Biochemistry. 2004 Dec 14;43(49):15494-502.

Requirements for pYXXM motifs in Cbl for binding to the p85 subunit of phosphatidylinositol 3-kinase and Crk, and activation of atypical protein kinase C and glucose transport during insulin action in 3T3/L1 adipocytes.

Standaert ML, Sajan MP, Miura A, Bandyopadhyay G, Farese RV.

Research Service, James A. Haley Veterans Medical Center, and Department of Internal Medicine, University of South Florida College of Medicine, Tampa, Florida 33612, USA.

Cbl is phosphorylated by the insulin receptor and reportedly functions within the flotillin/CAP/Cbl/Crk/C3G/TC10 complex during insulin-stimulated glucose transport in 3T3/L1 adipocytes. Cbl, via pYXXM motifs at tyrosine-371 and tyrosine-731, also activates phosphatidylinositol (PI) 3-kinase, which is required to activate atypical protein kinase C (aPKC) and glucose transport during thiazolidinedione action in 3T3/L1 and human adipocytes [Miura et al. (2003) Biochemistry 42, 14335-14341]. Presently, we have examined the importance of Cbl in activating PI 3-kinase and aPKC during insulin action in 3T3/L1 adipocytes by expressing Y371F and Y731F Cbl mutants, which nullify pYXXM binding of Cbl to SH2 domains of downstream effectors. Interestingly, these mutants inhibited insulin-induced increases in (a) binding of Cbl to both Crk and the p85 subunit of PI 3-kinase, (b) activation of Cbl-dependent PI 3-kinase, (c) activation and translocation of aPKC to the plasma membrane, (d) translocation of Glut4 to the plasma membrane, (e) and glucose transport. Importantly, coexpression of wild-type Cbl reversed the inhibitory effects of Cbl mutants. In contrast to Cbl-dependent PI 3-kinase, Cbl mutants did not significantly inhibit the activation of PI 3-kinase by IRS-1, which is also required during insulin action. Our findings suggest that (a) Cbl uses pYXXM motifs to simultaneously activate PI 3-kinase and Crk/C3G/TC10 pathways and (b) Cbl, along with IRS-1, functions upstream of PI 3-kinase and aPKCs during insulin-stimulated glucose transport in 3T3/L1 adipocytes.

すこしマニアックですが，最近の僕の研究テーマですので，のせておきます。

Nature 410, 944-948(19 April 2001)

インスリン刺激によるGLUT4の移行にはCAPに依存したTC10活性化が必要である

Shian-Huey Chiang1,2, Christian A. Baumann2,3, Makoto Kanzaki4, Debbie C. Thurmond4, Robert T. Watson4, Cheryl L. Neudauer5, Ian G. Macara5, Jeffrey E. Pessin4and Alan R. Saltiel2,3

Top of page筋肉や脂肪組織でインスリンによってグルコース取込みが促進されるには,グルコース輸送タンパク質GLUT4が細胞内の貯蔵部位から細胞表面へと移行する必要がある。GLUT4小胞の細胞内移動は詳しく解明されているが，インスリン受容体とGLUT4移行とを結びつける情報伝達経路についてはほとんどわかっていない。GLUT4移行にはホスファチジルイノシトール‐3‐OHキナーゼ（PI(3)K）の活性化が必要だが，それだけではGLUT4移行は起こらない。我々はこれまでに，インスリン刺激によるCblのチロシンリン酸化がかかわる経路を報告した。Cblはアダプタータンパク質CAPによってインスリン受容体へと運ばれる。Cblはリン酸化されると細胞膜の脂質微小領域へと移行するが，この移行を妨げると，インスリンによるGLUT4移行の促進が完全に阻害された。ここでは，リン酸化されたCblの働きでCrkII-C3G複合体が脂質微小領域へ移行し，そこでC3Gが低分子量GTP結合タンパク質TC10を特異的に活性化することを明らかにする。この過程にはPI(3)Kは無関係だが，CblとCrk，C3Gの脂質微小領域への移行は必要である。インスリン刺激によるグルコース取込みの促進とGLUT4の移行には，このTC10の活性化が不可欠である。このTC10経路は，PI(3)K経路と並行して，インスリンによるGLUT4の移行を促進する働きをしている

Am J Physiol Endocrinol Metab 286: E201-E207, 2004

Altered expression of nuclear hormone receptors and coactivators in mouse heart during the acute-phase response
Kenneth Feingold, Min Sun Kim, Judy Shigenaga, Art Moser, and Carl Grunfeld
Metabolism Section, Department of Medicine, University of California San Francisco, Medical Service, Department of Veterans Affairs Medical Center, San Francisco, California 94121


Severe sepsis results in the decreased uptake and oxidation of fatty acids in the heart and cardiac failure. Some of the key proteins required for fatty acid uptake and oxidation in the heart have been shown to be downregulated after endotoxin (LPS) administration. The nuclear hormone receptors, peroxisome proliferator-activated receptor (PPAR) and thyroid receptor (TR), which heterodimerize with the retinoid X receptor (RXR), are important regulators of fatty acid metabolism and decrease in the liver after LPS administration. In the present study, we demonstrate that LPS treatment produces a rapid and marked decrease in the mRNA levels of all three RXR isoforms, PPAR and PPAR, and TR and TR in the heart. Moreover, LPS administration also decreased the expression of the coactivators CREB-binding protein (CBP)/p300, steroid receptor coactivator (SRC)-1, SRC-3, TR-associated protein (TRAP)220, and PPAR coactivator (PGC)-1, all of which are required for the transcriptional activity of RXR-PPAR and RXR-TR. In addition, the mRNA levels of the target genes malic enzyme, Spot 14, sarcoplasmic reticulum Ca2+-ATPase, or SERCA2, the VLDL receptor, fatty acyl-CoA synthetase, fatty acid transporter/CD36, carnitine palmitoyltransferase I, and lipoprotein lipase decrease in the heart after LPS treatment. The decrease in expression of RXR, -, and -, PPAR and -, and TR and -, and of the coactivators CBP/p300, SRC-1, SRC-3, TRAP220, and PGC-1 and the genes they regulate, induced by LPS in the heart, could account for the decreased expression of key proteins required for fatty acid oxidation and thereby play an important role in cardiac contractility. These alterations could contribute to the myocardial dysfunction that occurs during sepsis.