A potent complement factor C3-specific nanobody inhibiting multiple functions in the alternative pathway of human and murine complement

TY - JOUR

T1 - A potent complement factor C3-specific nanobody inhibiting multiple functions in the alternative pathway of human and murine complement

AU - Jensen, Rasmus K

AU - Pihl, Rasmus

AU - Gadeberg, Trine A F

AU - Jensen, Jan K

AU - Andersen, Kasper R

AU - Thiel, Steffen

AU - Laursen, Nick S

AU - Andersen, Gregers Rom

N1 - Published under license by The American Society for Biochemistry and Molecular Biology, Inc.

PY - 2018/4/27

Y1 - 2018/4/27

N2 - The complement system is a complex, carefully regulated proteolytic cascade for which suppression of aberrant activation is of increasing clinical relevance, and inhibition of the complement alternative pathway is a subject of intense research. Here, we describe the nanobody hC3Nb1 that binds to multiple functional states of C3 with subnanomolar affinity. The nanobody causes a complete shutdown of alternative pathway activity in human and murine serum when present in concentrations comparable with that of C3, and hC3Nb1 is shown to prevent proconvertase assembly, as well as binding of the C3 substrate to C3 convertases. Our crystal structure of the C3b– hC3Nb1 complex and functional experiments demonstrate that proconvertase formation is blocked by steric hindrance between the nanobody and an Asn-linked glycan on complement factor B. In addition, hC3Nb1 is shown to prevent factor H binding to C3b, rationalizing its inhibition of factor I activity. Our results identify hC3Nb1 as a versatile, inexpensive, and powerful inhibitor of the alternative pathway in both human and murine in vitro model systems of complement activation.

AB - The complement system is a complex, carefully regulated proteolytic cascade for which suppression of aberrant activation is of increasing clinical relevance, and inhibition of the complement alternative pathway is a subject of intense research. Here, we describe the nanobody hC3Nb1 that binds to multiple functional states of C3 with subnanomolar affinity. The nanobody causes a complete shutdown of alternative pathway activity in human and murine serum when present in concentrations comparable with that of C3, and hC3Nb1 is shown to prevent proconvertase assembly, as well as binding of the C3 substrate to C3 convertases. Our crystal structure of the C3b– hC3Nb1 complex and functional experiments demonstrate that proconvertase formation is blocked by steric hindrance between the nanobody and an Asn-linked glycan on complement factor B. In addition, hC3Nb1 is shown to prevent factor H binding to C3b, rationalizing its inhibition of factor I activity. Our results identify hC3Nb1 as a versatile, inexpensive, and powerful inhibitor of the alternative pathway in both human and murine in vitro model systems of complement activation.

UR - http://www.scopus.com/inward/record.url?scp=85046034101&partnerID=8YFLogxK

U2 - 10.1074/jbc.RA117.001179

DO - 10.1074/jbc.RA117.001179

M3 - Journal article

C2 - 29497000

SN - 0021-9258

VL - 293

SP - 6269

EP - 6281

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

IS - 17

ER -