Natural variants of human apolipoprotein A-I: structural perturbations associated to protein misfolding

GISONNO, R.; RAMELLA, N.; CORTEZ, M. F; FINARELLI, G. S.; GADDI, G. M.; ROSÚ, S A.; TRICERRI, M. A.

Mexico

Congreso; VI Latin American Protein Society Meeting and VII Congreso de la Rama de Fisicoquímica, Estructura y Diseño de Proteínas; 2019

Latin American Protein Society

The reason that determines the pathological deposition of human apolipoprotein A-I variants inducing organfailure has been under research since the early description of natural mutations in patients. To shed light into theevents associated with protein aggregation, we studied the structural perturbations that may occur in the naturalvariant that shows a substitution of a Leucine by an Arginine in position 60 (L60R). Circular dichroism, intrinsicfluorescence measurements, and proteolysis analysis indicated that L60R was more unstable, more sensitive tocleavage and the N-terminus was more disorganized than the protein with the native sequence (Wt). A highertendency to aggregate was also detected when L60R was incubated at physiological pH. In addition, the smallstructural rearrangement observed for the freshly folded variant led to the release of tumor necrosis factor-α andinterleukin-1β from a model of macrophages. However, the mutant preserved both its dimeric conformation andits lipid-binding capacity. Our results strongly suggest that the chronic disease may be a consequence of thenative conformation loss which elicits the release of protein conformations that could be either cytotoxic orprecursors of amyloid conformations.