title: Rapid degradation of the complement regulator, CD59, by a novel inhibitor.
abstract: There is increased interest in immune-based monoclonal antibody therapies for different malignancies because of their potential specificity and limited toxicity. The activity of some therapeutic monoclonal antibodies is partially dependent on complement-dependent cytolysis (CDC), in which the immune system surveys for invading pathogens, infected cells, and malignant cells and facilitates their destruction. CD59 is a ubiquitously expressed cell-surface glycosylphosphatidylinositol-anchored protein that protects cells from CDC. However, in certain tumors, CD59 expression is enhanced, posing a significant obstacle for treatment, by hindering effective monoclonal antibody-induced CDC. In this study, we used non-small lung carcinoma cells to characterize the mechanism of a novel CD59 inhibitor: the 114-amino acid recombinant form of the 4th domain of intermedilysin (rILYd4), a pore forming toxin secreted by Streptococcus intermedius. We compared the rates of internalization of CD59 in the presence of rILYd4 or anti-CD59 antibodies and determined that rILYd4 induces more rapid CD59 uptake at early time points. Most significantly, upon binding to rILYd4, CD59 is internalized and undergoes massive degradation in lysosomes within minutes. The remaining rILYd4·CD59 complexes recycle to the PM and are shed from the cell. In comparison, upon internalization of CD59 via anti-CD59 antibody binding, the antibody·CD59 complex is recycled via early and recycling endosomes, mostly avoiding degradation. Our study supports a novel role for rILYd4 in promoting internalization and rapid degradation of the complement inhibitor CD59, and highlights the potential for improving CDC-based immunotherapy.
authors.affiliation: Department of Biochemistry and Molecular Biology and the Fred and Pamela Buffett Cancer Center, The University of Nebraska Medical Center, Omaha, Nebraska 68198.
authors.forename: Bishuang
authors.initials: B
authors.lastname: Cai
authors.affiliation: Department of Biochemistry and Molecular Biology and the Fred and Pamela Buffett Cancer Center, The University of Nebraska Medical Center, Omaha, Nebraska 68198.
authors.forename: Shuwei
authors.initials: S
authors.lastname: Xie
authors.affiliation: Department of Neuroscience and Center for Neurovirology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
authors.forename: Fengming
authors.initials: F
authors.lastname: Liu
authors.affiliation: Department of Biochemistry and Molecular Biology and the Fred and Pamela Buffett Cancer Center, The University of Nebraska Medical Center, Omaha, Nebraska 68198.
authors.forename: Laura C
authors.initials: LC
authors.lastname: Simone
authors.affiliation: Department of Biochemistry and Molecular Biology and the Fred and Pamela Buffett Cancer Center, The University of Nebraska Medical Center, Omaha, Nebraska 68198. Electronic address: scaplan@unmc.edu.
authors.forename: Steve
authors.initials: S
authors.lastname: Caplan
authors.affiliation: Department of Neuroscience and Center for Neurovirology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140. Electronic address: xuebin.qin@temple.edu.
authors.forename: Xuebin
authors.initials: X
authors.lastname: Qin
authors.affiliation: Department of Biochemistry and Molecular Biology and the Fred and Pamela Buffett Cancer Center, The University of Nebraska Medical Center, Omaha, Nebraska 68198. Electronic address: nnaslavsky@unmc.edu.
authors.forename: Naava
authors.initials: N
authors.lastname: Naslavsky
mesh_terms: D018957:CD59 Antigens / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D045744:Cell Line, Tumor; D004705:Endocytosis; D006801:Humans; D006868:Hydrolysis; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: D018957:CD59 Antigens; D034741:RNA, Small Interfering
keywords: Bacterial Toxin; CD59; Complement; Degradation; Endocytosis; Endosomes; Glycosyl Phosphatidylinositol Anchors; Intracellular Trafficking; Lysosomes; Shedding