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Papers by Abdelkader Marzouki

Research paper thumbnail of Heterogeneity of ribosomal autoantibodies from human, murine and canine connective tissue diseases

Immunology Letters, 1989

Antiribosomal auto-antibodies (anti-Rib.Ab) have been studied in connective tissue diseases (huma... more Antiribosomal auto-antibodies (anti-Rib.Ab) have been studied in connective tissue diseases (human, dog and mouse) by immunoblotting after one-dimensional (1D) or two-dimensional (2D) gel electrophoresis of rat ribosomes. Anti-Rib.Ab could be found in systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and other connective tissue diseases (progressive systemic sclerosis, PSS; Sjögren syndrome, SjS; mixed connective tissue disease, MCTD; and dermatomyositis, DM with the frequencies 41.7%, 54.6% and 33%, respectively. Immunoblotting after 1D gel electrophoresis showed the great heterogeneity of ribosomal proteins recognized by the anti-Rib.Ab. In the SLE, however, the most frequent antibodies stained bands of the 40S subunit: 30 kDa (34% of positive sera), 19.5 kDa (24.5%) and 43 kDa (17%). In RA, the 25-kDa band of the 60S subunit was the most common (54% of positive sera). In the other human connective tissue diseases, there was no particular predominance. In the MRL/1, anti-Rib.Ab were very frequent (92.6%). The 43-kDa band of the 40S subunit was found in 100% of positive sera. Seventeen out of nineteen dogs with SLE gave positive results on immunoblot, and all of them stained the 43-kDa band of the 40S subunit. 2D gel electrophoresis gave identification of Po, L7, L5, Sb, S19, S13 and L2 proteins in SLE, S3 and SjS, L35a and L37a in RA, and L7, S6 and/or L7a in MRL/1.

Research paper thumbnail of Effect of ADP-ribosylation and phosphorylation on the interaction of elongation factor 2 with guanylic nucleotides

Biochimie, 1991

Samples of unmodified EF-2, EF-2 ADP-ribosylated with diphtheria toxin and NAD, and/or phosphoryl... more Samples of unmodified EF-2, EF-2 ADP-ribosylated with diphtheria toxin and NAD, and/or phosphorylated using ATP and the Ca(2+)-calmodulin dependent kinase III partially purified, were irradiated at 254 nm with 32P-labeled GDP or GTP, and analyzed by one- and two-dimensional gel electrophoresis. By this method we showed that unmodified EF-2 formed a stable complex with GDP but not with GTP, whereas phosphorylated EF-2 and ADP-ribosylated + phosphorylated EF-2 formed stable complexes even in the absence of irradiation, with GTP but not GDP. ADP-ribosylated EF-2 did not form stable complexes with either GDP or GTP. Prior ADP-ribosylation of EF-2 increased its ability to the phosphorylated. These results show that the structures of the two domains containing diphtamide 715 and the phosphorylatable threonines (between Ala 51 and Arg 60) are interdependent; modifications of these residues induce different conformational changes of EF-2 which alter the interactions of the factor with guanylic nucleotides as well with ribosomes.

Research paper thumbnail of Change in the Magnetic Resonance Imaging Signal of the Mandibular Condyle Due to Bisphosphonate-Related Osteonecrosis of the Jaw

Journal of Hard Tissue Biology

Marx was the first to report osteonecrosis of the jaw due to administration of BPs in 2003. Bisph... more Marx was the first to report osteonecrosis of the jaw due to administration of BPs in 2003. Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is the result of an adverse drug reaction. Moreover, many studies worldwide have reported an association between a range of serious dental diseases and the use of bisphosphonates (BPs). Few studies, however, have evaluated BRONJ based on an abnormal signal detected by MRI in the bone marrow of the mandibular condyle. The aim of this study was to assess changes in the magnetic resonance imaging (MRI) signal from the mandibular condyle that could be due to BRONJ. In particular, we focused on the presence of an abnormal MRI signal emanating from mandibular condyle bone marrow. Twenty-eight patients (11 men, 17 women; 56 temporomandibular joints) with BRONJ were evaluated for jaw pain. The patients, whose mean age was 72.9 ± 9.4 years (range 48-88 years), underwent MRI examination of the jawbone at our hospital from August 2006 to December 2015 and were included in the study. Overall, 80.0% of the patients diagnosed with BRONJ exhibited an abnormal bone marrow signal in the mandibular condyle on the same side of the face that suffered jaw pain. This abnormal signal was present significantly more frequently on the side of the face with the jaw symptoms than on the side without symptoms. Patients with BRONJ displayed an abnormal MRI signal in the mandibular condyle on the side of the face with jaw symptoms, suggesting that MRI findings could be useful clinically for detecting BRONJ in the mandibular condyle.

