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F Solomon

Publications and source records attributed to F Solomon.

At least 19 recordsLinked to original sources
PubMed1992

Identification of a mouse brain cDNA that encodes a protein related to the Alzheimer disease-associated amyloid beta protein precursor.

We have isolated a cDNA from a mouse brain library that encodes a protein whose predicted amino acid sequence is 42% identical and 64% similar to that of the amyloid beta protein precursor (APP). This 653-amino acid protein, which we have termed the amyloid precursor-like protein (APLP), appears to be similar to APP in overall structure as well as amino acid sequence. The amino acid homologies are concentrated within three distinct regions of the two proteins where the identities are 47%, 54%, and 56%. The APLP cDNA hybridizes to two messages of approximately 2.4 and 1.6 kilobases that are present in mouse brain and neuroblastoma cells. Polyclonal antibodies raised against a peptide derived from the C terminus of APLP stain the cytoplasm in a pattern reminiscent of Golgi staining. In addition to APP, APLP also displays significant homology to the Drosophila APP-like protein APPL and a rat testes APP-like protein. These data indicate that the APP gene is a member of a strongly conserved gene family. Studies aimed at determining the functions of the proteins encoded by this gene family should provide valuable clues to their potential role in Alzheimer disease neuropathology.

Amino Acid Sequence↗
PubMed1992

Neuronal cytoskeleton and growth.

The involvement of the cytoskeleton in the expression of neuronal morphology is most obvious in its support of neurite extension and the motile activity of growth cones. Techniques permitting direct observation of the dynamics of proteins in living cells, along with attempts to assay protein function in vivo, are testing existing models for cytoskeletal function in neurons, as well as generating more detailed models at the molecular level.

Animals↗
PubMed1992

Microtubule assembly and phage morphogenesis: new results and classical paradigms.

The classical analyses of phage morphogenesis provide experimental paradigms for dissecting other assembly pathways. A new set of results, derived from examination of the quantitative controls of tubulin levels and microtubule assembly in Saccharomyces cerevisiae, evokes the 'balance of components' hypothesis. These results show that balanced levels of the tubulin proteins are crucial for microtubule assembly. Imbalances leading to excess beta tubulin have far more deleterious consequences than those leading to excess alpha tubulin, including dramatic cellular toxicity, quantitative depolymerization of cellular microtubules, and self-aggregation of the excess beta tubulin. These and other results suggest that beta tubulin may possess a unique ability to interact with a component of microtubule nucleating sites, and provide a rationale for the universal polarity of nucleated microtubules.

Bacteriophages↗
PubMed1992

Molecular genetic analysis of the Escherichia coli phoP locus.

We have cloned the Escherichia coli phoP gene, a member of the family of environmentally responsive two-component systems, and found its deduced amino acid sequence to be 93% identical to that of the Salmonella typhimurium homolog, which encodes a major virulence regulator necessary for intramacrophage survival and resistance to cationic peptides of phagocytic cells. The phoP gene was mapped to kilobase 1202 on the Kohara map (25-min region) of the E. coli genome (Y. Kohara, K. Akiyama, and K. Isono, Cell 50:495-508, 1987) and found to be transcribed in a counterclockwise direction. Both E. coli and S. typhimurium phoP mutants were more sensitive than their isogenic wild-type strains to the frog-derived antibacterial peptide magainin 2, suggesting a role for PhoP in the response to various stresses in both enteric species.

Amino Acid Sequence↗
PubMed1991

A role for microtubule bundles in the morphogenesis of chicken erythrocytes.

The acquisition of cellular asymmetry is one of the post-mitotic events in development. The cells of the avian erythropoietic lineage acquire a simple invariant asymmetry as they mature. Erythrocytes develop in suspension from spherical through discoid to lentil-shaped (lentiform) cells, with a single rigorously specified microtubule bundle, the marginal band. We show here that developing erythrocytes can express highly asymmetric morphologies, including elongated cell bodies and long processes in response to two stimuli: mechanical manipulation (repeated washing) and exposure to cytochalasin D. These experiments suggest that erythrocytes pass through a developmental stage during which microtubules are able to exert elongating forces on the cell. That stage is one in which these cells normally change shape, from spherical to discoid. The results suggest that microtubules may both guide and drive the formation of the marginal band and the characteristic morphology of these cells.

Actins↗
PubMed1991

Association of ezrin isoforms with the neuronal cytoskeleton.

We are studying the changes in the organization of the cytoskeleton which accompany expression of differentiated neuronal morphology. Of particular interest is the elaboration of growth cones, the motile domains of the neuronal plasma membrane, and the cytoskeletal structures that underlie them. A candidate for a component of the growth cone cytoskeleton of cultured hippocampal neurons is the antigen recognized by the monoclonal antibody, 13H9 (Birgbauer and Solomon, J Cell Biol 109:1609-1620, 1989; Goslin et al., J Cell Biol 109:1621-1631, 1989). That antibody binds strongly to growth cones, but barely stains neurites. The characterization of the antigen, both biochemical and microscopic, suggests that it may interact with microfilaments and microtubules. We have established that 13H9 recognizes a subset of the isoforms of ezrin (unpublished results). Here, we describe the properties and localization of ezrin isoforms in differentiating neuronal cells, using two in vitro systems and developing spinal cord. In embryonal carcinoma cells, both the abundance of ezrin and the proportion of ezrin associated with the cytoskeletal fraction increase upon induction of neuronal differentiation with retinoic acid. In the neuronal cells within such cultures, the 13H9-positive forms of ezrin are enriched in the growth cone, while the bulk of ezrin identified by a polyclonal antibody shows no specific localization. In mouse DRG neurons, 13H9 staining is asymmetrically distributed along the edges of the complex growth cones of these cells. Staining of developing spinal cord in rat embryos also demonstrates that the 13H9-positive forms of ezrin do not colocalize with the majority of ezrin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

A codon change in beta-tubulin which drastically affects microtubule structure in Drosophila melanogaster fails to produce a significant phenotype in Saccharomyces cerevisiae.

