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Antoni J. Duleba - One of the best experts on this subject based on the ideXlab platform.
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simvastatin reduces steroidogenesis by inhibiting cyp17a1 gene expression in rat ovarian theca interstitial cells
Biology of Reproduction, 2012Co-Authors: Israel Ortega, Donna H. Wong, Amanda B. Cress, Jesus A. Villanueva, Anna Sokalska, Benjamin C Moeller, Scott D Stanley, Antoni J. DulebaAbstract:Polycystic ovary syndrome (PCOS) is characterized by ovarian enlargement, theca-interstitial hyperplasia, and increased androgen production by theca cells. Previously, our group has demonstrated that statins (competitive inhibitors of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, a rate-limiting step of the mevalonate pathway) reduce proliferation of theca-interstitial cells in vitro and decrease serum androgen levels in women with PCOS. The present study evaluated the effect of simvastatin on rat ovarian theca-interstitial cell steroidogenesis. Because actions of statins may be due to reduced cholesterol availability and/or Isoprenylation of proteins, the present study also investigated whether steroidogenesis was affected by cell- and mitochondrion-permeable 22-hydroxycholesterol, Isoprenylation substrates (farnesyl-pyrophosphate [FPP] and geranylgeranyl-pyrophosphate [GGPP]), as well as selective inhibitors of farnesyltransferase (FTI) and geranylgeranyltransferase (GGTI). Theca-interstitial cells were cultured for 12, 24, and 48 h with or without simvastatin, GGPP, FPP, FTI, GGTI, and/or 22-hydroxycholesterol. Simvastatin decreased androgen levels in a time- and concentration-dependent fashion. This inhibitory effect correlated with a decrease in mRNA levels of Cyp17a1, the gene encoding the key enzyme regulating androgen biosynthesis. After 48 h, GGPP alone and FPP alone had no effect on Cyp17a1 mRNA expression; however, the inhibitory action of simvastatin was partly abrogated by both GGPP and FPP. The present findings indicate that statin-induced reduction of androgen levels is likely due, at least in part, to the inhibition of Isoprenylation, resulting in decreased expression of CYP17A1.
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Role of Isoprenylation in Simvastatin-Induced Inhibition of Ovarian Theca-Interstitial Growth in the Rat
Biology of Reproduction, 2009Co-Authors: Izabela J. Rzepczynska, P. Piotrowski, Donna H. Wong, Amanda B. Cress, Jesus A. Villanueva, Antoni J. DulebaAbstract:Statins are competitive inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, a rate-limiting step of the mevalonate pathway. The pleiotropic effects of statins may be due to inhibition of cholesterol synthesis, as well as decreased availability of several biologically important intermediate components of the mevalonate pathway, including two substrates for Isoprenylation (farnesyl pyrophosphate [FPP] and geranylgeranyl pyrophosphate [GGPP]). Recently, we demonstrated statin-induced inhibition of ovarian theca-interstitial cell proliferation in vitro, as well as reduction of testosterone levels in women with polycystic ovary syndrome (PCOS). This study evaluates the relative contribution of inhibition of Isoprenylation and/or cholesterol availability to the modulation of theca-interstitial proliferation. Rat theca-interstitial cells were cultured in chemically defined media with or without simvastatin, FPP, GGPP, squalene, and/or two membrane-permeable forms of cholesterol (25-hydroxycholesterol and 22-hydroxycholesterol). Simvastatin inhibited DNA synthesis and the count of viable cells. The effects of simvastatin were partly abrogated by FPP and GGPP but not by squalene or cholesterol. Inhibition of farnesyl transferase and geranylgeranyl transferase reduced cell proliferation. The present findings indicate that simvastatin inhibits proliferation of theca-interstitial cells, at least in part, by reduction of Isoprenylation. These observations provide likely mechanisms explaining clinically observed improvement of ovarian hyperandrogenism in women with PCOS.
Dring N. Crowell - One of the best experts on this subject based on the ideXlab platform.
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A role for plastids in plant protein Isoprenylation.
