Discovering AKAP signaling islands – Model
Hormones often transmit signals through adenosine 3’,5’-monophosphate (cAMP) cascades to promote protein phosphorylation at precise intracellular locations. The fidelity of these responses relies on the activation of anchored protein kinase A (PKA) holoenzymes. Using single-particle electron microscopy and other structural approaches we demonstrated that the anchoring protein AKAP79 constrains RII-C sub-assemblies within 150 to 250Å of proteins targeted for phosphorylation. Native mass spectrometry established that these macromolecular assemblies incorporated stoichiometric amounts of cAMP. Moreover, catalytically active PKA holoenzymes remained intact within the cytoplasm. Hence the parameters of anchored PKA action are much more restricted than originally anticipated. It suggests that this key regulatory enzyme operates within spatially constrained “AKAP signaling islands”. This has radically changed the way we think about AKAPs and PKA function inside cells.
More details are provided in:
Smith, F.D., Esseltine, J.L., Nygren, P.J., Vessler, D., Byrne, D.P., Vonderach, M., Strashnov, I., Eyers, C.E., Eyers, P.A., Langeberg, L.K., and Scott, J.D. (2017) Local protein kinase A action proceeds through intact holoenzymes. Science. 356:1288-1293. (link)
Nygren, P.J., Mehta, S., Schweppe, D.K., Langeberg, L.K., Whiting, J.L., Weisbrod, C.R., Bruce, J.E., Zhang, J., Veesler, D., and Scott, J.D. (2017) Intrinsic disorder within AKAP79 fine-tunes anchored phosphatase activity toward substrates and drug sensitivity. eLife. (link)
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Omar MH, Lauer SM, Lau H-T, Golkowski M, Ong, SE, Scott JD (2023) Proximity biotinylation to define the local environment of PKA catalytic subunit in adrenal cells. Star Protocol. 4(1): 101992. PMCID: PMC9826815 (link)
Chan GKL, Maisel S, Hwang YC, Pascual BC, Wolber RRB, Vu P, Patra KC, Bouhaddou M, Kenerson HL, Lim HC, Long D, Yeung RS, Swaney DL, Krogan NJ, Sethupathy P, Turnham RE, Riehle KJ, Scott JD, Bardeesy N, Gordan JD. (2023) Oncogenic PKA increases MYC protein expression through targetable signaling mechanisms. elife. 2023 Jan 24;12:e69521. doi: 10.7554/eLife.69521. Online ahead of print. PMID: 36692000 (link)