Activation of AMP-activated protein kinase by MAPO1 and FLCN induces apoptosis triggered by alkylated base mismatch in DNA.
O₆-methylguanine produced in DNA by the action of simple alkylating agents, such as N-methyl-N-nitrosourea (MNU), causes base-mispairing during DNA replication, thus leading to mutations and cancer. To prevent such outcomes, the cells carrying O⁶-methylguanine undergo apoptosis in a mismatch repair protein-dependent manner. We previously identified MAPO1 as one of the components required for the induction of apoptosis triggered by O⁶-methylguanine. MAPO1, also known as FNIP2 and FNIPL, forms a complex with AMP-activated protein kinase (AMPK) and folliculin (FLCN), which is encoded by the BHD tumor suppressor gene. We describe here the involvement of the AMPK-MAPO1-FLCN complex in the signaling pathway of apoptosis induced by O⁶-methylguanine. By the introduction of siRNAs specific for these genes, the transition of cells to a population with sub-G₁ DNA content following MNU treatment was significantly suppressed. After MNU exposure, phosphorylation of AMPKα occurred in an MLH1-dependent manner, and this activation of AMPK was not observed in cells in which the expression of either the Mapo1 or the Flcn gene was downregulated. When cells were treated with AICA-ribose (AICAR), a specific activator of AMPK, activation of AMPK was also observed in a MAPO1- and FLCN-dependent manner, thus leading to cell death which was accompanied by the depolarization of the mitochondrial membrane, a hallmark of the apoptosis induction. It is therefore likely that MAPO1, in its association with FLCN, may regulate the activation of AMPK to control the induction of apoptosis triggered by O⁶-methylguanine.
Department of Medical Biophysics and Radiation Biology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
Teik How
TH
Lim
Ryosuke
R
Fujikane
Shiori
S
Sano
Ryuji
R
Sakagami
Yoshimichi
Y
Nakatsu
Teruhisa
T
Tsuzuki
Mutsuo
M
Sekiguchi
Masumi
M
Hidaka
D055372:AMP-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000478:Alkylation / Q000187:drug effects; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D020137:Base Pair Mismatch / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D004247:DNA / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D008770:Methylnitrosourea; D051379:Mice; D011485:Protein Binding / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
D051017:Apoptosis Regulatory Proteins; C526060:Bhd protein, mouse; D002352:Carrier Proteins; C574800:MAPO1 protein, mouse; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins; D008770:Methylnitrosourea; D004247:DNA; D055372:AMP-Activated Protein Kinases