Research paper thumbnail of Heterogeneity of native rat liver elongation factor 2

FEBS Letters, 1989

The high heterogeneity of native rat liver EF-2 prepared from either 105000 x g supernatant or mi... more The high heterogeneity of native rat liver EF-2 prepared from either 105000 x g supernatant or microsome high-salt extract was detected by two-dimensional equilibrium isoelectric focusing-SDS-polyacrylamide gel electrophoresis in the presence of 9.5 M urea. Five spots were always detected, all of Mr 95000, which were not artefactual for their amount varied when EF-2 was specifically ADP-ribosylatecl by diphtheria toxin in the presence of NAD +, and/or phosphorylated on a threonine residue by a Ca2+/calmodulin-dependent protein kinase (most likely Ca2+/calmodulin-dependent protein kinase III described by others [(1987) J. Biol. Chem. 262, 17299-17303; 0988) Nature 334, 170-173]). Results of ADPribosylation and/or phosphorylation experiments with either unlabeled or labeled reagents ([14C]NAD and p2p]ATP) strongly suggest that our preparation contained native ADP-ribosylated and native phosphorylated forms which could be estimated at about 20% and 40% of the whole EF-2. Phosphorylated and ADP-ribosylated forms of EF-2 could be ADP-ribosylated and phosphorylated, respectively, but a native form both ADP-ribosylated and phosphorylated was not detected. Our results also suggest the existence of a minor native form of EF-2 and of its phosphorylated and ADPribosylated derivatives.

Research paper thumbnail of Topography and stoichiometry of acidic phosphoproteins in rat liver 60 S ribosomal subunit

FEBS letters, Jan 9, 1988

In reconstitution experiments of active 60 S subunits from inactive core particles obtained by us... more In reconstitution experiments of active 60 S subunits from inactive core particles obtained by using dimethyl maleic anhydride (DMMA), we observed that the phosphoproteins P1-P2 were extracted from the subunit by DMMA as a complex with other proteins. This complex was separated by electrophoresis and zonal centrifugation and shown, after 125I iodination of its components, to contain L22 and S12 in addition to P1-P2. Results suggest that it contains two copies of P1-P2 for one of L22 and S12.

Research paper thumbnail of Reconstitution of the active rat liver 60 S ribosomal subunit from different preparations of core particles and split proteins

FEBS letters, Jan 29, 1988

Proteins extracted from the 60 S rat liver ribosomal subunit with 50% ethanol/0.5 M K Cl produced... more Proteins extracted from the 60 S rat liver ribosomal subunit with 50% ethanol/0.5 M K Cl produced only a partial reactivation of the corresponding core particles. In contrast, the same split proteins were able to reactivate the core particles prepared with dimethyl-maleic anhydride (DMMA) to the same level as that observed using the DMMA-split proteins, i.e. 60-80% of the control according to the catalytic activities tested. Comparative analysis of the two split protein fractions showed only four common proteins: P1-P2, which alone restored part of the activities, especially the EF-2-dependent GTPase one, and L10a, L12, which must be responsible for the additional reactivation. The poor ability of the ethanol/KCl core particles to be reactivated was shown to be probably related to a conformational alteration which destabilized the 5 S RNA-protein complex. Proteins present in the ethanol/KCl wash of Saccharomyces cerevisiae 60 S subunits were found to be partly active in subunit reco...

