Apoptosis induced by SRC-family tyrosine kinase inhibitors in cultured rat cortical cells.
ABSTRACT In the central nervous system, members of the Src family of tyrosine kinases (SFKs) are widely expressed and are abundant in neurons. The purpose of this study is to examine whether glycogen synthase-3 (GSK-3) is involved in SFK inhibitor-induced apoptosis. PP2 and SU6656, SFK inhibitors, increased apoptotic cell death with morphological changes that were characterized by cell shrinkage, chromatin condensation, or nuclear fragmentation. Moreover, both activation of caspase-9 and caspase-3 were accompanied by the cell death. GSK-3 inhibitors, such as alsterpaullone and SB216763, prevented the PP2-induced apoptosis. In addition, insulin-like growth factor-I prevented the PP2-induced cell death and PP2 inhibited phosphorylation of focal adhesion kinase (FAK). Phosphorylation of FAK on Tyr 576 by Src activates FAK. These results suggest that inhibition of SFK induces apoptosis possibly via blocking of FAK/phosphatidylinositol-3 kinase/Akt signaling pathway and activation of GSK-3 is involved in the cell death in rat cortical neurons.
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ABSTRACT: Excitotoxicity resulting from over-stimulation of glutamate receptors is a major cause of neuronal death in cerebral ischemic stroke. The over-stimulated ionotropic glutamate receptors exert their neurotoxic effects in part by over-activation of calpains which induce neuronal death by catalyzing limited proteolysis of specific cellular proteins. Here, we report that in cultured cortical neurons and in vivo in a rat model of focal ischemic stroke, the tyrosine kinase Src is cleaved by calpains at a site in the N-terminal unique domain. This generates a truncated Src fragment of approximately 52 kDa, which we localized predominantly to the cytosol. A cell membrane-permeable fusion peptide derived from the unique domain of Src prevents calpain from cleaving Src in neurons and protects against excitotoxic neuronal death. To explore the role of the truncated Src fragment in neuronal death, we expressed a recombinant truncated Src fragment in cultured neurons and examined how it affects neuronal survival. Expression of this fragment, which lacks the myristoylation motif and unique domain, was sufficient to induce neuronal death. Furthermore, inactivation of the pro-survival kinase Akt is a key step in its neurotoxic signaling pathway. As Src maintains neuronal survival, our results implicate calpain cleavage as a molecular switch converting Src from a promoter of cell survival to a mediator of neuronal death in excitotoxicity. Besides unveiling a new pathological action of Src, our discovery of the neurotoxic action of the truncated Src fragment suggests new therapeutic strategies with potential to minimize brain damage in ischemic stroke.Journal of Biological Chemistry 02/2013; · 4.65 Impact Factor
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ABSTRACT: The integrity of retinal pigment epithelial cells is critical for photoreceptor survival and vision. Pituitary adenylate cyclase activating polypeptide (PACAP) exerts retinoprotective effects against several types of injuries in vivo, including optic nerve transection, retinal ischemia, excitotoxic injuries, UVA-induced lesion, and diabetic retinopathy. In a recent study, we have proven that PACAP is also protective in oxidative stress-induced injury in human pigment epithelial cells (ARPE-19 cells). The aim of the present study was to investigate the possible mechanisms of this protection. ARPE cells were exposed to a 24-h hydrogen peroxide treatment. Expressions of kinases and apoptotic markers were studied by complex array kits and Western blot. Oxidative stress induced the activation of several apoptotic markers, including Bad, Bax, HIF-1α, several heat shock proteins, TNF-related apoptosis-inducing ligand, and Fas-associated protein with death domain, while PACAP treatment decreased them. The changes in the expression of MAP kinases showed that PACAP activated the protective ERK1/2 and downstream CREB, and decreased the activation of the pro-apoptotic p38MAPK and c-Jun N-terminal kinase, an effect opposite to that observed with only oxidative stress. Furthermore, PACAP increased the activation of the protective Akt pathway. In addition, the effects of oxidative stress on several other signaling molecules were counteracted by PACAP treatment (Chk2, Yes, Lyn, paxillin, p53, PLC, STAT4, RSK). These play a role in cell death, cell cycle, inflammation, adhesion, differentiation and proliferation. In summary, PACAP, acting at several levels, influences the balance between pro- and anti-apoptotic factors in favor of anti-apoptosis, thereby providing protection in oxidative stress-induced injury of human retinal pigment epithelial cells.Journal of Molecular Neuroscience 05/2012; 48(3):493-500. · 2.89 Impact Factor