Glucocorticoid receptors in lymphoma cells in culture: relationship to glucocorticoid killing activity

Mouse lymphoma cells in culture which are killed by adrenal steroids contain specific cortisol receptors that may be involved in the initial events of hormone action. The similarity of these receptors to those in hepatoma tissue culture cells, where adrenal steroids induce tyrosine aminotransferase, suggests that certain aspects of steroid action are similar in the two systems. In three steroid-resistant lymphoma cell populations specific binding was less than in the parent lines, suggesting that conversion to steroid resistance may be associated with changes in specific steroid binding.     

Apolipoprotein L-I promotes trypanosome lysis by forming pores in lysosomal membranes

Apolipoprotein L-I is the trypanolytic factor of human serum. Here we show that this protein contains a membrane pore-forming domain functionally similar to that of bacterial colicins, flanked by a membrane-addressing domain. In lipid bilayer membranes, apolipoprotein L-I formed anion channels. In Trypanosoma brucei, apolipoprotein L-I was targeted to the lysosomal membrane and triggered depolarization of this membrane, continuous influx of chloride, and subsequent osmotic swelling of the lysosome until the trypanosome lysed.     

Antibodies to peptides detect new hepatitis B antigen: serological correlation with hepatocellular carcinoma

The expression of a previously unidentified gene product, encoded by the hepatitis B virus (HBV) genome, has been achieved with a recombinant SV40 expression vector. Antibodies against synthetic peptides representing defined regions of this protein were used to screen cells infected with recombinant virus as well as tissues naturally infected with HBV. A 24,000-dalton protein (p24) was detected in cells infected with recombinant virus and a 28,000-dalton protein (p28) was detected in tissues infected with HBV. The peptides or recombinant-derived protein were used as antigens to screen sera from individuals infected with HBV. Specific antibodies were detected predominantly in sera from patients with hepatocellular carcinoma. The presence of p28 in tissues infected with HBV and the appearance of specific antibodies in infectious sera establish the existence of an additional marker for HBV infection.     

H-2 antigen on cell membranes: an explanation for the alteration of distribution by indirect labeling techniques

The distribution of H-2 isoantigens on the plasma membrane of lymphocytes and thymocytes was studied with ferritin-conjugated alloantibody. The spatial arrangement of the membrane components which possess H-2 isoantigens is markedly altered by the attachment of a second antibody, directed toward mouse gamma globulin or ferritin; the second anitibody appears to cause the aggregation of the sensitized H-2 antigens into discrete zones on the cell membrane. Other membrane antigens may be equally affected by indirect labeling techniques and, thus, topographic analysis of the antigenic structure should be done with antibody that is directly conjugated.     

Adenosine 3'5'-monophosphate: inhibition of complement-mediated cell lysis

An increase in adenosine 3',5'-monophosphate (cyclic AMP) in rat mast cells, achieved by stimulating the cells with prostaglandin E(1), by preventing cyclic AMP breakdown with aminophylline, or by adding exogenous dibutyryl cyclic AMP, prevented complement-mediated cytolysis as assessed by both histamine release and vital dye exclusion. Dibutyryl cyclic AMP also suppressed water-induced osmotic lysis.     

B cell antigen receptor signaling: roles in cell development and disease

Signals propagated through the B cell antigen receptor (BCR) are vital for the development and survival of B lymphocytes in both the bone marrow and the periphery. These signals not only guide maturation and activation but also affect the removal of potentially self-reactive B lymphocytes. Interestingly, these signals are known to be either ligand-independent ("tonic" signals) or induced by ligand (antigen) binding to the BCR. We focus on the problems that occur in B cell development due to defects in signals emanating from the BCR. In addition, we present the B Cell Antigen Receptor Pathway, an STKE Connections Map that illustrates the events involved in B cell signaling.     

Structure of membranes: reaction of red blood cell membranes with phospholipase C

Treatment of human red blood cell membranes with phospholipase C releases 68 to 74 percent of the total membrane phosphorus into solution, through hydrolysis of membrane phospholipids to diglycerides and water-soluble phosphorylated amines. In spite of this drastic change, the membrane remains intact in phase microscopy, and the average protein conformation in the membranes, as determined by circular dichroism measurements in the ultraviolet, is unaffected. These results are readily explained by a model of membrane structure that is stabilized by hydrophobic interactions and in which the polar and ionic heads of lipids are on the outer surfaces of the membrane, in contact with the bulk aqueous phase and accessible to the action of phospholipase C.     

