Preventing and reversing the cellular consequences of Z alpha-1 antitrypsin accumulation by targeting s4A

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• 作者：Sam Alam¹ ; Jicun Wang¹ ; Sabina Janciauskiene² ; Ravi Mahadeva¹ ; ^{rm232@cam.ac.uk}
• 关键词：AT ; ¦Á1-antitrypsin ; Z-AT (E342K ; PiZ) ; AT deficiency ; HEK-M- or Z cells ; HEK293 cells expressing human either M- or Z-AT gene ; Hep-M- or Z cells ; HepG2 cells expressing human either M- or Z-AT gene ; 4M ; Ac-TTAI-NH2 4-mer peptide ; 6M ; Ac-FLEAIG-NH2 6-mer p
• 刊名：Journal of Hepatology
• 出版年：2012
• 出版时间：July, 2012
• 年：2012
• 卷：57
• 期：1
• 页码：116-124
• 全文大小：1243 K

文摘

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Background & Aims

The Z variant (Glu342Lys) of ¦Á₁-antitrypsin (AT) polymerizes and accumulates in the hepatocyte endoplasmic reticulum (ER) predisposing to neonatal hepatitis and liver cirrhosis. The resultant secretory defect leaves the lungs vulnerable to elastolysis and early-onset emphysema. Our aim in this study was to evaluate the effect of targeting strand 4a (s4A) as a strategy to inhibit polymerization and restore plasma secretion.

Methods

HEK293 cells and HepG2 cells were transfected with Z-AT (Z-AT cells) or control M-AT (M-AT cells). The effect of Ac-TTAI-NH₂ (4M), Ac-FLEAIG-NH₂ (6M), and Ac-SEAAASTAVVIA-NH₂ (12M) on preventing and reversing intracellular Z-AT polymers and secretion of AT was evaluated by pulse-chase/immunoprecipitation, ELISA, and immunoblot with a polymer-specific antibody (ATZII). The ER overload response was assessed by RT-PCR for PERK, calnexin, and RGS16, and ELISA for NF-¦ÊB, IL-6, and IL-8.

Results

All peptides prevented the intracellular accumulation of Z-AT (4M > 6M > 12M) in comparison with control peptides, with detection of the AT-Inhibitor complex in inclusion bodies. In so doing, 4M also significantly increased the concentration of secreted Z-AT and the elastase inhibitory activity. Furthermore, the 4M peptide was able to reverse the intracellular aggregation of Z-AT. The ER accumulation of Z-AT was shown to induce PERK-dependent NF-¦ÊB, IL-6, IL-8, and RGS16 and calnexin; all of which could be abrogated effectively by 4M. 4M had no effect on apoptosis or cell viability.

Conclusions

These findings are the first evidence that targeting s4A can prevent the cellular accumulation and deleterious effects of Z-AT and restore its plasma concentrations. As such, this is a major step towards treatment of patients with Z-AT-related disease.