PURPOSE: To compare PDGF- and insulin/IGF-1-induced class I(A) PI 3-kinase/Akt survival signaling in normal retinas and retinal ganglion cells (RGCs). METHODS: Normal rat retinas and RGC-5 cells were used for (1) immunohistochemical and immunoblot studies to detect PDGF receptor (PDGFR) subtypes and (2) immunoprecipitation, immunoblot, and in vitro lipid kinase assays to determine basal and PDGF-induced class I(A) PI 3-kinase/Akt survival signaling, in comparison with insulin or IGF-1 responses. Furthermore, RGC-5 cells were exposed to broad-spectrum (LY294002) or p110 isoform-selective (PI-103) PI 3-kinase inhibitors (versus Akt inhibitor) to assess the consequent effects on Akt phosphorylation, caspase-3/PARP cleavage, apoptotic phenotype, and cell viability, as a function of serum trophic factors. RESULTS: PDGFR-alpha and -beta immunoreactivity was observed in rat retinal Müller cells and in the RGC layer and blood vessels, respectively. In addition, PDGFR-alpha and -beta protein expression was observed in RGC-5 cells. Both retinas and RGC-5 cells exhibited a similar pattern of subunit-specific basal class I(A) PI 3-kinase activity, which was stimulated in a temporal and signal-specific manner by PDGF and insulin/IGF-1. Furthermore, RGC-5 cells showed PDGFR-alpha/beta tyrosine phosphorylation that induced the p85alpha regulatory subunit to activate p110alpha/beta-associated class I(A) PI 3-kinase, which in turn enhanced Akt phosphorylation. Exposure of serum-deprived RGC-5 cells to PI 3-kinase or Akt inhibitors increased susceptibility to apoptotic phenotype as revealed by caspase-3 and PARP cleavage. CONCLUSIONS: The present findings provide direct evidence of two distinct modes of retinal class I(A) PI 3-kinase activation that occurs in response to PDGF receptor and insulin/IGF-1 receptor stimulation. PDGF-induced PI 3-kinase/PIP3/Akt axis may provide new therapeutic approaches to ameliorate cell death in diabetic retinopathy and other retinal neurodegenerations.
PURPOSE: To compare PDGF- and insulin/IGF-1-induced class I(A) PI 3-kinase/Akt survival signaling in normal retinas and retinal ganglion cells (RGCs). METHODS: Normal rat retinas and RGC-5 cells were used for (1) immunohistochemical and immunoblot studies to detect PDGF receptor (PDGFR) subtypes and (2) immunoprecipitation, immunoblot, and in vitro lipid kinase assays to determine basal and PDGF-induced class I(A) PI 3-kinase/Akt survival signaling, in comparison with insulin or IGF-1 responses. Furthermore, RGC-5 cells were exposed to broad-spectrum (LY294002) or p110 isoform-selective (PI-103) PI 3-kinase inhibitors (versus Akt inhibitor) to assess the consequent effects on Akt phosphorylation, caspase-3/PARP cleavage, apoptotic phenotype, and cell viability, as a function of serum trophic factors. RESULTS:PDGFR-alpha and -beta immunoreactivity was observed in rat retinal Müller cells and in the RGC layer and blood vessels, respectively. In addition, PDGFR-alpha and -beta protein expression was observed in RGC-5 cells. Both retinas and RGC-5 cells exhibited a similar pattern of subunit-specific basal class I(A) PI 3-kinase activity, which was stimulated in a temporal and signal-specific manner by PDGF and insulin/IGF-1. Furthermore, RGC-5 cells showed PDGFR-alpha/beta tyrosine phosphorylation that induced the p85alpha regulatory subunit to activate p110alpha/beta-associated class I(A) PI 3-kinase, which in turn enhanced Akt phosphorylation. Exposure of serum-deprived RGC-5 cells to PI 3-kinase or Akt inhibitors increased susceptibility to apoptotic phenotype as revealed by caspase-3 and PARP cleavage. CONCLUSIONS: The present findings provide direct evidence of two distinct modes of retinal class I(A) PI 3-kinase activation that occurs in response to PDGF receptor and insulin/IGF-1 receptor stimulation. PDGF-induced PI 3-kinase/PIP3/Akt axis may provide new therapeutic approaches to ameliorate cell death in diabetic retinopathy and other retinal neurodegenerations.
Authors: Thomas V Johnson; Nicholas W DeKorver; Victoria A Levasseur; Andrew Osborne; Alessia Tassoni; Barbara Lorber; Janosch P Heller; Rafael Villasmil; Natalie D Bull; Keith R Martin; Stanislav I Tomarev Journal: Brain Date: 2013-10-30 Impact factor: 13.501
Authors: Yan Zhao; Swarajit K Biswas; Patrick H McNulty; Mark Kozak; John Y Jun; Lakshman Segar Journal: Am J Physiol Cell Physiol Date: 2011-02-16 Impact factor: 4.249
Authors: Nundehui Díaz-Lezama; Anne Wolf; Susanne Koch; Anna M Pfaller; Josef Biber; Xavier Guillonneau; Thomas Langmann; Antje Grosche Journal: Int J Mol Sci Date: 2021-01-25 Impact factor: 5.923
Authors: Keirnan Willett; Reas S Khan; Kimberly Dine; Howard Wessel; Ziv Z Kirshner; Jodie L Sauer; Ashley Ellis; Larry R Brown; Kenneth S Shindler Journal: PLoS One Date: 2021-01-06 Impact factor: 3.240