Plant Signaling & Behavior, 2009Co-Authors: Dring N. Crowell, Andréa Hemmerlin, Esther Gerber, Michael Hartmann, Dimitri Heintz, Michel Rohmer, Thomas J. BachAbstract:Protein Isoprenylation refers to the attachment of a C15 farnesyl or C20 geranylgeranyl moiety to a carboxyl terminal cysteine residue. Because protein isoprenyltransferases are cytosolic enzymes, it has long been assumed that the isoprenyl diphosphates used for protein Isoprenylation are synthesized in the cytosol. However, in the present work, we established that the plastidial 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway is predominantly responsible for providing the geranylgeranyl diphosphate for protein geranylgeranylation in tobacco BY-2 cells.
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Protein Isoprenylation: the fat of the matter.
Trends in Plant Science, 2009Co-Authors: Dring N. Crowell, David HuizingaAbstract:Protein Isoprenylation refers to the covalent attachment of a 15-carbon farnesyl or 20-carbon geranylgeranyl moiety to a cysteine residue at or near the carboxyl terminus. This post-translational lipid modification, which mediates protein–membrane and protein–protein interactions, is necessary for normal control of abscisic acid and auxin signaling, meristem development, and other fundamental processes. Recent studies have also revealed roles for protein Isoprenylation in cytokinin biosynthesis and innate immunity. Most isoprenylated proteins are further modified by carboxyl terminal proteolysis and methylation and, collectively, these modifications are necessary for the targeting and function of isoprenylated proteins.
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Functional implications of protein Isoprenylation in plants.
Progress in Lipid Research, 2000Co-Authors: Dring N. CrowellAbstract:Plant protein Isoprenylation has received considerable attention in the past decade. Since the initial discovery of isoprenylated plant proteins and their respective protein isoprenyltransferases, several research groups have endeavored to understand the physiological significance of this process in plants. Various experimental approaches, including inhibitor studies, systematic methods of protein identification, and mutant analyses in Arabidopsis thaliana, have enabled these groups to elucidate important roles for isoprenylated proteins in cell cycle control, signal transduction, cytoskeletal organization, and intracellular vesicle transport. This article reviews recent progress in understanding the functional implications of protein Isoprenylation in plants.
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Changes in Protein Isoprenylation during the Growth of Suspension-Cultured Tobacco Cells
Plant Physiology, 1995Co-Authors: T. A. Morehead, Dring N. Crowell, Brenda J. Biermann, Stephen K. RandallAbstract:Isoprenylation facilitates the association of proteins with intracellular membranes and/or other proteins. In mammalian and yeast cells, isoprenylated proteins are involved in signal transduction, cell division, organization of the cytoskeleton, and vesicular transport. Recently, protein Isoprenylation has been demonstrated in higher plants, but little is currently known about the functions of isoprenylated plant proteins. We report that inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (lovastatin) or prenyl:protein transferases (perilly alcohol) severely impair the growth of cultured tobacco (Nicotiana tabacum) cells but only when added within the first 2 d following transfer to fresh medium, before any increase in culture volume is detectable. This “window” of sensitivity to inhibitors of protein Isoprenylation correlates temporally with an increase in [14C]mevalonate incorporation into tobacco cell proteins in vitro. We have also observed a marked increase in farnesyl:protein transferase activity at this early time in the growth of tobacco cultures. In contrast, type I geranylgeranyl:protein transferase activity does not change significantly during culture growth. Although these events coincide with the replication of DNA, I [mu]M lovastatin-treated cells are capable of DNA synthesis, suggesting that lovastatin-induced cell growth arrest is not due to inhibition of DNA replication. Together, these data support the hypothesis that protein Isoprenylation is necessary for the early stages of growth of tobacco cultures.
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Protein Isoprenylation in suspension-cultured tobacco cells.
The Plant Cell, 1993Co-Authors: Stephen K. Randall, Mark S. Marshall, Dring N. CrowellAbstract:Many mammalian and yeast proteins, including small ras-like GTP binding proteins, heterotrimeric G protein gamma subunits, and nuclear lamins, have been shown to be covalently linked to isoprenoid derivatives of mevalonic acid. Isoprenylation of these proteins is required for their assembly into membranes and, hence, for their biological activity. In this report, it is shown that cultured tobacco cells, when pretreated with an inhibitor of endogenous mevalonic acid synthesis (lovastatin), incorporate radioactivity from 14C-mevalonic acid into proteins. Most of these proteins are membrane associated, and many are similar in mass to mammalian ras-like GTP binding proteins and nuclear lamins. Furthermore, it is shown that tobacco cell extracts catalyze the transfer of radioactivity from 3H-farnesyl pyrophosphate and 3H-geranylgeranyl pyrophosphate to protein substrates in vitro. These studies indicate the presence of at least two distinct prenyl:protein transferases in tobacco extracts: one that utilizes farnesyl pyrophosphate and preferentially modifies a substrate protein with a CAIM carboxy terminus (farnesyl:protein transferase) and one that utilizes geranylgeranyl pyrophosphate and preferentially modifies a substrate protein with a CAIL carboxy terminus (geranylgeranyl:protein transferase type I). This work provides a basis for future work on the role of protein Isoprenylation in plant cell growth, signal transduction, and membrane biogenesis.