Research paper thumbnail of Modification of the accessibility of ribosomal proteins after elongation factor 2 binding to rat liver ribosomes and during translocation

Free-and EF-2-bound 80 S ribosomes, within the high-affinity complex with the non-hydrolysable GT... more Free-and EF-2-bound 80 S ribosomes, within the high-affinity complex with the non-hydrolysable GTP analog: guanylylmethylenediphosphonate (GuoPP(CH 2)P), and the low-affinity complex with GDP, were treated with trypsin under conditions that modified neither their protein synthesis ability nor their sedimentation constant nor the bound EF-2 itself. Proteins extracted from trypsin-digested ribosomes were unambiguously identified using three different two-dimensional gel electrophoresis systems and 5 S RNA release was checked by submitting directly free-and EF-2-bound 80 S ribosomes, incubated with trypsin, to two-dimensional gel electrophoresis. Our results indicate that the binding of (EF-2)-GuoPP[CH2]P to 80 S ribosomes modified the behavior of a cluster of five proteins which were trypsin-resistant within free 80 S ribosomes and trypsin-sensitive within the high-affinity complex (proteins: L3, L10, Ll3a, L26, L27a). As for the binding of (EF-2)-GDP to 80 S ribosomes, it induced an intermediate conformational change of ribosomes, unshielding only protein L13a and L27a. Quantitative release of free intact 5 S RNA which occurred in the first case but not in the second one, should be related to the trypsinolysis of protein(s) L3 and/or LI0 and/or L26. Results were discussed in relation to structural and functional data available on the ribosomal proteins we found to be modified by EF-2 binding.

Research paper thumbnail of Modification of the accessibility of ribosomal proteins after

Free- and EF-2-bound 80 S ribosomes, within the high-affinity complex with the non-hydrolysable G... more Free- and EF-2-bound 80 S ribosomes, within the high-affinity complex with the non-hydrolysable GTP analog: guanylylmethylenediphosphonate (GuoPP(CH2)P), and the low-affinity complex with GDP, were treated with trypsin under conditions that modified neither their protein synthesis ability nor their sedimentation constant nor the bound EF-2 itself. Proteins extracted from trypsin-digested ribosomes were unambiguously identified using three different two-dimensional gel electrophoresis systems and 5 S RNA release was checked by submitting directly free- and EF-2-bound 80 S ribosomes, incubated with trypsin, to two-dimensional gel electrophoresis. Our results indicate that the binding of (EF-2)-GuoPP[CH2]P to 80 S ribosomes modified the behavior of a cluster of five proteins which were trypsin-resistant within free 80 S ribosomes and trypsin-sensitive within the high-affinity complex (proteins: L3, L10, L13a, L26, L27a). As for the binding of (EF-2)-GDP to 80 S ribosomes, it induced an intermediate conformational change of ribosomes, unshielding only protein L13a and L27a. Quantitative release of free intact 5 S RNA which occurred in the first case but not in the second one, should be related to the trypsinolysis of protein(s) L3 and/or L10 and/or L26. Results were discussed in relation to structural and functional data available on the ribosomal proteins we found to be modified by EF-2 binding.

Research paper thumbnail of Modification of the reactivity of three amino-acid residues in

The accessibility of three amino acids of EF-2, located within highly conserved regions near the ... more The accessibility of three amino acids of EF-2, located within highly conserved regions near the N- and C-terminal extremities of the molecule (the E region and the ADPR region, respectively) to modifying enzymes has been compared within nucleotide-complexed EF-2 and ribosomal complexes that mimic the pre- and posttranslocational ones: the high-affinity complex (EF-2)-nonhydrolysable GTP analog GuoPP[CH2]P ribosome and the low-affinity (EF-2)-GDP-ribosome complex, EF-2 and ribosomes being from rat liver. We studied the reactivity of two highly conserved residues diphthamide-715 and Arg-66, to diphtheria-toxin-dependent ADP-ribosylation and trypsin attack, and of a threonine that probably lies between residues 51 and 60, to phosphorylation by a Ca2+/calmodulin-dependent protein kinase. Diphthamide 715 and this threonine residue were unreactive within the high-affinity complex but seemed fully reactive in the low-affinity complex. Arg-66 was resistant to trypsin in both complexes. The possible involvement of the E and ADPR regions of EF-2 in the interaction with ribosome in the two complexes is discussed.

