Abstract
Serum amyloid P component (SAP) is a non-fibrillar glycoprotein belonging to the pentraxin family of the innate immune system. SAP is present in plasma, basement membranes, and amyloid deposits. This study demonstrates, for the first time, that the Goodpasture antigen-binding protein (GPBP) binds to human SAP. GPBP is a nonconventional Ser/Thr kinase for basement membrane type IV collagen. Also GPBP is found in plasma and in the extracellular matrix. In the present study, we demonstrate that GPBP specifically binds SAP in its physiological conformations, pentamers and decamers. The START domain in GPBP is important for this interaction. SAP and GPBP form complexes in blood and partly colocalize in amyloid plaques from Alzheimer disease patients. These data suggest the existence of complexes of SAP and GPBP under physiological and pathological conditions. These complexes are important for understanding basement membrane, blood physiology, and plaque formation in Alzheimer disease.
Highlights
The Goodpasture antigen-binding protein (GPBP) and serum amyloid P component (SAP) bind to type IV collagen and are found in plasma
Binding of Serum amyloid P component (SAP) and GPBP to Type IV Collagen—Previously, it has been reported that both SAP and GPBP bind to ␣3(IV)NC1 monomer [20, 33]
In order to analyze if this binding occurs in vivo, we studied whether SAP and GPBP colocalize in GBM, which expresses collagen IV
Summary
The Goodpasture antigen-binding protein (GPBP) and serum amyloid P component (SAP) bind to type IV collagen and are found in plasma. Conclusion: GPBP and SAP form complexes under physiological and pathological conditions. This study demonstrates, for the first time, that the Goodpasture antigen-binding protein (GPBP) binds to human SAP. SAP and GPBP form complexes in blood and partly colocalize in amyloid plaques from Alzheimer disease patients. These data suggest the existence of complexes of SAP and GPBP under physiological and pathological conditions. These complexes are important for understanding basement membrane, blood physiology, and plaque formation in Alzheimer disease
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