B. Therese Kinsella - One of the best experts on this subject based on the ideXlab platform.
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The effect of the farnesyl protein transferase inhibitor SCH66336 on Isoprenylation and signalling by the prostacyclin receptor.
The Biochemical journal, 2005Co-Authors: Simon J P Meara, B. Therese KinsellaAbstract:Like Ras, farnesylation of the IP (prostacyclin receptor) is required for its efficient intracellular signalling, and hence the IP represents a potential target for inhibition by FTIs [FTase (farnesyl protein transferase) inhibitors]. Herein, the effect of SCH66336 on the Isoprenylation and function of the human and mouse IPs overexpressed in human embryonic kidney 293 cells, and by the IP endogenously expressed in human erythroleukaemia cells, was investigated. SCH66336 yielded concentration-dependent decreases in IP-mediated cAMP generation (IC50 0.27-0.62 nM), [Ca2+]i mobilization (IC50 26.6-48.3 nM) and IP internalization, but had no effect on signalling by the non-isoprenylated beta2 adrenergic receptor or b isoform of the TP (prostanoid thromboxane A2 receptor). Additionally, SCH66336 impaired IP-mediated crossdesensitization of TPa signalling (IC50 56.1 nM) and reduced farnesylation of the molecular chaperone protein HDJ-2 (IC50 3.1 nM). To establish whether farnesylation of the IP is inhibited and/or whether its 'CaaX motif' might undergo alternative geranylgeranylation in the presence of SCH66336, a series of chimaeric Ha (Harvey)-Ras fusions were generated by replacing its CaaX motif (-CVLS) with that of the IP (-CSLC) or, as controls, of Ki (Kirsten)-Ras 4B (-CVIM) or Rac 1 (-CVLL). Whereas SCH66336 had no effect on Ha-RasCVLL Isoprenylation in vitro or in whole cells, it supported alternative geranylgeranylation of Ha-RasCVIM, but completely impaired Isoprenylation of both Ha-RasCVLS and Ha-RasCSLC. These data confirm that the -CSLC motif of the IP is a direct target for inhibition by the FTI SCH66336, and in the presence of strong FTase inhibition, the IP does not undergo compensatory geranylgeranylation
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The effect of the farnesyl protein transferase inhibitor SCH66336 on Isoprenylation and signalling by the prostacyclin receptor
Biochemical Journal, 2005Co-Authors: Simon J P Meara, B. Therese KinsellaAbstract:Like Ras, farnesylation of the IP (prostacyclin receptor) is required for its efficient intracellular signalling, and hence the IP represents a potential target for inhibition by FTIs [FTase (farnesyl protein transferase) inhibitors]. Herein, the effect of {"type":"entrez-protein","attrs":{"text":"SCH66336","term_id":"1052737610","term_text":"SCH66336"}}SCH66336 on the Isoprenylation and function of the human and mouse IPs overexpressed in human embryonic kidney 293 cells, and by the IP endogenously expressed in human erythroleukaemia cells, was investigated. {"type":"entrez-protein","attrs":{"text":"SCH66336","term_id":"1052737610","term_text":"SCH66336"}}SCH66336 yielded concentration-dependent decreases in IP-mediated cAMP generation (IC50 0.27–0.62 nM), [Ca2+]i mobilization (IC50 26.6–48.3 nM) and IP internalization, but had no effect on signalling by the non-isoprenylated β2 adrenergic receptor or β isoform of the TP (prostanoid thromboxane A2 receptor). Additionally, {"type":"entrez-protein","attrs":{"text":"SCH66336","term_id":"1052737610","term_text":"SCH66336"}}SCH66336 impaired IP-mediated crossdesensitization of TPα signalling (IC50 56.1 nM) and reduced farnesylation of the molecular chaperone protein HDJ-2 (IC50 3.1 nM). To establish whether farnesylation of the IP is inhibited and/or whether its ‘CaaX motif’ might undergo alternative geranylgeranylation in the presence of {"type":"entrez-protein","attrs":{"text":"SCH66336","term_id":"1052737610","term_text":"SCH66336"}}SCH66336, a series of chimaeric Ha (Harvey)-Ras fusions were generated by replacing its CaaX motif (-CVLS) with that of the IP (-CSLC) or, as controls, of Ki (Kirsten)-Ras 4B (-CVIM) or Rac 1 (-CVLL). Whereas {"type":"entrez-protein","attrs":{"text":"SCH66336","term_id":"1052737610","term_text":"SCH66336"}}SCH66336 had no effect on Ha-RasCVLL Isoprenylation in vitro or in whole cells, it supported alternative geranylgeranylation of Ha-RasCVIM, but completely impaired Isoprenylation of both Ha-RasCVLS and Ha-RasCSLC. These data confirm that the -CSLC motif of the IP is a direct target for inhibition by the FTI {"type":"entrez-protein","attrs":{"text":"SCH66336","term_id":"1052737610","term_text":"SCH66336"}}SCH66336, and in the presence of strong FTase inhibition, the IP does not undergo compensatory geranylgeranylation.
