Structural basis for the HMGCR interaction with UBIAD1 mutants causing Schnyder corneal dystrophy

Abstract

AbstractSchnyder corneal dystrophy (SCD) is an autosomal dominant disease characterized by abnormal deposition of cholesterol and lipid in the cornea. The molecular mechanism underlying this process, which involves the interaction between UBAID1 and HMGCR, remains unclear. Here we investigate these events within silicoapproaches. We built the homology models of UBIAD1 and HMGCR based on the existing crystal and cryo-EM structures. The UBIAD1 and HMGCR models are docked and their binding interactions are interrogated by MD simulation. We find that the transmembrane helices of UBIAD1 bind to sterol sensing domain of HMGCR. Upon binding of the GGPP substrate, UBIAD1 shows lower structural flexibility in the TM regions binding to HMGCR. The N102S and G177R mutations disrupts GGPP binding, thereby lowering the binding affinity of HMGCR. Overall, our modeling suggests that SCD mutations in UBIAD1 or lower GGPP concentration increase the structural flexibility of UBIAD1, thereby facilitating its association with HMGCR.