Effects of ML-236B (Compactin) on Sterol Synthesis and Low Density Lipoprotein Receptor Activities in Fibroblasts of Patients with Homozygous Familial Hypercholesterolemia

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Abstract

We studied biochemical genetics of low density lipoprotein (LDL) receptor mutations in fibroblasts from six homozygous and five heterozygous patients with familial hypercholesterolemia (FH). Three of six homozygotes are receptor-negative type and the other three homozygotes are receptor-defective type. In the cells from three receptor-negative homozygotes, the receptor binding, internalization, and degradation of 125I-LDL were 0.5±0.3 ng/mg protein (mean±SEM), 14±8 and 8±6 ng/mg protein per 6 h (four normal cells; 44±3, 386±32, and 1,335±214 ng/mg protein per 6 h), respectively. In the cells from three receptor-defective homozygotes, the receptor binding, internalization, and degradation of 125I-LDL were 6±2, 29±8, and 90±32 ng/mg protein per 6 h, respectively. In these six homozygotes, two pairs of siblings are included. Two siblings in the same family were classified as receptor-negative and two siblings in another family were classified as receptor-defective. The receptor-negative phenotypes and the receptor-defective phenotypes bred true in individual families. The cells from five heterozygotes showed ∼46% of the normal activities of receptor.

Authors

Toshihiro Haba, Hiroshi Mabuchi, Akira Yoshimura, Akira Watanabe, Takanobu Wakasugi, Ryozo Tatami, Kosei Ueda, Ryosei Ueda, Tomio Kametani, Junji Koizumi, Susumu Miyamoto, Ryoyu Takeda