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Investigation of the effect of the farnesyl protein transferase inhibitor R115777 on Isoprenylation and intracellular signalling by the prostacyclin receptor.
British Journal of Pharmacology, 2004Co-Authors: Simon J P Meara, B. Therese KinsellaAbstract:The human (h) and mouse (m) prostacyclin receptors (IPs) undergo Isoprenylation through attachment of a C-15 farnesyl moiety within their conserved carboxyl terminal -CSLC sequences. Herein, the effects of a novel farnesyl transferase inhibitor R115777 on signalling by the hIP and mIP, overexpressed in human embryonic kidney 293 cells, and by the hIP endogenously expressed in human erythroleukaemia cells were investigated. R115777 significantly impaired IP-mediated cyclic AMP generation (IC50 0.37–0.60 nM) and intracellular calcium ([Ca2+]i) mobilization (IC50 37–65 nM), but had no effect on signalling by the control nonisoprenylated β2 adrenergic receptor or the α or β isoforms of the human thromboxane A2 receptor (TP). Additionally, R115777 significantly reduced IP-mediated cross-desensitization of signalling by the TPα, but not by the TPβ, isoform of the human TP and impaired the farnesylation-dependent processing of the chaperone HDJ-2 protein (IC50 4.5 nM). Furthermore, R115777 fully impaired Isoprenylation of both the Ha-RasWT and Ha-RasCSLCin vitro and in whole cells confirming that, unlike N-Ras and Ki-Ras, the -CSLC motif associated with the IP cannot support alternative geranylgeranylation in the presence of R115777 and does not act as a substrate for geranylgeranyl transferase 1 in vitro or in whole cells. In conclusion, these data confirm that R115777 potently impairs IP Isoprenylation and signalling, and suggest that clinically it may not only target Ras proteins but may also disrupt IP Isoprenylation, events which could impact on physiologic processes in which prostacyclin and its receptor are implicated. British Journal of Pharmacology (2004) 143, 318–330. doi:10.1038/sj.bjp.0705956
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Investigation of a functional requirement for Isoprenylation by the human prostacyclin receptor.
FEBS Journal, 2002Co-Authors: Sinead M. Miggin, Orlaith A. Lawler, B. Therese KinsellaAbstract:In the current study, we have established that the human (h) prostacyclin receptor (IP) is isoprenylated in whole cells. Through site directed mutagenesis and generation of the Isoprenylation defective hIPSSLC, it was established that while Isoprenylation of hIP does not influence ligand binding, it is obligatory for agonist activation of adenylyl cyclase and cAMP generation. Overexpression of GαS significantly augmented cAMP generation by the hIP but not by the hIPSSLC. Moreover, GαS co-immunoprecipitated with hIP following agonist activation but did not co-immunoprecipitate with hIPSSLC. Whereas hIP mediated concentration-dependent activation of phospholipase C (PLC); the extent of PLC activation by hIPSSLC was impaired compared to hIP. Co-expression of Gαq significantly augmentated intracellular calcium mobilization by the hIP but not by hIPSSLC. Moreover, whereas Gαq co-immunoprecipitated with hIP, it failed to co-immunoprecipitate with hIPSSLC. While both the hIP and hIPSSLC underwent agonist-induced internalization, the kinetics and extent of hIPSSLC internalization was impaired compared to hIP. Altering the CAAX motif of the hIP from a farnesyl (–CSLC) to a geranylgeranyl (–CSLL) isoprene acceptor, to generate hIPCSLL, did not affect ligand binding and yielded a receptor that exhibited identical signalling through both Gs- and Gq-coupled effectors to that of hIP. Thus, whereas Isoprenylation of hIP does not influence ligand binding, it is functionally imperative in regulating post-receptor events including agonist-activation of adenylyl cyclase, for efficient activation of PLC and for receptor internalization. Though the nature of the isoprenoid attached to hIP does not act as a major determinant, the presence of an isoprenoid group, for example farnesyl or geranylgeranyl, is required for functional receptor–G protein interaction and coupling and for efficient agonist- induced receptor internalization.
