title: Role of TAPP1 and TAPP2 adaptor binding to PtdIns(3,4)P2 in regulating insulin sensitivity defined by knock-in analysis.
abstract: Insulin sensitivity is critically dependent on the activity of PI3K (phosphoinositide 3-kinase) and generation of the PtdIns(3,4,5)P(3) second messenger. PtdIns(3,4,5)P(3) can be broken down to PtdIns(3,4)P(2) through the action of the SHIPs (Src-homology-2-domain-containing inositol phosphatases). As PtdIns(3,4)P(2) levels peak after those of PtdIns(3,4,5)P(3), it has been proposed that PtdIns(3,4)P(2) controls a negative-feedback loop that down-regulates the insulin and PI3K network. Previously, we identified two related adaptor proteins termed TAPP [tandem PH (pleckstrin homology)-domain-containing protein] 1 and TAPP2 that specifically bind to PtdIns(3,4)P(2) through their C-terminal PH domain. To determine whether TAPP1 and TAPP2 play a role in regulating insulin sensitivity, we generated knock-in mice that express normal endogenous levels of mutant TAPP1 and TAPP2 that are incapable of binding PtdIns(3,4)P(2). These homozygous TAPP1(R211L/R211L) TAPP2(R218L/R218L) double knock-in mice are viable and exhibit significantly enhanced activation of Akt, a key downstream mediator of insulin signalling. Consistent with increased PI3K and Akt activity, the double knock-in mice display enhanced whole body insulin sensitivity and disposal of glucose uptake into muscle tissues. We also generated wild-type and double TAPP1(R211L/R211L) TAPP2(R218L/R218L) knock-in embryonic fibroblasts and found that insulin triggered enhanced production of PtdIns(3,4,5)P(3) and Akt activity in the double knock-in fibroblasts. These observations provide the first genetic evidence to support the notion that binding of TAPP1 and TAPP2 adap-tors to PtdIns(3,4)P(2) function as negative regulators of the insulin and PI3K signalling pathways.
authors.affiliation: MRC Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK. s.wullschleger@dundee.ac.uk
authors.forename: Stephan
authors.initials: S
authors.lastname: Wullschleger
authors.forename: David H
authors.initials: DH
authors.lastname: Wasserman
authors.forename: Alex
authors.initials: A
authors.lastname: Gray
authors.forename: Kei
authors.initials: K
authors.lastname: Sakamoto
authors.forename: Dario R
authors.initials: DR
authors.lastname: Alessi
mesh_terms: D000818:Animals; D001665:Binding Sites; D004622:Embryo, Mammalian / Q000378:metabolism; D005260:Female; D055879:Gene Knock-In Techniques; D007328:Insulin / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D007328:Insulin; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D018129:Phosphatidylinositol Phosphates; C461495:Plekha1 protein, mouse; C461496:Plekha2 protein, mouse; C060974:phosphatidylinositol 3,4,5-triphosphate; C060980:phosphatidylinositol 3,4-diphosphate; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt