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.
Huang
J H
JH
Department of Pathology and Laboratory Medicine, University of Pennsylvania, 6 Gates Pavilion, 3400 Spruce Street, Philadelphia, PA 19104-4283, USA.
Tykocinski
M L
ML
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