Obinutuzumab is thought to exert its effects through its high antibody-dependent cellular cytotoxicity (ADCC) via glyco-engineering of the Fc region. In addition, obinutuzumab causes direct binding-induced cell death (DCD) only by specifically binding to its target CD20, a Ca2+ channel. However, the specific features of CD20 related to obinutuzumab binding-induction of cell death are not clearly understood. In this study, we evaluated the relationship between the Ca2+ channel features of CD20 as a store-operated Ca2+ channel (SOC) and obinutuzumab binding-induced cell death. Ca2+ channel function and biochemical analysis revealed that CD20 is an Orai1- and stromal interaction molecule (STIM1)-dependent Ca2+ pore. However, binding of obinutuzumab on CD20 did not have any effect on Ca2+ influx activity of CD20; the direct cell death rate mediated by obinutuzumab binding was almost equivalent with or without the extracellular Ca2+ condition. Given the apparent interaction between STIM1 and CD20, we observed Triton-X solubilized obinutuzumab-bound CD20 accompanied by STIM1. Subsequently, obinutuzumab binding and cell death were decreased by STIM1 knock-down in Ramos B cells. Thus, STIM1 directly contributes to cell death by increasing the affinity of cells for obinutuzumab by transferring CD20 to the Triton-soluble membrane region.
|Number of pages||12|
|Journal||Clinical and Experimental Immunology|
|Publication status||Published - 2020 Jun 1|
Bibliographical noteFunding Information:
This work was supported by grants from the National Research Foundation of Korea, Project no. NFR-2018R1A2B4010319, and a faculty research grant from the Yonsei University College of Medicine (6-2018-0070) to J. Y. K. The authors thank MID (Medical Illustration and Design), a part of the Medical Research Support Services of Yonsei University College of Medicine, for all artistic support related to this work.
© 2020 British Society for Immunology
All Science Journal Classification (ASJC) codes
- Immunology and Allergy