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Abnormal epidermal turnover in psoriatic skin impairs its barrier function and tissue repair capabilities. Therefore, studies of hyperkeratinization and hyperproliferation have been conducted to better understand the disease. Here, the administration of heavy water and a tape stripping method are used to measure skin protein turnover in psoriatic skin and surrounding tissues. Results demonstrate benefits over other proliferation measurements. [ABSTRACT FROM AUTHOR]

Many biophysical experiments depend on large amounts of pure, soluble protein. Indeed, the revolution in structural biology has depended on molecular biology's potential to make experiments possible by allowing the overexpression of normally rare proteins in a heterologous host. All too often, however, overexpressed proteins are poorly soluble in buffers that attempt to mimic physiological conditions. Often in such cases the overexpressed protein is assumed to be present in inclusion bodies and hopes of obtaining the desired sample from the overexpression vector are abandoned. We have developed a sparse matrix approach to the solubilization of such proteins that is often successful. This approach relies on well accepted theories of protein solubility and folding to build a sparse matrix that samples `solubility space' effectively. The buffers of the sparse matrix are used to make crude extracts that are rapidly assayed for soluble protein using gel electrophoresis. We describe our approach and give examples of its application.

The Ly-6E/A antigen is expressed on activated murine T cells. Using probes made from the previously characterized cDNA, we have isolated a genomic DNA clone encoding the Ly-6A antigen. We determined the DNA sequence of the genomic clone and conducted a functional analysis of the promoter region. Mouse fibroblast BALB/3T3 cells transfected with this genomic clone constitutively expressed Ly-6A antigen on their cell surface. This expression was inducible by alpha/beta and gamma interferons. The Ly-6E 5'-flanking region was analyzed by chloramphenicol acetyltransferase assays in fibroblast cells for cis-acting elements. At least two positive elements were found to be needed for maximum constitutive promoter activity in L cells. One of the positive elements was specifically bound by a CCAAT box-binding protein from crude nuclear extract, as shown by electrophoretic mobility shift assays and footprinting. The other element, which contains a GGAAA motif and has homology to various known enhancers, also showed a specific binding activity. This second positive element when multimerized became a very powerful enhancing element. Interferon treatment could enhance expression of the chloramphenicol acetyltransferase gene fused to the Ly-6E 5'-flanking region in stably transfected BALB/3T3 cells. The elements responsible for this enhancement lie, at least in part, between positions -1760 and -900 of the gene. Surprisingly, there is no sequence homology between this region of Ly-6E and the established consensus for the interferon-stimulated response element, which has been shown functionally important to all previously characterized alpha/beta interferon-inducible promoters. The Ly-6E gene may prove to be a novel system for the study of interferon induction.

The murine Ly-6A/E gene is transcriptionally induced in cells exposed to interferon alpha/beta or gamma (IFN-alpha/beta or IFN-gamma). Analysis of the 5' flanking sequence using reporter plasmids that contain upstream elements of the Ly-6E gene has previously identified an approximately 850-base-pair IFN-responsive region that lacked an IFN-alpha-stimulated response element (ISRE), the element present and required for an IFN-alpha response of a number of genes. Analysis by deletion and stable transfection of the IFN-responsive region of the Ly-6E promoter has defined an 80-base-pair region containing an IFN-gamma activation site (GAS) but no ISRE that allows IFN-gamma and IFN-alpha inducibility of the Ly-6E gene. As tested by specific antiserum, a 91-kDa protein known to be activated in IFN-alpha- or IFN-gamma-treated cells binds to the GAS element from the Ly-6E promoter. The 91-kDa protein exists as an inactive cytoplasmic precursor and depends on tyrosine phosphorylation for its activation. Thus the same 91-kDa protein appears to act in the signal transduction pathways of both types of IFN for the Ly-6-A/E gene.

Conjugation of xenobiotics with glutathione occurs commonly within the liver, and these glutathione conjugates are then preferentially excreted into bile. We have characterized this excretory process using primary cultured hepatocytes (24 h). 1-Chloro-2,4-dinitrobenzene rapidly entered the cells and formed a glutathione conjugate, S-(dinitrophenyl)glutathione, irrespective of the temperature of incubation. In contrast, the efflux of the glutathione conjugate was essentially absent in the cold but recovered rapidly upon rewarming of the cells. Therefore, initial rates of efflux of the conjugate at 37 degrees C were measured from cells preloaded biosynthetically at 10 degrees C. Efflux was a saturable process with respect to intracellular S-(dinitrophenyl)glutathione with an apparent Km of 0.58 +/- 0.12 mM and Vmax of 0.15 +/- 0.05 nmol/min/mg of protein. The excretion of S-(dinitrophenyl)glutathione had an energy of activation of 15.3 kcal/mol. The glutathione conjugate of p-nitrobenzylchloride when formed within the hepatocytes acted as a competitive inhibitor of S-(dinitrophenyl)glutathione efflux. Cultured hepatocytes, therefore, appeared to have a specific transport process for the excretion of glutathione conjugates. The addition of S-(dinitrophenyl)glutathione, but not GSH, GSSG, or methionine, to the medium caused a decrease in the rate of efflux of radiolabeled S-(dinitrophenyl)glutathione. The hepatocytes were able, however, to excrete the glutathione conjugate against an excess of extracellular S-(dinitrophenyl)glutathione. This observation suggested that extracellular S-(dinitrophenyl)glutathione, although capable of binding to the carrier, entered the hepatocytes quite slowly relative to rates of efflux. This carrier may function in a manner that would minimize the reuptake by hepatocytes of conjugates that have been excreted into the bile.

Tau is a family of closely related proteins known for its ability to copolymerize with tubulin, inducing the formation of microtubules. When tau was stripped of phosphate by treatment with alkaline phosphatase it underwent a pronounced change in electrophoretic mobility, probably reflecting a conformational change. The dephosphorylated tau promoted significantly more rapid and more extensive polymerization of microtubules though there was no obvious difference in the microtubules formed. Partially purified microtubule protein contains a kinase that can rephosphorylate tau.