Influence of heparin molecular size on the induction of C- terminal unfolding in β2-microglobulin.

Dialysis-related amyloidosis (DRA) is characterized by accumulation of amyloid β2- microglobulin (β2m) in the interstitial matrix. Matrix substances such as heparin have reportedly been strongly implicated in the pathogenesis of dialysis-related amyloidosis. In clinical setting of hemodialysis, two types of heparin, i.e., high and low molecular heparin (H.M.H. and L.M.H.) have been routinely used. Still commonly used is H.M.H., followed by L.M.H. preparations with distinct advantages. Here, we studied that the interaction of native and two amyloidogenic β2m variants: ΔN6β2m and D76N β2m with H.M.H. and L.M.H. We also investigated whether heparin could induce β2m to have an amyloidogenic conformation. Biolayer interferometry revealed that ΔN6β2m had a strong reaction and D76N β2m had a moderate reaction with H.M.H.. Furthermore,H.M.H. induced the C-terminal unfolding in a native β2m. By contrast, L.M.H. showed no reaction even with ΔN6β2m. This study showed firstly a direct binding of β2m with H.M.H.. H.M.H. would provoked a C-terminal unfolding of β2m, which indicated production of an amyloidogenic intermediate, i.e., β2m92-99. In addition, our findings also suggest that L.M.H. may provide beneficial effects against the development of the DRA.