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the prostacyclin receptor is isoprenylated Isoprenylation is required for efficient receptor effector coupling
Journal of Biological Chemistry, 1999Co-Authors: J. S. Hayes, Marietherese Walsh, Orlaith A. Lawler, B. Therese KinsellaAbstract:Abstract The prostacyclin receptor (IP), a G protein-coupled receptor, mediates the actions of the prostanoid prostacyclin and its mimetics. IPs from a number of species each contain identically conserved putative Isoprenylation CAAXmotifs, each with the sequence CSLC. Metabolic labeling of human embryonic kidney (HEK) 293 cells stably overexpressing the hemagluttinin epitope-tagged IP in the presence of [3H]mevalonolactone established that the mouse IP is isoprenylated. Studies involving in vitro assays confirmed that recombinant forms of the human and mouse IP are modified by carbon 15 farnesyl isoprenoids. Disruption of Isoprenylation, by site-directed mutagenesis of Cys414 to Ser414, within the CAAX motif, abolished Isoprenylation of IPSSLC both in vitro and in transfected cells. Scatchard analysis of the wild type (IP) and mutant (IPSSLC) receptor confirmed that each receptor exhibited high and low affinity binding sites for [3H]iloprost, which were not influenced by receptor Isoprenylation. Whereas stable cell lines overexpressing IP generated significant agonist (iloprost and cicaprost)-mediated increases in cAMP relative to nontransfected cells, cAMP generation by IPSSLC cells was not significantly different from the control, nontransfected HEK 293 cells. Moreover, co-expression of the alpha (α) subunit of Gs generated significant augmentations in cAMP by IP but not by IPSSLCcells. Whereas IP also demonstrated significant, dose-dependent increases in [Ca2+]i in response to iloprost or cicaprost compared with the nontransfected HEK 293 cells, mobilization of [Ca2+]i by IPSSLC was significantly impaired. Co-transfection of cells with either Gαq or Gα11 resulted in significant augmentation of agonist-mediated [Ca2+]i mobilization by IP cells but not by IPSSLC cells or by the control, HEK 293 cells. In addition, inhibition of Isoprenylation by lovastatin treatment significantly reduced agonist-mediated cAMP generation by IP in comparison to the nonisoprenylated β2 adrenergic receptor or nontreated cells. Hence, Isoprenylation of IP does not influence ligand binding but is required for efficient coupling to the effectors adenylyl cyclase and phospholipase C.
Yan Huang - One of the best experts on this subject based on the ideXlab platform.
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Simvastatin suppresses LPS-induced MMP-1 expression in
2015Co-Authors: John J. S, Maria F. Lopes-virella, Yan HuangAbstract:U937 mononuclear cells by inhibiting protein Isoprenylation-mediated ERK activatio
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Simvastatin suppresses LPS-induced MMP-1 expression in U937 mononuclear cells by inhibiting protein Isoprenylation-mediated ERK activation.
