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Erdj3 Has an Essential Role for Z Variant Alpha-1-Antitrypsin Degradation.

ABSTRACT: Alpha-1-antitrypsin deficiency (AATD) is an inherited disease characterized by emphysema and liver disease. AATD is most often caused by a single amino acid substitution at amino acid 342 in the mature protein, resulting in the Z mutation of the alpha-1-antitrypsin gene (ZAAT). This substitution is associated with misfolding and accumulation of ZAAT in the endoplasmic reticulum (ER) of hepatocytes and monocytes, causing a toxic gain of function. Retained ZAAT is eliminated by ER-associated degradation and autophagy. We hypothesized that alpha-1-antitrypsin (AAT)-interacting proteins play critical roles in quality control of human AAT. Using co-immunoprecipitation, we identified ERdj3, an ER-resident Hsp40 family member, as a part of the AAT trafficking network. Depleting ERdj3 increased the rate of ZAAT degradation in hepatocytes by redirecting ZAAT to the ER calreticulin-EDEM1 pathway, followed by autophagosome formation. In the Huh7.5 cell line, ZAAT ER clearance resulted from enhancing ERdj3-mediated ZAAT degradation by silencing ERdj3 while simultaneously enhancing autophagy. In this context, ERdj3 suppression may eliminate the toxic gain of function associated with polymerization of ZAAT, thus providing a potential new therapeutic approach to the treatment of AATD-related liver disease. J. Cell. Biochem. 118: 3090-3101, 2017. © 2017 The Authors. Journal of Cellular Biochemistry Published by Wiley Periodicals Inc.

SUBMITTER: Khodayari N

PROVIDER: S-EPMC5575529 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Erdj3 Has an Essential Role for Z Variant Alpha-1-Antitrypsin Degradation.

Khodayari Nazli N Marek George G Lu Yuanqing Y Krotova Karina K Wang Rejean Liqun RL Brantly Mark M

Journal of cellular biochemistry 20170620 10

Alpha-1-antitrypsin deficiency (AATD) is an inherited disease characterized by emphysema and liver disease. AATD is most often caused by a single amino acid substitution at amino acid 342 in the mature protein, resulting in the Z mutation of the alpha-1-antitrypsin gene (ZAAT). This substitution is associated with misfolding and accumulation of ZAAT in the endoplasmic reticulum (ER) of hepatocytes and monocytes, causing a toxic gain of function. Retained ZAAT is eliminated by ER-associated degra ...[more]

PMID: 28419579

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Project description:BACKGROUND:Alpha-1-antitrypsin (AAT) deficiency (AATD) of Z, Mmalton, Siiyama type is associated with liver storage of the mutant proteins and liver disease. The Z variant can be diagnosed on isoelectric focusing (IEF) while Mmalton and Siiyama may be missed or misdiagnosed with this technique. Therefore, molecular analysis is mandatory for their characterization. In particular, that holds true for the Mmalton variant as on IEF profile it resembles the wild M2 subtype. METHODS:This is a retrospective analysis involving review of medical records and of liver biopsy specimens from a series of Mmalton, Z and Siiyama Alpha-1-antitrypsin deficiency patients. The review has been implemented by additional histological stains, electron microscopic observations and 3-D modeling studies of the sites of the mutations. RESULTS:Z, Mmalton and Siiyama liver specimen contained characteristic intrahepatocytic PAS-D globules. The globules differed in the three variants as only Mmalton cases showed dark basophilic precipitates within the AAT inclusions. The precipitates were visualized in haematoxylin-eosin (H.E.) stained preparations and corresponded to calcium precipitates as demonstrated by von Kossa staining. On immunohistochemistry, ZAAT inclusions were stained by polyclonal as well as monoclonal noncommercial anti-AAT antibody (AZT11), whilst Mmalton and Siiyama inclusion bodies remained negative with the monoclonal anti-Z antibody. 3-D protein analysis allowed to predict more severe misfolding of the Mmalton molecule as compared to Z and Siiyama that could trigger anomalous interaction with endoplasmic reticulum chaperon proteins, namely calcium binding proteins. CONCLUSIONS:Mmalton AAT inclusion bodies contain calcium precipitates inside them that allow the differential diagnosis with Siiyama and ZAAT inclusions in routine histological sections. The study has confirmed the specificity of the monoclonal AZT11 for the Z mutant. Thus, the combination of these two features is crucial for the distinction between the three variants and for predicting the genotype, whose confirmation would definitely require molecular analysis. Our study provides new data on the pathomorphogenesis of Mmalton inclusion bodies whose mineralization could play a central role in disease pathogenesis of Mmalton that is distinct from the Z and Siiyama variants. Calcium is known to be a major effector of cell death either via the increased intracellular concentration or the alteration of homeostasis.

Project description:SERPINA1/AAT/?-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.

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Erdj3 Has an Essential Role for Z Variant Alpha-1-Antitrypsin Degradation.

Publications

Erdj3 Has an Essential Role for Z Variant Alpha-1-Antitrypsin Degradation.

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