ABSTRACT
In view of the observations that Schwann cells contain insulin receptors, in the present study, we have investigated the developmental regulation of insulin receptor gene in the sciatic nerves of different postnatal age group rats. We have also investigated the role of insulin in the expression of the major PNS myelin glycoprotein P zero (P0) in normal as well as high glucose conditions in primary rat Schwann cells. The expression of insulin receptor gene in sciatic nerves appeared to be differentially regulated. The steady-state levels of insulin receptor mRNA increased remarkably during development and after postnatal day 10, when the peak of myelin structural gene (P0) expression occur and slowly increased further until at least postnatal day 90 in parallel with the growth of the myelin sheath. By employing immunofluorescence and RT-PCR, we observed significant increase in the P0 protein and mRNA levels in Schwann cells in response to the insulin than in insulin deprived counterparts. The presence of insulin in the high glucose medium ameliorated the altered protein and mRNA of P0 in Schwann cells compared to the insulin deprived counterparts. These studies demonstrate the importance of insulin and its receptor as possible regulatory factors in the PNS and also emphasizes their novel therapeutic applications in demyelinating diseases, especially in diabetic poly-neuropathy.
Subject(s)
Gene Expression Regulation, Developmental , Insulin/physiology , Myelin P0 Protein/metabolism , Receptor, Insulin/genetics , Schwann Cells/metabolism , Sciatic Nerve/metabolism , Animals , Cells, Cultured , Diabetic Neuropathies/metabolism , Female , Glucose/pharmacology , Glucose/physiology , Insulin/pharmacology , Male , Myelin P0 Protein/genetics , Phenotype , Rats , Rats, Wistar , Real-Time Polymerase Chain Reaction , Receptor, Insulin/metabolismABSTRACT
The objective of the present study was to examine for the presence of the IRs (insulin receptors) in the primary dissociated culture preparation of SCs (Schwann cells). This was achieved using immunological techniques using a rabbit polyclonal anti-IR antibody and at molecular level by RT (reverse transcription)-PCR. Light microscopic immune cytochemistry revealed that almost all SCs in cluster and associated neuritis exhibited positive immune reaction with the antibody, confirming the presence of IRs in them. Immunoblotting detected a prominent protein band of 90 kDa, which is consistent with those reported by the manufacturer. Like the peripheral nerve, primary SC cultures showed a predominantly high affinity IR mRNA lacking exon 11. Ultrastructural immune localization confined the presence of the IRs in the basal lamina, plasma membrane and the cytoplasmic processes of the SCs.
