Venkatakrishnan Varun, Laremore Tatiana N, Buckley Theresa S C, Armache Jean-Paul, Anand Ganesh S
Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
J Am Chem Soc. 2025 Apr 30;147(17):14174-14190. doi: 10.1021/jacs.4c16269. Epub 2025 Apr 16.
How protein kinase A (PKA) is reset to a basal state following 3'5'-cyclic adenosine monophosphate (cAMP)-mediated activation is unknown. Here we describe the mechanism of cAMP-PKA type I signal termination leading to a reset of PKA by holoenzyme formation through the obligatory action of phosphodiesterases (PDEs). We report a catalytic subunit (Cα)-assisted mechanism for the reset of type I PKA and describe for the first time multiple structures of the reset PKA holoenzyme (RIα:Cα) that capture an ensemble of multiple conformational end-states through integrative electron microscopy and structural mass spectrometry approaches. Together these complementary methods highlight the large conformational dynamics of the regulatory subunit (RIα) within the tetrameric reset PKA holoenzyme. The cAMP-free reset PKA holoenzyme adopts multiple distinct conformations of RIα with contributions from the N-terminal linker and CNB-B dynamics. Our findings highlight the interplay between RIα, Cα, and PDEs (PDE8) in cAMP-PKA signalosomes to offer a new paradigm for PDE-mediated regulation of cAMP-PKA signaling.
蛋白激酶A（PKA）在3',5'-环磷酸腺苷（cAMP）介导的激活后如何重置为基础状态尚不清楚。在此，我们描述了cAMP-PKA I型信号终止的机制，该机制通过磷酸二酯酶（PDE）的强制性作用导致全酶形成从而使PKA重置。我们报告了一种用于I型PKA重置的催化亚基（Cα）辅助机制，并首次描述了重置的PKA全酶（RIα:Cα）的多个结构，这些结构通过整合电子显微镜和结构质谱方法捕获了多个构象终态的集合。这些互补方法共同突出了四聚体重置PKA全酶中调节亚基（RIα）的大构象动力学。无cAMP的重置PKA全酶采用RIα的多种不同构象，这受到N端连接子和CNB-B动力学的影响。我们的研究结果突出了RIα、Cα和PDE（PDE8）在cAMP-PKA信号小体中的相互作用，为PDE介导的cAMP-PKA信号调节提供了一种新范式。
