Format

Send to

Choose Destination
J Biol Chem. 2014 Jun 13;289(24):17228-39. doi: 10.1074/jbc.M113.522565. Epub 2014 Apr 24.

Dissection of the neonatal Fc receptor (FcRn)-albumin interface using mutagenesis and anti-FcRn albumin-blocking antibodies.

Author information

1
From the Centre for Immune Regulation (CIR) and Department of Biosciences, University of Oslo, N-0316 Oslo, Norway, CIR and Department of Immunology, Oslo University Hospital Rikshospitalet and University of Oslo, Norway, N-0424 Oslo, Norway.
2
the Department for Microbiology, Oslo University Hospital Rikshospitalet and University of Oslo, Nydalen, N-0424 Oslo, Norway, the Department of Medical Biochemistry, Oslo University Hospital Rikshospitalet and University of Oslo, Nydalen, N-0424 Oslo, Norway.
3
The Jackson Laboratory, Bar Harbor, Maine 04609, and.
4
Novozymes Biopharma UK, Ltd., Castle Court, 59 Castle Boulevard, NG7 1FD Nottingham, United Kingdom.
5
CIR and Department of Immunology, Oslo University Hospital Rikshospitalet and University of Oslo, Norway, N-0424 Oslo, Norway, j.t.andersen@ibv.uio.no.

Abstract

Albumin is the most abundant protein in blood and plays a pivotal role as a multitransporter of a wide range of molecules such as fatty acids, metabolites, hormones, and toxins. In addition, it binds a variety of drugs. Its role as distributor is supported by its extraordinary serum half-life of 3 weeks. This is related to its size and binding to the cellular receptor FcRn, which rescues albumin from intracellular degradation. Furthermore, the long half-life has fostered a great and increasing interest in utilization of albumin as a carrier of protein therapeutics and chemical drugs. However, to fully understand how FcRn acts as a regulator of albumin homeostasis and to take advantage of the FcRn-albumin interaction in drug design, the interaction interface needs to be dissected. Here, we used a panel of monoclonal antibodies directed towards human FcRn in combination with site-directed mutagenesis and structural modeling to unmask the binding sites for albumin blocking antibodies and albumin on the receptor, which revealed that the interaction is not only strictly pH-dependent, but predominantly hydrophobic in nature. Specifically, we provide mechanistic evidence for a crucial role of a cluster of conserved tryptophan residues that expose a pH-sensitive loop of FcRn, and identify structural differences in proximity to these hot spot residues that explain divergent cross-species binding properties of FcRn. Our findings expand our knowledge of how FcRn is controlling albumin homeostasis at a molecular level, which will guide design and engineering of novel albumin variants with altered transport properties.

KEYWORDS:

Albumin; Antibody; Biodegradation; Bioengineering; Fc Receptor; FcRn; Half-life; Hydrophobic; pH Regulation

PMID:
24764301
PMCID:
PMC4059163
DOI:
10.1074/jbc.M113.522565
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central Icon for Norwegian BIBSYS system
Loading ...
Support Center