Biomedical subjects

Z Xie

Publications and source records attributed to Z Xie.

At least 145 records · Page 8Linked to original sources

PubMed1998

Lymphotactin gene-modified bone marrow dendritic cells act as more potent adjuvants for peptide delivery to induce specific antitumor immunity.

Dendritic cells (DC) are regarded as attractive candidates for cancer immunotherapy. Our aim is to improve the therapeutic efficacy of DC-based tumor vaccine by augmenting DC preferential chemotaxis on T cells. Mouse bone marrow-derived DC were transduced with lymphotactin (Lptn) gene by adenovirus vector. The supernatants from Lptn gene-modified DC (Lptn-DC) were capable of attracting CD4+ and CD8+ T cells in a chemotaxis assay, whereas their mock control could not. Lptn expression of Lptn-DC was further confirmed by RT-PCR. Lptn-DC were pulsed with Mut1 peptide and used for vaccination. Immunization with the low dose (1 x 10(4)) of Mut1 peptide-pulsed DC induced weak CTL activity, whereas the same amounts of Mut1 peptide-pulsed Lptn-DC markedly induced specific CTL against 3LL tumor cells. A single immunization with 1 x 10(4) Mut1 peptide-pulsed Lptn-DC could render mice resistant to a 5 x 10(5) 3LL tumor cell challenge completely, but their counterpart could not. The protective immunity induced by Mut1 peptide-pulsed Lptn-DC depends on both CD4+ T cells and CD8+ T cells rather than NK cells in the induction phase and depends on CD8+ T cells rather than CD4+ T cells and NK cells in the effector phase. Moreover, the involvement of CD28/CTLA4 costimulation pathway and IFN-gamma are also necessary. When 3LL tumor-bearing mice were treated with 1 x 10(4) Mut1 peptide-pulsed Lptn-DC, their pulmonary metastases were significantly reduced, whereas the same low dose of Mut1 peptide-pulsed DC had no obvious therapeutic effects. Our data suggest that Lptn-DC are more potent adjuvants for peptide delivery to induce protective and therapeutic antitumor immunity.

Adenoviridae↗

PubMed1998

Cytoprotection by Bcl-2 requires the pore-forming alpha5 and alpha6 helices.

We explored whether the putative channel-forming fifth and sixth alpha-helices of Bcl-2 and Bax account for Bcl-2-mediated cell survival and Bax-induced cell death in mammalian cells and in the yeast Saccharomyces cerevisiae. When alpha5-alpha6 were either deleted or swapped with each other, the Bcl-2Deltaalpha5alpha6 deletion mutant and Bcl-2-Bax(alpha5alpha6) chimeric protein failed to block apoptosis induced by either Bax or staurosporine in human cells and were unable to prevent Bax-induced cell death in yeast, implying that the alpha5-alpha6 region of Bcl-2 is essential for its cytoprotective function. Additional experiments indicated that, although alpha5-alpha6 is necessary, it is also insufficient for the anti-apoptotic activity of Bcl-2. In contrast, deletion or substitution of alpha5-alpha6 in Bax reduced but did not abrogate apoptosis induction in human cells, whereas it did completely nullify cytotoxic activity in yeast, implying that the pore-forming segments of Bax are critical for conferring a lethal phenotype in yeast but not necessarily in human cells. BaxDeltaalpha5alpha6 and Bax-Bcl-2(alpha5alpha6) also retained the ability to dimerize with Bcl-2. Bax therefore may have redundant mechanisms for inducing apoptosis in mammalian cells, based on its ability to form alpha5-alpha6-dependent channels in membranes and to dimerize with and antagonize anti-apoptotic proteins such as Bcl-2.

Apoptosis↗

PubMed1998

Molecular cloning of human ABPL, an actin-binding protein homologue.

