Factor VIII exhibits chaperone-dependent and glucose-regulated reversible amyloid formation in the endoplasmic reticulum

• Published in: Blood Vol. 135; no. 21; pp. 1899 - 1911
• Main Authors: Poothong, Juthakorn, Pottekat, Anita, Siirin, Marina, Campos, Alexandre Rosa, Paton, Adrienne W., Paton, James C., Lagunas-Acosta, Jacqueline, Chen, Zhouji, Swift, Mark, Volkmann, Niels, Hanein, Dorit, Yong, Jing, Kaufman, Randal J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 21.05.2020; American Society of Hematology
• Subjects: Amyloid - chemistry; Amyloid - drug effects; Endoplasmic Reticulum - drug effects; Endoplasmic Reticulum - metabolism; Endoplasmic Reticulum Stress - drug effects; Factor VIII - genetics; Factor VIII - metabolism; Glucose - pharmacology; Hemostatics; Hep G2 Cells; Humans; Life Sciences; Molecular Chaperones - genetics; Molecular Chaperones - metabolism; Sweetening Agents - pharmacology; Thrombosis and Hemostasis
• ISSN: 0006-4971; 1528-0020; 1528-0020
• DOI: 10.1182/blood.2019002867

Hemophilia A, an X-linked bleeding disorder caused by deficiency of factor VIII (FVIII), is treated by protein replacement. Unfortunately, this regimen is costly due to the expense of producing recombinant FVIII as a consequence of its low-level secretion from mammalian host cells. FVIII expression activates the endoplasmic reticulum (ER) stress response, causes oxidative stress, and induces apoptosis. Importantly, little is known about the factors that cause protein misfolding and aggregation in metazoans. Here, we identified intrinsic and extrinsic factors that cause FVIII to form aggregates. We show that FVIII forms amyloid-like fibrils within the ER lumen upon increased FVIII synthesis or inhibition of glucose metabolism. Significantly, FVIII amyloids can be dissolved upon restoration of glucose metabolism to produce functional secreted FVIII. Two ER chaperone families and their cochaperones, immunoglobulin binding protein (BiP) and calnexin/calreticulin, promote FVIII solubility in the ER, where the former is also required for disaggregation. A short aggregation motif in the FVIII A1 domain (termed Aggron) is necessary and sufficient to seed β-sheet polymerization, and BiP binding to this Aggron prevents amyloidogenesis. Our findings provide novel insight into mechanisms that limit FVIII secretion and ER protein aggregation in general and have implication for ongoing hemophilia A gene-therapy clinical trials. •In the ER, FVIII forms amyloid aggregates that are dissolved in a chaperone- and glucose-dependent manner to produce secreted functional FVIII.•A short amino acid motif in the A1 domain seeds β-sheet polymerization; binding of ER chaperone BiP to this motif prevents aggregation. [Display omitted]