Menon V, Thomason D B
Department of Physiology and Biophysics, University of Tennessee Health Science Center, Memphis 38163, USA.
Am J Physiol. 1995 Sep;269(3 Pt 1):C802-4. doi: 10.1152/ajpcell.1995.269.3.C802.
We previously demonstrated that head-down tilt in rats decreases heart polypeptide initiation rate and proposed a mechanism whereby redistribution of the chaperone heat-shock cognate/heat-shock protein-70 (HSC/HSP-70) facilitates the phosphorylation of eukaryotic initiation factor-2 alpha (eIF-2 alpha). In this study, two-dimensional gel electrophoretic analysis of eIF-2 alpha showed no phosphorylation in control hearts. At 8 h of head-down tilt, there was a 45% increase in total eIF-2 alpha, and 79% was phosphorylated. At 18 h, eIF-2 alpha increased to 142% of control, of which 4% was phosphorylated. This is consistent with the previous study where, at 8 h, there was a 78% increase in polysomal HSC/HSP-70 and a shift in the polysome center-of-mass to lighter polysomes (indicating decreased initiation). After 18 h of suspension, polysomal HSC/HSP-70 levels were 24% relative to control, and the center-of-mass returned toward control. We conclude that the decrease in polypeptide initiation during head-down tilt is mediated by HSC/HSP-70 via phosphorylation of eIF-2 alpha.
我们之前证明，大鼠头低位倾斜会降低心脏多肽起始速率，并提出了一种机制，即伴侣蛋白热休克同源蛋白/热休克蛋白-70（HSC/HSP-70）的重新分布促进了真核起始因子-2α（eIF-2α）的磷酸化。在本研究中，对eIF-2α进行的二维凝胶电泳分析显示，对照心脏中无磷酸化现象。头低位倾斜8小时时，eIF-2α总量增加了45%，其中79%发生了磷酸化。在18小时时，eIF-2α增加至对照的142%，其中4%发生了磷酸化。这与之前的研究一致，在之前的研究中，在8小时时，多核糖体HSC/HSP-70增加了78%，并且多核糖体质量中心向较轻的多核糖体转移（表明起始减少）。悬吊18小时后，多核糖体HSC/HSP-70水平相对于对照为24%，质量中心恢复至对照水平。我们得出结论，头低位倾斜期间多肽起始的减少是由HSC/HSP-70通过eIF-2α的磷酸化介导的。
