Analysis of AtBI-1-mediated cell death suppression through sphingolipid-related enzymes

Abstract

In higher plants, programmed cell death is highly regulated by various factors. Bax Inhibitor-1 (BI-1) is a widely conserved cell death suppressor. Arabidopsis BI-1 (AtBI-1) is approximately 26kDa protein with 7 transmembrane domains and localizes in ER. Overexpression of AtBI-1 suppresses H₂O₂-. SA- and elicitor-induced cell death in plant cells. Moreover, AtBI-1 possesses coiled-coil structure in the C-terminus, which is essential in AtBI-1 function and interacts with calmodulin. However, the mechanism of AtBI-1-mediated cell death suppression has not yet been elucidated.
Recently, we revealed that AtBI-1 interacted with AtFAH (Arabidopsis fatty acid hydroxylase) via cytochrome b₅ (Cb5). Cb5 is an electron transfer protein, which is related to fatty acid synthesis, and AtFAH is a hydroxylase of sphingolipid fatty acid localizing in ER. Lately, the relationships between sphingolipids and cell death have been discussed vigorously. AtBI-1 may suppress cell death through sphingolipid regulation.