β2-Microglobulin Binding to Collagen : An Amyloidogenic Factor in Chronic Hemodialysis Patients
Recently, the increased incidence of systemic amyloidosis seen frequently in chronic hemodialysis patients has been received increasing attention. In particular, hemodialysis-associated amyloidosis has been osteoarthropathic symptoms such as carpal tunnel syndrome, trigger finger, joint pain in the shoulder and knee, and pathologic fracture of femoral head and neck. Gejyo et al.1 performed biochemical analysis of the tendosynovial amyloid causing carpal tunnel syndrome and first reported in 1985 that β2-microglobulin (B2M) is the structural protein of this amyloid. Subsequently, amyloid deposits in the synovia and in bone cysts of other joints in hemodialysis patients were proven to consist of B2M2. Clinically hemodialysis-related amyloid deposition characteristically occurs in tissues with abundant collagen fibers, such as joint and bone, and histologically, collagen fibers are in close proximity to the amyloid fibers on electron microscopy3.4.5. These finding led us to attempt to determine whether an affinity exists between B2M and collagen. Joint and bone tissues do not only contain collagens, but GAG chains such as proteoglycan and heparan sulfate as well. To establish a specific affinity of B2M for collagen, we compared the binding activity of B2M to collagen with the binding affinities of B2M to proteoglycan and heparan sulfate. Additionally, since hemodialysis-associated amyloidosis occurs in ectopic calcified tissue, such as the cardiac wall (unpublished finding), and urinary stone6, we also investigated the influence of calcium ion on binding activity of B2M to collagen.
KeywordsBinding Activity Heparan Sulfate Carpal Tunnel Syndrome Systemic Amyloidosis Chronic Hemodialysis Patient
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