Research paper thumbnail of Heterogeneity of ribosomal autoantibodies from human, murine and canine connective tissue diseases

Immunology Letters, 1989

Antiribosomal auto-antibodies (anti-Rib.Ab) have been studied in connective tissue diseases (huma... more Antiribosomal auto-antibodies (anti-Rib.Ab) have been studied in connective tissue diseases (human, dog and mouse) by immunoblotting after one-dimensional (1D) or two-dimensional (2D) gel electrophoresis of rat ribosomes. Anti-Rib.Ab could be found in systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and other connective tissue diseases (progressive systemic sclerosis, PSS; Sjögren syndrome, SjS; mixed connective tissue disease, MCTD; and dermatomyositis, DM with the frequencies 41.7%, 54.6% and 33%, respectively. Immunoblotting after 1D gel electrophoresis showed the great heterogeneity of ribosomal proteins recognized by the anti-Rib.Ab. In the SLE, however, the most frequent antibodies stained bands of the 40S subunit: 30 kDa (34% of positive sera), 19.5 kDa (24.5%) and 43 kDa (17%). In RA, the 25-kDa band of the 60S subunit was the most common (54% of positive sera). In the other human connective tissue diseases, there was no particular predominance. In the MRL/1, anti-Rib.Ab were very frequent (92.6%). The 43-kDa band of the 40S subunit was found in 100% of positive sera. Seventeen out of nineteen dogs with SLE gave positive results on immunoblot, and all of them stained the 43-kDa band of the 40S subunit. 2D gel electrophoresis gave identification of Po, L7, L5, Sb, S19, S13 and L2 proteins in SLE, S3 and SjS, L35a and L37a in RA, and L7, S6 and/or L7a in MRL/1.

Research paper thumbnail of Effect of ADP-ribosylation and phosphorylation on the interaction of elongation factor 2 with guanylic nucleotides

Biochimie, 1991

Samples of unmodified EF-2, EF-2 ADP-ribosylated with diphtheria toxin and NAD, and/or phosphoryl... more Samples of unmodified EF-2, EF-2 ADP-ribosylated with diphtheria toxin and NAD, and/or phosphorylated using ATP and the Ca(2+)-calmodulin dependent kinase III partially purified, were irradiated at 254 nm with 32P-labeled GDP or GTP, and analyzed by one- and two-dimensional gel electrophoresis. By this method we showed that unmodified EF-2 formed a stable complex with GDP but not with GTP, whereas phosphorylated EF-2 and ADP-ribosylated + phosphorylated EF-2 formed stable complexes even in the absence of irradiation, with GTP but not GDP. ADP-ribosylated EF-2 did not form stable complexes with either GDP or GTP. Prior ADP-ribosylation of EF-2 increased its ability to the phosphorylated. These results show that the structures of the two domains containing diphtamide 715 and the phosphorylatable threonines (between Ala 51 and Arg 60) are interdependent; modifications of these residues induce different conformational changes of EF-2 which alter the interactions of the factor with guanylic nucleotides as well with ribosomes.

Research paper thumbnail of Change in the Magnetic Resonance Imaging Signal of the Mandibular Condyle Due to Bisphosphonate-Related Osteonecrosis of the Jaw

Journal of Hard Tissue Biology

Marx was the first to report osteonecrosis of the jaw due to administration of BPs in 2003. Bisph... more Marx was the first to report osteonecrosis of the jaw due to administration of BPs in 2003. Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is the result of an adverse drug reaction. Moreover, many studies worldwide have reported an association between a range of serious dental diseases and the use of bisphosphonates (BPs). Few studies, however, have evaluated BRONJ based on an abnormal signal detected by MRI in the bone marrow of the mandibular condyle. The aim of this study was to assess changes in the magnetic resonance imaging (MRI) signal from the mandibular condyle that could be due to BRONJ. In particular, we focused on the presence of an abnormal MRI signal emanating from mandibular condyle bone marrow. Twenty-eight patients (11 men, 17 women; 56 temporomandibular joints) with BRONJ were evaluated for jaw pain. The patients, whose mean age was 72.9 ± 9.4 years (range 48-88 years), underwent MRI examination of the jawbone at our hospital from August 2006 to December 2015 and were included in the study. Overall, 80.0% of the patients diagnosed with BRONJ exhibited an abnormal bone marrow signal in the mandibular condyle on the same side of the face that suffered jaw pain. This abnormal signal was present significantly more frequently on the side of the face with the jaw symptoms than on the side without symptoms. Patients with BRONJ displayed an abnormal MRI signal in the mandibular condyle on the side of the face with jaw symptoms, suggesting that MRI findings could be useful clinically for detecting BRONJ in the mandibular condyle.

