CTLA-4-Fas ligand functions as a trans signal converter protein in bridging antigen-presenting cells and T cells.
Co-stimulator blockade and trans inhibitory signaling, using agents such as CTLA-4-Ig and Fas ligand (FasL) respectively have been invoked as alternative strategies for suppressing pathogenic T cells. This study describes a novel hetero-bifunctional fusion protein, CTLA-4-FasL, designed to combine within a single protein both co-stimulator blocking and trans inhibitory signaling potentials. A chimeric expression cassette, in which the ectodomain coding sequences for CTLA-4 and FasL were linked in-frame, was used to produce a CTLA-4-FasL fusion protein. CTLA-4-FasL binding to both B7-1/B7-2-expressing Daudi B cells and Fas-expressing Jurkat T cells was documented by immunofluorescence and flow cytometry. The capacity of CTLA-4-FasL to induce apoptosis in Jurkat targets was markedly enhanced by the addition of Daudi and other B7-1/B7-2(+) B cell lines, which provided a membrane platform for the otherwise soluble CTLA-4-fusion protein. Moreover, in dual-chamber experiments, Daudi cells pre-coated with CTLA-4-FasL demonstrated Jurkat inhibitory activity that was cell-contact dependent. Significantly, when used to inhibit in vitro cellular proliferation of peripheral blood mononuclear cells, CTLA-4-FasL was approximately 1000-fold more potent than the extensively characterized CTLA-4-Ig fusion protein. Furthermore, the degree of inhibition induced by CTLA-4-FasL substantially surpassed that observed for CTLA-4-Ig and a soluble FasL when used in combination. CTLA-4-FasL represents the first of a novel class of fusion proteins, designated here as 'trans signal converter proteins', that combine trans signal masking and direct trans signaling functions.
Department of Pathology and Laboratory Medicine, University of Pennsylvania, 6 Gates Pavilion, 3400 Spruce Street, Philadelphia, PA 19104-4283, USA.
J H
JH
Huang
M L
ML
Tykocinski
D000069594:Abatacept; D000938:Antigen-Presenting Cells / Q000276:immunology* / Q000378:metabolism; D015703:Antigens, CD / Q000378:metabolism; D000943:Antigens, Differentiation / Q000502:physiology*; D017209:Apoptosis; D018122:B7-1 Antigen / Q000378:metabolism; D051940:B7-2 Antigen; D060908:CTLA-4 Antigen; D002448:Cell Adhesion / Q000276:immunology; D002460:Cell Line; D053222:Fas Ligand Protein; D006801:Humans; D018796:Immunoconjugates; D019169:Jurkat Cells; D008222:Lymphokines / Q000502:physiology; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000502:physiology*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism
D015703:Antigens, CD; D000943:Antigens, Differentiation; D018122:B7-1 Antigen; D051940:B7-2 Antigen; C497964:CD86 protein, human; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D018796:Immunoconjugates; D008222:Lymphokines; D008562:Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; D000069594:Abatacept