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Biomedical subjects

D S Latchman

Publications and source records attributed to D S Latchman.

At least 253 records · Page 14Linked to original sources
PubMed1993

Transactivation by the herpes simplex virus virion protein Vmw65 and viral permissivity in a neuronal cell line with reduced levels of the cellular transcription factor Oct-1.

Transactivation of the herpes simplex virus (HSV) immediate-early (IE) genes is dependent upon the formation of a complex between the viral protein Vmw65 and the cellular transactivation factor Oct-1. Differentiation of the proliferating ND7 neuronal cell to a nondividing phenotype results in a large fall in the amount of Oct-1 to a level characteristic of nondividing neuronal cells but does not dramatically affect the level of IE gene expression following infection or the ability of Vmw65 to transactivate the IE promoter in transfection experiments. This suggests that the low levels of Oct-1 in nonproliferating neuronal cells do not play a key role in the failure of IE gene expression following initial infection of these cells, which is an essential step in the establishment of latent infections with HSV.

Base Sequence↗
PubMed1993

Elevated levels of the 90 kD heat shock protein in patients with systemic lupus erythematosus are dependent upon enhanced transcription of the hsp90 beta gene.

The level of the 90 kD heat shock protein (hsp90) has been shown to be elevated in the peripheral blood mononuclear cells of a subset of SLE patients. We show that this increased level of hsp90 is primarily dependent upon the enhanced transcription of the hsp90 beta gene which is observed in these patients but not in normal controls or SLE patients without elevated protein levels. Elevated transcription of the hsp90 beta gene in SLE patients is not in general paralleled by enhanced transcription of the hsp70 or ubiquitin genes indicating that the hsp90 beta gene is specifically activated in some SLE patients.

Adult↗
PubMed1993

The cardiac form of the tissue-specific SmN protein is identical to the brain and embryonic forms of the protein.

The SmN protein is a component of small nuclear ribonucleoprotein particles and closely related to the ubiquitously expressed SmB and B' splicing proteins. However, SmN is only expressed in a limited range of tissues and cell types such as brain, heart and early embryonic cells. The isolation of cDNA clones derived from the mRNA encoding SmN in different cell types has indicated that the brain and embryonic forms of the protein are identical and are encoded by a distinct gene to that encoding SmB and B'. It has been suggested however, that the cardiac form of SmN is encoded by a distinct mRNA which is derived from a different gene from that encoding the brain and embryonic forms of SmN. By using the polymerase chain reaction as well as cDNA cloning we have shown that this is not the case and that the cardiac, brain and embryonic forms of the protein are identical and are translated from the same mRNA encoded by a single gene. The significance of this finding is discussed in terms of the complex expression pattern of this gene and the possible functional role of SmN.

Amino Acid Sequence↗
PubMed1993

Attenuation by heat stress of a submaximal calcium paradox in the rabbit heart.

Heat stress limits the injury associated with myocardial ischaemia and reperfusion, an effect previously attributed to enhanced endogenous anti-oxidant activity. We examined the influence of heat stress on the calcium paradox, an injury in which oxidant stress is not thought to play a major role. Twenty-four hours following sham or true heat stress, rabbits were re-anaesthetized and hearts either removed for stress protein analysis (n = 8), or Langendorff-perfused (n = 20) and subjected to a calcium paradox. Ten minutes following calcium repletion (Ca2+ = 1.3 mM), left ventricular developed pressure was better preserved in heat stress vs control hearts (38.3 +/- 5.0 vs 18.8 +/- 4.1 mmHg, respectively, P = 0.003) whilst contracture, measured by left ventricular end-diastolic pressure, was diminished (21.6 +/- 4.7 vs 39.9 +/- 5.2 mmHg, respectively, P = 0.02). Creatine phosphokinase release at 1 min was less in heat stress vs control hearts (10.6 +/- 8.6 vs 86.4 +/- 33.7 U/min/g, respectively, P = 0.01). The myocardial content of the 72 kDa stress protein was elevated eight-fold in heat stress vs control hearts (2.8 +/- 0.2 vs 0.4 +/- 0.1 U, respectively, P = 0.01). This study suggests that some portion of the stress protein response represents a form of cardiac adaptation capable of limiting myocyte injury independent of antioxidant mechanisms.

Animals↗
PubMed1993

The octamer binding protein Oct-2 inhibits transactivation of the herpes simplex virus immediate-early genes by the virion protein Vmw65.