Research paper thumbnail of Heterogeneity of native rat liver elongation factor 2

FEBS Letters, 1989

The high heterogeneity of native rat liver EF-2 prepared from either 105000 x g supernatant or mi... more The high heterogeneity of native rat liver EF-2 prepared from either 105000 x g supernatant or microsome high-salt extract was detected by two-dimensional equilibrium isoelectric focusing-SDS-polyacrylamide gel electrophoresis in the presence of 9.5 M urea. Five spots were always detected, all of Mr 95000, which were not artefactual for their amount varied when EF-2 was specifically ADP-ribosylatecl by diphtheria toxin in the presence of NAD +, and/or phosphorylated on a threonine residue by a Ca2+/calmodulin-dependent protein kinase (most likely Ca2+/calmodulin-dependent protein kinase III described by others [(1987) J. Biol. Chem. 262, 17299-17303; 0988) Nature 334, 170-173]). Results of ADPribosylation and/or phosphorylation experiments with either unlabeled or labeled reagents ([14C]NAD and p2p]ATP) strongly suggest that our preparation contained native ADP-ribosylated and native phosphorylated forms which could be estimated at about 20% and 40% of the whole EF-2. Phosphorylated and ADP-ribosylated forms of EF-2 could be ADP-ribosylated and phosphorylated, respectively, but a native form both ADP-ribosylated and phosphorylated was not detected. Our results also suggest the existence of a minor native form of EF-2 and of its phosphorylated and ADPribosylated derivatives.

Research paper thumbnail of Topography and stoichiometry of acidic phosphoproteins in rat liver 60 S ribosomal subunit

FEBS letters, Jan 9, 1988

In reconstitution experiments of active 60 S subunits from inactive core particles obtained by us... more In reconstitution experiments of active 60 S subunits from inactive core particles obtained by using dimethyl maleic anhydride (DMMA), we observed that the phosphoproteins P1-P2 were extracted from the subunit by DMMA as a complex with other proteins. This complex was separated by electrophoresis and zonal centrifugation and shown, after 125I iodination of its components, to contain L22 and S12 in addition to P1-P2. Results suggest that it contains two copies of P1-P2 for one of L22 and S12.

Research paper thumbnail of Reconstitution of the active rat liver 60 S ribosomal subunit from different preparations of core particles and split proteins

FEBS letters, Jan 29, 1988

Proteins extracted from the 60 S rat liver ribosomal subunit with 50% ethanol/0.5 M K Cl produced... more Proteins extracted from the 60 S rat liver ribosomal subunit with 50% ethanol/0.5 M K Cl produced only a partial reactivation of the corresponding core particles. In contrast, the same split proteins were able to reactivate the core particles prepared with dimethyl-maleic anhydride (DMMA) to the same level as that observed using the DMMA-split proteins, i.e. 60-80% of the control according to the catalytic activities tested. Comparative analysis of the two split protein fractions showed only four common proteins: P1-P2, which alone restored part of the activities, especially the EF-2-dependent GTPase one, and L10a, L12, which must be responsible for the additional reactivation. The poor ability of the ethanol/KCl core particles to be reactivated was shown to be probably related to a conformational alteration which destabilized the 5 S RNA-protein complex. Proteins present in the ethanol/KCl wash of Saccharomyces cerevisiae 60 S subunits were found to be partly active in subunit reco...

