Actin mutations in a human fibroblast model for carcinogenesis

We assessed the modulation of gene expression accompanying neoplastic transformation by computerized microdensitometry of autoradiographic patterns of [35S]-methionine-labeled polypeptides separated by two-dimensional polyacrylamide gel electrophoresis. Nearly 1000 polypeptide species of parent diploid human fibroblasts (KD strain) and clonally-derived malignant fibroblasts (HUT-14 strain) were compared. We found that the neoplastic HUT-14 fibroblasts express a mutation in one of the two functional beta-actin genes. In addition, of the 700 more-abundant polypeptides measured, 13 were lost and 14 new ones gained after this neoplastic transformation. We estimate that although 2% of fewer of the genes expressing abundant polypeptides were either activated or shut off, at least 32% were modulated quantitatively. A substrain of HUT-14--HUT-14T--shows increased tumorigenicity, producing larger, faster-growing fibrosarcomas in the nude mouse than does the present parent HUT-14 strain, and with fewer inoculated cells. This increase in tumorigenicity is accompanied by three subsequent changes in the mutant beta-actin polypeptide expression. A more variant mutant actin species is synthesized in HUT-14T, which differs from the original mutant polypeptide by (i) one additional negative net charge, (ii) a short half-life in the cell, (iii) a greatly diminished ability to incorporate into the detergent-resistant cytoskeleton, (iv) a decrease in affinity for deoxyribonuclease I (EC 3.1.21.1), and (v) a faster rate of synthesis. Our results suggest that a second-site mutation in the mutant beta-actin of HUT-14 was selected for during a subcloning step in the presence of 6-thioguanine before derivation of the HUT-14T substrain. This apparent mutation and two subsequent defective beta-actin expressions are accompanied by incremental increases of malignant potential.

Actin mutations in a human fibroblast model for carcinogenesis

We assessed the modulation of gene expression accompanying neoplastic transformation by computerized microdensitometry of autoradiographic patterns of [35S]-methionine-labeled polypeptides separated by two-dimensional polyacrylamide gel electrophoresis. Nearly 1000 polypeptide species of parent diploid human fibroblasts (KD strain) and clonally-derived malignant fibroblasts (HUT-14 strain) were compared. We found that the neoplastic HUT-14 fibroblasts express a mutation in one of the two functional beta-actin genes. In addition, of the 700 more-abundant polypeptides measured, 13 were lost and 14 new ones gained after this neoplastic transformation. We estimate that although 2% of fewer of the genes expressing abundant polypeptides were either activated or shut off, at least 32% were modulated quantitatively. A substrain of HUT-14--HUT-14T--shows increased tumorigenicity, producing larger, faster-growing fibrosarcomas in the nude mouse than does the present parent HUT-14 strain, and with fewer inoculated cells. This increase in tumorigenicity is accompanied by three subsequent changes in the mutant beta-actin polypeptide expression. A more variant mutant actin species is synthesized in HUT-14T, which differs from the original mutant polypeptide by (i) one additional negative net charge, (ii) a short half-life in the cell, (iii) a greatly diminished ability to incorporate into the detergent-resistant cytoskeleton, (iv) a decrease in affinity for deoxyribonuclease I (EC 3.1.21.1), and (v) a faster rate of synthesis. Our results suggest that a second-site mutation in the mutant beta-actin of HUT-14 was selected for during a subcloning step in the presence of 6-thioguanine before derivation of the HUT-14T substrain. This apparent mutation and two subsequent defective beta-actin expressions are accompanied by incremental increases of malignant potential.

Changes in gene expression accompanying chemically-induced malignant transformation of human fibroblasts

The modulation of gene expression accompanying neoplastic transformation has been assessed by computerized microdensitometry or autoradiographic patterns of [35S]methionine labeled polypeptides separated by two-dimensional polyacrylamide gel electrophoresis. Nearly 1000 polypeptide species of parent diploid human fibroblasts (KD strain) and clonally-derived malignant fibroblasts (HUT-14 strain) were compared. HUT-14 fibroblasts express a mutation in one of the two functional beta-actin genes and possess properties that distinguish them as neoplastic cells. Of the 700 more abundant polypeptides measured, 13 were lost and 14 were gained following this neoplastic transformation. It is estimated that less than or equal to 2% of the genes expressing abundant polypeptides were either activated or shut off, but at least 32% were modulated quantitatively as a consequence of this neoplastic transformation. Classes of "highly variable" and "marginally variable" polypeptides were assigned. Among the "highly variable" polypeptides, two related species barely detectable in KD parental cells were synthesized at a 25-31-fold higher rate in the transformed cells, and the cell-associated and extracellular matrix forms of fibronectin were each diminished by greater than 90%. Principles emerging from this study may form a basis for interpretation of the role of individual genes in the expression of neoplastic characteristics of HUT-14 cells.