Based on two partial cDNA sequences, a full-length cDNA sequence for an actin-binding like protein previously named ABPL has been isolated and characterized. ABPL is homologous to the human actin-binding proteins ABP-280 and ABP-278. The predicted sequence for ABPL is 2,705 amino acids in length with a calculated molecular mass of 289 kDa. It contains an amino terminal actin-binding domain followed by 24 tandem repeats of approximately 96 amino acids. Two hinge regions, Hinge I and Hinge II, were located prior to repeats 16 and 24, respectively. An isoform of ABPL lacking Hinge I, with a calculated molecular mass of 286 kDa, was also identified by the reverse transcriptase PCR (RT-PCR) method. A comparison with genomic sequences indicated the isoform resulted from alternative RNA splicing. ABPL has a unique insertion sequence of 82 amino acids in repeat 20 that was not present in the other two homologues and has a tissue distribution that was also different from the other two homologues.

Actins↗

PubMed1998

Phospholipase D activity is required for suppression of yeast phosphatidylinositol transfer protein defects.

Yeast phosphatidylinositol transfer protein (Sec14p) function is essential for production of Golgi-derived secretory vesicles, and this requirement is bypassed by mutations in at least seven genes. Analyses of such 'bypass Sec14p' mutants suggest that Sec14p acts to maintain an essential Golgi membrane diacylglycerol (DAG) pool that somehow acts to promote Golgi secretory function. SPO14 encodes the sole yeast phosphatidylinositol-4,5-bisphosphate-activated phospholipase D (PLD). PLD function, while essential for meiosis, is dispensable for vegetative growth. Herein, we report specific physiological circumstances under which an unanticipated requirement for PLD activity in yeast vegetative Golgi secretory function is revealed. This PLD involvement is essential in 'bypass Sec14p' mutants where normally Sec14p-dependent Golgi secretory reactions are occurring in a Sec14p-independent manner. PLD catalytic activity is necessary but not sufficient for 'bypass Sec14p', and yeast operating under 'bypass Sec14p' conditions are ethanol-sensitive. These data suggest that PLD supports 'bypass Sec14p' by generating a phosphatidic acid pool that is somehow utilized in supporting yeast Golgi secretory function.

Carrier Proteins↗

PubMed1998

A human RNA polymerase II transcription termination factor is a SWI2/SNF2 family member.

We obtained protein sequence information from Drosophila factor 2, an ATP-dependent RNA polymerase II transcription termination factor, and discovered that it was identical to a SWI2/SNF2 family member called lodestar. Portions of putative human and Caenorhabditis elegans homologues were found in the sequence data bases and a complete cDNA for the human factor was generated using polymerase chain reaction techniques. Recombinant human factor 2 was produced in a baculovirus expression system, purified, and characterized. Similar to the authentic Drosophila factor, the human factor displayed a strong double-stranded DNA-dependent ATPase activity that was inhibited by single-stranded DNA and exhibited RNA polymerase II termination activity. Both factors were able to work on elongation complexes from either species. We discuss the mechanism of termination by factor 2 and the implications for the role of factor 2 in cellular activities.

Adenosine Triphosphatases↗

PubMed1998

Bax and adenine nucleotide translocator cooperate in the mitochondrial control of apoptosis.

The proapoptotic Bax protein induces cell death by acting on mitochondria. Bax binds to the permeability transition pore complex (PTPC), a composite proteaceous channel that is involved in the regulation of mitochondrial membrane permeability. Immunodepletion of Bax from PTPC or purification of PTPC from Bax-deficient mice yielded a PTPC that could not permeabilize membranes in response to atractyloside, a proapoptotic ligand of the adenine nucleotide translocator (ANT). Bax and ANT coimmunoprecipitated and interacted in the yeast two-hybrid system. Ectopic expression of Bax induced cell death in wild-type but not in ANT-deficient yeast. Recombinant Bax and purified ANT, but neither of them alone, efficiently formed atractyloside-responsive channels in artificial membranes. Hence, the proapoptotic molecule Bax and the constitutive mitochondrial protein ANT cooperate within the PTPC to increase mitochondrial membrane permeability and to trigger cell death.

