SPARC interacts with AMPK and regulates GLUT4 expression.
AMP-activated protein kinase (AMPK) is a critical regulator of glucose metabolism. To elucidate the biochemical mechanisms by which AMPK regulates glucose and fat metabolism, we conducted a yeast two-hybrid screen to identify its interacting partners. A yeast two-hybrid system was used to screen a mouse embryo cDNA library for proteins able to bind mouse AMPK alpha 1. We also demonstrated an endogenous interaction between AMPK alpha 1 and its interacting partner by co-immunoprecipitation of the endogenous proteins using specific antibodies in HepG2 cells, and in rat kidney, liver, skeletal muscle, and fat tissue. We show that secreted protein acidic and rich in cysteine (SPARC) is an AMPK-interacting protein, and the two proteins enhance each other. AMPK activation increases SPARC expression, and knockdown of AMPK to inhibit endogenous AMPK expression reduces SPARC protein levels. On the other hand, SPARC siRNA reduces AICAR-stimulated AMPK phosphorylation. SPARC affects AMPK-mediated glucose metabolism through regulation of Glut4 expression in L6 myocytes. Our findings suggest that SPARC may be involved in regulating glucose metabolism via AMPK activation. These results provide a starting point for efforts to clarify the relationship between AMPK and SPARC, and deepen our understanding of their roles in fat and glucose metabolism.
Song
Haiyan
H
Department of Endocrinology and Metabolism, The Second Affiliated Hospital of Harbin Medical University, Xuefu Road 246, Harbin 150080, China. songhy@ems.hrbmu.edu.cn
Guan
Yuanyuan
Y
Zhang
Liping
L
Li
Kun
K
Dong
Chunli
C
D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000096:biosynthesis*; D006801:Humans; D008297:Male; D051379:Mice; D032342:Muscle Cells / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D020798:Two-Hybrid System Techniques
D051275:Glucose Transporter Type 4; D034741:RNA, Small Interfering; C495693:Slc2a4 protein, mouse; C548179:Prkaa1 protein, mouse; D055372:AMP-Activated Protein Kinases; D005947:Glucose