Parkin prevents mitochondrial swelling and cytochrome c release in mitochondria-dependent cell death

Abstract

Parkin gene mutations have been implicated in autosomal-recessive early-onset parkinsonism and lead to specific degeneration of dopaminergic neurons in midbrain. To investigate the role of Parkin in neuronal cell death, we overproduced this protein in PC12 cells in an inducible manner. In this cell line, neuronally differentiated by nerve growth factor, Parkin overproduction protected against cell death mediated by ceramide, but not by a variety of other cell death inducers (H(2)O(2), 4-hydroxynonenal, rotenone, 6-OHDA, tunicamycin, 2-mercaptoethanol and staurosporine). Protection was abrogated by the proteasome inhibitor epoxomicin and disease-causing variants, indicating that it was mediated by the E3 ubiquitin ligase activity of Parkin. Interestingly, Parkin acted by delaying mitochondrial swelling and subsequent cytochrome c release and caspase-3 activation observed in ceramide-mediated cell death. Subcellular fractionation demonstrated enrichment of Parkin in the mitochondrial fraction and its association with the outer mitochondrial membrane. Together, these results suggest that Parkin may promote the degradation of substrates localized in mitochondria and involved in the late mitochondrial phase of ceramide-mediated cell death. Loss of this function may underlie the degeneration of nigral dopaminergic neurons in patients with Parkin mutations.

The ubiquitin E3 ligase parkin regulates the proapoptotic function of Bax

“…Parkin expression protects against caspase activation and cell death induced by stressors such as staurosporine, C2 ceramide, rotenone, and 6-OHDA (10,(12)(13)(14), and we extended these observations to include another stressor, etoposide. Neuronal dopaminergic MES and MES cells stably overexpressing human parkin (MES-Parkin) were treated with vehicle (DMSO) or etoposide (100 μM), and caspase 3/7 activity was measured at 18 h. Parental MES cells demonstrated a 100% increase in caspase 3/7 activity that was prevented by the stable over-expression of parkin (Fig.…”

Revisiting oxidative stress and mitochondrial dysfunction in the pathogenesis of Parkinson disease—resemblance to the effect of amphetamine drugs of abuse

“…However, the most possibly relevant activity of parkin is related to its neuroprotective function against a variety of pathogenic factors. Particularly, this neuroprotection is given by delaying mitochondrial swelling and rupture and the subsequent cytochrome c release and caspase 3 activation, as shown in cells overexpressing parkin [227]. As mentioned above, parkin can associate to mitochondrial outer membrane, suggesting a direct and local protective effect [231].…”

Tumorigenesis and neurodegeneration: two sides of the same coin?

“…(49,50) Parkin has been shown to protect neurons in several in vitro systems from a broad range of insults, including partial proteasome inhibition, (51) nerve growth factor (NGF) withdrawal and exogenous administration of the plasma membrane lipid ceramide, (52) and kainatemediated excitotoxicity. (53) By contrast, parkin does not appear to protect neurons against other toxins such as the mitochondrial toxin 1-methyl-4-phenylpyridinium (MPP þ ); (53) tunicamycin, an inducer of the unfolded protein response; (52) and staurosporine, an inhibitor of protein kinase C. (52) Interestingly, the insults against which parkin overexpression is protective induce apoptotic cascades that contribute to or overlap with pathways of cell-cycle activation. For instance, withdrawal of NGF from cultured PC12 (pheochromocytoma) cells induces pro-apoptotic cyclin-associated activities that are blocked by CDK inhibitors such as flavopiridol and dominant negative forms of CDK4 and CDK6.…”

“…(56) Parkin may also act at a downstream step involving, for instance, release of cytochrome C from mitochondria. (52,57) Conversely, the insults against which parkin fails to protect neurons may share the property that they are pro-apoptotic but do not appear to upregulate cell-cycle components. For instance, staurosporine is a protein kinase C inhibitor with anti-tumorigenic effects (58) and induces apoptosis but not cellcycle activation in postmitotic cortical neurons.…”