SIRT1 modulation of the acetylation status, cytosolic localization, and activity of LKB1. Possible role in AMP-activated protein kinase activation.
SIRT1, a histone/protein deacetylase, and AMP-activated protein kinase (AMPK) are key enzymes responsible for longevity and energy homeostasis. We examined whether a mechanistic connection exists between these molecules that involves the major AMPK kinase LKB1. Initial studies demonstrated that LKB1 is acetylated in cultured (HEK293T) cells, mouse white adipose tissue, and rat liver. In the 293T cells, SIRT1 overexpression diminished lysine acetylation of LKB1 and concurrently increased its activity, cytoplasmic/nuclear ratio, and association with the LKB1 activator STRAD. In contrast, short hairpin RNA for SIRT1, where studied, had opposite effects on these parameters. Mass spectrometric analysis established that acetylation of LKB1 occurs on multiple, but specific, lysine residues; however, only mutation of lysine 48 to arginine, which mimics deacetylation, reproduced all of the effects of activated SIRT1. SIRT1 also affected downstream targets of LKB1. Thus its overexpression increased AMPK and acetyl-CoA carboxylase phosphorylation, and conversely, RNA interference-mediated SIRT1 knockdown reduced AMPK phosphorylation and that of another LKB1 target MARK1. Consistent with the results in cultured cells, total LKB1 lysine acetylation was decreased by 60% in the liver of 48-h starved rats compared with starved-refed rats, and this was associated with modest but significant increases in both LKB1 and AMPK activities. These results suggest that LKB1 deacetylation is regulated by SIRT1 and that this in turn influences its intracellular localization, association with STRAD, kinase activity, and ability to activate AMPK.
Lan
Fan
F
Diabetes and Metabolism Research Unit, Department of Medicine, Section of Endocrinology, Boston University School of Medicine, Boston, Massachusetts 02118.
Cacicedo
Jose M
JM
Diabetes and Metabolism Research Unit, Department of Medicine, Section of Endocrinology, Boston University School of Medicine, Boston, Massachusetts 02118; Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, Massachusetts 02118.
Ruderman
Neil
N
Diabetes and Metabolism Research Unit, Department of Medicine, Section of Endocrinology, Boston University School of Medicine, Boston, Massachusetts 02118.
Ido
Yasuo
Y
Diabetes and Metabolism Research Unit, Department of Medicine, Section of Endocrinology, Boston University School of Medicine, Boston, Massachusetts 02118. Electronic address: yido@bu.edu.
D000091162:AMP-Activated Protein Kinase Kinases; D000107:Acetylation; D021581:Active Transport, Cell Nucleus / Q000235:genetics; D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000201:enzymology* / Q000235:genetics; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology*; D004789:Enzyme Activation / Q000235:genetics; D006801:Humans; D008099:Liver / Q000201:enzymology; D051379:Mice; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D051381:Rats; D017207:Rats, Sprague-Dawley; D056564:Sirtuin 1; D037761:Sirtuins / Q000235:genetics / Q000378:metabolism*; D013217:Starvation / Q000201:enzymology / Q000235:genetics
D033942:Adaptor Proteins, Vesicular Transport; C476400:STRADA protein, human; C105547:MARK1 protein, human; D017346:Protein Serine-Threonine Kinases; C109790:STK11 protein, human; C488755:Stk11 protein, rat; D017868:Cyclic AMP-Dependent Protein Kinases; D000091162:AMP-Activated Protein Kinase Kinases; C447939:SIRT1 protein, human; C488368:Sirt1 protein, rat; D056564:Sirtuin 1; D037761:Sirtuins