Implications of compound heterozygous insulin receptor mutations in congenital muscle fibre type disproportion myopathy for the receptor kinase activation

TY - JOUR

T1 - Implications of compound heterozygous insulin receptor mutations in congenital muscle fibre type disproportion myopathy for the receptor kinase activation

AU - Klein, H H

AU - Müller, R

AU - Vestergaard, H

AU - Pedersen, O

PY - 1999/2

Y1 - 1999/2

N2 - We studied insulin receptor kinase activation in two brothers with congenital muscle fibre type disproportion myopathy and compound heterozygous mutations of the insulin receptor gene, their parents, and their unaffected brother. In the father who has a heterozygote Arg1174-->Gln mutation, in situ activation of the receptor kinase in skeletal muscle was reduced about 70%. Selection of only those receptors that bound to anti-phosphotyrosine antibody showed that these receptors had normal kinase activity and that the reduction in overall kinase activity was due to the inability of about 70% of the receptors to become insulin-dependently activated. The mother carries a point mutation at the last base pair in exon 17 which, due to abnormal alternative splicing, could lead to normally transcribed receptor or truncated receptor lacking the kinase region. Kinase activation was normal in the mother's skeletal muscle, suggesting that virtually no truncated receptor was expressed. Receptor kinase activity was, however, reduced by 95 and 91% in the compound heterozygous brothers. This suggests that the mother's mutated allele contributes little to the generation of functional receptor protein and that the receptors in the mother's skeletal muscle are transcribed almost exclusively from the non-mutated allele. The mutation in exon 17 could lead to reduced transcription or rapid degradation of a predominantly transcribed truncated gene product or both.

AB - We studied insulin receptor kinase activation in two brothers with congenital muscle fibre type disproportion myopathy and compound heterozygous mutations of the insulin receptor gene, their parents, and their unaffected brother. In the father who has a heterozygote Arg1174-->Gln mutation, in situ activation of the receptor kinase in skeletal muscle was reduced about 70%. Selection of only those receptors that bound to anti-phosphotyrosine antibody showed that these receptors had normal kinase activity and that the reduction in overall kinase activity was due to the inability of about 70% of the receptors to become insulin-dependently activated. The mother carries a point mutation at the last base pair in exon 17 which, due to abnormal alternative splicing, could lead to normally transcribed receptor or truncated receptor lacking the kinase region. Kinase activation was normal in the mother's skeletal muscle, suggesting that virtually no truncated receptor was expressed. Receptor kinase activity was, however, reduced by 95 and 91% in the compound heterozygous brothers. This suggests that the mother's mutated allele contributes little to the generation of functional receptor protein and that the receptors in the mother's skeletal muscle are transcribed almost exclusively from the non-mutated allele. The mutation in exon 17 could lead to reduced transcription or rapid degradation of a predominantly transcribed truncated gene product or both.

KW - Adult

KW - Antibodies

KW - Enzyme Activation

KW - Erythrocytes

KW - Heterozygote

KW - Humans

KW - Insulin

KW - Insulin Resistance

KW - Male

KW - Muscle Fibers, Skeletal

KW - Muscle, Skeletal

KW - Muscular Diseases

KW - Mutation

KW - Phosphotyrosine

KW - Point Mutation

KW - Receptor, Insulin

U2 - 10.1007/s001250051145

DO - 10.1007/s001250051145

M3 - Journal article

C2 - 10064106

SN - 0012-186X

VL - 42

SP - 245

EP - 249

JO - Diabetologia

JF - Diabetologia

IS - 2

ER -