Transglutaminase overexpression sensitizes neuronal cell lines to apoptosis by increasing mitochondrial membrane potential and cellular oxidative stress.
'Tissue' transglutaminase (tTG) selectively accumulates in cells undergoing apoptosis both in vivo and in vitro. Considering the central role played by mitochondria in apoptosis, we investigated the relationships existing amongst tTG expression, apoptosis and mitochondrial function. To this aim we studied the mechanisms of apoptosis in a neuronal cell line (SK-N-BE (2)) in which the tTG-expression was driven by a constitutive promoter. Furthermore, a tet-off inducible promoter was also used in 3T3 fibroblastic cells used as control. Both cell lines, when expressing tTG, appeared 'sensitized' to apoptosis. Strikingly, we found major differences in the morphological features of mitochondria among cell lines in the absence of apoptotic stimuli. In addition, these ultrastructural characteristics were associated with specific functional features: (i) constitutively hyperpolarized mitochondria and (ii) increased reactive oxygen intermediates production. Importantly, after mitochondrial-mediated apoptosis by staurosporine, a rapid loss of mitochondrial membrane potential was found in tTG cells only. Taken together, these results seem to suggest that, via hyperpolarization, tTG might act as a 'sensitizer' towards apoptotic stimuli specifically targeted to mitochondria. These results could also be of pathogenetic relevance for those diseases that are characterized by increased tTG and apoptotic rate together with impaired mitochondrial function, e.g. in some neurodegenerative disease.
Piacentini
Mauro
M
Department of Biology, University of Rome Tor Vergata Rome, Italy.
Farrace
Maria Grazia
MG
Piredda
Lucia
L
Matarrese
Paola
P
Ciccosanti
Fabiola
F
Falasca
Laura
L
Rodolfo
Carlo
C
Giammarioli
Anna Maria
AM
Verderio
Elisabetta
E
Griffin
Martin
M
Malorni
Walter
W
D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002648:Child; D016572:Cyclosporine / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D015870:Gene Expression; D006801:Humans; D007425:Intracellular Membranes / Q000502:physiology; D007473:Ion Channels / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D009447:Neuroblastoma / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D013752:Tetracycline / Q000494:pharmacology; D014162:Transfection; D011503:Transglutaminases / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D004791:Enzyme Inhibitors; D007473:Ion Channels; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D016572:Cyclosporine; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins; D013752:Tetracycline