Fujishiro M, Gotoh Y, Katagiri H, Sakoda H, Ogihara T, Anai M, Onishi Y, Ono H, Funaki M, Inukai K, Fukushima Y, Kikuchi M, Oka Y, Asano T
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
J Biol Chem. 2001 Jun 8;276(23):19800-6. doi: 10.1074/jbc.M101087200. Epub 2001 Feb 27.
p38 mitogen-activated protein kinase (MAPK), which is situated downstream of MAPK kinase (MKK) 6 and MKK3, is activated by mitogenic or stress-inducing stimuli, as well as by insulin. To clarify the role of the MKK6/3-p38 MAPK pathway in the regulation of glucose transport, dominant negative p38 MAPK and MKK6 mutants and constitutively active MKK6 and MKK3 mutants were overexpressed in 3T3-L1 adipocytes and L6 myotubes using an adenovirus-mediated transfection procedure. Constitutively active MKK6/3 mutants up-regulated GLUT1 expression and down-regulated GLUT4 expression, thereby significantly increasing basal glucose transport but diminishing transport induced by insulin. Similar effects were elicited by chronic (24 h) exposure to tumor necrosis factor alpha, interleukin-1beta, or 200 mm sorbitol, all activate the MKK6/3-p38 MAPK pathway. SB203580, a specific p38 MAPK inhibitor, attenuated these effects, further confirming that both MMK6 and MMK3 act via p38 MAPK, whereas they had no effect on the increase in glucose transport induced by a constitutively active MAPK kinase 1 (MEK1) mutant or by myristoylated Akt. In addition, suppression of p38 MAPK activation by overexpression of a dominant negative p38 MAPK or MKK6 mutant did not diminish insulin-induced glucose uptake by 3T3-L1 adipocytes. It is thus apparent that activation of p38 MAPK is not essential for insulin-induced increases in glucose uptake. Rather, p38 MAPK activation leads to a marked down-regulation of insulin-induced glucose uptake via GLUT4, which may underlie cellular stress-induced insulin resistance caused by tumor necrosis factor alpha and other factors.
p38丝裂原活化蛋白激酶（MAPK）位于MAPK激酶（MKK）6和MKK3的下游，可被促有丝分裂或应激诱导刺激以及胰岛素激活。为了阐明MKK6/3-p38 MAPK途径在葡萄糖转运调节中的作用，使用腺病毒介导的转染程序，在3T3-L1脂肪细胞和L6肌管中过表达显性负性p38 MAPK和MKK6突变体以及组成型活性MKK6和MKK3突变体。组成型活性MKK6/3突变体上调GLUT1表达并下调GLUT4表达，从而显著增加基础葡萄糖转运，但减少胰岛素诱导的转运。长期（24小时）暴露于肿瘤坏死因子α、白细胞介素-1β或200 mM山梨醇也会产生类似的效果，这些都会激活MKK6/3-p38 MAPK途径。特异性p38 MAPK抑制剂SB203580减弱了这些作用，进一步证实MKK6和MKK3均通过p38 MAPK发挥作用，而它们对组成型活性MAPK激酶1（MEK1）突变体或肉豆蔻酰化Akt诱导的葡萄糖转运增加没有影响。此外，过表达显性负性p38 MAPK或MKK6突变体抑制p38 MAPK激活并不会减少3T3-L1脂肪细胞中胰岛素诱导的葡萄糖摄取。因此，显然p38 MAPK的激活对于胰岛素诱导的葡萄糖摄取增加并非必不可少。相反，p38 MAPK激活会导致通过GLUT4的胰岛素诱导的葡萄糖摄取显著下调，这可能是肿瘤坏死因子α和其他因素引起的细胞应激诱导的胰岛素抵抗的基础。