Research paper thumbnail of Modification of the accessibility of ribosomal proteins after elongation factor 2 binding to rat liver ribosomes and during translocation

Free-and EF-2-bound 80 S ribosomes, within the high-affinity complex with the non-hydrolysable GT... more Free-and EF-2-bound 80 S ribosomes, within the high-affinity complex with the non-hydrolysable GTP analog: guanylylmethylenediphosphonate (GuoPP(CH 2)P), and the low-affinity complex with GDP, were treated with trypsin under conditions that modified neither their protein synthesis ability nor their sedimentation constant nor the bound EF-2 itself. Proteins extracted from trypsin-digested ribosomes were unambiguously identified using three different two-dimensional gel electrophoresis systems and 5 S RNA release was checked by submitting directly free-and EF-2-bound 80 S ribosomes, incubated with trypsin, to two-dimensional gel electrophoresis. Our results indicate that the binding of (EF-2)-GuoPP[CH2]P to 80 S ribosomes modified the behavior of a cluster of five proteins which were trypsin-resistant within free 80 S ribosomes and trypsin-sensitive within the high-affinity complex (proteins: L3, L10, Ll3a, L26, L27a). As for the binding of (EF-2)-GDP to 80 S ribosomes, it induced an intermediate conformational change of ribosomes, unshielding only protein L13a and L27a. Quantitative release of free intact 5 S RNA which occurred in the first case but not in the second one, should be related to the trypsinolysis of protein(s) L3 and/or LI0 and/or L26. Results were discussed in relation to structural and functional data available on the ribosomal proteins we found to be modified by EF-2 binding.

Research paper thumbnail of Modification of the accessibility of ribosomal proteins after

Free- and EF-2-bound 80 S ribosomes, within the high-affinity complex with the non-hydrolysable G... more Free- and EF-2-bound 80 S ribosomes, within the high-affinity complex with the non-hydrolysable GTP analog: guanylylmethylenediphosphonate (GuoPP(CH2)P), and the low-affinity complex with GDP, were treated with trypsin under conditions that modified neither their protein synthesis ability nor their sedimentation constant nor the bound EF-2 itself. Proteins extracted from trypsin-digested ribosomes were unambiguously identified using three different two-dimensional gel electrophoresis systems and 5 S RNA release was checked by submitting directly free- and EF-2-bound 80 S ribosomes, incubated with trypsin, to two-dimensional gel electrophoresis. Our results indicate that the binding of (EF-2)-GuoPP[CH2]P to 80 S ribosomes modified the behavior of a cluster of five proteins which were trypsin-resistant within free 80 S ribosomes and trypsin-sensitive within the high-affinity complex (proteins: L3, L10, L13a, L26, L27a). As for the binding of (EF-2)-GDP to 80 S ribosomes, it induced an intermediate conformational change of ribosomes, unshielding only protein L13a and L27a. Quantitative release of free intact 5 S RNA which occurred in the first case but not in the second one, should be related to the trypsinolysis of protein(s) L3 and/or L10 and/or L26. Results were discussed in relation to structural and functional data available on the ribosomal proteins we found to be modified by EF-2 binding.

Research paper thumbnail of Modification of the reactivity of three amino-acid residues in

The accessibility of three amino acids of EF-2, located within highly conserved regions near the ... more The accessibility of three amino acids of EF-2, located within highly conserved regions near the N- and C-terminal extremities of the molecule (the E region and the ADPR region, respectively) to modifying enzymes has been compared within nucleotide-complexed EF-2 and ribosomal complexes that mimic the pre- and posttranslocational ones: the high-affinity complex (EF-2)-nonhydrolysable GTP analog GuoPP[CH2]P ribosome and the low-affinity (EF-2)-GDP-ribosome complex, EF-2 and ribosomes being from rat liver. We studied the reactivity of two highly conserved residues diphthamide-715 and Arg-66, to diphtheria-toxin-dependent ADP-ribosylation and trypsin attack, and of a threonine that probably lies between residues 51 and 60, to phosphorylation by a Ca2+/calmodulin-dependent protein kinase. Diphthamide 715 and this threonine residue were unreactive within the high-affinity complex but seemed fully reactive in the low-affinity complex. Arg-66 was resistant to trypsin in both complexes. The possible involvement of the E and ADPR regions of EF-2 in the interaction with ribosome in the two complexes is discussed.