Nicos Anthony Nicola

Negative Regulators of Cytokine Signaling

The interaction of a cytokine with its specific cell surface receptor triggers the activation of intracellular signaling pathways that ultimately program the cellular response. Although the specific components and actions of the pathways driving these responses, such as the Janus kinase (JAK)/signal transducers and activators of transcription (STAT) pathway, are relatively well defined, it is becoming clear that important mechanisms exist to restrain these signaling cascades.This review discusses the key biochemical actions and biological roles of the phosphatase SHP-1, the protein inhibitors of activated STATs (PIAS) and the suppressor of cytokine signaling (SOCS) protein family in the negative regulation of cytokine signal transduction.

Preparation of colony stimulating factors from human placental conditioned medium

Abstract Human placental conditioned medium is able to stimulate human bone marrow cells to form neutrophilic granulocyte-monocyte colonies and eosinophil colonies in agar cultures. Methods are described for preparing highly active preparations (capable of supramaximal stimulation of colony formation) by partial purification of the conditioned medium using calcium phosphate absorption and gel filtration chromatography. Partially purified calcium phosphate gel eluates appear to increase in specific activity after concentration by ultrafiltration. This phenomenon was not observed with the active fractions after further purification on Sephadex G-100. Fractionation of the conditioned medium using gel filtration and hydrophobic chromatography (Cibacron Blue-Sepharose) showed that distinct and partially separable factors were responsible for stimulating granulocyte-macrophage and eosinophil colony formation. From the gel filtration data the apparent molecular weight of the eosinophil colony stimulating factor was higher than the molecular weight of the granulocyte-macrophage colony stimulating factor. Cibacron Blue-Sepharose chromatography led to the separation of one molecular species of granulocyte-macrophage colony stimulating factor from eosinophil colony stimulating factor so that a specific stimulus for human neutrophilic granulocyte and/or monocyte-macrophage progenitors is now available.

Binding, Internalization, and Degradation of 125I-Multipotential Colony-Stimulating Factor (Interleukin-3) By FDCP-1 Cells

The kinetic parameters involved in determining the steady-state interaction of Multi-CSF with FDCP-1 cells at 37 degrees C have been determined by kinetic analysis under steady-state conditions and by curve-fitting the rate of approach to steady-state conditions. The two methods are in substantial agreement and yield values of Vr = 28 receptors/cell/min for the rate of appearance of receptors at the cell surface, ke and kt = 0.061 min-1 and 0.0044 min-1 for the rate constants of internalization of occupied and unoccupied receptors, respectively, kh = 0.008 min-1 for the rate constant of degradation of internalized ligand, ka = 2.9 X 10(8) M-1 min-1 for the rate constant of association and kd = 0.11 min-1 for the rate constant of dissociation of ligand with receptor. Analysis of steady-state conditions indicated that Multi-CSF caused substantial down-regulation of surface receptors and that considerably more Multi-CSF was inside the cell than at the cell surface. The implications of these results for utilization rates of Multi-CSF by FDCP-1 cells and the relationship of receptor occupancy to biological activity are discussed.

Molecular Properties of a Factor Inducing Differentiation in Murine Myelomonocytic Leukemic Cells

The possibility of therapeutic manipulation of normal regulatory molecules in leukemia has recently gained interest with the demonstration, both in vivo and in vitro, that terminal differentiation and leukemic stem cell suppression can be induced in several mouse myeloid leukemic cell lines by normal tissue products [2–4, 8, 9].

Effect of Colony-stimulating Factors on the Proteins Synthesized by Normal and Leukemic Myeloid Progenitor Cells

The proliferation and differentiation of normal granulocyte-macrophage (GM) progenitor cells is dependent on the presence of GM colony stimulating factor (GM-CSF). The proliferation of primary leukemic cells is also dependent on GMCSF, and some established myelomonocytic cell lines (e.g., WEHI3B D+) can be induced to differentiate by G-CSF.