ABSTRACT
p73, like its family member p53, can induce programmed cell death following DNA damage. Here, we report that this mechanism also involves endoplasmic reticulum (ER) stress and the transactivation of scotin, a protein identified recently as a p53 target able to induce ER stress. By using Tet-On inducible cell lines (Saos 2 osteosarcoma cells that lack p53), we observed that TAp73alpha elicits significant alterations in the morphology of the ER system, namely in the fine subcellular localization of calnexin. We found that both TAp73alpha and p53 are strong inducers of scotin. On the other hand, the transcriptionally deficient short isoforms DeltaNp73alpha did not upregulate the steady-state mRNA level of scotin, as evaluated by real-time RT-PCR. Following the induction of scotin, ER staining with calnexin showed evidence of morphological alteration, with variations in the intracellular concentration of free calcium, visualized by fluo-3 staining. The induction of ER stress by p73 was further supported by the transcriptional induction of Gadd 153, a transcription factor induced under ER stress conditions. In conclusion, the data reported indicate the ability of TAp73alpha and p53 (not DeltaNp73alpha) to elicit scotin transactivation and ER stress. This molecular mechanism might contribute to the effector events inducing apoptosis downstream of p73.
Subject(s)
Apoptosis/physiology , DNA-Binding Proteins/metabolism , Endoplasmic Reticulum/metabolism , Nuclear Proteins/metabolism , Transcription Factors/metabolism , Animals , Apoptosis Regulatory Proteins , Genes, Tumor Suppressor , Humans , Membrane Proteins , Polymerase Chain Reaction , Transcription Factors/genetics , Tumor Protein p73 , Tumor Suppressor ProteinsSubject(s)
Connexins/genetics , Erythema/genetics , Keratosis/genetics , Mutation , Skin Diseases, Genetic/genetics , Adolescent , Erythema/drug therapy , Erythema/pathology , Female , Humans , Keratosis/drug therapy , Keratosis/pathology , Skin Diseases, Genetic/drug therapy , Skin Diseases, Genetic/pathologyABSTRACT
Administration of tacrine (5 mg/kg ip), an anticholinesterase agent, in rats pretreated (24 h beforehand) with lithium chloride (LiCl; 12 mEq/kg ip) provides a useful experimental model to study limbic seizures and delayed hippocampal damage. Here we report Western blotting evidence demonstrating that in rat LiCl and tacrine enhance the expression of neuronal nitric oxide synthase (nNOS), but not eNOS, enzyme protein in the hippocampus during the preconvulsive period and this triggers seizures and hippocampal damage. In fact, systemic administration of 7-nitro indazole (7-NI; 50 mg/kg given ip 30 min before tacrine), a selective inhibitor of nNOS, prevented the expression of motor and electrocortical (ECoG) seizures and abolished neuronal cell death in the hippocampus. A lower dose (5 mg/kg ip) of 7-NI was ineffective. In conclusion, the present data support a role for abnormal nNOS expression in the mechanism which triggers limbic seizures and delayed excitotoxic damage in the hippocampus of rat.