Common antigen in meningioma-derived cell cultures

Serums of patients with intracranial meningiomas reacted in immunofluorescence assays with cell cultures and tumor imprints prepared from human meningiomas. Antibody in these serums appears to be specific for antigens in meningioma tissue and shows some cross-reactivity with neoplastic tissue of glial origin.     

Endothelial cell membranes: polarity of particles as seen by freeze-fracturing

Freeze-fracturing shows particles within membranes. In plasma membranes of most cells the particles are more strongly bound to the inner half. In unfixed endothelial cells, this polarity is reversed. Glutaraldehyde fixation results in conventional polarity. The reverse polarity may be related to a mechanism for preferential fusion of pinocytotic vesicles with the plasma membrane.     

Ferroin-collodion membranes: dynamic concentration patterns in planar membranes

Patterns and waves of the Belousov-Zhabotinskii reaction are produced in membranes in which one reactant is immobilized. Convection is eliminated, the generation and deformation of wave forms are studied, and patterns are permnanently fixed. Wave shape, frequency, length, and phase velocity are explained theoretically by the interactions of diffusion with reaction.     

Boradeption: a new procedure for transferring water-insoluble agents across cell membranes

A new process has been developed which is called "Boradeption" to signify boronic acid--dependent phase transfer of water-insoluble agents. Highly fluorescent boronic acid dervatives, FluoroBoras, are solubilized with a physiologically compatible carrier buffer containing a receptor group for boronate adduct formation. The system can be used to stain living cells. In another variation of the Boradeption concept, an insoluble reporter molecule containing a boronate receptor is solubilized with a carrier buffer containing a boronic acid functional group. The boronate-receptor complexes, which are in dynamic equilibrium, can be designed as vital stains and reagents for a variety of biological and medical applications.     

Artificial membranes: a new type of cell for measuring diffusional resistance

A novel technique allows determination of membrane diffusivities and eliminates the complications of the fluid resistance to mass transfer on either side of the membrane. Results on the permeability of a dialysis membrane of the type used in artificial kidneys agree with previous data and are obtained in much shorter time. The measured activation energy for diffusion demonstrates that the transport of salt through the membrane occurs by the same mechanism as the diffusion of salt in water, but that only 10 percent of the membrane surface is effective.     

Differential antigen processing by dendritic cell subsets in vivo

Dendritic cells (DCs) process and present self and foreign antigens to induce tolerance or immunity. In vitro models suggest that induction of immunity is controlled by regulating the presentation of antigen, but little is known about how DCs control antigen presentation in vivo. To examine antigen processing and presentation in vivo, we specifically targeted antigens to two major subsets of DCs by using chimeric monoclonal antibodies. Unlike CD8+ DCs that express the cell surface protein CD205, CD8- DCs, which are positive for the 33D1 antigen, are specialized for presentation on major histocompatibility complex (MHC) class II. This difference in antigen processing is intrinsic to the DC subsets and is associated with increased expression of proteins involved in MHC processing.     

Development of excitability in embryonic muscle cell membranes in certain tunicates

During the course of development of muscle cells in certain tunicates, a sign of regenerative membrane response appears in the gastrula stage. In the early tadpole larva, the action potential consists of a spike followed by a plateau. The latter-disappears in fully differentiated cells, conceivably in association with the establishment of delayed rectification.     

Early signal transduction by the antigen receptor without commitment to T cell activation

The T lymphocyte antigen-receptor complex mediates antigen-specific cell activation, at least in part, through the production of inositolphospholipid-derived second messengers. Little is known about how second messenger events, typically measured within minutes of ligand binding, eventually lead to distal biologic responses such as expression of lymphokine genes. Several monoclonal antibodies directed against the receptor complex were tested for their ability to elicit transmembrane signaling in the parental Jurkat line and in a somatic mutant (J.CaM1) with a deficient receptor function. One antibody elicited substantial early Ca2+ mobilization responses in both cells but was unable to promote expression of the interleukin-2 gene in J.CaM1. In J.CaM1 there was a diminished production of phosphatidylinositol second messengers, and the elevation in intracellular free Ca2+ was transient. Thus, short-term Ca2+ mobilization does not always indicate complete signal transmission and lead to a full cellular response.     