Animals↗

PubMed1998

Characterization of interactions between the anti-apoptotic protein BAG-1 and Hsc70 molecular chaperones.

The anti-cell death protein BAG-1 binds to 70-kDa heat shock proteins (Hsp70/Hsc70) and modulates their chaperone activity. Among other facilitory roles, BAG-1 may serve as a nucleotide exchange factor for Hsp70/Hsc70 family proteins and thus represents the first example of a eukaryotic homologue of the bacterial co-chaperone GrpE. In this study, the interactions between BAG-1 and Hsc70 are characterized and compared with the analogous GrpE-DnaK bacterial system. In contrast to GrpE, which binds DnaK as a dimer, BAG-1 binds to Hsc70 as a monomer with a 1:1 stoichiometry. Dynamic light scattering, sedimentation equilibrium, and circular dichroism measurements provided evidence that BAG-1 exists as an elongated, highly helical monomer in solution. Isothermal titration microcalorimetry was used to determine the complex stoichiometry and an equilibrium dissociation constant, KD, of 100 nM. Kinetic analysis using surface plasmon resonance yielded a KD consistent with the calorimetrically determined value. Molecular modeling permitted a comparison of structural features between the functionally homologous BAG-1 and GrpE proteins. These data were used to propose a mechanism for BAG-1 in the regulation of Hsp70/Hsc70 chaperone activity.

Amino Acid Sequence↗

PubMed1998

A novel human actin-binding protein homologue that binds to platelet glycoprotein Ibalpha.

Glycoprotein (GP)Ib-IX-V is one of the major transmembrane complexes present on the platelet surface. Its extracellular domain binds von Willebrand factor (vWF) and thrombin, while its intracellular domain associates tightly with the cytoskeleton through the actin-binding protein (ABP)-280, also known as filamin. In the present study, a full-length cDNA coding for a human ABP homologue has been cloned and sequenced. This protein was identified by the yeast two-hybrid screening procedure via its interaction with the intracellular domain of GPIbalpha. Initially, a 1.3-kb partial cDNA was isolated from a megakaryocyte-like cell line (K562) cDNA library followed by a full-length cDNA of 9.4 kb that was identified in a human placenta library. The full-length cDNA encoded a protein of 2,578 amino acids with a calculated molecular weight of 276 kD (ABP-276). The amino terminal 248 amino acids contained an apparent actin binding domain followed by 24 tandem repeats each containing about 96 amino acids. The amino acid sequence of the protein shared a high degree of homology with human endothelial ABP-280 (70% identity) and chicken filamin (83% identity). However, the 32 amino acid Hinge I region in ABP-280 that contains a calpain cleavage site conferring flexibility on the molecule, was absent in the homologue. An isoform containing a 24 amino acid insertion with a unique sequence at the missing Hinge I region was also identified (ABP-278). This isoform resulted from alternative RNA splicing. ABP-276 and/or ABP-278 were present in all tissues examined, but the relative amount varied in that some tissue contained both forms, while other tissue contained predominately one or the other.

Amino Acid Sequence↗

PubMed1998

Multiple signal transduction pathways link Na+/K+-ATPase to growth-related genes in cardiac myocytes. The roles of Ras and mitogen-activated protein kinases.

