ABSTRACT
In the present study, we have examined the effect of perforin (pfp) deficiency in 4 models of mouse B-cell lymphomagenesis. We have examined pfp loss on the background of either Mlh1 tumor suppressor allele loss or oncogene expression [Ig heavy chain (Emu)-v-Abl, Emu-myc, and vav-bcl2]. Pfp was shown to act as a suppressor of B-cell malignancies characteristically driven by v-Abl or bcl-2, whereas Mlh loss cooperated in accelerating spontaneous B-cell lymphomas characteristic of pfp loss. No protective role for pfp was observed in the more aggressive Emu-myc model of B-cell lymphoma. These transgenic models have allowed us to distinguish the role of pfp in surveillance of B-cell lymphomagenesis, as opposed to its loss simply driving the onset of a spontaneous lymphoma characteristic of pfp deficiency.
Subject(s)
Lymphoma, B-Cell/genetics , Perforin/physiology , Adaptor Proteins, Signal Transducing/genetics , Animals , Lymphoma, B-Cell/physiopathology , Mice , Mice, Inbred C57BL , Mice, Transgenic , MutL Protein Homolog 1 , Nuclear Proteins/genetics , Oncogene Proteins v-abl/genetics , Plasmacytoma/genetics , Transplantation, Heterologous , Tumor Suppressor Protein p53/geneticsABSTRACT
Recent progress has been made in discovering structure/function relationships of the cytotoxic lymphocyte pore-forming protein - perforin - and its role in immune regulation. Long recognized as a key component of the granule exocytosis mechanism of lymphocyte-mediated apoptosis and in host defence against a variety of pathogens and tumors, more recent attention has focused upon mutations of the perforin gene in some patients with hemophagocytic lymphohistiocytosis. This clinical picture has prompted further work to uncover the molecular structure of perforin and to define its precise role in immune regulation and immunopathology.
Subject(s)
Apoptosis/immunology , Cytotoxicity, Immunologic , Membrane Glycoproteins/immunology , Models, Immunological , Pore Forming Cytotoxic Proteins/immunology , T-Lymphocytes/immunology , Animals , Granzymes/immunology , Granzymes/metabolism , Humans , Membrane Glycoproteins/chemistry , Membrane Glycoproteins/metabolism , Perforin , Pore Forming Cytotoxic Proteins/chemistry , Pore Forming Cytotoxic Proteins/metabolism , T-Lymphocytes/metabolismABSTRACT
Apolipoprotein C-III (apoC-III) is an important regulator of lipoprotein metabolism. Radioisotope and stable isotope kinetic studies show differing results in relation to the kinetics of apoC-III in HDL. Kinetic analysis of HDL apoC-III may be difficult because of its low concentration, as well as the presence of other apoproteins at higher concentration, in the HDL fraction. We used Intralipid(R) (IL), known to preferentially extract apoC proteins from plasma, as a means of extracting apoC-III from HDL before apoprotein separation by isoelectric focusing gel electrophoresis for the measurement of tracer enrichment. Protein purity was assessed by an isoleucine-to-leucine (Ile/Leu) ratio, as apoC-III contains no isoleucine. We compared apoC-III kinetics in 14 men using a bolus infusion of deuterated leucine. The Ile/Leu ratio for IL-extracted HDL (IL-HDL) apoC-III (3.0 +/- 0.7%) was not different from that of VLDL apoC-III (2.6 +/- 0.6%) but was significantly lower than that of untreated HDL apoC-III (9.0 +/- 2.9%) (P < 0.001). The isotopic enrichment curves and fractional catabolic rates (FCRs) for IL-HDL apoC-III were not different from those of VLDL apoC-III. In contrast, HDL apoC-III had significantly lower isotopic enrichments and FCRs than IL-HDL apoC-III (P < 0.001). In conclusion, this simple IL method can be used to isolate apoC-III from HDL with minimal interference from other HDL apoproteins, and it demonstrates that the kinetics of apoC-III in VLDL and HDL are similar, supporting the concept of a single kinetically homogeneous pool of apoC-III in plasma.