Nelfinavir-induced insulin resistance is associated with impaired plasma membrane recruitment of the PI 3-kinase effectors Akt/PKB and PKC-zeta.
OBJECTIVE
Chronic exposure of 3T3-L1 adipocytes to the HIV protease inhibitor nelfinavir induces insulin resistance, recapitulating key metabolic alterations of adipose tissue in the lipodystrophy syndrome induced by these agents. Our goal was to identify the defect in the insulin signal transduction cascade leading to nelfinavir-induced insulin resistance.


METHODS
Fully differentiated 3T3-L1 adipocytes were exposed to 30 micro mol/l nelfinavir for 18 h, after which the amount, the phosphorylation and the localisation of key proteins in the insulin signalling cascade were evaluated.


RESULTS
Insulin-induced interaction of phosphatidylinositol 3'-kinase (PI 3-kinase) with IRS proteins was normal in cells treated with nelfinavir, as was IRS-1-associated PI 3-kinase activity. Yet insulin-induced phosphorylation of Akt/protein kinase B (PKB), p70S6 kinase and extracellular signal-regulated kinase 1/2 was significantly impaired. This could not be attributed to increased protein phosphatase 2A activity or to increased expression of phosphoinositide phosphatases (SHIP2 or PTEN). However, insulin failed to induce translocation of the PI 3-kinase effectors Akt/PKB and protein kinase C-zeta (PKC-zeta) to plasma membrane fractions of nelfinavir-treated adipocytes.


CONCLUSIONS
We therefore conclude that nelfinavir induces a defect in the insulin signalling cascade downstream of the activation of PI 3-kinase. This defect manifests itself by impaired insulin-mediated recruitment of Akt/PKB and PKC-zeta to the plasma membrane.
Ben-Romano
R
R
Department of Clinical Biochemistry, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel 84103.
Rudich
A
A
Tirosh
A
A
Potashnik
R
R
Sasaoka
T
T
Riesenberg
K
K
Schlaeffer
F
F
Bashan
N
N
D064413:3-Phosphoinositide-Dependent Protein Kinases; D041721:3T3-L1 Cells; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism* / Q000473:pathology; D003847:Deoxyglucose / Q000037:antagonists & inhibitors / Q000378:metabolism; D004353:Drug Evaluation, Preclinical / Q000379:methods; D005260:Female; D005947:Glucose / Q000378:metabolism; D007333:Insulin Resistance; D007564:Japan; D051379:Mice; D019888:Nelfinavir / Q000009:adverse effects*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010749:Phosphoprotein Phosphatases / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054648:Protein Phosphatase 2; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D000099221:Protein Kinase C zeta
D064413:3-Phosphoinositide-Dependent Protein Kinases; D003847:Deoxyglucose; D005947:Glucose; D019888:Nelfinavir; D019869:Phosphatidylinositol 3-Kinases; D010716:Phosphatidylinositols; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010749:Phosphoprotein Phosphatases; D011493:Protein Kinase C; D054648:Protein Phosphatase 2; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D000099221:Protein Kinase C zeta