cDNA sequence analysis of the human brain insulin receptor.

Brain tissue mRNA was amplified using polymerase chain reaction (PCR) with eight overlapping sets of primers that span the cDNA coding sequence for the human placental insulin receptor. Only the A isoform (lacking exon 11) of the receptor was detected. No difference was found in the predicted amino acid sequence of brain derived insulin receptor cDNA compared with the receptor from human placenta. A silent polymorphism was detected at nucleotide position 1698 (amino acid 523), confirming that mRNA corresponding to both alleles of the human brain receptor was sequenced. Our findings indicate that the unique glycosylation properties of brain insulin receptors do not stem from differences in primary structure, but rather are due to tissue-specific differences in post-translational processing.