Direct demonstration of a neonatal Fc receptor (FcRn)-driven endosomal sorting pathway for cellular recycling of albumin

Schmidt, E. G.; Hvam, Michael Lykke; Antunes, Filipa; Cameron, Jason; Viuff, Dorthe; Andersen, Birgitte; Kristensen, Nanna Ny; Howard, Kenneth A.

doi:10.1074/jbc.m117.794248

Cited by 67 publications

(90 citation statements)

References 42 publications

(42 reference statements)

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“…But considering the size of these conjugated molecules ranging from 5 to 30 kDa, strong steric hindrance impairing FcRn binding is not necessarily surprising. Our results demonstrate that the specific oxidation of Cys 34 , either reversibly with Cys and Cys‐Gly disulfide linkage or irreversibly as a sulfinic acid, altered the FcRn binding with consequences of an impaired FcRn recycling mechanism and a probably reduced HSA half‐life …”

Section: Discussionmentioning

confidence: 84%

“…The N-terminus indicated by His 3 is depicted in magenta, the C-terminal Leu 585 in cyan, Cys 34 either reversibly with Cys and Cys-Gly disulfide linkage or irreversibly as a sulfinic acid, altered the FcRn binding with consequences of an impaired FcRn recycling mechanism and a probably reduced HSA half-life. 40 C-terminal truncated forms of HSA were reported in 2000 in the plasma of a patient having chronic pancreatic pseudocyst. 41 The major truncated detected form had lost only the C-terminal Leu 585 amino acid and the truncation was suggested to be the result of exposure of HSA to "leaking" pancreatic endo and exoproteases.…”

Section: Discussionmentioning

confidence: 99%

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Human serum albumin presents isoform variants with altered neonatal Fc receptor interactions

et al. 2019

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Human serum albumin (HSA) is the most abundant protein in plasma and presents the particularity, with IgG, to have an extraordinary long serum half‐life conferred by its interaction with the neonatal Fc receptor (FcRn). If the impact of IgG post‐translational modifications (PTMs) on FcRn binding is well documented, it is far less reported for HSA despite numerous PTMs occurring on the protein in plasma. HSA is susceptible to numerous degradation reactions in plasma, because of aging, oxidative stress or liver and pancreas related pathologies. In the present study, we combined FcRn affinity chromatography and mass spectrometry to investigate the impact of HSA PTMs upon FcRn binding. This methodology presents the advantage to distinguish the effect of a single modification from a plasma HSA preparation made of a mixture of different isoforms. Cys34 oxidation, Lys525 glycation, and Leu585 C‐terminal truncation, which are modifications related to several pathological conditions, were demonstrated to act negatively on HSA‐FcRn interaction. The HSA‐FcRn binding alteration generated by these modifications is consistent with their vicinity with the interaction interface of the two proteins. Results were discussed regarding altered half‐life of HSA observed in several disease states and pave the way toward new understandings of the hypoalbuminemia pathogenesis. Significance statement In this study, we investigated the impact of several post‐translational modifications of HSA toward its ability to bind to the neonatal Fc receptor using in vitro affinity chromatography, mass spectrometry, and surface plasmon resonance. Cys34 oxidation, Lys525 glycation, and Leu585 C‐terminal truncation were demonstrated to decrease HSA‐FcRn binding. These modifications occurring in circulating HSA were discussed in relation to several pathologies as well as for the use of HSA as a therapeutic protein.

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Section: Discussionmentioning

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Human serum albumin presents isoform variants with altered neonatal Fc receptor interactions

et al. 2019

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“…Recombinant albumin was engineered to have high or low affinity to bind FcRn. Albumin with high affinity was recycled whereas low affinity albumin underwent lysosomal degradation (Schmidt et al, 2017). These cellular interactions with albumin demonstrate that cells selectively dictate the fate of albumin based on the albumin's ligand conformation.…”

Section: Introductionmentioning

confidence: 99%

Albumin promotes proliferation of G1 arrested serum starved hepatocellular carcinoma cells

Ibrahim

Stange

Dominik

et al. 2020

PeerJ

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Albumin is the most abundant plasma protein and functions as a transport molecule that continuously interacts with various cell types. Because of these properties, albumin has been exploited by the pharmaceutical industry to improve drug delivery into target cells. The immediate effects of albumin on cells, however, require further understanding. The cell interacting properties and pharmaceutical applications of albumin incentivises continual research into the immediate effects of albumin on cells. The HepG2/C3A hepatocellular carcinoma cell line is used as a model for studying cancer pathology as well as liver biosynthesis and cellular responses to drugs. Here we investigated the direct effect of purified albumin on HepG2/C3A cell proliferation in the absence of serum, growth factors and other serum originating albumin bound molecules. We observed that the reduced cell counts in serum starved HepG2/C3A cultures were increased by the inclusion of albumin. Cell cycle analysis demonstrated that the percentage of cells in G1 phase during serum starvation was reduced from 86.4 ± 2.3% to 78.3 ± 3.2% by the inclusion of albumin whereas the percentage of cells in S phase was increased from 6.5 ± 1.5% to 14.3 ± 3.6%. A significant reduction in the cell cycle inhibitor protein, P21, accompanied the changes in the proportions of cell cycle phases upon treatment with albumin. We have also observed that the levels of dead cells determined by DNA fragmentation and membrane permeabilization caused by serum starvation (TUNEL: 16.6 ± 7.2%, ethidium bromide: 13.8 ± 4.8%) were not significantly altered by the inclusion of albumin (11.6 ± 10.2%, ethidium bromide: 16.9 ± 8.9%). Therefore, the increase in cell number was mainly caused by albumin promoting proliferation rather than protection against cell death. These primary findings demonstrate that albumin has immediate effects on HepG2/C3A hepatocellular carcinoma cells. These effects should be taken into consideration when studying the effects of albumin bound drugs or pathological ligands bound to albumin on HepG2/C3A cells.

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“…Thus, this binding-and-release mechanism is based on strict pH-dependent binding between FcRn and IgG. Similarly, FcRn binds albumin at slightly acidic pH and not at neutral pH, and recent reports support that albumin is recycled via the same route, independently of IgG [18][19][20][21] .…”

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confidence: 97%

An intact C-terminal end of albumin is required for its long half-life in humans

et al. 2020

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Albumin has an average plasma half-life of three weeks and is thus an attractive carrier to improve the pharmacokinetics of fused therapeutics. The half-life is regulated by FcRn, a cellular receptor that protects against intracellular degradation. To tailor-design the therapeutic use of albumin, it is crucial to understand how structural alterations in albumin affect FcRn binding and transport properties. In the blood, the last C-terminal residue (L585) of albumin may be enzymatically cleaved. Here we demonstrate that removal of the L585 residue causes structural stabilization in regions of the principal FcRn binding domain and reduces receptor binding. In line with this, a short half-life of only 3.5 days was measured for cleaved albumin lacking L585 in a patient with acute pancreatitis. Thus, we reveal the structural requirement of an intact C-terminal end of albumin for a long plasma half-life, which has implications for design of albumin-based therapeutics.

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Direct demonstration of a neonatal Fc receptor (FcRn)-driven endosomal sorting pathway for cellular recycling of albumin

Cited by 67 publications

References 42 publications

Human serum albumin presents isoform variants with altered neonatal Fc receptor interactions

Human serum albumin presents isoform variants with altered neonatal Fc receptor interactions

Albumin promotes proliferation of G1 arrested serum starved hepatocellular carcinoma cells

An intact C-terminal end of albumin is required for its long half-life in humans

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