We showed before that in neonatal rat cardiac myocytes partial inhibition of Na+/K+-ATPase by nontoxic concentrations of ouabain causes hypertrophic growth and transcriptional regulations of genes that are markers of cardiac hypertrophy. In view of the suggested roles of Ras and p42/44 mitogen-activated protein kinases (MAPKs) as key mediators of cardiac hypertrophy, the aim of this work was to explore their roles in ouabain-initiated signal pathways regulating four growth-related genes of these myocytes, i.e. those for c-Fos, skeletal alpha-actin, atrial natriuretic factor, and the alpha3-subunit of Na+/K+-ATPase. Ouabain caused rapid activations of Ras and p42/44 MAPKs; the latter was sustained longer than 90 min. Using high efficiency adenoviral-mediated expression of a dominant-negative Ras mutant, and a specific inhibitor of MAPK kinase (MEK), activation of Ras-Raf-MEK-p42/44 MAPK cascade by ouabain was shown. The effects of the mutant Ras, an inhibitor of Ras farnesylation, and the MEK inhibitor on ouabain-induced changes in mRNAs of the four genes indicated that (a) skeletal alpha-actin induction was dependent on Ras but not on p42/44 MAPKs, (b) alpha3 repression was dependent on the Ras-p42/44 MAPK cascade, and (c) induction of c-fos or atrial natriuretic factor gene occurred partly through the Ras-p42/44 MAPK cascade, and partly through pathways independent of Ras and p42/44 MAPKs. All ouabain effects required extracellular Ca2+, and were attenuated by a Ca2+/calmodulin antagonist or a protein kinase C inhibitor. The findings show that (a) signal pathways linked to sarcolemmal Na+/K+-ATPase share early segments involving Ca2+ and protein kinase C, but diverge into multiple branches only some of which involve Ras, or p42/44 MAPKs, or both; and (b) there are significant differences between this network and the related gene regulatory pathways activated by other hypertrophic stimuli, including those whose responses involve increases in intracellular free Ca2+ through different mechanisms.

Actins↗

PubMed1998

A novel pathway for cytochromes c biogenesis in chloroplasts.

The cytochromes c are a useful model for the study of the pathways and mechanisms of assembly of the cofactor-containing components of energy transducing membranes. Genetic analyses have identified proteins that are required for the assembly of c-type cytochromes in mitochondria, bacteria and chloroplasts. The components of the pathway operating in fungal and animal mitochondria, i.e. the cytochrome (cyt) c and c1 heme lyases in the intermembrane space, were identified over a decade ago through the study of cytochrome deficiencies in Neurospora crassa and Saccharomyces cerevisiae. More recently, a large number of membrane or membrane-associated components were identified in various alpha- and gamma-proteobacteria as c-type cytochrome assembly factors; they comprise an assembly pathway that is evolutionarily and mechanistically distinct from that in fungal and animal mitochondria. The components function not only in the lyase reaction but also in the delivery and maintenance of the substrates in a state that is suitable for reaction in the bacterial periplasm. Yet a third pathway is required for cytochrome maturation in chloroplasts. Genetic analyses of Chlamydomonas reinhardtii ccs mutants, which are pleiotropically deficient in both the membrane-anchored cytochrome f and the soluble cytochrome c6, revealed a minimum of six loci, plastid ccsA and nuclear CCS1 through CCS5, that are required for the conversion of the chloroplast apocytochromes to their respective holo forms. Sequence analysis of the cloned ccsA and Ccs1 genes indicates that the predicted protein products are integral membrane proteins with homologues in cyanobacteria, some gram-positive bacteria (Bacillus subtilis, Mycobacterium spp.), beta-proteobacteria (Neisseria spp.) and an epsilon-proteobacterium (Helicobacter pylori). CcsA and Ccs1 require each other for accumulation in vivo and are therefore proposed to function in a complex, possibly with the products of some of the other CCS loci. A tryptophan-rich motif, which has been proposed to represent a heme binding site in bacterial cytochrome biogenesis proteins (CcmC and CcmF), is functionally important in plastid CcsA. As is the case for CcmC and CcmF, the tryptophan-rich sequence is predicted to occur in a loop on the p-side of the membrane, where the heme attachment reaction occurs. Conserved histidine residues in the CcsA and Ccs1 may serve as ligands to the heme iron. A multiple alignment of the tryptophan-rich regions of the CcsA-, CcmC- and CcmF-like sequences in the genome databases indicates that they represent three different families.

Amino Acid Sequence↗

PubMed1998

Cloning genes encoding receptors related to chemoattractant receptors.