The relative uniformity of microtubule ultrastructure in almost all eukaryotic cells is thought to be a consequence of the conserved elements of tubulin sequence. In support of this idea, a mutation in a beta-tubulin gene of Drosophila melanogaster, occurring at a highly conserved position, produces U-shaped microtubules, suggesting a defect in either nucleation or packing during assembly (M. T. Fuller, J. H. Caulton, J. A. Hutchens, T. C. Kaufman, and E. C. Raff, J. Cell Biol. 104:385-394, 1987, and J. E. Rudolph, M. Kimble, H. D. Hoyle, M. A. Subler, and E. C. Raff, Mol. Cell. Biol. 7:2231-2242, 1987). Surprisingly, we find that introducing the same mutation into the sole beta-tubulin gene of Saccharomyces cerevisiae has virtually no consequences for microtubule structure or function in that organism.

Animals↗
PubMed1979

Sleeping pills.

Explore the source record for details and available documents.

Anti-Anxiety Agents↗
PubMed1979

Identification with cellular microtubules of one of the co-assemlbing microtubule-associated proteins.

In this paper we describe a procedure for detecting proteins associated with cytoplasmic microtubules in vivo. Detergent-extracted cytoskeletons of NIL8 hamster cells are prepared under conditions which preserve the microtubules. The cytoskeletons are then extracted in the presence of calcium, which depolymerizes the microtubules and quantitatively extracted cytoskeletons are prepared from cells that have been incubated with colchicine. The cytoskeletons from these cells contain no microtubules or tubulin. Electrophoretic analysis of the calcium extracts of the colchicine-treated and untreated cells reveals several radioactively labeled polypeptides. There is, however, no apparent quantitative or qualitative difference between the two extracts other than the tubulin polypeptides. Each of the extracts is mixed with an excess of unlabeled calf brain microtubule protein and carried through cycles of temperature-dependent microtubule assembly. Distinct species from each extract co-assemble at a constant ratio, but only one polypeptide is uniquely derived from cells containing intact microtubules. The molecular weight of this polypeptide is similar to that proposed for the tau species detected in brain microtubule preparations.

Animals↗
PubMed1979

Detailed neurite morphologies of sister neurolbastoma cells are related.

Neuroblastoma cells exhibit a wide variety of patterns of neurite morphology. However, when these cells are induced to extend neurites under conditions in which mitotic sister cells are readily identifiable, 60% of these sister pairs display analogous morphologies. These cells are related either as identical twins or as mirror images of each other. The relatedness is expressed in considerable detail of neurite morphology. These relationshiops can persist through at least two cell divisions. The results suggest that animal cells can inherit specific determinants of shape.

Animals↗
PubMed1979

The outer boundary of the cytoskeleton: a lamina derived from plasma membrane proteins.

We prepared the cytoskeletal framework by gently extracting cells with Triton X-100. Lipids and soluble proteins were removed, leaving a complex meshlike structure which contains the cell nucleus and is composed of the major cell filament networks as well as the microtrabeculae with attached polyribosomes. The surface sheet or lamina covering this structure contains most of the cell surface proteins by the following criteria. Intact cells are labeled externally with radioiodine and then extracted with detergent. The iodinated poteins remain almost entirely with skeletal framework. A new major integral protein, the coat protein of Sindbis virus, is inserted into the plasma membrane of infected cells. This new protein is heavily iodinated and remains almost completely associated with the framework after extraction. Lectin binding and poliovirus binding sites are also retained after detergent extraction. Our results indicate that plasma membrane proteins form a sheet or lamina upon removal of lipids. This lamina reproduces even complex surface convolutions and appears to be supported by and intimately connected to the underlying skeleton. In this case, the surface lamina, and hence the plasma membrane of the original intact cell, might be viewed as a component of the cytoskeletal framework.

Animals↗
PubMed1979

Crawling movements of lymphocytes on and beneath fibroblasts in culture.

Some lymphocytes become highly motile upon immunological stimulation in vivo or in vitro. When introduced into a culture of 3T3 or L cells and followed by live-cell microscopy, some of these lymphocytes were observed to crawl on top of, along the edges of, and preferentially beneath the attached fibroblasts. The crawling could be as rapid as 20 mum/min, easily detectable without a time-lapse device. The striking ability of crawling lymphocytes to penetrate beneath attached 3T3 cells provided a quantitative means to compare the crawling activity of different lymphocyte populations under various conditions. Crawling was diminished by inhibitors of energy metabolism, by agents that disrupt the cytoskeleton, and by absence of Mg(2+) and Ca(2+), but not of Ca(2+) alone. Crawling lymphocytes were virtually absent in normal thymus and spleen cells. They increased greatly in 5-day mixed lymphocyte cultures and in peritoneal exudate lymphocytes taken after mice had been immunized with allogeneic tumor cells. T cells accounted for most of the crawlers. Of two T-cell leukemias tested, R1(+) cells were crawlers whereas EL-4 cells were not. The H-2 haplotype of the 3T3 fibroblasts (i.e., whether syngeneic or allogeneic) had no apparent effect on lymphocyte crawling activity. The crawling may relate to the exploration of cell surface antigens by lymphocytes (immune surveillance), to the mode of action of cytotoxic T cells, to the migration of lymphocytes across blood vessel walls, or to the penetration of lymphocytes into "solid" masses of normal tissue or tumor cells.

Animals↗