Functions of interleukin 1 receptor antagonist in gene knockout and overproducing mice.

Interleukin 1 receptor antagonist (IL-1ra) is a cytokine whose only known action is competitive inhibition of the binding of interleukin 1 (IL-1) to its receptor. To investigate the physiological roles of endogenously produced IL-1ra, we generated mice that either lack IL-1ra or overproduce it under control of the endogenous promoter. Mice lacking IL-1ra have decreased body mass compared with wild-type controls. They are more susceptible than controls to lethal endotoxemia but are less susceptible to infection with Listeria monocytogenes. Conversely, IL-1ra overproducers are protected from the lethal effects of endotoxin but are more susceptible to listeriosis. Serum levels of IL-1 following an endotoxin challenge are decreased in IL-1ra nulls and increased in IL-1ra overproducers in comparison to controls. These data demonstrate critical roles for endogenously produced IL-1ra in growth, responses to infection and inflammation, and regulation of cytokine expression.

Separation of the transcriptional coactivator and antirepression functions of transcription factor IIA.

Human transcription factor IIA (TFIIA) is composed of three subunits (alpha, beta, and gamma). TFIIA interacts with the TATA-box binding protein and can overcome repression of transcription. TFIIA was found to be necessary for VP16-mediated transcriptional activation through a coactivator function. We have separated the coactivator and antirepression activities of TFIIA. A TFIIA lacking the alpha subunit was isolated from HeLa cells. This "mini-TFIIA" interacts with the TATA-box binding protein and can overcome repression of transcription, but it is defective in transcriptional coactivator function.

Differential functions of the two Src homology 2 domains in protein tyrosine phosphatase SH-PTP1.

SH-PTP1 (also known as PTP1C, HCP, and SHP) is a non-transmembrane protein tyrosine phosphatase (PTPase) containing two tandem Src homology 2 (SH2) domains. We show here that the two SH2 (N-SH2 and C-SH2) domains in SH-PTP1 have different functions in regulation of the PTPase domain and thereby signal transduction. While the N-terminal SH2 domain is both necessary and sufficient for autoinhibition through an intramolecular association with the PTPase domain, truncation of the C-SH2 domain [SH-PTP1 (delta CSH2) construct] has little effect on SH-PTP1 activity. A synthetic phosphotyrosine residue (pY) peptide derived from the erythropoietin receptor (EpoR pY429) binds to the N-SH2 domain and activates both wild-type SH-PTP1 and SH-PTP1 (delta CSH2) 60- to 80-fold. Another pY peptide corresponding to a phosphorylation site on the IgG Fc receptor (Fc gamma RIIB1 pY309) associates with both the C-SH2 domain (Kd = 2.8 microM and the N-SH2 domain (Kd = 15.0 microM) and also activates SH-PTP1 12-fold. By analysis of the effect of the Fc gamma RIIB1 pY309 peptide on SH-PTP1 (delta CSH2), SH-PTP1 (R30K/R33E), SH-PTP1 (R30K/R136K), and SH-PTP1 (R136K) mutants in which the function of either the N- or C-SH2 domain has been impaired, we have determined that both synthetic pY peptides stimulate SH-PTP1 by binding to its N-SH2 domain; binding of pY ligand to the C-SH2 domain has no effect on SH-PTP1 activity. We propose that the N-terminal SH2 domain serves both as a regulatory domain and as a recruiting unit, whereas the C-terminal SH2 domain acts merely as a recruiting unit.

Subunit-specific functions of N-linked oligosaccharides in human thyrotropin: role of terminal residues of alpha- and beta-subunit oligosaccharides in metabolic clearance and bioactivity.