We report the cloning of a novel human gene (GPR32) encoding a putative G-protein-coupled receptor (GPCR) of 356 amino acids and a related pseudogene psi GPR32. The deduced amino acid sequence of GPR32 shares 35-39% identity with members of the chemoattractant receptor family. psi GPR32 shares 93% nucleotide identity with GPR32. We identified a mouse EST encoding a putative GPCR (GPR33) of 309 amino acids. The deduced amino acid sequence of GPR33 shares 30-35% identity with members of the chemoattractant receptor family and 36% identity with the receptor encoded by GPR32. The human orthologue of GPR33 contains a single basepair substitution with respect to the mouse, resulting in the presence of an in-frame stop codon within the predicted second intracellular loop, demonstrating that it is a pseudogene. Through fluorescence in situ hybridization and physical mapping of YACs, both GPR32 and psi GPR32 were mapped to chromosomal 19, region q13.3, while psi GPR33 was mapped to chromosome 14q12.

Amino Acid Sequence↗

PubMed1998

Acidic pH promotes dimerization of Bcl-2 family proteins.

Several members of the apoptosis-regulating Bcl-2 family of proteins can homo- or heterodimerize with each other at neutral pH and can also form ion channels in synthetic membranes at low pH. The effects of low pH on dimerization among these proteins, however, have not heretofore been examined. Surface plasmon resonance was used to examine the kinetics of dimerization as a function of pH between the anti-apoptotic protein Bcl-XL (applied in the mobile phase) and three other members of the Bcl-2 family: Bcl-2, Bax, and Bid (immobilized on biosensor chips). In all cases, the relative affinity of dimerization was substantially increased at pH 4.0 compared to pH 7.0-7.4, ranging from a approximately 10-fold enhancement for Bcl-XL/Bcl-XL homodimers to >60-fold for Bcl-XL/Bid heterodimers. Comparison of the apparent association (ka) and dissociation (kd) rates at neutral and acidic pH revealed that the major contributor to increased affinity at low pH was a decreased rate of dimer dissociation. Thus, low pH stabilizes homo- and heterodimeric complexes comprised of Bcl-XL and these other Bcl-2 family proteins. At pH 4.0, the circular dichroism spectra of Bcl-XL and Bax were essentially unchanged relative to pH 7.0-7.4, indicating a complete retention of alpha-helical secondary structure at low pH and excluding gross denaturation of the proteins. Size-exclusion chromatography and bisANS (4,4'-dianilino-1, 1'-binaphthyl-5,5'-disulfonic acid) labeling studies provided indirect evidence that Bcl-XL may undergo conformational changes at low pH. The findings are discussed with respect to the mechanisms of ion-channel formation by Bcl-2 family proteins and the putative molten globule state that has been proposed for these and structurally similar proteins.

Amino Acid Sequence↗

PubMed1998

Bax directly induces release of cytochrome c from isolated mitochondria.

Bax is a pro-apoptotic member of the Bcl-2 protein family that resides in the outer mitochondrial membrane. It is controversial whether Bax promotes cell death directly through its putative function as a channel protein versus indirectly by inhibiting cellular regulators of the cell death proteases (caspases). We show here that addition of submicromolar amounts of recombinant Bax protein to isolated mitochondria can induce cytochrome c (Cyt c) release, whereas a peptide representing the Bax BH3 domain was inactive. When placed into purified cytosol, neither mitochondria nor Bax individually induced proteolytic processing and activation of caspases. In contrast, the combination of Bax and mitochondria triggered release of Cyt c from mitochondria and induced caspase activation in cytosols. Supernatants from Bax-treated mitochondria also induced caspase processing and activation. Recombinant Bcl-XL protein abrogated Bax-induced release of Cyt c from isolated mitochondria and prevented caspase activation. In contrast, the broad-specificity caspase inhibitor benzyloxycarbonyl-valinyl-alaninyl-aspartyl-(0-methyl)- fluoromethylketone (zVAD-fmk) and the caspase-inhibiting protein X-IAP had no effect on Bax-induced release of Cyt c from mitochondria in vitro but prevented the subsequent activation of caspases in cytosolic extracts. Unlike Ca2+, a classical inducer of mitochondrial permeability transition, Bax did not induce swelling of mitochondria in vitro. Because the organellar swelling caused by permeability transition causes outer membrane rupture, the findings, therefore, dissociate these two events, implying that Bax uses an alternative mechanism for triggering release of Cyt c from mitochondria.

