Impaired phosphorylation and insulin-stimulated translocation to the plasma membrane of protein kinase B/Akt in adipocytes from Type II diabetic subjects

Carvalho, Eugénia; Eliasson, Björn; Wesslau, Christian; Smith, Ulf

doi:10.1007/s001250051501

Cited by 58 publications

(45 citation statements)

References 31 publications

(58 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Among the three highly homologous Akt isoforms, increasing evidence suggests that Akt2 plays a major role in glucose metabolism [30,31]. Although conflicting results have been obtained on whether Akt activation in adipose tissue and skeletal muscle is impaired in conditions of insulin resistance [21][22][23][24][25][26][27], defects in Ser473 phosphorylation and activation of Akt2, but not of Akt1 have been observed in skeletal muscle of insulin-resistant morbidly obese and type 2 diabetic participants [33][34][35]. Mechanisms by which Akt is inactivated have, until recently, been poorly documented.…”

Section: Discussionmentioning

confidence: 99%

“…Akt plays a pivotal role in mediating metabolic responses induced by insulin, including stimulation of glucose transport, translocation of glucose transporters to the cell surface, inactivation of glycogen synthase kinase (GSK)-3 and stimulation of glycogen synthesis [19,20]. Some [21][22][23], but not all [24][25][26][27] studies have reported impaired Akt activation in adipose tissue and skeletal muscle in conditions of insulin resistance such as obesity and type 2 diabetes. A possible explanation of these conflicting observations may be related to the fact that three highly homologous Akt isoforms, termed Akt1, Akt2 and Akt3, are produced in mammalian cells as products of distinct genes.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Increased levels of the Akt-specific phosphatase PH domain leucine-rich repeat protein phosphatase (PHLPP)-1 in obese participants are associated with insulin resistance

et al. 2011

View full text Add to dashboard Cite

Aims/hypothesis We determined the contribution to insulin resistance of the PH domain leucine-rich repeat protein phosphatase (PHLPP), which dephosphorylates Akt at Ser473, inhibiting its activity. We measured the abundance of PHLPP in fat and skeletal muscle from obese participants. To study the effect of PHLPP on insulin signalling, PHLPP (also known as PHLPP1) was overexpressed in HepG2 and L6 cells. Methods Subcutaneous fat samples were obtained from 82 morbidly obese and ten non-obese participants. Skeletal muscle samples were obtained from 12 obese and eight non-obese participants. Quantification of PHLPP-1 in human tissues was performed by immunoblotting. The functional consequences of recombinant PHLPP1 overexpression in hepatoma HepG2 cells and L6 myoblasts were investigated. Results Of the 82 obese participants, 31 had normal fasting glucose, 33 impaired fasting glucose and 18 type 2 diabetes. PHLPP-1 abundance was twofold higher in the three obese groups than in non-obese participants (p=0.004). No differences were observed between obese participants with normal fasting glucose, impaired fasting glucose or type 2 diabetes. PHLPP-1 abundance was correlated with basal Akt Ser473 phosphorylation (r=−0.48; p=0.001), BMI (r=0.44; p< 0.0001), insulin (r=0.35; p<0.0001) and HOMA (r=0.38; p<0.0001). PHLPP-1 abundance was twofold higher in the skeletal muscle of 12 obese participants than in that of eight non-obese participants (p<0.0001). Insulin treatment of HepG2 cells resulted in a dose-and time-dependent upregulation of PHLPP-1. Overexpression of PHLPP1 in HepG2 cells and L6 myoblasts resulted in impaired insulin signalling involving Akt/glycogen synthase kinase 3, glycogen synthesis and glucose transport. Conclusions/interpretation Increased abundance of PHLPP-1, production of which is regulated by insulin, may represent a new molecular defect in insulin-resistant states such as obesity.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Increased levels of the Akt-specific phosphatase PH domain leucine-rich repeat protein phosphatase (PHLPP)-1 in obese participants are associated with insulin resistance

et al. 2011

View full text Add to dashboard Cite

show abstract

“…Thus, it appears that the reduced active forms of Akt in caveolae modulated by insulin resistance subsequently attenuate the insulin action of glucose uptake in H9c2 cardiomyoblasts. Carvalho et al, (2000) reported the impaired phosphorylation and insulin-stimulated translocation to the plasma membrane of Akt in adipocytes from type 2 diabetic subjects. Recent studies in rat adipocytes demonstrated that cholesterol depletion, which disrupts cholesterol-rich caveolae domain in the plasma membrane, impaired insulin-stimulated Akt activation and glucose uptake Parpal et al, 2001;Karlsson et al, 2002;Muller et al, 2002).…”