The recombinant human thyroid stimulating hormone (rhTSH) containing oligosaccharides terminated with NeuAc(alpha 2-3)Gal(beta 1-4)GlcNAc beta 1 showed higher in vivo activity and lower metabolic clearance rate (MCR) than pituitary human TSH (phTSH), which contains oligosaccharides terminating predominantly in SO(4)4GalNAc(beta 1-4)GlcNAc beta 1. To elucidate the relative contribution of the sulfated and sialylated carbohydrate chains of each subunit in the MCR and bioactivity of the hormone, the alpha and beta subunits of phTSH, rhTSH, and enzymatically desialylated rhTSH (asialo-rhTSH; asrhTSH) were isolated, their oligosaccharides were analyzed, and the respective subunits were dimerized in various combinations. The hybrids containing alpha subunit from phTSH or asrhTSH showed higher in vitro activity than those with alpha subunit from rhTSH, indicating that sialylation of alpha but not beta subunit attenuates the intrinsic activity of TSH. In contrast, hybrids with beta subunit from rhTSH displayed lower MCR compared to those with beta subunit from phTSH. The phTSH alpha-rhTSH beta hybrid had the highest in vivo bioactivity followed by rhTSH alpha-rhTSH beta, rhTSH alpha-phTSH beta, phTSH alpha-phTSH beta, and asrhTSH dimers. These differences indicated that hybrids with beta subunit from rhTSH displayed the highest in vivo activity and relatively low MCR, probably due to higher sialylation, more multiantennary structure, and/or the unique location of the beta-subunit oligosaccharide chain in the molecule. Thus, the N-linked oligosaccharides of the beta subunit of glycoprotein hormones have a more pronounced role than those from the alpha subunit in the metabolic clearance and thereby in the in vivo bioactivity. In contrast, the terminal residues of alpha-subunit oligosaccharides have a major impact on TSH intrinsic potency.

Distinct functions of SR proteins in recruitment of U1 small nuclear ribonucleoprotein to alternative 5' splice sites.

Alternative splicing of precursor messenger RNAs (pre-mRNAs) is an important mechanism for the regulation of gene expression. The members of the SR protein family of pre-mRNA splicing factors have distinct functions in promoting alternative splice site usage. Here we show that SR proteins are required for the first step of spliceosome assembly, interaction of the U1 small nuclear ribonucleoprotein complex (U1 snRNP) with the 5' splice site of the pre-mRNA. Further, we find that individual SR proteins have distinct abilities to promote interaction of U1 snRNP with alternative 5' splice junctions. These results suggest that SR proteins direct 5' splice site selection by regulation of U1 snRNP assembly onto the pre-mRNA.

Disipation Functions of Flow Equations in Models of Complex Systems

In an open system, each disequilibrium causes a force. Each force causes a flow process, these being represented by a flow variable formally written as an equation called flow equation, and if each flow tends to equilibrate the system, these equations mathematically represent the tendency to that equilibrium. In this paper, the authors, based on the concepts of forces and conjugated fluxes and dissipation function developed by Onsager and Prigogine, they expose the following hypothesis: Is replaced in Prigogine’s Theorem the flow by its equation or by a flow orbital considering conjugate force as a gradient. This allows to obtain a dissipation function for each flow equation and a function of orbital dissipation.

Chemical diversity and potential biological functions of the pygidial gland secretions in two species of Neotropical dung roller beetles

Dung roller beetles of the genus Canthon (Coleoptera: Scarabaeinae) emit an odorous secretion from a pair of pygidial glands. To investigate the chemical composition of these secretions, we used stir bar sorptive extraction (SBSE), coupled with gas chromatography–mass spectrometry (GC–MS) for analysis of extracts of pygidial gland secretions secreted by the dung roller beetles Canthon femoralis femoralis and Canthon cyanellus cyanellus. Chemical analyses of volatiles collected from pygidial gland secretions comprise a great diversity of the functional groups. Chemical profile comparisons showed high intra- and interspecific variability. The pygidial gland secretion of Canthon f. femoralis was dominated by sesquiterpene hydrocarbons, whereas the profile of Canthon c. cyanellus was dominated by carboxylic acids. The different pygidial secretions have a high diversity of chemical compounds suggesting a multifunctional nature involving some key functions in the biology. We discuss the biological potential of these compounds found in the pygidial glands of each species with respect to their ecological and behavioral relevance.