Animals↗

PubMed1998

Unusual nucleic acid binding properties of factor 2, an RNA polymerase II transcript release factor.

Drosophila factor 2, an RNA polymerase II transcript release factor, exhibits a DNA-dependent ATPase activity (Xie, Z., and Price D. H. (1997) J. Biol. Chem. 272, 31902-31907). We examined the nucleic acid requirement and found that only double-stranded DNA (dsDNA) effectively activated the ATPase. Single-stranded DNA (ssDNA) not only failed to activate the ATPase, but suppressed the dsDNA-dependent ATPase. Gel mobility shift assays showed that factor 2 formed stable complexes with dsDNA or ssDNA in the absence of ATP. However, in the presence of ATP, the interaction of factor 2 with dsDNA was destabilized, while the ssDNA-factor 2 complexes were not affected. The interaction of factor 2 with dsDNA was sensitive to increasing salt concentrations and was competed by ssDNA. In both cases, loss of binding of factor 2 to dsDNA was mirrored by a decrease in ATPase and transcript release activity, suggesting that the interaction of factor 2 with dsDNA is important in coupling the ATPase with the transcript release activity. Although the properties of factor 2 suggested that it might have helicase activity, we were unable to detect any DNA unwinding activity associated with factor 2.

Adenosine Triphosphatases↗

PubMed1998

Alginate, inorganic polyphosphate, GTP and ppGpp synthesis co-regulated in Pseudomonas aeruginosa: implications for stationary phase survival and synthesis of RNA/DNA precursors.

The regulatory protein AlgR2 in Pseudomonas aeruginosa positively regulates nucleoside diphosphate kinase (Ndk) and succinyl-CoA synthetase, enzymes critical in nucleoside triphosphate (NTP) formation. AlgR2 positively regulates the production of alginate, GTP, ppGpp and inorganic polyphosphate (poly P). An algR2 mutant with low levels of these metabolites has them restored by introducing and overexpressing either the algR2 or the ndk gene into the algR2 mutant. Thus, Ndk is involved in the formation of these compounds and largely prevents the death of the algR2 mutant, which occurs early in the stationary phase. We demonstrate that the 12 kDa Ndk-pyruvate kinase (Pk) complex, previously shown to generate predominantly GTP instead of all the NTPs, has a low affinity for the deoxynucleoside diphosphates and cannot generate the dNTPs needed for DNA replication and cell division; this complex may thus be involved in regulating the levels of both NTPs and dNTPs that modulate cell division and survival in the stationary phase.

Alginates↗

PubMed1998

Differential regulation of vitamin D responsive elements in normal and transformed keratinocytes.

