Insulin receptors in the mammalian central nervous system: binding characteristics and subunit structure.
Insulin receptors in rat and human central nervous system have been identified by binding of 125I-insulin on purified synaptic plasma membranes; affinity labelling of receptors by chemical cross-linking 125I-insulin; or phosphorylation of receptors with [gamma-32P]ATP. Brain insulin receptors showed significant differences in their binding characteristics and subunit structure when compared with receptors in other tissues like adipose and liver cells: absence of negatively cooperative interactions; a distinct binding specificity i.e. porcine proinsulin, coypu insulin and insulin-like growth factor I and II showed 2-5 times higher binding affinity in brain than in other cell types; a smaller molecular size of the brain receptor alpha-subunit than in other tissues (Mr approximately 115,000 instead of 130,000). In contrast, the size (Mr approximately 94,000) and function of the insulin receptor beta-subunit kinase was identical with that described in other cells. We conclude, that insulin receptors in mammalian brain represent a receptor subtype which may mediate growth rather than metabolic activity of insulin.
D000255:Adenosine Triphosphate / Q000378:metabolism; D000273:Adipose Tissue / Q000378:metabolism; D000345:Affinity Labels; D000818:Animals; D001921:Brain / Q000254:growth & development / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000031:analogs & derivatives; D007457:Iodine Radioisotopes; D008099:Liver / Q000378:metabolism; D046911:Macromolecular Substances; D008970:Molecular Weight; D010766:Phosphorylation; D010777:Photochemistry; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism*; D013570:Synaptic Membranes / Q000378:metabolism
D000345:Affinity Labels; D006023:Glycoproteins; D007328:Insulin; D007457:Iodine Radioisotopes; D046911:Macromolecular Substances; D000255:Adenosine Triphosphate; D011972:Receptor, Insulin