Transactivation by a complex of the cellular transcription factor Oct-1 and the virion protein Vmw65 is necessary for the high-level activity of the HSV immediate-early promoters during lytic infection. We show that this trans-activation can be inhibited by two forms of the Oct-2 transcription factor which are expressed at high levels in neuronal cells as well as by the isolated DNA binding, POU domain of Oct-2. The inhibition of Oct-1-Vmw65 DNA binding by these neuronal forms of Oct-2 is likely to play a critical role in the nonpermissivity of neuronal cells for the HSV lytic cycle and therefore in the establishment of latent infections.

Alternative Splicing↗
PubMed1993

The tissue specific SmN protein does not influence the alternative splicing of endogenous N-Cam and C-SRC RNAs in transfected 3T3 cells.

The SmN protein is closely related to the constitutively expressed RNA splicing protein SmB but is expressed only in brain and heart tissue. The inclusion of the VASE exon in the N-Cam mRNA and of the N1 exon in the c-src mRNA correlates with the expression pattern of SmN, being observed in brain and heart but not in other tissues and increasing in amount as SmN levels increase during brain development. However, the artificial expression of SmN in cells in which it is normally absent does not affect the pattern of N-Cam and c-src splicing whilst a cell line lacking detectable SmN is able to include the VASE exon. Hence SmN does not appear to be necessary or sufficient for these tissue-specific and developmentally regulated alternative splicing events.

3T3 Cells↗
PubMed1993

Heat shock protects neuronal cells from programmed cell death by apoptosis.

The programmed cell death (apoptosis) of a proportion of the neurons which form plays a critical role in the development of the nervous system and ensures that the correct number of mature neurons are ultimately present. We show that the prior exposure of neuronal cells to an elevated temperature sufficient to induce the heat-shock response partially protects the cells from apoptotic cell death following subsequent transfer to serum-free medium. The degree of protection observed in experiments using different heat-shock or recovery times correlates with the extent of heat-shock protein synthesis. Similarly activation of heat-shock protein synthesis by inducers other than elevated temperature also results in protection from apoptosis. The mechanism by which the heat-shock proteins may protect neuronal cells from apoptosis is discussed.

Animals↗
PubMed1993

Lupus autoantibodies discriminate between the highly homologous Sm polypeptides B/B' and SmN by binding an epitope restricted to B/B'.

The ubiquitous Sm polypeptides B/B' (28 and 29 kD) and the highly homologous tissue-specific Sm N polypeptide (29 kD) share several autoepitopes recognized by systemic lupus erythematosus (SLE) sera. Previous studies on the antigenicity of nuclear antigens recognized by human autoantibodies have not discriminated between ubiquitous and tissue-specific forms. We set out to examine whether a tissue-specific nuclear antigen, Sm N, is autoantigenic in SLE by comparing the immunoreactivity of the most unique sequences in this polypeptide. Synthetic peptides from the two regions of least sequence homology that occur between Sm N and Sm B/B', a dodecamer (amino acid residues 179-190 containing five substitutions) and an undecamer (residues 203-213 containing four substitutions) were coupled to a carrier protein. These conjugates were used to quantify IgG anti-peptide antibodies in sera from patients with SLE. Of 43 sera with anti-Sm specificity, six bound to the B/B' 179-190 peptide but not to the N version. None of 17 anti-Sm-negative SLE sera bound these peptides. The second region of least sequence homology between N and B/B' (203-213) was not antigenic. Our data suggest that a subset of SLE patients with anti-Sm reactivity have IgG autoantibodies capable of discriminating between Sm N and SmB/B' polypeptides by binding a previously unreported SmB/B'-specific autoepitope. The data also indicate that brain and heart-specific anti-Sm antibodies do not exist in SLE sera, suggesting that these tissues do not participate in the induction or maintenance of the autoimmune anti-Sm response.

Amino Acid Sequence↗
PubMed1993

Elevation of heat shock protein synthesis and hsp gene transcription during monocyte to macrophage differentiation of U937 cells.

During the phorbol myristate acetate (PMA)-induced differentiation of U937 cells to a macrophage-like phenotype, the levels of the heat shock proteins hsp90, hsp72 and hsp65 increased dramatically to a peak level following 24 h of treatment, and then declined. In contrast, no significant increase was observed in the level of the constitutive hsp73 protein in this process. The observed increases in hsp levels were preceded by an increase in the transcription of each of the genes encoding these hsps, including both of the two genes which encode hsp90. The mechanism of this effect and the possible role of the hsps in the function of differentiated macrophages and in the differentiation process are discussed.

