title: Non-T cell activation linker (NTAL) proteolytic cleavage as a terminator of activatory intracellular signals.
abstract: Non-T cell activation linker is an adaptor protein that is tyrosine phosphorylated upon cross-linking of immune receptors expressed on B lymphocytes, NK cells, macrophages, basophils, or mast cells, allowing the recruitment of cytosolic mediators for downstream signaling pathways. Fas receptor acts mainly as a death receptor, and when cross-linked with Fas ligand, many proteins are proteolytically cleaved, including several signaling molecules in T and B cells. Fas receptor triggering also interferes with TCR intracellular signals, probably by means of proteolytic cleavage of several adaptor proteins. We have previously found that the adaptor linker for activation of T cells, evolutionarily related to non-T cell activation linker, is cleaved upon proapoptotic stimuli in T lymphocytes and thymocytes, in a tyrosine phosphorylation-dependent fashion. Here, we describe non-T cell activation linker proteolytic cleavage triggered in human B cells and monocytes by Fas cross-linking and staurosporine treatment. Non-T cell activation linker is cleaved, producing an N-terminal fragment of ∼22 kDa, and such cleavage is abrogated in the presence of caspase 8/granzyme B and caspase 3 inhibitors. Moreover, we have identified an aspartic acid residue at which non-T cell activation linker is cleaved, which similar to linker for activation of T cells, this aspartic acid residue is located close to tyrosine and serine residues, suggesting an interdependence of phosphorylation and proteolytic cleavage. Consistently, induction of non-T cell activation linker phosphorylation by pervanadate inhibits its cleavage. Interestingly, the truncated isoform of non-T cell activation linker, generated after cleavage, has a decreased signaling ability when compared with the full-length molecule. Altogether, our results suggest that cleavage of transmembrane adaptors constitutes a general mechanism for signal termination of immune receptors.
authors.affiliation: Core Research Facility for Health Sciences, University of Cádiz and Puerto Real University Hospital Research Unit, Department of Biomedicine, Biotechnology and Public Health (Immunology), Cádiz, Spain.
authors.forename: Mikel M
authors.initials: MM
authors.lastname: Arbulo-Echevarria
authors.affiliation: Core Research Facility for Health Sciences, University of Cádiz and Puerto Real University Hospital Research Unit, Department of Biomedicine, Biotechnology and Public Health (Immunology), Cádiz, Spain.
authors.forename: Juan Pedro
authors.initials: JP
authors.lastname: Muñoz-Miranda
authors.affiliation: Core Research Facility for Health Sciences, University of Cádiz and Puerto Real University Hospital Research Unit, Department of Biomedicine, Biotechnology and Public Health (Immunology), Cádiz, Spain.
authors.forename: Andrés
authors.initials: A
authors.lastname: Caballero-García
authors.affiliation: Core Research Facility for Health Sciences, University of Cádiz and Puerto Real University Hospital Research Unit, Department of Biomedicine, Biotechnology and Public Health (Immunology), Cádiz, Spain.
authors.forename: José L
authors.initials: JL
authors.lastname: Poveda-Díaz
authors.affiliation: Core Research Facility for Health Sciences, University of Cádiz and Puerto Real University Hospital Research Unit, Department of Biomedicine, Biotechnology and Public Health (Immunology), Cádiz, Spain.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Fernández-Ponce
authors.affiliation: Department of Biomedicine, Biotechnology and Public Health (Biochemistry), University of Cádiz, Cádiz, Spain.
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Durán-Ruiz
authors.affiliation: Department of Biochemistry, Pharmacology and Toxicology, Wroclaw University of Environmental and Life Sciences, Wroclaw, Poland.
authors.forename: Arkadiusz
authors.initials: A
authors.lastname: Miazek
authors.affiliation: Core Research Facility for Health Sciences, University of Cádiz and Puerto Real University Hospital Research Unit, Department of Biomedicine, Biotechnology and Public Health (Immunology), Cádiz, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: García-Cózar
authors.affiliation: Core Research Facility for Health Sciences, University of Cádiz and Puerto Real University Hospital Research Unit, Department of Biomedicine, Biotechnology and Public Health (Immunology), Cádiz, Spain, enrique.aguado@uca.es.
authors.forename: Enrique
authors.initials: E
authors.lastname: Aguado
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D001402:B-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism*; D053181:Caspase 8 / Q000378:metabolism*; D002478:Cells, Cultured; D053222:Fas Ligand Protein / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D010766:Phosphorylation; D059748:Proteolysis; D015398:Signal Transduction; D014443:Tyrosine; D019014:fas Receptor / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D053222:Fas Ligand Protein; C419196:LAT2 protein, human; D019014:fas Receptor; D014443:Tyrosine; D053148:Caspase 3; D053181:Caspase 8
keywords: B lymphocytes; LAT2; caspases; monocytes; signal transduction