Transient GPI-anchored protein homodimers are units for raft organization and function |
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Authors: | Kenichi G N Suzuki Rinshi S Kasai Koichiro M Hirosawa Yuri L Nemoto Munenori Ishibashi Yoshihiro Miwa Takahiro K Fujiwara Akihiro Kusumi |
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Institution: | 1] Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto, Japan. [2] Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Saitama, Japan. |
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Abstract: | Advanced single-molecule fluorescent imaging was applied to study the dynamic organization of raft-associated glycosylphosphatidylinositol-anchored proteins (GPI-APs) in the plasma membrane and their stimulation-induced changes. In resting cells, virtually all of the GPI-APs are mobile and continually form transient (~200 ms) homodimers (termed homodimer rafts) through ectodomain protein interactions, stabilized by the presence of the GPI-anchoring chain and cholesterol. Heterodimers do not form, suggesting a fundamental role for the specific ectodomain protein interaction. Under higher physiological expression conditions , homodimers coalesce to form hetero- and homo-GPI-AP oligomer rafts through raft-based lipid interactions. When CD59 was ligated, it formed stable oligomer rafts containing up to four CD59 molecules, which triggered intracellular Ca(2+) responses that were dependent on GPI anchorage and cholesterol, suggesting a key part played by transient homodimer rafts. Transient homodimer rafts are most likely one of the basic units for the organization and function of raft domains containing GPI-APs. |
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