Chaperone-mediated autophagy degrades SERPINA1^E342K/α1-antitrypsin Z variant and alleviates cell stress

Chaperone-mediated autophagy (CMA) is a specific form of autophagy that selectively targets proteins containing a KFERQ-like motif and relies on the chaperone protein HSPA8/HSC70 for substrate recognition. In SERPINA1/a1-antitrypsin deficiency (AATD), a disease characterized by the hepatic buildup of the SERPINA1^E342K/ATZ, CMA's role had been unclear. This work demonstrates the critical role that CMA plays in preventing SERPINA1^E342K/ATZ accumulation; suppressing CMA worsens SERPINA1^E342K/ATZ accumulation while activating it through chemical stimulation or LAMP2A overexpression promotes SERPINA1^E342K/ATZ breakdown. Specifically, SERPINA1^E342K/ATZ's ₁₂₁QELLR₁₂₅ motif is critical for HSPA8/HSC70 recognition and LAMP2A's charged C-terminal cytoplasmic tail is vital for substrate binding, facilitating CMA-mediated degradation of SERPINA1^E342K/ATZ. This selective activation of CMA operates independently of other autophagy pathways and alleviates SERPINA1^E342K/ATZ aggregate-induced cellular stress. In vivo administration of AR7 promotes hepatic SERPINA1^E342K/ATZ elimination and mitigates hepatic SERPINA1^E342K/ATZ aggregation pathology. These findings highlight CMA's critical function in cellular protein quality control of SERPINA1^E342K/ATZ and place it as a novel target for AATD treatment.Abbreviation: AR7: atypical retinoid 7; ATG16L1: autophagy related 16 like 1; AATD: SERPINA1/alpha-1 antitrypsin deficiency; CHX: cycloheximide; CMA: chaperone-mediated autophagy; CQ: chloroquine; ER: endoplasmic reticulum; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; HSPA8/HSC70: heat shock protein family A (Hsp70) member 8; LAMP2A: lysosomal associated membrane protein 2A; LAMP2B: lysosomal associated membrane protein 2B; LAMP2C: lysosomal associated membrane protein 2C; MG132: carbobenzoxy-L-leucyl-L-leucyl-L-leucinal; PAS-D: periodic acid-Schiff plus diastase; SERPINA1/A1AT: serpin family A member 1; SERPINA1^E342K/ATZ: Z variant of SERPINA1; TMRE: tetramethyl rhodamine ethyl ester perchlorate.