Section: Discussionmentioning

confidence: 99%

Modulation of the caveolin-3 and Akt status in caveolae by insulin resistance in H9c2 cardiomyoblasts

Pak²

2005

Exp Mol Med

View full text Add to dashboard Cite

show abstract

“…The PH-domain-PIP3 interaction is thought to cause a conformational change that allows Akt to be activated by phosphorylation on Thr309 (in Akt2; T308 in Akt1, T305 in Akt3) and Ser474 (in Akt2; S473 in Akt1, S472 in Akt3) residues by the kinases PDK1 (also known as PDPK1) and mTORC2, respectively (Alessi et al, 1997;Sarbassov, 2005). Subcellular fractionation and immunofluorescence imaging of endogenous Akt suggest that it is strongly recruited to the PM in response to growth factor stimulation (Carvalho et al, 2000;Currie et al, 1999;. Furthermore, live-cell imaging of fluorescent Akt reporter constructs have revealed important insights such as isoform specificity, chemotaxis, phospholipid binding, conformational changes in Akt, nuclear activation and membrane diffusion rates, across a range of cell lines (Calleja et al, 2003;Gonzalez and McGraw, 2009;Kontos et al, 1998;Lasserre et al, 2008;Servant et al, 2000;Wang and Brattain, 2006).…”

Section: Introductionmentioning

confidence: 99%

An improved Akt reporter reveals intra- and inter-cellular heterogeneity and oscillations in signal transduction

Norris

Yang

Krycer

et al. 2017

Journal of Cell Science

View full text Add to dashboard Cite

Akt is a key node in a range of signal transduction cascades and play a critical role in diseases such as cancer and diabetes. Fluorescentlytagged Akt reporters have been used to discern Akt localisation, yet it has not been clear how well these tools recapitulate the behaviour of endogenous Akt proteins. Here, we observed that fusion of eGFP to Akt2 impaired both its insulin-stimulated plasma membrane recruitment and its phosphorylation. Endogenous-like responses were restored by replacing eGFP with TagRFP-T. The improved response magnitude and sensitivity afforded by TagRFP-T-Akt2 over eGFP-Akt2 enabled monitoring of signalling outcomes in single cells at physiological doses of insulin with subcellular resolution and revealed two previously unreported features of Akt biology. In 3T3-L1 adipocytes, stimulation with insulin resulted in recruitment of Akt2 to the plasma membrane in a polarised fashion. Additionally, we observed oscillations in plasma membrane localised Akt2 in the presence of insulin with a consistent periodicity of 2 min. Our studies highlight the importance of fluorophore choice when generating reporter constructs and shed light on new Akt signalling responses that may encode complex signalling information.This article has an associated First Person interview with the first author of the paper.

show abstract

Impaired phosphorylation and insulin-stimulated translocation to the plasma membrane of protein kinase B/Akt in adipocytes from Type II diabetic subjects

Cited by 58 publications

References 31 publications

Increased levels of the Akt-specific phosphatase PH domain leucine-rich repeat protein phosphatase (PHLPP)-1 in obese participants are associated with insulin resistance

Increased levels of the Akt-specific phosphatase PH domain leucine-rich repeat protein phosphatase (PHLPP)-1 in obese participants are associated with insulin resistance

Modulation of the caveolin-3 and Akt status in caveolae by insulin resistance in H9c2 cardiomyoblasts

An improved Akt reporter reveals intra- and inter-cellular heterogeneity and oscillations in signal transduction

Contact Info

Product

Resources

About