title: Ubiquitin ligase SYVN1/HRD1 facilitates degradation of the SERPINA1 Z variant/α-1-antitrypsin Z variant via SQSTM1/p62-dependent selective autophagy.
abstract: SERPINA1/AAT/α-1-antitrypsin (serpin family A member 1) deficiency (SERPINA1/ AAT-D) is an autosomal recessive disorder characterized by the retention of misfolded SERPINA1/AAT in the endoplasmic reticulum (ER) of hepatocytes and a significant reduction of serum SERPINA1/AAT level. The Z variant of SERPINA1/AAT, containing a Glu342Lys (E342K) mutation (SERPINA1E342K/ATZ), the most common form of SERPINA1/AAT-D, is prone to misfolding and polymerization, which retains it in the ER of hepatocytes and leads to liver injury. Both proteasome and macroautophagy/autophagy pathways are responsible for disposal of SERPINA1E342K/ATZ after it accumulates in the ER. However, the mechanisms by which SERPINA1E342K/ATZ is selectively degraded by autophagy remain unknown. Here, we showed that ER membrane-spanning ubiquitin ligase (E3) SYVN1/HRD1 enhances the degradation of SERPINA1E342K/ATZ through the autophagy-lysosome pathway. We found that SYVN1 promoted SERPINA1E342K/ATZ, especially Triton X 100-insoluble SERPINA1E342K/ATZ clearance. However, the effect of SYVN1 in SERPINA1E342K/ATZ clearance was impaired after autophagy inhibition, as well as in autophagy-related 5 (atg5) knockout cells. On the contrary, autophagy induction enhanced SYVN1-mediated SERPINA1E342K/ATZ degradation. Further study showed that SYVN1 mediated SERPINA1E342K/ATZ ubiquitination, which is required for autophagic degradation of SERPINA1E342K/ATZ by promoting the interaction between SERPINA1E342K/ATZ and SQSTM1/p62 for formation of the autophagy complex. Interestingly, SYVN1-mediated lysine 48 (K48)-linked polyubiquitin chains that conjugated onto SERPINA1E342K/ATZ might predominantly bind to the ubiquitin-associated (UBA) domain of SQSTM1 and couple the ubiquitinated SERPINA1E342K/ATZ to the lysosome for degradation. In addition, autophagy inhibition attenuated the suppressive effect of SYVN1 on SERPINA1E342K/ATZ cytotoxicity, and the autophagy inducer rapamycin enhanced the suppressive effect of SYVN1 on SERPINA1E342K/ATZ-induced cell apoptosis. Therefore, this study proved that SYVN1 enhances SERPINA1E342K/ATZ degradation through SQSTM1-dependent autophagy and attenuates SERPINA1E342K/ATZ cytotoxicity.
authors.affiliation: a School of Basic Medical Sciences , Anhui Medical University , Hefei, Anhui , China.|b Institute of Biopharmaceuticals, Anhui Medical University , Hefei, Anhui , China.
authors.forename: Lijie
authors.initials: L
authors.lastname: Feng
authors.affiliation: b Institute of Biopharmaceuticals, Anhui Medical University , Hefei, Anhui , China.
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang
authors.affiliation: b Institute of Biopharmaceuticals, Anhui Medical University , Hefei, Anhui , China.|c The 4th Affiliated Hospital, Anhui Medical University , Hefei, Anhui , China.
authors.forename: Na
authors.initials: N
authors.lastname: Zhu
authors.affiliation: a School of Basic Medical Sciences , Anhui Medical University , Hefei, Anhui , China.|b Institute of Biopharmaceuticals, Anhui Medical University , Hefei, Anhui , China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Ding
authors.affiliation: a School of Basic Medical Sciences , Anhui Medical University , Hefei, Anhui , China.|b Institute of Biopharmaceuticals, Anhui Medical University , Hefei, Anhui , China.
authors.forename: Xiaojie
authors.initials: X
authors.lastname: Zhang
authors.affiliation: a School of Basic Medical Sciences , Anhui Medical University , Hefei, Anhui , China.|b Institute of Biopharmaceuticals, Anhui Medical University , Hefei, Anhui , China.
authors.forename: Jishuang
authors.initials: J
authors.lastname: Yu
authors.affiliation: a School of Basic Medical Sciences , Anhui Medical University , Hefei, Anhui , China.|b Institute of Biopharmaceuticals, Anhui Medical University , Hefei, Anhui , China.
authors.forename: Weimin
authors.initials: W
authors.lastname: Qiang
authors.affiliation: a School of Basic Medical Sciences , Anhui Medical University , Hefei, Anhui , China.|b Institute of Biopharmaceuticals, Anhui Medical University , Hefei, Anhui , China.
authors.forename: Zhetao
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: a School of Basic Medical Sciences , Anhui Medical University , Hefei, Anhui , China.|b Institute of Biopharmaceuticals, Anhui Medical University , Hefei, Anhui , China.
authors.forename: Yuyang
authors.initials: Y
authors.lastname: Ma
authors.affiliation: a School of Basic Medical Sciences , Anhui Medical University , Hefei, Anhui , China.
authors.forename: Dake
authors.initials: D
authors.lastname: Huang
authors.affiliation: a School of Basic Medical Sciences , Anhui Medical University , Hefei, Anhui , China.|b Institute of Biopharmaceuticals, Anhui Medical University , Hefei, Anhui , China.
authors.forename: Yujun
authors.initials: Y
authors.lastname: Shen
authors.affiliation: a School of Basic Medical Sciences , Anhui Medical University , Hefei, Anhui , China.|b Institute of Biopharmaceuticals, Anhui Medical University , Hefei, Anhui , China.|d Center for Biomedical Engineering and Technology , University of Maryland , Baltimore , MD , USA.
authors.forename: Shengyun
authors.initials: S
authors.lastname: Fang
authors.affiliation: e Actuarial Science, School of Continuing Education , Columbia University , New York , NY , USA.
authors.forename: Yifan
authors.initials: Y
authors.lastname: Yu
authors.affiliation: a School of Basic Medical Sciences , Anhui Medical University , Hefei, Anhui , China.|b Institute of Biopharmaceuticals, Anhui Medical University , Hefei, Anhui , China.
authors.forename: Haiping
authors.initials: H
authors.lastname: Wang
authors.affiliation: a School of Basic Medical Sciences , Anhui Medical University , Hefei, Anhui , China.|b Institute of Biopharmaceuticals, Anhui Medical University , Hefei, Anhui , China.
authors.forename: Yuxian
authors.initials: Y
authors.lastname: Shen
mesh_terms: D000818:Animals; D001343:Autophagy; D016923:Cell Death; D057809:HEK293 Cells; D056945:Hep G2 Cells; D006801:Humans; D008239:Lysine / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D025821:Polyubiquitin / Q000378:metabolism; D011485:Protein Binding; D059748:Proteolysis; D000071456:Sequestosome-1 Protein / Q000378:metabolism*; D015398:Signal Transduction; D012995:Solubility; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D054875:Ubiquitination; D000515:alpha 1-Antitrypsin / Q000378:metabolism*
chemical_list: C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; C101343:Sqstm1 protein, mouse; D000515:alpha 1-Antitrypsin; D025821:Polyubiquitin; C482345:SYVN1 protein, human; C498235:Syvn1 protein, mouse; D044767:Ubiquitin-Protein Ligases; D008239:Lysine
keywords: SQSTM1/p62; SYVN1/HRD1; autophagy; protein degradation; ubiquitination; α 1-antitrypsin Z variant