Squamous cell carcinomas (SCC) derived from human epidermis fail to differentiate normally under the influence of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] despite the presence of the vitamin D receptor. Previous studies from our laboratory showed that phospholipase C-gamma1 (PLC-gamma1) was upregulated transcriptionally by 1,25(OH)2D3 in normal human keratinocytes, and a vitamin D responsive element (VDRE) in its promoter region has been identified. To examine the inducibility of human PLC-gamma1 transcription by 1,25(OH)2D3 and/or retinoic acid in SCC cell lines, we transiently transfected SCC4 and SCC12B2 cells with human PLC-gamma1 promoter-luciferase constructs containing the VDRE and tested the response of these constructs to 1,25(OH)2D3 and/or all-trans retinoic acid. The induction of the human PLC-gamma1 VDRE by 1,25(OH)2D3 was synergistic with all-trans retinoic acid in normal human keratinocytes, but none of the constructs was induced by 1,25(OH)2D3 and/or all-trans retinoic acid in SCC4 and SCC12B2 cells. In contrast, the construct containing the VDRE of the human 24-hydroxylase gene was induced several fold by 1,25(OH)2D3 in normal human keratinocytes and by both 1,25(OH)2D3 and all-trans retinoic acid in SCC4 and SCC12B2 cells. DNA mobility shift assays showed that both the vitamin D receptor and the retinoic acid receptor in SCC4 and SCC12B2 cells bound the human PLC-gamma1 VDRE similarly to that seen in normal keratinocytes. The data indicate that the VDRE in the human PLC-gamma1 gene is not functional in SCC4 and SCC12B2 cells, unlike normal human keratinocytes, even though vitamin D receptors bind normally to it. Failure of transcriptional control of the PLC-gamma1 gene by 1,25(OH)2D3 suggests the lack of a cofactor(s) linking the VDRE to the transcriptional machinery.

Calcitriol↗

PubMed1998

Genetic analysis of chloroplast c-type cytochrome assembly in Chlamydomonas reinhardtii: One chloroplast locus and at least four nuclear loci are required for heme attachment.

Chloroplasts contain up to two c-type cytochromes, membrane-anchored cytochrome f and soluble cytochrome c6. To elucidate the post-translational events required for their assembly, acetate-requiring mutants of Chlamydomonas reinhardtii that have combined deficiencies in both plastid-encoded cytochrome f and nucleus-encoded cytochrome c6 have been identified and analyzed. For strains ct34 and ct59, where the phenotype displays uniparental inheritance, the mutations were localized to the chloroplast ccsA gene, which was shown previously to be required for heme attachment to chloroplast apocytochromes. The mutations in another eight strains were localized to the nuclear genome. Complementation tests of these strains plus three previously identified strains of the same phenotype (ac206, F18, and F2D8) indicate that the 11 ccs strains define four nuclear loci, CCS1-CCS4. We conclude that the products of the CCS1-CCS4 loci are not required for translocation or processing of the preproteins but, like CcsA, they are required for the heme attachment step during assembly of both holocytochrome f and holocytochrome c6. The ccsA gene is transcribed in each of the nuclear mutants, but its protein product is absent in ccs1 mutants, and it appears to be degradation susceptible in ccs3 and ccs4 strains. We suggest that Ccsl may be associated with CcsA in a multisubunit "holocytochrome c assembly complex," and we hypothesize that the products of the other CCS loci may correspond to other subunits.

Animals↗

PubMed1998

Rearrangement of the ventricular capillary network in stroke-prone spontaneously hypertensive rats (SHRSP) following a late start of treatment with the angiotensin converting enzyme blocker temocapril.

The effects of the angiotensin converting enzyme (ACE) blocker temocapril on the capillary network of the left ventricle were studied in stroke-prone spontaneously hypertensive rats (SHRSP). The ACE blocker was dissolved in the drinking water and supplied to 24 and 32 week old SHRSP ad libitum for 5 weeks. The capillaries of the wall of the left ventricle were studied using a double staining method to differentiate the arteriolar, intermediate and venular capillary portions. Capillary density increased and capillary domain areas decreased in all capillary portions compared with untreated control SHRSP in both age groups. The proportion of venular capillary portions was increased by temocapril treatment. The results indicate that the late start of ACE blockade caused the regression of the hypertrophied cardiomyocytes, which is characteristic of SHRSP, and the rearrangement of capillary portions. The plasma concentration of angiotensin II was significantly lower in temocapril-treated SHRSP compared to the control group. The implication is that intrinsic angiotensin II exerts an appreciable effect on the function, structure and capillary network in the left ventricular wall in SHRSP.

Angiotensin II↗