Cell Differentiation↗
PubMed1993

Cell cycle arrest of proliferating neuronal cells by serum deprivation can result in either apoptosis or differentiation.

Apoptotic cell death plays a critical role in the development of the nervous system. The death of mature nondividing neurons that fail to receive appropriate input from the target field has been extensively studied. However, the mechanisms mediating the extensive cell death occurring in areas of the developing brain where proliferating neuroblasts differentiate into mature nondividing neurons have not been analyzed. We show here that the cell cycle arrest of a proliferating cell of neuronal origin by removal of serum results in either apoptotic cell death or differentiation to a mature nondividing neuronal cell. The proportion of cells undergoing death or differentiation is influenced in opposite directions by treatment of the cells with cyclic AMP and retinoic acid. This suggests that following the withdrawal of signals stimulating neuroblast cell division, neuronal cells either can cease to suppress a constitutive suicide pathway and hence die by apoptosis or, alternatively, can differentiate into a mature neuronal cell. Regulation of the balance between apoptosis and neuronal differentiation could therefore play a critical role in controlling the numbers of mature neurons that form.

Animals↗
PubMed1993

Differential heat shock protein overexpression and its clinical relevance in systemic lupus erythematosus.

OBJECTIVES: To determine which heat shock proteins (hsps) are overexpressed in systemic lupus erythematosus (SLE), and to examine the relevance of these findings to clinical disease activity. METHODS: Hsp levels in peripheral blood mononuclear cells (PBMC) of patients with SLE and normal controls were measured. Levels were analysed with respect to detailed clinical activity scores. Other hsps were also quantified in 30-50% of these samples. RESULTS: There was significant increase of the 90 kilodalton heat shock protein (hsp90) in patients with SLE and active neuropsychiatric (p < 0.005) and cardiorespiratory (p < 0.01) disease. There was also significant increase of the inducible 72 kilodalton member (hsp72), but not the constitutive 73 kilodalton member (hsp73) of the hsp70 family, and no increase of the 60 kilodalton hsp (hsp60) was seen in patients compared with controls. There was no association of hsp72 with disease activity, and no correlation between hsp90 and hsp72 levels was seen in individual patients. CONCLUSION: There may a specific role for hsp90 in distinct, clinically active subsets of patients with SLE.

Adolescent↗
PubMed1993

Cardiac stress protein elevation 24 hours after brief ischemia or heat stress is associated with resistance to myocardial infarction.

BACKGROUND: To test the hypothesis that the heat shock response is associated with myocardial salvage, the heat stress protein (HSP) content of cardiac tissue was increased by either ischemic or thermal stress. METHODS AND RESULTS: Rabbits were divided into four groups. Ischemic pretreatment (n = 15) comprised four 5-minute episodes of coronary ligation separated by 10 minutes of reperfusion. The corresponding control group (n = 21) underwent surgical preparation without coronary ligation. Thermal pretreatment (n = 16) involved whole-body temperature elevation to 42 degrees C for 15 minutes; corresponding controls (n = 15) were treated with anesthetic alone. Twenty-four hours later, hearts were removed for HSP estimation or infarct size assessment after a 30-minute coronary ligation. Myocardial HSP72 content assessed by Western blotting was elevated by both ischemic and thermal pretreatments (2.5 +/- 0.2 units, n = 4, and 2.8 +/- 0.3 units, n = 4, mean +/- SEM; P = NS, respectively) compared with the corresponding control groups (1.0 +/- 0.3, n = 4, P < or = .01 and 0.3 +/- 0.1, n = 4, P < or = .01, respectively). HSP60 was preferentially elevated by ischemic pretreatment. After a 30-minute coronary occlusion and 120 minutes of reperfusion, ischemic and thermal pretreatments limited infarct size as a percentage of the volume at risk by 28.8 +/- 5.2% vs 52.0 +/- 5.2%, P < or = .01 and 32.8 +/- 3.8% vs 56.9 +/- 6.5%, P < or = .01, respectively. CONCLUSIONS: Myocardial stress protein induced by either sublethal thermal or ischemic injury is associated with myocardial salvage. Our findings suggest that stress protein elevation, rather than the nonspecific effects of thermal or ischemic stress, may be responsible for the myocardial protection seen in this model. Our observations may have important implications regarding myocardial adaptation to brief periods of ischemia.

