Role of Protein Disulfide Isomerases (PDIs) in the Reversible Folding of Proinsulin in Beta Cells
Abstract
The production of mature, bioactive insulin depends on the precise oxidative folding of its precursor, proinsulin, within the endoplasmic reticulum (ER). This process requires the formation of three conserved disulfide bonds. Only when correctly folded, proinsulin is recognized as trafficking-competent for export to the Golgi and subsequent maturation in secretory granules. Disruptions in ER-to-Golgi trafficking induce proinsulin misfolding, characterized by the accumulation of high-molecular-weight disulfide-linked complexes, a key driver of beta-cell failure in neonatal and Type 2 diabetes. While the pathways to ER stress are well-mapped, the mechanisms of proteostatic recovery remain a critical gap in cell biology. Our previous results show that the proteostasis is restored upon relief of an ER-to-Golgi trafficking block, as indicated by the reappearance of properly folded proinsulin and a decrease in misfolded proinsulin species. We hypothesize that this restoration of homeostasis is driven by the oxidative refolding of non-native proinsulin by specific ER oxidoreductases known as the Protein Disulfide Isomerases (PDIs), rather than by degradative clearance machinery in beta cells. Focusing on PDIA1, PDIA4, and PDIA6, we utilize a reversible Brefeldin A (BFA) model in INS-1 beta cells to monitor the resolution of misfolded proinsulin species in real-time. Preliminary data demonstrate that proinsulin folding recovery persists despite the pharmacological blockade of proteasomal and lysosomal degradation, suggesting a dominant role for PDI-mediated repair. By integrating biochemical assays including immunoblotting with live-cell and electron microscopy, we seek to delineate the functional necessity of individual PDI isoforms in the restoration of beta-cell homeostasis. These findings will shift the therapeutic focus toward enhancing endogenous repair mechanisms to preserve insulin production in metabolic disease.
Start Time
15-4-2026 1:30 PM
End Time
15-4-2026 4:30 PM
Room Number
Culp Ballroom 316
Poster Number
14
Presentation Type
Poster
Presentation Subtype
Posters - Competitive
Presentation Category
Science, Technology, and Engineering
Student Type
Graduate and Professional Degree Students, Residents, Fellows
Faculty Mentor
Anoop Arunagiri
Role of Protein Disulfide Isomerases (PDIs) in the Reversible Folding of Proinsulin in Beta Cells
Culp Ballroom 316
The production of mature, bioactive insulin depends on the precise oxidative folding of its precursor, proinsulin, within the endoplasmic reticulum (ER). This process requires the formation of three conserved disulfide bonds. Only when correctly folded, proinsulin is recognized as trafficking-competent for export to the Golgi and subsequent maturation in secretory granules. Disruptions in ER-to-Golgi trafficking induce proinsulin misfolding, characterized by the accumulation of high-molecular-weight disulfide-linked complexes, a key driver of beta-cell failure in neonatal and Type 2 diabetes. While the pathways to ER stress are well-mapped, the mechanisms of proteostatic recovery remain a critical gap in cell biology. Our previous results show that the proteostasis is restored upon relief of an ER-to-Golgi trafficking block, as indicated by the reappearance of properly folded proinsulin and a decrease in misfolded proinsulin species. We hypothesize that this restoration of homeostasis is driven by the oxidative refolding of non-native proinsulin by specific ER oxidoreductases known as the Protein Disulfide Isomerases (PDIs), rather than by degradative clearance machinery in beta cells. Focusing on PDIA1, PDIA4, and PDIA6, we utilize a reversible Brefeldin A (BFA) model in INS-1 beta cells to monitor the resolution of misfolded proinsulin species in real-time. Preliminary data demonstrate that proinsulin folding recovery persists despite the pharmacological blockade of proteasomal and lysosomal degradation, suggesting a dominant role for PDI-mediated repair. By integrating biochemical assays including immunoblotting with live-cell and electron microscopy, we seek to delineate the functional necessity of individual PDI isoforms in the restoration of beta-cell homeostasis. These findings will shift the therapeutic focus toward enhancing endogenous repair mechanisms to preserve insulin production in metabolic disease.
