TNFalpha-induced insulin resistance in adipocytes as a membrane microdomain disorder: involvement of ganglioside GM3.
Membrane microdomains (lipid rafts) are now recognized as critical for proper compartmentalization of insulin signaling, but their role in the pathogenesis of insulin resistance has not been investigated. Detergent-resistant membrane microdomains (DRMs), isolated in the low-density fractions, are highly enriched in cholesterol, glycosphingolipids and various signaling molecules. Tumor necrosis factor alpha (TNFalpha) induces insulin resistance in type 2 diabetes, but its mechanism of action is not fully understood. In other studies we have found a selective increase in the acidic glycosphingolipid ganglioside GM3 in 3T3-L1 adipocytes treated with TNFalpha, suggesting a specific function for GM3. In the DRMs from TNFalpha-treated 3T3-L1 adipocytes, GM3 levels were doubled compared with results in normal adipocytes. Additionally, insulin receptor (IR) accumulations in the DRMs were diminished, whereas caveolin and flotillin levels were unchanged. Furthermore, insulin-dependent IR internalization and intracellular movement of the IR substrate 1(IRS-1) were both greatly suppressed in the treated cells, leading to an uncoupling of IR-IRS-1 signaling. GM3 depletion was able to counteract the TNFalpha-induced inhibitions of IR internalization and accumulation into DRMs. Together, these findings provide compelling evidence that in insulin resistance the insulin metabolic signaling defect can be attributed to a loss of IRs in the microdomains due to an accumulation of GM3.
Kabayama
Kazuya
K
Department of Biomembrane and Biofunctional Chemistry, Graduate School of Pharmaceutical Sciences, Frontier Research Center for Post-Genomic Science and Technology, Hokkaido University, Kita 21-Nishi 11, Kita-ku, Sapporo 001-0021, Japan.
Sato
Takashige
T
Kitamura
Futoshi
F
Uemura
Satoshi
S
Kang
Byoung Won
BW
Igarashi
Yasuyuki
Y
Inokuchi
Jin-Ichi
J
D017667:Adipocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D002518:Ceramides / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D004789:Enzyme Activation; D005679:G(M3) Ganglioside / Q000378:metabolism*; D006801:Humans; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D002518:Ceramides; D003902:Detergents; D005679:G(M3) Ganglioside; C526292:IRS1 protein, human; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; D010750:Phosphoproteins; D014409:Tumor Necrosis Factor-alpha; D019000:Phosphotyrosine; D020928:Mitogen-Activated Protein Kinases