Animals↗
PubMed1993

Elevated levels of the 70 kD heat shock protein in patients with systemic lupus erythematosus are not dependent on enhanced transcription of the hsp70 gene.

The level of the heat inducible hsp70 protein (hsp72) has been shown to be elevated in the peripheral blood mononuclear cells of a subset of SLE patients. We show that this increased level of hsp70 is not dependent on enhanced transcription of the hsp70 gene or elevated levels of the hsp70 mRNA, neither of which are observed in SLE patients with enhanced protein levels. This indicates that posttranscriptional processes involving either improved translatability of the hsp70 mRNA or increased protein stability are responsible for the observed increase in protein levels in these patients.

Adult↗
PubMed1992

Alternative splicing of the Oct-2 transcription factor RNA is differentially regulated in neuronal cells and B cells and results in protein isoforms with opposite effects on the activity of octamer/TAATGARAT-containing promoters.

The RNA encoding the octamer-binding transcription factor Oct-2 is alternatively spliced in both neuronal cells and in B cells to yield multiple mRNAs encoding different isoforms of the protein. We show that, compared with B cells, neuronal cells overexpress the mRNAs encoding Oct 2.4 and 2.5 which differ from the other forms (Oct 2.1, 2.2, and 2.3) at the C terminus of the protein. When introduced into cells lacking endogenous Oct-2, the various Oct-2 isoforms have different effects on octamer-containing promoters. The Oct 2.1, 2.2, and 2.3 forms stimulate all octamer-containing promoters. However, the Oct 2.4 and 2.5 forms can repress some promoters and stimulate others, depending on the sequence of the octamer motif and its context within the promoter. In contrast, when introduced into neuronal cells which express a high endogenous level of the inhibitory Oct 2.4 and 2.5 forms, all the Oct-2 isoforms can repress octamer-mediated gene expression. The significance of these findings is discussed with regard to the known inhibitory effect of the octamer motif on viral and cellular gene expression in neuronal cells.

Alternative Splicing↗
PubMed1992

A novel POU family transcription factor is closely related to Brn-3 but has a distinct expression pattern in neuronal cells.

The use of the polymerase chain reaction in conjunction with degenerate oligonucleotides has allowed the isolation of cDNA clones derived from each of the POU family transcription factors expressed in the proliferating ND7 neuronal cell line. In addition to the previously characterized Oct-1, Oct-2 and Brn-3 factors, ND7 cells have been shown by this means to express a novel POU factor. This factor is closely related to Brn-3 but differs at seven amino acids in the POU domain, one of which is located in a region which is critical for protein-protein interactions between different POU proteins. Like Brn-3, the novel factor is expressed at high levels in embryonic brain and declines in abundance during neuronal development. In contrast to Brn-3 however, it is absent in mature sensory neurons and its expression declines during the in vitro differentiation of ND7 cells to a non-dividing phenotype whilst Brn-3 expression increases. The significance of these distinct but overlapping expression patterns is discussed in terms of the possible role of these two factors in regulating neuronal gene expression.

Amino Acid Sequence↗
PubMed1992

Regulation of expression of the neuronal POU protein Oct-2 by nerve growth factor.

POU proteins are a class of homeobox-containing transcription factors that regulate tissue-specific gene expression and influence cell differentiation and function. We have investigated the possible role of such factors in mediating the actions of nerve growth factor (NGF) on sensory neurons. NGF has been found to have differential effects on the levels of three POU protein transcription factors that are expressed in adult rat sensory neurons. A sensory neuron octamer-binding protein with the properties of the transcription factor Oct-2 is up-regulated 3-4-fold by NGF, as measured by mobility shift assays using nuclear extracts from adult rat dorsal root ganglion neurons grown in the presence or absence of NGF. Quantitation of Oct-2 mRNA by polymerase chain reaction amplification of RNA from such cells shows a parallel increase in Oct-2 mRNA levels. In contrast, the levels of mRNA encoding the ubiquitous POU protein Oct-1 or the neuron-specific POU protein Brn-3, also present in sensory neurons, are unaffected by NGF. These observations suggest a role for Oct-2 in mediating transcriptional effects induced by NGF. In particular, as Oct-2 is known to inhibit herpes simplex virus immediate-early gene expression in neuronal cells, these findings provide a mechanism for the known action of NGF in the maintenance of latent herpes virus infections in sensory neurons.

Animals↗