Bcl-2/adenovirus E1B 19-kDa interacting protein 1 (BNIP1), which is 
predominantly localized to the endoplasmic reticulum (ER), is a pro-apoptotic 
Bcl-2 homology domain 3 (BH3)-only protein. Here, we show that the expression of 
BNIP1 induced not only a highly interconnected ER network but also mitochondrial 
fragmentation in a BH3 domain-dependent manner. Functional analysis demonstrated 
that BNIP1 expression increased dynamin-related protein 1 (Drp1) expression 
followed by the mitochondrial translocation of Drp1 and subsequent mitochondrial 
fission. Both BNIP1-induced mitochondrial fission and the translocation of Drp1 
were abrogated by Bcl-2 overexpression. These results collectively indicate that 
ER-specific BNIP1 plays an important role in mitochondrial dynamics by 
modulating the mitochondrial fission protein Drp1 in a BH3 domain-dependent 
fashion.