The PP1-R6 protein phosphatase holoenzyme is involved in the glucose-induced dephosphorylation and inactivation of AMP-activated protein kinase, a key regulator of insulin secretion, in MIN6 beta cells.
Mammalian AMP-activated protein kinase (AMPK) is a serine/threonine protein kinase that acts as a sensor of cellular energy status. It is activated by phosphorylation of the catalytic subunit on Thr172. The main objective of this study was the identification of a phosphatase involved in the regulation of AMPK activity. Mouse MIN6 β cells were used to study the glucose-induced regulation of the phosphorylation of AMPK. Small interfering RNA (siRNA) technology was used to deplete putative phosphatase candidate genes that could affect AMPK regulation. The effect of the siRNAs used in the study was compared with the effect observed using a negative control siRNA. A protein phosphatase complex composed of the catalytic subunit of protein phosphatase-1 (PP1) and the regulatory subunit R6 participates in the glucose-induced dephosphorylation of AMPK. R6 interacts physically with the β-subunit of the AMPK complex and recruits PP1 to dephosphorylate the catalytic α-subunit on Thr172. siRNA depletion of R6 decreases glucose-induced insulin secretion due to the presence of a constitutively active AMPK complex. The characterization of the PP1-R6 complex identifies this holoenzyme as a possible target for therapeutic intervention with the aim of regulating the activity of AMPK in pancreatic β cells.
Garcia-Haro
Luisa
L
Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Cientificas and Centro de Investigación en Red de Enfermecedes Raras, Valencia, Spain.
Garcia-Gimeno
Maria Adelaida
MA
Neumann
Dietbert
D
Beullens
Monique
M
Bollen
Mathieu
M
Sanz
Pascual
P
D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D045744:Cell Line, Tumor; D005816:Genetic Complementation Test; D005947:Glucose / Q000494:pharmacology*; D015151:Immunoblotting; D047468:Immunoprecipitation; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D054645:Protein Phosphatase 1 / Q000235:genetics / Q000378:metabolism*; D000071636:Protein Phosphatase 2C; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020798:Two-Hybrid System Techniques
D007328:Insulin; D021122:Protein Subunits; D034741:RNA, Small Interfering; D055372:AMP-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D000071636:Protein Phosphatase 2C; D005947:Glucose