Protective roles of SLC30A3 against endoplasmic reticulum stress via ERK1/2 activation

Endoplasmic reticulum (ER) stress has been thought to be involved to neurodegenerative diseases such as Alzheimer's disease (AD) or Amyotrophic lateral sclerosis (ALS). The previous studies have shown that SLC30A3 level is decreased in prefrontal cortex of AD patients. In addition, we have shown that level of zinc (Zn) is increased in cerebrospinal fluid and SLC30A3 level is decreased in spinal cord of ALS patients. It was thought that both SLC30A3 and ER stress could be related to the cause of AD and ALS, however the relationship between ER stress and SLC30A3 has not been elucidated. Therefore we investigated that the role of SLC30A3 against ER stress. The level of SLC30A3 mRNA was significantly increased by tunicamycin treatment in human neuroblastoma cell line (SH-SY5Y) and human embryonic kidney cell line (HEK293). Cell viability under tunicamycin treatment was significantly decreased in SLC30A3 knockdown cells by siRNA in comparison with negative control (NC) cells. Cleaved caspase-3 level was significantly increased in SLC30A3 knockdown cells, not in NC cells. These results showed that SLC30A3 has a protective role to ER stress-induced toxicities. The previous study has shown that SLC30A3 protect cells from oxidative stress in ERK1/2 signal dependent manner, thus we determined the activity of ERK1/2 in SLC30A3 knockdown cells under ER stress condition. The level of ERK1/2 phosphorylation was significantly increased by tunicamycin treatment in NC cells, not in SLC30A3 knockdown cells. The ERK1/2 pathway is thought to have an association with defensive effects of SLC30A3 on cellular stress such as ER stress. In conclusion, this study suggested that SLC30A3 is supposed to play a protective role against ER stress, which is related to ERK1/2 activation.