18 - Retinal Insulin Receptors

Abstract

Insulin receptors are widely distributed throughout the central nervous system (CNS), as in the case of the periphery; however, fewer details are known about the neuronal receptors. Included in the CNS is the retina that represents a highly specialized and accessible portion of the brain and expresses neuronal insulin receptors. This chapter presents a methodological base with which to approach future studies on neuronal insulin receptors in the retina and other regions of the CNS. The biochemical comparisons of insulin receptors from the CNS and periphery show that two subtypes of insulin receptor exist. These subtypes are distinguishable on the basis of the molecular weights of α subunits, with the neuronal receptor α subunit having a molecular weight of ∼115K (∼10,000 less than the α subunit from peripheral tissues). A direct identification of insulin receptor α subunits in retinal membranes can be accomplished using the technique of affinity labeling or chemical cross-linking.