ABSTRACT
The proliferation of stem cell research, conflated with its ethical and moral implications, has led governments to attempt regulation of both the science and funding of stem cells. Due to a diversity of opinions and cultural viewpoints, no single policy or set of rules exist to govern stem cell research. Instead, each country has developed its own policy. The following map catalogs the general legal and political milleu regarding stem cell research by country.
Subject(s)
Biomedical Research/legislation & jurisprudence , Embryonic Stem Cells/cytology , Government Regulation , Australia , Biomedical Research/methods , Brazil , China , Humans , Japan , Mexico , Republic of Korea , Singapore , South Africa , Switzerland , United Kingdom , United StatesABSTRACT
X-linked lymphoproliferative disease (XLP) is a rare congenital immunodeficiency that leads to an extreme, usually fatal increase in the number of lymphocytes upon infection with EBV. It is most commonly defined molecularly by loss of expression of SLAM-associated protein (SAP). Despite this, there is little understanding of how SAP deficiency causes lymphocytosis following EBV infection. Here we show that T cells from individuals with XLP are specifically resistant to apoptosis mediated by TCR restimulation, a process that normally constrains T cell expansion during immune responses. Expression of SAP and the SLAM family receptor NK, T, and B cell antigen (NTB-A) were required for TCR-induced upregulation of key pro-apoptotic molecules and subsequent apoptosis. Further, SAP/NTB-A signaling augmented the strength of the proximal TCR signal to achieve the threshold required for restimulation-induced cell death (RICD). Strikingly, TCR ligation in activated T cells triggered increased recruitment of SAP to NTB-A, dissociation of the phosphatase SHP-1, and colocalization of NTB-A with CD3 aggregates. In contrast, NTB-A and SHP-1 contributed to RICD resistance in XLP T cells. Our results reveal what we believe to be novel roles for NTB-A and SAP in regulating T cell homeostasis through apoptosis and provide mechanistic insight into the pathogenesis of lymphoproliferative disease in XLP.
Subject(s)
Apoptosis/physiology , Intracellular Signaling Peptides and Proteins/deficiency , Lymphoproliferative Disorders/immunology , T-Lymphocytes/physiology , Animals , Antigens, CD/genetics , Antigens, CD/immunology , Apoptosis Regulatory Proteins/genetics , Apoptosis Regulatory Proteins/immunology , Bcl-2-Like Protein 11 , Fas Ligand Protein/genetics , Fas Ligand Protein/metabolism , Gene Expression Profiling , Humans , Intracellular Signaling Peptides and Proteins/genetics , Lymphoproliferative Disorders/physiopathology , Membrane Proteins/genetics , Membrane Proteins/immunology , Mice , Microarray Analysis , Proto-Oncogene Proteins/genetics , Proto-Oncogene Proteins/immunology , RNA Interference , Receptors, Antigen, T-Cell/genetics , Receptors, Antigen, T-Cell/immunology , Receptors, Cell Surface/genetics , Receptors, Cell Surface/immunology , Signal Transduction/physiology , Signaling Lymphocytic Activation Molecule Associated Protein , Signaling Lymphocytic Activation Molecule Family , Signaling Lymphocytic Activation Molecule Family Member 1 , T-Lymphocytes/cytologyABSTRACT
The Bcl-x(L)/Bak protein-protein interaction has emerged as an important target for cancer therapy due to its role in apoptosis. Inhibition of this interaction by small-molecule antagonists induces apoptosis in unhealthy cells. Bak, a pro-apoptotic Bcl-2 protein, projects four hydrophobic side chains (V74, L78, I81, and I85), corresponding to the i, i+4, i+7, and i+11 positions of an alpha-helix, into a hydrophobic cleft on Bcl-x(L). Herein, we present a novel family of rationally designed alpha-helix mimetics with improved solubility and synthetic feasibility based on a benzoylurea scaffold. These benzoylurea derivatives favor a linear conformation stabilized by an intramolecular hydrogen bond, and are able to mimic the spatial projection of the i, i+4, and i+7 residues of an alpha-helix. The binding of the benzoylurea derivatives to Bcl-x(L) was assessed using fluorescence polarization competition assays, isothermal titration calorimetry, and (15)N-HSQC experiments. These experiments showed that these agents bind to and disrupt Bcl-x(L) with low micromolar inhibition and dissociation constants, with (15)N-HSQC experiments confirming binding to the hydrophobic pocket of Bcl-x(L) normally occupied by the Bak helix.
