Tyrosine phosphorylation is essential for microfilament assembly in B lymphocytes

The B cell antigen receptor regulates the tyrosine kinase signal transduction pathway and it mediates a variety of morphological changes such as capping and membrane ruffling. The relationship between these two events is unclear. We show here that cross-linking the antigen receptor on human B lymphocytes, in addition to increasing tyrosine phosphorylation of specific substrates, induces the conversion of G-actin to F-actin. Preincubation of B lymphocytes with two different tyrphostins blocked anti-IgM-induced tyrosine phosphorylation and actin polymerization. The ability of the tyrphostins to block anti-IgM induced conversion of G-actin to F-actin indicates that a tyrosine kinase acts as an essential link between the B cell antigen receptor the early changes in cytoskeletal reorganization.     

Identification and biochemical analysis of novel olfactory-specific cytochrome P-450IIA and UDP-glucuronosyl transferase

Two major transmembranal polypeptides of bovine olfactory epithelium were identified by SDS electrophoretic analysis of Triton X-114 solubilized membranes. Both polypeptides were present in large amounts in membranes of the olfactory epithelium but were barely detectable in membranes of the nasal respiratory epithelium. Both polypeptides are enriched in the deciliated epithelium as compared with isolated cilia. One of them is a glycoprotein with an apparent molecular mass of 56 kDa (gp56); the other is an unglycosylated protein with an apparent molecular mass of 52 kDa (p52). Sequence analysis of peptides obtained by CNBr cleavage of purified gp56 indicates that it is highly homologous to UDP-glucuronosyl transferase (UDPGT). Parallel analysis shows that p52 is highly homologous to cytochrome P-450 sequences of the IIA subfamily. This protein is assigned the name P-450olf2. Polyclonal antibodies were raised against synthetic peptides corresponding to gp56 and p52 peptide sequences. Immunoblots with these antibodies reveal the following properties of gp56 and p52: (1) they are enriched in the microsomal fraction of the bovine olfactory epithelium; (2) they are possibly specific to the olfactory epithelium, as we could not detect reactivity in microsomes derived from respiratory epithelium or lung, and only a very small amount of basal reactivity was seen with liver microsomes; (3) cross-reacting proteins exist in microsomes derived from the rat olfactory epithelium. These results are consistent with a mechanism whereby the microsomal enzymes are involved in odorant modification and clearance from the nasal tissue.     

Effect of divalent metal ions on the digestibility of concanavalin A by endopeptidases.

Demetallized concanavalin A is degraded rapidly at pH 7.0 and 8.2 by alpha-chymotrypsin, thermolysin or trypsin, yielding peptide fragments devoid of ability to bind to Sephadex G-75. Addition of Ni2+ and of Ca2+ confers on concanavalin A high resistance towards proteolytic attack so that even after long periods of exposure to the enzymes, almost all of the saccharide-binding capacity is preserved. Ni2+ alone protects strongly at pH 7.0 but not at pH 8.2. Apparently, both the transition metal ion and Ca2+ play an important role in stabilizing the native conformation of the protein molecule. Digestion of demetallized concanavalin A with alpha-chymotrypsin or thermolysin readily yields small peptide fragments (Mr less than 10 000), while trypsin yields as the major product(s) larger peptide(s) (Mr approximately 20 000) of appreciable resistance to further fragmentation.     

Conformation of RNA in situ as studied by acridine orange staining and automated cytofluorometry.

Human erythroblasts which are prereticulocyte maturation stages of red blood cells were studied by light microscopic cytochemistry and electron microscopy to provide more information on the ultrastructure of the micronucleoli which are terminal stages of nucleolar changes found during maturation of these cells. As indicated by light microscopy of smeared cells, micronucleoli were virtually the only types of nucleoli present in the last stages of maturing erythroblasts, i.e., polychromatic and orthochromatic (late polychromatic) erythroblasts. Accordingly, they were not portions of the periphery of other nucleoli. Inasmuch as most of the micronucleoli exhibited characteristic segregation of nucleolar fibrillar and granular components they presumably are producing little if any preribosomal RNA, since such segregation generally reflects inhibition of nucleolar RNA synthesis.     

The cleavage of transfer RNA by a single strang specific endonuclease from Neurospora crassa.

Endonuclease from Neurospora crassa (NcNase), an enzyme with specificity for polynucleotides lacking an ordered structure, was shown to cleave su+3 tRNATyr from E. coli preferentially in the anticodon region. The enzyme cleaved unfractionated tRNA primarily to 30 - 50 nucleotide size fragments, implying that most or all tRNA species are also cleaved in the anticodon region. The 3' terminal sequence C-A was cleaved as well. The results are discussed with respect to the three dimensional structure of tRNA.     

Incorporating physiology into species distribution models moderates the projected impact of warming on selected Mediterranean marine species

Species distribution models (SDMs) correlate species occurrences with environmental predictors, and can be used to forecast distributions under future climates. SDMs have been criticized for not explicitly including the physiological processes underlying the species response to the environment. Recently, new methods have been suggested to combine SDMs with physiological estimates of performance (physiology-SDMs). In this study, we compare SDM and physiology-SDM predictions for select marine species in the Mediterranean Sea, a region subjected to exceptionally rapid climate change. We focused on six species and created physiology-SDMs that incorporate physiological thermal performance curves from experimental data with species occurrence records. We then contrasted projections of SDMs and physiology-SDMs under future climate (year 2100) for the entire Mediterranean Sea, and particularly the ‘warm’ trailing edge in the Levant region. Across the Mediterranean, we found cross-validation model performance to be similar for regular SDMs and physiology-SDMs. However, we also show that for around half the species the physiology-SDMs substantially outperform regular SDM in the warm Levant. Moreover, for all species the uncertainty associated with the coefficients estimated from the physiology-SDMs were much lower than in the regular SDMs. Under future climate, we find that both SDMs and physiology-SDMs showed similar patterns, with species predicted to shift their distribution north-west in accordance with warming sea temperatures. However, for the physiology-SDMs predicted distributional changes are more moderate than those predicted by regular SDMs. We conclude, that while physiology-SDM predictions generally agree with the regular SDMs, incorporation of the physiological data led to less extreme range shift forecasts. The results suggest that climate-induced range shifts may be less drastic than previously predicted, and thus most species are unlikely to completely disappear with warming climate. Taken together, the findings emphasize that physiological experimental data can provide valuable supplemental information to predict range shifts of marine species.     

Mutant p53 Attenuates the Anti-Tumorigenic Activity of Fibroblasts-Secreted Interferon Beta

Mutations in the p53 tumor suppressor protein are highly frequent in tumors and often endow cells with tumorigenic capacities. We sought to examine a possible role for mutant p53 in the cross-talk between cancer cells and their surrounding stroma, which is a crucial factor affecting tumor outcome. Here we present a novel model which enables individual monitoring of the response of cancer cells and stromal cells (fibroblasts) to co-culturing. We found that fibroblasts elicit the interferon beta (IFNβ) pathway when in contact with cancer cells, thereby inhibiting their migration. Mutant p53 in the tumor was able to alleviate this response via SOCS1 mediated inhibition of STAT1 phosphorylation. IFNβ on the other hand, reduced mutant p53 RNA levels by restricting its RNA stabilizer, WIG1. These data underscore mutant p53 oncogenic properties in the context of the tumor microenvironment and suggest that mutant p53 positive cancer patients might benefit from IFNβ treatment.