Protective Effects of SKF-96365, a Non-specific Inhibitor of SOCE, Against MPP+-induced Cytotoxicity in PC12 Cells: Potential Role of Homer1

Parkinson's disease (PD) is the most common neurodegenerative movement disorder, characterized by loss of dopominergic (DA) neurons in substantia nigra pars compacta (SNpc), and can be experimentally mimicked by the neurotoxin MPP(+) in vitro models. In this study, we investigated the potential protective effect of SKF-96365, a non-specific inhibitor of SOCE (store-operated calcium entry), on MPP(+) induced cytotoxicity in PC12 cells. We found that pretreatment with SKF-96365 (10 µM and 50 µM) 30 min before injury significantly increased cell viability, decreased LDH release, prevented nuclear damage, and inhibited apoptotic cell death in MPP(+) stressed PC12 cells. The results of calcium image using the ratiometric calcium indicator Fura-2-AM also showed that SKF-96365 reduced the intracellular calcium overload induced by MPP(+) in PC12 cells. In addition, SKF-96365 decreased the expression of Homer1, a more recently discovered postsynaptic scaffolding protein with calcium modulating function, following MPP(+) administration in PC12 cells, while had no statistically significant effects on endoplasmic reticulum (ER) calcium concentration. Furthermore, overexpression of Homer1 by using recombinant lentivirus partly reversed protective effects of SKF-96365 against MPP(+) injury. The ER Ca(2+) release was further amplified and ER calcium recovery was delayed by Homer1 upregulation in PC12 cells following MPP(+) insult. Taken together, these data suggest that SKF-96365 protects PC12 cells against MPP(+) induced cytotoxicity, and this protection may be at least in part on the inhibition of intracellular calcium overload and suppression of Homer1-mediated ER Ca(2+) release.