Journal of Leukocyte Biology, 2008Co-Authors: Kamala P. Sundararaj, Maria F. Lopes-virella, Devadoss J. Samuvel, Alena Nareika, Elizabeth H. Slate, John J. Sanders, Yan HuangAbstract:Matrix metalloproteinase (MMP) plays a crucial role in periodontal disease and is up-regulated by oral Gram-negative, pathogen-derived LPS. In this study, we reported that simvastatin, a 3-hydroxyl-3-methylglutaryl-CoA reductase inhibitor, effectively inhibited LPS-stimulated MMP-1 as well as MMP-8 and MMP-9 expression by U937 mononuclear cells. Our studies showed that the geranylgeranyl transferase inhibitor inhibited LPS-stimulated MMP-1 expression, and addition of isoprenoid intermediate geranylgeranyl pyrophosphate (GGPP) reduced the inhibitory effect of simvastatin on LPS-stimulated MMP-1 expression. We also demonstrated that simvastatin inhibited the activation of Ras and Rac, and the inhibition was abolished by addition of GGPP. The above results indicate that protein Isoprenylation is involved in the regulation of MMP-1 expression by LPS and simvastatin. Moreover, we showed that simvastatin inhibited LPS-stimulated nuclear AP-1, but not NF-κB activity, and the inhibition was reversed by addition of GGPP. Simvastatin also inhibited LPS-stimulated ERK but not p38 MAPK and JNK. Finally, we showed that the inhibition of LPS-stimulated ERK activation by simvastatin was reversed by GGPP. Taken together, this study showed that simvastatin suppresses LPS-induced MMP-1 expression in U937 mononuclear cells by targeting protein Isoprenylation-mediated ERK activation.
Stephen K. Randall - One of the best experts on this subject based on the ideXlab platform.
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Changes in Protein Isoprenylation during the Growth of Suspension-Cultured Tobacco Cells
Plant Physiology, 1995Co-Authors: T. A. Morehead, Dring N. Crowell, Brenda J. Biermann, Stephen K. RandallAbstract:Isoprenylation facilitates the association of proteins with intracellular membranes and/or other proteins. In mammalian and yeast cells, isoprenylated proteins are involved in signal transduction, cell division, organization of the cytoskeleton, and vesicular transport. Recently, protein Isoprenylation has been demonstrated in higher plants, but little is currently known about the functions of isoprenylated plant proteins. We report that inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (lovastatin) or prenyl:protein transferases (perilly alcohol) severely impair the growth of cultured tobacco (Nicotiana tabacum) cells but only when added within the first 2 d following transfer to fresh medium, before any increase in culture volume is detectable. This “window” of sensitivity to inhibitors of protein Isoprenylation correlates temporally with an increase in [14C]mevalonate incorporation into tobacco cell proteins in vitro. We have also observed a marked increase in farnesyl:protein transferase activity at this early time in the growth of tobacco cultures. In contrast, type I geranylgeranyl:protein transferase activity does not change significantly during culture growth. Although these events coincide with the replication of DNA, I [mu]M lovastatin-treated cells are capable of DNA synthesis, suggesting that lovastatin-induced cell growth arrest is not due to inhibition of DNA replication. Together, these data support the hypothesis that protein Isoprenylation is necessary for the early stages of growth of tobacco cultures.
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Protein Isoprenylation in suspension-cultured tobacco cells.
The Plant Cell, 1993Co-Authors: Stephen K. Randall, Mark S. Marshall, Dring N. CrowellAbstract:Many mammalian and yeast proteins, including small ras-like GTP binding proteins, heterotrimeric G protein gamma subunits, and nuclear lamins, have been shown to be covalently linked to isoprenoid derivatives of mevalonic acid. Isoprenylation of these proteins is required for their assembly into membranes and, hence, for their biological activity. In this report, it is shown that cultured tobacco cells, when pretreated with an inhibitor of endogenous mevalonic acid synthesis (lovastatin), incorporate radioactivity from 14C-mevalonic acid into proteins. Most of these proteins are membrane associated, and many are similar in mass to mammalian ras-like GTP binding proteins and nuclear lamins. Furthermore, it is shown that tobacco cell extracts catalyze the transfer of radioactivity from 3H-farnesyl pyrophosphate and 3H-geranylgeranyl pyrophosphate to protein substrates in vitro. These studies indicate the presence of at least two distinct prenyl:protein transferases in tobacco extracts: one that utilizes farnesyl pyrophosphate and preferentially modifies a substrate protein with a CAIM carboxy terminus (farnesyl:protein transferase) and one that utilizes geranylgeranyl pyrophosphate and preferentially modifies a substrate protein with a CAIL carboxy terminus (geranylgeranyl:protein transferase type I). This work provides a basis for future work on the role of protein Isoprenylation in plant cell growth, signal transduction, and membrane biogenesis.
