CD81, LDL receptor, and C1q receptor as assessed by RT-PCR. Incubation of activated but not quiescent human HSCs with recombinant core and NS3 protein increased intracellular calcium concentration and reactive oxygen species production, as well as stimulated intracellular signaling pathways. Adenoviruses encoding core and nonstructural proteins (NS3-NS5) were used to express HCV proteins in HSCs. Expression of core protein increased cell proliferation in a Ras/ERK and PI3K/AKT dependent manner. In contrast, NS3-NS5 protein expression preferentially induced proinflammatory actions, such as increased chemokine secretion and expression of intercellular cell adhesion molecule type 1 (ICAM-1) through the NF-kappa B and c-Jun N-terminal kinase pathways. These effects were attenuated by antioxidants. Infection of freshly isolated rat HSCs with adenovirus-encoding core protein resulted in accelerated cell activation, as assessed by alpha-smooth muscle actin expression. Moreover, adenovirus-encoding core and NS3-NS5 proteins increased the secretion of bioactive TGF beta 1 and the expression of procollagen alpha1(I) in early cultured rat HSCs, as assessed by ELISA and RNase protection assay, respectively. CONCLUSIONS HCV core and nonstructural proteins regulate distinct biologic functions in HSCs. A direct interaction between HCV proteins and HSCs may contribute to HCV-induced liver fibrosis.
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Affiliation(s)
- Ramó Bataller
- Department of Medicine and Biochemistry & Biophysics, University of North Carolina at Chapel Hill 27599-7038, USA.
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Lindquist JN, Kauschke SG, Stefanovic B, Burchardt ER, Brenner DA. Characterization of the interaction between alphaCP(2) and the 3'-untranslated region of collagen alpha1(I) mRNA. Nucleic Acids Res 2000; 28:4306-16. [PMID: 11058131 PMCID: PMC113122 DOI: 10.1093/nar/28.21.4306] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Activated hepatic stellate cells produce increased type I collagen in hepatic fibrosis. The increase in type I collagen protein results from an increase in mRNA levels that is mainly mediated by increased mRNA stability. Protein-RNA interactions in the 3'-UTR of the collagen alpha1(I) mRNA correlate with stabilization of the mRNA during hepatic stellate cell activation. A component of the binding complex is alphaCP(2). Recombinant alphaCP(2) is sufficient for binding to the 3'-UTR of collagen alpha1(I). To characterize the binding affinity of and specificity for alphaCP(2), we performed electrophoretic mobility shift assays using the poly(C)-rich sequence in the 3'-UTR of collagen alpha1(I) as probe. The binding affinity of alphaCP(2) for the 3'-UTR sequence is approximately 2 nM in vitro and the wild-type 3' sequence binds with high specificity. Furthermore, we demonstrate a system for detecting protein-nucleotide interactions that is suitable for high throughput assays using molecular beacons. Molecular beacons, developed for DNA-DNA hybridization, are oligonucleotides with a fluorophore and quencher brought together by a hairpin sequence. Fluorescence increases when the hairpin is disrupted by binding to an antisense sequence or interaction with a protein. Molecular beacons displayed a similar high affinity for binding to recombinant alphaCP(2) to the wild-type 3' sequence, although the kinetics of binding were slower.
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Affiliation(s)
- J N Lindquist
- Department of Medicine and Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599-7038, USA
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Abstract
There are several independent metabolic steps that determine the level of a protein in eukaryotic cells. The steady-state level of the mRNA encoding the specific protein is determined by rate of transcription, percentage of transcripts that are ultimately processed and transported to the cytoplasm, and half-life of the mRNA in cytoplasm. The amount of protein that accumulates from a particular transcript is influenced not only by the amount of mRNA present in the cytoplasm but also by the rate of translation of the mRNA and stability of the protein product. There is compelling evidence that the steady-state level of many proteins is regulated at multiple steps, and when there is a large change in the amount of either mRNA or protein it is likely that multiple steps in the metabolism of the mRNA and protein have been altered. In the case of type I collagen production in the fibrotic liver, recent work has shown that there is regulation of multiple steps resulting in an approximately 70-fold increase in collagen production by the hepatic stellate cells. In addition to the well-documented relatively small effect on transcription, there are effects on processing/transport of the mRNA, translation of the mRNA, and stability of the mRNA. Large changes of protein levels are produced by altering the rates or efficiency of multiple steps. The molecular details of some of these posttranscriptional regulatory events are currently being elucidated. Here we review the various potential steps for regulation in the synthesis of a protein and discuss how the synthesis of type I collagen may be regulated in the fibrotic liver.
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Affiliation(s)
- J N Lindquist
- Department of Biochemistry and Biophysics and Medicine, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina 27514, USA.
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Lindquist JN, Stefanovic B, Brenner DA. Regulation of collagen alpha1(I) expression in hepatic stellate cells. J Gastroenterol 2000; 35 Suppl 12:80-3. [PMID: 10779224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The regulation of collagen alpha1(I) expression in hepatic stellate cells (HSCs) occurs in a complex fashion that is just beginning to be determined. The presence of regulatory sequences in both the 5' and 3' regions of the mRNA appear to be critical to its regulation in HSCs and are involved in the increased expression of collagen in activated HSCs. The 3' UTR contains a C-rich site that binds alphaCP, a known RNA-binding protein that is responsible for the increased stability of the mRNA in activated HSCs. Given that alphaCP is present in both activated and quiescent HSCs, there must be a mechanism for modifying alpha(CP to bind to the RNA in activated but not quiescent HSCs. The 5' region contains an evolutionary conserved stem-loop region that encompasses the translation initiation codon. This stem-loop can bind protein(s) in activated HSCs in an RNA cap-dependent manner. Such binding, together with the binding of alphaCP to the 3' UTR, can facilitate translation of collagen alpha1(I) mRNA, resulting in increased mRNA steady-state levels and collagen synthesis. A role of alphaCP in activating translation initiation has also been demonstrated. These two mechanisms work together to upregulate collagen alpha1(I) production in activated but not quiescent HSCs.
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Affiliation(s)
- J N Lindquist
- Department of Medicine and Biochemistry and Biophysics, University of North Carolina at Chapel Hill, 27599, USA
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Abstract
Hepatic stellate cells are the major source of extracellular matrix proteins in hepatic fibrosis, including Type I collagen. In response to liver injury, the hepatic stellate cells change from a quiescent to an activated phenotype. This activation process includes a phenotypic change to a myofibroblast-like cell, increased proliferation rate, loss of retinoid stores, increased production of extracellular matrix proteins, chemokines, and cytokines, and contractility. Ongoing studies are characterizing the genes that are differentially expressed in the quiescent and activated hepatic stellate cells. We have also investigated the regulation of Type I collagen expression, the cleavage of collagen propeptides, and the formation of collagen cross-links. Understanding these pathways may provide new insights into the molecular pathogenesis of hepatic fibrosis.
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Affiliation(s)
- D A Brenner
- University of North Carolina at Chapel Hill, School of Medicine, 27599, USA
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