Dependence on Vitamin K-dependent Protein S for Eukaryotic Cell Secretion of the beta-Chain of C4b-binding Protein
(2010) In Journal of Biological Chemistry 285(42). p.32038-32046- Abstract
- The anticoagulant vitamin K-dependent protein S (PS) circulates in plasma in two forms, 30% free and 70% being bound to the complement regulatory protein C4b-binding protein (C4BP). The major C4BP isoform consists of 7 alpha-chains and 1 beta-chain (C4BP beta(+)), the chains being linked by disulfide bridges. PS binds to the beta-chain with high affinity. In plasma, PS is in molar excess over C4BP beta(+) and due to the high affinity, all C4BP beta(+) molecules contain a bound PS. Taken together with the observation that PS-deficient patients have decreased levels of C4BP beta(+), this raises the question of whether PS is important for secretion of the beta-chain from the cell. To test this hypothesis, HEK293 cells were stably and... (More)
- The anticoagulant vitamin K-dependent protein S (PS) circulates in plasma in two forms, 30% free and 70% being bound to the complement regulatory protein C4b-binding protein (C4BP). The major C4BP isoform consists of 7 alpha-chains and 1 beta-chain (C4BP beta(+)), the chains being linked by disulfide bridges. PS binds to the beta-chain with high affinity. In plasma, PS is in molar excess over C4BP beta(+) and due to the high affinity, all C4BP beta(+) molecules contain a bound PS. Taken together with the observation that PS-deficient patients have decreased levels of C4BP beta(+), this raises the question of whether PS is important for secretion of the beta-chain from the cell. To test this hypothesis, HEK293 cells were stably and transiently transfected with beta-chain cDNA in combinations with cDNAs for PS and/or the alpha-chain. The concentration of beta-chains in the medium increased after co-transfection with PS cDNA, but not by alpha-chain cDNA, suggesting secretion of the beta-chains from the cells to be dependent on concomitant synthesis of PS, but not of the alpha-chains. Thus, beta-chains that were not disulfide-linked to the alpha-chains were secreted in complex with PS, either as monomers or dimers. Pulse-chase demonstrated that the complexes between PS and beta-chain were formed intracellularly, in the endoplasmic reticulum. In conclusion, our results demonstrate that successful secretion of beta-chains depends on intracellular complex formation with PS, but not on the alpha-chains. This provides an explanation for the decreased beta-chain levels observed in PS-deficient patients. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/1727049
- author
- Somajo, Sofia LU and Dahlbäck, Björn LU
- organization
- publishing date
- 2010
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Journal of Biological Chemistry
- volume
- 285
- issue
- 42
- pages
- 32038 - 32046
- publisher
- American Society for Biochemistry and Molecular Biology
- external identifiers
-
- wos:000282683000017
- pmid:20693287
- scopus:77957808702
- pmid:20693287
- ISSN
- 1083-351X
- DOI
- 10.1074/jbc.M110.148452
- language
- English
- LU publication?
- yes
- id
- bd6eef3c-492e-4590-8111-331d0f3abdca (old id 1727049)
- alternative location
- http://www.ncbi.nlm.nih.gov/pubmed/20693287?dopt=Abstract
- date added to LUP
- 2016-04-01 11:07:58
- date last changed
- 2022-01-26 05:44:35
@article{bd6eef3c-492e-4590-8111-331d0f3abdca,
abstract = {{The anticoagulant vitamin K-dependent protein S (PS) circulates in plasma in two forms, 30% free and 70% being bound to the complement regulatory protein C4b-binding protein (C4BP). The major C4BP isoform consists of 7 alpha-chains and 1 beta-chain (C4BP beta(+)), the chains being linked by disulfide bridges. PS binds to the beta-chain with high affinity. In plasma, PS is in molar excess over C4BP beta(+) and due to the high affinity, all C4BP beta(+) molecules contain a bound PS. Taken together with the observation that PS-deficient patients have decreased levels of C4BP beta(+), this raises the question of whether PS is important for secretion of the beta-chain from the cell. To test this hypothesis, HEK293 cells were stably and transiently transfected with beta-chain cDNA in combinations with cDNAs for PS and/or the alpha-chain. The concentration of beta-chains in the medium increased after co-transfection with PS cDNA, but not by alpha-chain cDNA, suggesting secretion of the beta-chains from the cells to be dependent on concomitant synthesis of PS, but not of the alpha-chains. Thus, beta-chains that were not disulfide-linked to the alpha-chains were secreted in complex with PS, either as monomers or dimers. Pulse-chase demonstrated that the complexes between PS and beta-chain were formed intracellularly, in the endoplasmic reticulum. In conclusion, our results demonstrate that successful secretion of beta-chains depends on intracellular complex formation with PS, but not on the alpha-chains. This provides an explanation for the decreased beta-chain levels observed in PS-deficient patients.}},
author = {{Somajo, Sofia and Dahlbäck, Björn}},
issn = {{1083-351X}},
language = {{eng}},
number = {{42}},
pages = {{32038--32046}},
publisher = {{American Society for Biochemistry and Molecular Biology}},
series = {{Journal of Biological Chemistry}},
title = {{Dependence on Vitamin K-dependent Protein S for Eukaryotic Cell Secretion of the beta-Chain of C4b-binding Protein}},
url = {{http://dx.doi.org/10.1074/jbc.M110.148452}},
doi = {{10.1074/jbc.M110.148452}},
volume = {{285}},
year = {{2010}},
}