Protein variations associated with Lesch-Nyhan syndrome

Patients having Lesch--Nyhan syndrome were studied by using enzymatic, immunologic, and two-dimensional electrophoretic techniques. Four hundred proteins were analyzed on each two-dimensional electrophoretogram for positional or quantitative variation. In autoradiograms of lymphocytes stimulated with phytohemagglutinin, there were 11 quantitative differences found in all patients that were significant at the 2P less than 0.01 level. A significant quantitative difference was also found in an analysis of silver-stained gels of unstimulated lymphocytes. Patients had trace amounts of erythrocyte hypoxanthine phosphoribosyl transferase (HPRT) activity and trace or no immunoprecipitable HPRT. However, HPRT was observed in silver-stained erythrocyte electrophoretograms and in autoradiograms from phytohemagglutinin-stimulated lymphocytes. Unstimulated lymphocytes contained 65% of the control HPRT concentration. Currently, the technology of two-dimensional electrophoresis detects a fraction of the total cellular proteins and defective proteins may not show electrophoretic alterations. However, specific secondary changes in other polypeptides may be observed and, when catalogued, will serve as an aid in the diagnosis and understanding of the pathophysiology of metabolic diseases.

Lectins activate lymphocyte pyruvate dehydrogenase by a mechanism sensitive to protease inhibitors

The mitogenic lectins concanavalin A and phytohemagglutinin were found to stimulate pyruvate oxidation in rat mesenteric lymphocytes. Marked cell agglutination accompanied this response. Wheat germ agglutinin, a nonmitogenic lectin, also aggregated lymphocytes but did not cause alteration of pyruvate oxidation. Cell lysates from lectin-treated cells retained their ability to oxidize pyruvate at an elevated rate, indicating that the observed stimulation of pyruvate oxidation was not due to increased transport of labeled pyruvate into the cells. Pyruvate oxidation activity in such lysates was readily sedimented in a mitochondria-enriched cellular fraction, indicating that it reflects mitochondrial pyruvate dehydrogenase. Stimulation of this activity by lectins in intact lymphocytes was inhibited when the cells were incubated under conditions expected to inhibit trypsin-like proteases. Thus, esters of arginine, but not of alanine or tyrosine, blocked stimulation of pyruvate dehydrogenase by the lectins. The data indicate that pyruvate dehydrogenase is activated in lymphocytes treated with mitogenic lectins by a mechanism involving one or more proteolytic reactions. The similarity between the results presented here and those recently reported for insulin action on its target cells [Seals, J. R. & Czech, M. P. (1980) J. Biol. Chem. 255, 6529-6531] suggests that these systems may have similar modes of transmembrane signalling.

Ultrasensitive stain for proteins in polyacrylamide gels shows regional variation in cerebrospinal fluid proteins

A new silver stain for electrophoretically separated polypeptides can be rapidly and easily used and can detect as little as 0.01 nanogram of protein per square millimeter. When employed with two-dimensional electrophoresis, it should permit qualitative and quantitative characterization of protein distributions in body fluids and tissues. It has been used to demonstrate regional variations in cerebrospinal fluid proteins.

Two-dimensional gel electrophoresis of cerebrospinal fluid proteins

Two-dimensional electrophoresis, with isoelectric focusing in the first dimension and sodium dodecyl sulfate/polyacrylamide gel electrophoresis in the second, has been adapted for the high-resolution analysis of cerebrospinal fluid proteins. Proteins were detected with a new, highly sensitive silver stain that made visible more than 300 polypeptides from 60 microL of spinal fluid, in highly reproducible patterns. We have mapped these patterns, noting difference between the proteins observed in spinal fluid and plasma, and have prepared a partial map of cerebrospinal fluid proteins.

Two-dimensional gel electrophoresis of cerebrospinal fluid proteins

Two-dimensional electrophoresis, with isoelectric focusing in the first dimension and sodium dodecyl sulfate/polyacrylamide gel electrophoresis in the second, has been adapted for the high-resolution analysis of cerebrospinal fluid proteins. Proteins were detected with a new, highly sensitive silver stain that made visible more than 300 polypeptides from 60 microL of spinal fluid, in highly reproducible patterns. We have mapped these patterns, noting difference between the proteins observed in spinal fluid and plasma, and have prepared a partial map of cerebrospinal fluid proteins.

Treatment of phenothiazine-induced dyskinesia

Previous experience indicated the possibility that a serotonin antagonist substance, was effective in relieving dyskinesia as a reaction to phenothiazine antipsychotic drugs. Since the substances used in the original observations did not become available on the United States market, a compound known to be a serotonin antagonist, cyproheptadine, which was readily available and safe, was used to treat three patients who had phenothiazine-induced dyskinesia. In these patients, cyproheptadine was definitely effective in relieving the dyskinesia over an extended period of time. Further controlled studies are required to confirm this report.