title: Four missense mutations identified in the protein S gene of thrombosis patients with protein S deficiency: effects on secretion and anticoagulant activity of protein S.
abstract: Four missense mutations, G54R, T589I, K155E, and Y595C, were identified in the protein S (PS) gene of the patients with PS deficiency and venous thrombosis. Three patients were heterozygous for the novel mutations, G54R, T589I, and Y595C, while a remaining one patient was homozygous for the K155E mutation, which is known to be a polymorphism in the Japanese population. A family study revealed that the Y595C mutation was associated with a Type I PS deficiency and the K155E mutation with a Type II PS deficiency, while no family study was performed for the patients with the G54R and T589I mutations. To determine whether these four mutations play a causative role in PS deficiency, the four PS mutants and wild-type PS were stably expressed in human embryo kidney (HEK) 293 cells. Pulse-chase experiments showed intracellular degradation and decreased secretion of the Y595C mutant. In the activated protein C (APC) cofactor assays, the specific activity of the K155E mutant decreased to 58% of that of wild-type PS. The APC cofactor activity of the three mutants, G54R, K155E, and T589I, were inhibited by C4b-binding protein (C4BP) with a dose dependency similar to that of wild-type PS. These results indicate that the Y595C and the K155E mutations are responsible for a secretion defect and a decreased anticoagulant activity of PS, respectively. The remaining two mutations, G54R and T589I, however, did not produce any definite abnormality leading to a low plasma PS activity.
authors.affiliation: Department of Clinical Chemistry and Laboratory Medicine, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Tsuda
authors.forename: Michiyo
authors.initials: M
authors.lastname: Urata
authors.forename: Tomohide
authors.initials: T
authors.lastname: Tsuda
authors.forename: Machiko
authors.initials: M
authors.lastname: Wakiyama
authors.forename: Hiroko
authors.initials: H
authors.lastname: Iida
authors.forename: Mutsuko
authors.initials: M
authors.lastname: Nakahara
authors.forename: Sachiko
authors.initials: S
authors.lastname: Kinoshita
authors.forename: Naotaka
authors.initials: N
authors.lastname: Hamasaki
mesh_terms: D000328:Adult; D006801:Humans; D008297:Male; D020125:Mutation, Missense; D017293:Protein S / Q000235:genetics* / Q000378:metabolism; D018455:Protein S Deficiency / Q000150:complications / Q000235:genetics*; D013927:Thrombosis / Q000150:complications / Q000235:genetics*
chemical_list: D017293:Protein S