title: Study of the pathways involved in apoptosis induced by PI3K inhibition in cerebellar granule neurons.
abstract: In the present study we focused in the PI3K/Akt pathway which plays a key role in neuronal survival. Here we show that inhibition of PI3K/Akt by means of LY294002 induces apoptosis via a caspase-dependent and calpain-independent pathway in cerebellar granule neurons (CGNs). This finding was confirmed using zVAD-fmk, a widely caspase inhibitor that prevents apoptosis. For this purpose, we compared two models of apoptosis in CGNs, namely inhibition of PI3K/Akt, and serum potassium deprivation (S/K deprivation). In contrast to the S/K deprivation model, caspase-3 was not activated when PI3K is inhibited. Likewise, CDK5 activation was not involved in this apoptotic process, because calpain activation is responsible for the formation of CDK5/p25 neurotoxic form. However, S/K deprivation activated calpain, as it is shown by α-spectrin breakdown, and favoured the formation of CDK5/p25. Moreover, although PI3K/Akt inhibition enhanced pRbser780 phosphorylation, no increase in the expression of cell-cycle proteins, namely: cyclin D, cyclin E, CDK2 or CDK4, was detected. Furthermore, BrdU incorporation assay did not shown any increase in DNA synthesis. Likewise, PI3K/Akt inhibition increased GSK3β activity and c-Jun phosphorylation, which implicates these two pathways in this apoptotic route. Although previous reports suggest that apoptosis induced in CGNs by LY294002 and S/K deprivation causes PI3K inhibition and increases GSK3β activity and c-Jun phosphorylation activation, our results demonstrate substantial differences between them and point to a key role of GSK3β in the apoptosis induced in CGNs in the two models tested.
authors.affiliation: Unitat de Farmacologia i Farmacognòsia, Facultat de Farmàcia, Centros de Investigación Biomédica en Red Enfermedades Neurodegenerativas (CIBERNED), Institut de Biomedicina, Universitat de Barcelona, Nucli Universitari de Pedralbes, 08028 Barcelona, Spain.
authors.forename: Aurelio
authors.initials: A
authors.lastname: Vazquez de la Torre
authors.forename: Felix
authors.initials: F
authors.lastname: Junyent
authors.forename: Jaume
authors.initials: J
authors.lastname: Folch
authors.forename: Carme
authors.initials: C
authors.lastname: Pelegrí
authors.forename: Jordi
authors.initials: J
authors.lastname: Vilaplana
authors.forename: Carme
authors.initials: C
authors.lastname: Auladell
authors.forename: Carlos
authors.initials: C
authors.lastname: Beas-Zarate
authors.forename: Mercè
authors.initials: M
authors.lastname: Pallàs
authors.forename: Antoni
authors.initials: A
authors.lastname: Camins
authors.forename: Ester
authors.initials: E
authors.lastname: Verdaguer
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002531:Cerebellum / Q000187:drug effects* / Q000201:enzymology; D003594:Cytoplasmic Granules / Q000187:drug effects* / Q000201:enzymology; D005434:Flow Cytometry; D051379:Mice; D009474:Neurons / Q000187:drug effects* / Q000201:enzymology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt