Protein C Sapporo (protein C Glu 25 --> Lys): a heterozygous missense mutation in the Gla domain provides new insight into the interaction between protein C and endothelial protein C receptor.
Interaction of the gamma-carboxyglutamic acid (Gla) domain of protein C with endothelial protein C receptor (EPCR) is a critical step for efficient activation of protein C, though interactions by mutants in the Gla domain of protein C with EPCR have been rarely evaluated. We identified a 44-year-old Japanese woman with a history of recurrent thromboembolism as an inherited missense mutation, the first such case reported in Japan, which involved a protein C Gla 25 mutation. Total protein C antigen and Gla protein C antigen levels in the proband were normal. Protein C activity measured with an anticoagulant assay was reduced, whereas that measured with an amidolytic assay was normal. She was therefore phenotypically diagnosed as type IIb protein C deficiency. Direct sequencing of the PCR fragments revealed a heterozygous G to A transition at nucleotide position 1462 in exon 3, which predicted an amino acid substitution of Glu 25 by Lys. Her mother and one son were also heterozygous for this mutation. A molecular dynamics simulation of Gla 25-->Lys/EPCR complex in water suggested that the affinity between the molecules was decreased compared to the wild type Gla domain/EPCR complex. Since Gla 25 has been shown to play an important role in protein C function, not only in membrane phospholipid binding but also in binding to EPCR, our findings provide new insight into the mechanism by which the Glu 25-->Lys mutation induces type IIb protein C deficiency in individuals.
Nakabayashi
Toru
T
Department of Internal Medicine, School of Dentistry, Health Sciences University of Hokkaido, Is-hikari-Tobetsu, Hokkaido, Japan.
Mizukami
Kazuhiro
K
Naitoh
Sumiyoshi
S
Takeda
Mika
M
Shikamoto
Yasuo
Y
Nakagawa
Takafumi
T
Kaneko
Hiroki
H
Tarumi
Takashi
T
Mizoguchi
Itaru
I
Mizuno
Hiroshi
H
Ieko
Masahiro
M
Koike
Takao
T
D000328:Adult; D000941:Antigens / Q000097:blood*; D015703:Antigens, CD; D001779:Blood Coagulation Factors; D000074283:Endothelial Protein C Receptor; D005192:Family Health; D005260:Female; D006023:Glycoproteins / Q000097:blood*; D006579:Heterozygote; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008297:Male; D020125:Mutation, Missense; D010375:Pedigree; D011486:Protein C / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D020151:Protein C Deficiency / Q000235:genetics* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000097:blood*; D015183:Restriction Mapping; D013927:Thrombosis / Q000235:genetics / Q000378:metabolism
D000941:Antigens; D015703:Antigens, CD; D001779:Blood Coagulation Factors; D000074283:Endothelial Protein C Receptor; D006023:Glycoproteins; C478370:PROCR protein, human; D011486:Protein C; D011956:Receptors, Cell Surface