Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
Am J Physiol Endocrinol Metab. 2011 Jan;300(1):E103-10. doi: 10.1152/ajpendo.00427.2010. Epub 2010 Oct 26.
The adaptor protein APPL1 mediates the stimulatory effect of adiponectin on p38 mitogen-activated protein kinase (MAPK) signaling, yet the underlying mechanism remains unclear. Here we show that, in C(2)C(12) cells, overexpression or suppression of APPL1 enhanced or suppressed, respectively, adiponectin-stimulated p38 MAPK upstream kinase cascade, consisting of transforming growth factor-β-activated kinase 1 (TAK1) and mitogen-activated protein kinase kinase 3 (MKK3). In vitro affinity binding and coimmunoprecipitation experiments revealed that TAK1 and MKK3 bind to different regions of APPL1, suggesting that APPL1 functions as a scaffolding protein to facilitate adiponectin-stimulated p38 MAPK activation. Interestingly, suppressing APPL1 had no effect on TNFα-stimulated p38 MAPK phosphorylation in C(2)C(12) myotubes, indicating that the stimulatory effect of APPL1 on p38 MAPK activation is selective. Taken together, our study demonstrated that the TAK1-MKK3 cascade mediates adiponectin signaling and uncovers a scaffolding role of APPL1 in regulating the TAK1-MKK3-p38 MAPK pathway, specifically in response to adiponectin stimulation.
衔接蛋白 APPL1 介导脂联素对 p38 丝裂原活化蛋白激酶 (MAPK) 信号的刺激作用，但潜在机制尚不清楚。在这里，我们发现，在 C(2)C(12)细胞中，APPL1 的过表达或抑制分别增强或抑制了脂联素刺激的 p38 MAPK 上游激酶级联反应，该级联反应由转化生长因子-β 激活激酶 1 (TAK1) 和丝裂原激活蛋白激酶激酶 3 (MKK3)组成。体外亲和结合和共免疫沉淀实验表明，TAK1 和 MKK3 结合到 APPL1 的不同区域，这表明 APPL1 作为一种支架蛋白，促进脂联素刺激的 p38 MAPK 激活。有趣的是，抑制 APPL1 对 C(2)C(12)肌管中 TNFα 刺激的 p38 MAPK 磷酸化没有影响，表明 APPL1 对 p38 MAPK 激活的刺激作用是选择性的。总之，我们的研究表明，TAK1-MKK3 级联反应介导脂联素信号，并揭示了 APPL1 在调节 TAK1-MKK3-p38 MAPK 通路中的支架作用，特别是在响应脂联素刺激时。
