2. Academic Validation
  3. Caspase cleavage releases a nuclear protein fragment that stimulates phospholipid scrambling at the plasma membrane

Caspase cleavage releases a nuclear protein fragment that stimulates phospholipid scrambling at the plasma membrane

  • Mol Cell. 2021 Apr 1;81(7):1397-1410.e9. doi: 10.1016/j.molcel.2021.02.025.
Masahiro Maruoka 1,  Panpan Zhang 2,  Hiromi Mori 3,  Eiichi Imanishi 3,  Daniel M Packwood 3,  Hiroshi Harada 4,  Hidetaka Kosako 5,  Jun Suzuki 6
Affiliations

Affiliations

  • 1 Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Honmachi, Sakyoku, Kyoto 606-8501, Japan; Center for Integrated Biosystems, Institute for Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
  • 2 Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Honmachi, Sakyoku, Kyoto 606-8501, Japan; Graduate School of Biostudies, Kyoto University, Konoe-cho, Yoshida, Sakyoku, Kyoto 606-8501, Japan.
  • 3 Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Honmachi, Sakyoku, Kyoto 606-8501, Japan.
  • 4 Graduate School of Biostudies, Kyoto University, Konoe-cho, Yoshida, Sakyoku, Kyoto 606-8501, Japan.
  • 5 Fujii Memorial Institute of Medical Sciences, Tokushima University, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan.
  • 6 Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Honmachi, Sakyoku, Kyoto 606-8501, Japan; Graduate School of Biostudies, Kyoto University, Konoe-cho, Yoshida, Sakyoku, Kyoto 606-8501, Japan; AMED-FORCE, Japanese Agency for Medical Research and Development, 1-7-1 Otemachi, Chiyodaku, Tokyo 100-0004, Japan; Center for Integrated Biosystems, Institute for Biomedical Sciences, Academia Sinica, Taipei, Taiwan. Electronic address: jsuzuki@icems.kyoto-u.ac.jp.
PMID: 33725486 DOI: 10.1016/j.molcel.2021.02.025
Abstract

Phospholipid scrambling in dying cells promotes phosphatidylserine exposure, a critical process for efferocytosis. We previously identified the Xkr family protein Xkr4 as a phospholipid-scrambling protein, but its activation mechanisms remain unknown. Here we show that Xkr4 is activated in two steps: dimer formation by caspase-mediated cleavage and structural change caused by activating factors. To identify the factors, we developed a new screening system, "revival screening," using a CRISPR sgRNA library. Applying this system, we identified the nuclear protein XRCC4 as the single candidate for the Xkr4 activator. Upon apoptotic stimuli, XRCC4, contained in the DNA repair complex, is cleaved by caspases, and its C-terminal fragment with an intrinsically disordered region is released into the cytoplasm. Protein interaction screening showed that the fragment interacts directly with the Xkr4 dimer to activate it. This study demonstrates that caspase-mediated cleavage releases a nuclear protein fragment for direct regulation of lipid dynamics on the plasma membrane.

Keywords

CRISPR-Cas9 sgRNA library screening; Caspase; DNA repair; Efferocytosis; Nuclear fragment; Phosphatidylserine; Phospholipid scrambling; XRCC4; Xkr4; cDNA library screening.

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