Targeted gene transfer to human hematopoietic progenitor cell lines through the c-kit receptor

In this report, we describe a novel gene therapy approach for hematopoietic stem/progenitor cells using a specific receptor-mediated gene transfection procedure to target c-kit+ cell lines. The vector consists of plasmid DNA containing a luciferase reporter gene that is condensed by electrostatic forces with polylysine (PL) covalently linked to streptavidin (binds biotinylated ligand) and PL covalently linked to adenovirus (AD; to achieve endosomal lysis) with the final addition of biotinylated steel factor (SLF-biotin). Targeted transfection of growth factor-dependent hematopoietic progenitor cell lines that express c-kit showed specific luciferase gene expression over cell lines that did not express c-kit. This effect was dependent on the dose of SLF-biotin and was competed by excess SLF or with monoclonal antibodies that recognize c-kit and block the binding of SLF to its receptor. Maximum transfection efficiency (> 90%) requires a 2-hour incubation period of the vector with the cells, and maximum gene expression occurred 30 hours later. Removal of the endosomalytic agent, AD, from the vector resulted in the loss of gene expression. Vector targeting was versatile and could be changed by the addition of other biotinylated ligands. In principle, this vector should be broadly applicable to deliver genes to hematopoietic stem/progenitor cells in vitro and in vivo.

Granulocyte-colony stimulating factor and lipopolysaccharide regulate the expression of interleukin 8 receptors on polymorphonuclear leukocytes

Interleukin 8 (IL-8) is a potent chemoattractant and activating factor for human polymorphonuclear leukocytes (PMN) and hence plays a critical role in the pathogenesis of acute inflammation. Two unique but homologous receptors for IL-8 have been cloned (IL-8RA and -B), each of which binds the IL-8 ligand with high affinity. PMN stimulated by cytokines or lipopolysaccharide (LPS) exhibit changes in IL-8R mRNA and 125I-IL-8 binding. Granulocyte-colony stimulating factor (G-CSF) treatment of PMN enhances, and LPS inhibits, IL-8R mRNA expression. Similarly, 125I-IL-8 ligand binding to PMN is increased by G-CSF and decreased by LPS treatment. The stimulatory effect of G-CSF on IL-8R expression is transcriptional as it is inhibited by actinomycin D and is evident in nuclear run-on analyses. In contrast, LPS down-regulates IL-8R by both transcriptional and post-transcriptional mechanisms. The alterations in IL-8R expression are associated with similar changes in the IL-8-induced chemotactic responses of PMN. In conclusion, the two types of IL-8 receptor differ in their cellular distribution and are regulated in response to cytokines and LPS. Regulation of IL-8R expression by endogenous and exogenous immunomodulators may be important in the in vivo control of PMN effector functions in inflammation.

Characterization of a 97-kDa phosphotyrosylprotein regulated by multiple cytokines

We have examined the signal transduction pathways of a number of cytokines that interact with receptors that are members of the hematopoietin receptor superfamily. A 97-kDa protein was phosphorylated on tyrosine in response to stimulation of appropriate target cells with interleukin (IL)-2, IL-3, granulocyte-macrophage colony-stimulating factor (CSF), granulocyte-CSF, or erythropoietin. These data suggest that a 97-kDa phosphotyrosylprotein represents a point of convergence for signal transduction by a number of growth factor receptors that do not have homology with any known protein tyrosine kinase. To address the possibility that p97 may represent a tyrosine kinase involved in multiple signal transduction pathways, we tested the capacity of this protein to bind a tyrosine kinase substrate or ATP. Indeed, a 97-kDa phosphotyrosylprotein purified from IL-2-stimulated lymphoid cells as well as granulocyte-macrophage-CSF-stimulated myeloid cells bound to a polymer of glutamic acid and tyrosine which is a tyrosine kinase substrate. Further, a 97-kDa phosphotyrosylprotein present in both lineages also bound 8-azido-ATP. These data indicate that a 97-kDa phosphotyrosylprotein with properties consistent with those of a protein tyrosine kinase is involved in the signal transduction pathways of certain members of the newly identified hematopoietin receptor superfamily and may represent an early point of convergence in the stimulus-response coupling of multiple cytokine receptors.

Simultaneous phosphorylation of three human calpactins by kinase C

We evaluated the concurrent phosphorylation of reconstituted mixtures of three purified human placental calpactins (or lipocortins) by purified bovine brain protein kinase C (PKC). Calpactin-I (p36 or lipocortin-II), calpactin-II (p38 or lipocortin-I), and a 70-kilodalton calpactin-related protein, calpactin-p70, when present together as substrates for PKC, all demonstrated comparable kinetic parameters (Vmax values = 0.3-0.5 nmol phosphate incorporated/min), with calpactin-II and calpactin-p70 exhibiting lower apparent Km values (40 and 30 nM, respectively) than did calpactin-I (Km, 200 nM). Because of the higher Vmax/Km ratios for calpactin-II and calpactin-70 (12.5 and 10.0, respectively) compared with the ratio for calpactin-I (2.0), our data suggest that, intracellularly, where all three calpactins might be co-localized, the higher molecular mass calpactins could be preferred substrates for PKC. Nonetheless, the requirement for relatively high calcium concentrations (greater than or equal to 0.5 mM) suggests that PKC-mediated phosphorylation of the calpactins may take place only in restricted intracellular compartments, wherein calcium concentrations might transiently reach levels much higher than those that are normally found intracellularly (less than or equal to 0.25 mM).