Translocation of C. elegans CED-4 to nuclear membranes during programmed cell death

The Caenorhabditis elegans Bcl-2-like protein CED-9 prevents programmed cell death by antagonizing the Apaf-1-like cell-death activator CED-4. Endogenous CED-9 and CED-4 proteins localized to mitochondria in wild-type embryos, in which most cells survive. By contrast, in embryos in which cells had been induced to die, CED-4 assumed a perinuclear localization. CED-4 translocation induced by the cell-death activator EGL-1 was blocked by a gain-of-function mutation in ced-9 but was not dependent on ced-3 function, suggesting that CED-4 translocation precedes caspase activation and the execution phase of programmed cell death. Thus, a change in the subcellular localization of CED-4 may drive programmed cell death.     

HTLV-V: a new human retrovirus isolated in a Tac-negative T cell lymphoma/leukemia

A new human retrovirus was isolated from a continuous cell line derived from a patient with CD4+ Tac- cutaneous T cell lymphoma/leukemia. This virus is related to but distinct from human T cell leukemia/lymphoma virus types I and II (HTLV-I and HTLV-II) and human immunodeficiency virus (HIV-1). With the use of a fragment of provirus cloned from one patient with T cell leukemia, closely related sequences were found in DNA of the cell line and of tumor cells from seven other patients with the same disease; these sequences were only distantly related to HTLV-I. The phenotype of the cells and the clinical course of the disease were clearly distinguishable from leukemia associated with HTLV-I. All patients and the wife of one patient showed a weak serological cross-reactivity with both HTLV-I and HIV-1 antigens. None of the patients proved to be at any apparent risk for HIV-1 infection. The name proposed for this virus is HTLV-V, and the date indicate that it may be a primary etiological factor in the major group of cutaneous T cell lymphomas/leukemias, including the sporadic lymphomas known as mycoses fungoides.     

Lymphocyte stimulation: transfer of cellular hypersensitivity to antigen in vitro

Tuberculin-sensitive human lymphocytes cultured for 36 hours with tuberculin elaborate a soluble material which causes nonsensitive lymphocytes to respond to tuberculin in vitro by transformation and proliferation.     

Cholesterol hydroperoxide formation in red cell membranes and photohemolysis in erythropoietic protoporphyria

3beta-Hydroxy-5alpha-hydroperoxy-Delta(6)-cholestene is produced in protoporphyrin-containing red blood cell ghosts irradiated with approximately 400-nanometer light in the presence of oxygen. Incorporation of this cholesterol photooxidation product into normal red blood cells leads to increased osmotic fragility and eventual hemolysis. These results may be relevant to photohemolysis associated with erythropoietic protoporphyria.     

Oncogenic CARD11 mutations in human diffuse large B cell lymphoma

Diffuse large B cell lymphoma (DLBCL) is the most common form of non-Hodgkin's lymphoma. In the least curable (ABC) subtype of DLBCL, survival of the malignant cells is dependent on constitutive activation of the nuclear factor-kappaB (NF-kappaB) signaling pathway. In normal B cells, antigen receptor-induced NF-kappaB activation requires CARD11, a cytoplasmic scaffolding protein. To determine whether CARD11 contributes to tumorigenesis, we sequenced the CARD11 gene in human DLBCL tumors. We detected missense mutations in 7 of 73 ABC DLBCL biopsies (9.6%), all within exons encoding the coiled-coil domain. Experimental introduction of CARD11 coiled-coil domain mutants into lymphoma cell lines resulted in constitutive NF-kappaB activation and enhanced NF-kappaB activity upon antigen receptor stimulation. These results demonstrate that CARD11 is a bona fide oncogenein DLBCL, providing a genetic rationale for the development of pharmacological inhibitors of the CARD11 pathway for DLBCL therapy.