COBRE: INSULIN RECEPTOR SIGNALING IN DIABETIC RETINOPATHY

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Background: Neurodegeneration is an important component of diabetic retinopathy as demonstrated by increased neural apoptosis in the retina during experimental and human diabetes. Insulin receptor (IR) activation has been shown to rescue retinal neurons from apoptosis. Retinal IR is constitutively active; however, this constitutive activation is impaired in diabetic retinopathy. This study has been undertaken to identify the factors that modulate the IR kinase activation. Methods: Immunoprecipitation, Mass spec analysis and Western blot analysis were used for the identification of IR interacting protein(s). Hyperglycemic mice were generated by injecting streptozotocin (STZ). IR kinase activity was measured in retina samples of either saline or STZ injected mice. Results: A 43 kDa protein associated with the retinal IR was identified as the cytoplasmic actin. Co-immunoprecipitation experiment clearly indicates the in vivo interaction between retinal IR and actin. Similar to insulin, actin also induced autophosphorylation on IR at tyrosines 1158, 1162 and 1163 in the catalytic loop. Actin also activated the IR kinase activity in vitro and the actin association with retinal IR was decreased in hyperglycemic mice. Conclusions: Our studies clearly demonstrate that cytoplasmic actin regulates the autophosphorylation of retinal IR. The loss of association between IR and actin may be an important contributory factor for the initial pathology of diabetic retinopathy. Understanding the regulation IR function might allow development of therapeutic strategies to protect the dying retinal cells. Core Module Usage: Animal and Proteomic Core Modules are vital to this study.