title: Proinsulin/insulin is synthesized locally and prevents caspase- and cathepsin-mediated cell death in the embryonic mouse retina.
abstract: Programmed cell death is an essential, highly regulated process in neural development. Although the role of insulin-like growth factor I in supporting the survival of neural cells has been well characterized, studies on proinsulin/insulin are scarce. Here, we characterize proinsulin/insulin effects on cell death in embryonic day 15.5 mouse retina. Both proinsulin mRNA and proinsulin/insulin immunoreactivity were found in the developing retina. Organotypic embryonic day 15.5 retinas cultured under growth factor deprivation showed an increase in cell death that was reversed by proinsulin, insulin and insulin-like growth factor I, with similar median effective concentration values via phosphatidylinositol-3-kinase activation. Although insulin and insulin-like growth factor I provoked a sustained Akt phosphorylation, proinsulin-induced phosphorylation of Akt was not found. Analysis of the growth factor deprivation-induced cell death mechanisms, using caspase and cathepsin inhibitors, demonstrated that both protease families were required for the effective execution of cell death. The insulin survival effect, which decreased the extent and distribution of cell death to levels similar to those found in vivo, was not enhanced by simultaneous treatment with caspase and cathepsin inhibitors, suggesting that insulin interferes with these protease pathways in the embryonic mouse retina. The mechanisms characterized in this study provide new details on early neural cell death and its genuine regulation by insulin/proinsulin.
authors.affiliation: Group of Growth Factors in Vertebrate Development, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain.
authors.forename: Ana I
authors.initials: AI
authors.lastname: Valenciano
authors.forename: Silvia
authors.initials: S
authors.lastname: Corrochano
authors.forename: Flora
authors.initials: F
authors.lastname: de Pablo
authors.forename: Pedro
authors.initials: P
authors.lastname: de la Villa
authors.forename: Enrique J
authors.initials: EJ
authors.lastname: de la Rosa
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D020169:Caspases / Q000378:metabolism; D002403:Cathepsins / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007328:Insulin / Q000096:biosynthesis* / Q000235:genetics / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D009924:Organ Culture Techniques; D010447:Peptide Hydrolases / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011384:Proinsulin / Q000096:biosynthesis* / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012160:Retina / Q000166:cytology / Q000196:embryology* / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D007328:Insulin; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D011384:Proinsulin; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D002403:Cathepsins; D010447:Peptide Hydrolases; D020169:Caspases