Kusari J, Takata Y, Hatada E, Freidenberg G, Kolterman O, Olefsky J M
Department of Medicine, University of California, La Jolla 92093.
J Biol Chem. 1991 Mar 15;266(8):5260-7.
Mutations in the insulin receptor gene can lead to in vivo and in vitro insulin resistance and can be the cause of diabetes mellitus in selected patients. We have studied a 22-year-old diabetic woman with Type A insulin resistance and acanthosis nigricans. Insulin binding to the patient's erythrocytes, monocytes, adipocytes, fibroblasts, and transformed lymphocytes was decreased. Receptor autophosphorylation and tyrosine kinase activity toward an exogenous substrate were reduced in partially purified insulin receptors from the proband's transformed lymphocytes. Determination of the nucleotide sequence of the patient's insulin receptor cDNA revealed that the subject was a compound heterozygote who inherited two different mutant insulin receptor gene alleles. The paternal allele contains a missense mutation encoding the substitution of glutamine for arginine at position 981 in the tyrosine kinase domain of the receptor. The maternal allele contains a nonsense mutation causing premature termination after amino acid 988 in the beta-subunit, thereby deleting most of the kinase domain. The mRNA encoded by the allele with the premature stop codon is likely to be unstable, since mRNA transcripts from this allele were decreased markedly compared with the other allele. The mother, who is heterozygous for the nonsense mutation, exhibited only mild insulin resistance, whereas the proband was severely insulin-resistant; this indicates that the missense mutation is biologically significant. In summary, (1) we have identified a patient and her family with a genetic form of insulin resistance and diabetes due to a defect at the level of the insulin receptor; (2) the proband is a compound heterozygote displaying a missense mutation (position 981) in one allele and a nonsense mutation (position 988) in the other insulin receptor gene allele; (3) the missense mutation is in the kinase domain and encodes a receptor with impaired in vitro kinase activity; and (4) based on the in vitro and in vivo phenotype, the kinase domain mutation at position 981 is biologically significant leading to insulin resistance.
胰岛素受体基因突变可导致体内和体外胰岛素抵抗，并可能是特定患者患糖尿病的原因。我们研究了一名患有A型胰岛素抵抗和黑棘皮病的22岁糖尿病女性。胰岛素与该患者的红细胞、单核细胞、脂肪细胞、成纤维细胞和转化淋巴细胞的结合减少。在先证者转化淋巴细胞中部分纯化的胰岛素受体的受体自身磷酸化和对外源底物的酪氨酸激酶活性降低。对患者胰岛素受体cDNA的核苷酸序列测定显示，该患者是一个复合杂合子，继承了两个不同的突变胰岛素受体基因等位基因。父本等位基因包含一个错义突变，编码受体酪氨酸激酶结构域第981位的精氨酸被谷氨酰胺替代。母本等位基因包含一个无义突变，导致β亚基中第988位氨基酸后提前终止，从而缺失大部分激酶结构域。带有提前终止密码子的等位基因编码的mRNA可能不稳定，因为与另一个等位基因相比，该等位基因的mRNA转录物明显减少。母亲是无义突变的杂合子，仅表现出轻度胰岛素抵抗，而先证者则严重胰岛素抵抗；这表明错义突变具有生物学意义。总之，（1）我们鉴定了一名患者及其家族，其患有由于胰岛素受体水平缺陷导致的遗传性胰岛素抵抗和糖尿病；（2）先证者是一个复合杂合子，一个等位基因显示错义突变（第981位），另一个胰岛素受体基因等位基因显示无义突变（第988位）；（3）错义突变位于激酶结构域，编码一个体外激酶活性受损的受体；（4）基于体外和体内表型，第981位的激酶结构域突变具有生物学意义，导致胰岛素抵抗。
