Role of DAKAPs in Mitochondrial Function

对于第二信使向线粒体发出信号的情况，人们知之甚少。然而，近年来，在这个细胞器中发现了一些底物，它们以cAMP依赖的方式被磷酸化。这些底物已经在这个细胞器中被确定，它们以cAMP依赖的方式被磷酸化。这些底物包括电子传递链成分和促凋亡蛋白BAD，提示线粒体中cAMP依赖的蛋白激酶(PKA)具有生理作用。在泰勒实验室进行的实验已经确定了两个新的AKAP(D=AKAP)定位于线粒体。D-AKAP1在NH2末端含有30个氨基酸，足以靶向线粒体膜外膜，而初步研究表明D-AKAP2定位于基质。有趣的是，D-AKAP2还含有两个假定的PGS结构域，这两个结构域能够结合Galpha亚基，从而推测D-AKAP2可能是一个能够共同定位多个信号分子的支架蛋白。我们推测，PKA在改变特定线粒体功能中的作用是通过它与这些新的锚定蛋白的联系而介导的。为了验证这一假设，这项研究建议识别PKA磷酸化的底物，作为这种与AKAP关联的结果。由于RI和RII亚型之间的生化差异，PKA对线粒体功能的相对影响可能是通过亚型与锚定蛋白结合的功能实现的。因此，这项研究将试图确定RI和RII亚型锚定在线粒体中的相对意义。最后，将进行实验以确定除了PKA之外，还有哪些蛋白质与线粒体中的D-AKAP2结合。

Relatively little is known about second messenger signaling to mitochondria. In recent years though, a number of substrates have been identified in this organelle that are phosphorylated in a cAMP-dependent manner. These substrates have been identified in this organelle that are phosphorylated in a cAMP-dependent manner. These substrates including electron transport chain components and the proapoptotic protein, BAD, suggest a physiological role for cAMP-dependant protein kinase (PKA) in mitochondria. Experiments performed in the Taylor laboratory have identified two new AKAPs (D=AKAPs) are localized to the mitochondria. D-AKAP1 contains 30 amino acids at the NH2- terminus that are sufficient for targeting to the outer mitochondrial membrane, while preliminary studies suggest D-AKAP2 localizes to the matrix. Interestingly, D-AKAP2 also contains two putative PGS domains, sites capable of binding Galpha subunits and leading to speculation that D-AKAP2 may be a scaffolding protein capable of co- localizing multiple signaling molecules. We hypothesize that PKA's role in altering specific mitochondrial functions is mediated by its association with these novel anchoring proteins. To test this hypothesis, this research proposes to identify substrates phosphorylated by PKA as a consequence of this association with the AKAPs. Because of the biochemical differences between RI and RII isoforms, the relative effect of PKA on mitochondrial function may be a function of which isoform is bound to the anchoring protein. This research will thus seek to determine the relative significance of RI versus RII isoform anchoring in mitochondria. Finally, experiments will be performed to determine what proteins, in addition to PKA, are bound to D-AKAP2 in mitochondria.