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Crystal structure of cGMP dependent protein kinase I alpha (PKG I alpha)CNB-A domain with R177Q mutation
Structural highlights
FunctionKGP1_HUMAN Serine/threonine protein kinase that acts as key mediator of the nitric oxide (NO)/cGMP signaling pathway. GMP binding activates PRKG1, which phosphorylates serines and threonines on many cellular proteins. Numerous protein targets for PRKG1 phosphorylation are implicated in modulating cellular calcium, but the contribution of each of these targets may vary substantially among cell types. Proteins that are phosphorylated by PRKG1 regulate platelet activation and adhesion, smooth muscle contraction, cardiac function, gene expression, feedback of the NO-signaling pathway, and other processes involved in several aspects of the CNS like axon guidance, hippocampal and cerebellar learning, circadian rhythm and nociception. Smooth muscle relaxation is mediated through lowering of intracellular free calcium, by desensitization of contractile proteins to calcium, and by decrease in the contractile state of smooth muscle or in platelet activation. Regulates intracellular calcium levels via several pathways: phosphorylates MRVI1/IRAG and inhibits IP3-induced Ca(2+) release from intracellular stores, phosphorylation of KCNMA1 (BKCa) channels decreases intracellular Ca(2+) levels, which leads to increased opening of this channel. PRKG1 phosphorylates the canonical transient receptor potential channel (TRPC) family which inactivates the associated inward calcium current. Another mode of action of NO/cGMP/PKGI signaling involves PKGI-mediated inactivation of the Ras homolog gene family member A (RhoA). Phosphorylation of RHOA by PRKG1 blocks the action of this protein in myriad processes: regulation of RHOA translocation; decreasing contraction; controlling vesicle trafficking, reduction of myosin light chain phosphorylation resulting in vasorelaxation. Activation of PRKG1 by NO signaling alters also gene expression in a number of tissues. In smooth muscle cells, increased cGMP and PRKG1 activity influence expression of smooth muscle-specific contractile proteins, levels of proteins in the NO/cGMP signaling pathway, down-regulation of the matrix proteins osteopontin and thrombospondin-1 to limit smooth muscle cell migration and phenotype. Regulates vasodilator-stimulated phosphoprotein (VASP) functions in platelets and smooth muscle.[1] [2] [3] [4] [5] [6] [7] [8] [9] Publication Abstract from PubMedCyclic GMP-dependent protein kinases (PKGs) are key mediators of the nitric oxide/cGMP signaling pathway that regulates biological functions as diverse as smooth muscle contraction, cardiac function, and axon guidance. Understanding how cGMP differentially triggers mammalian PKG isoforms could lead to new therapeutics that inhibit or activate PKGs, complementing drugs that target nitric oxide synthases and cyclic nucleotide phosphodiesterases in this signaling axis. Alternate splicing of PRKG1 transcripts confers distinct leucine zippers, linkers, and auto-inhibitory pseudo-substrate sequences to PKG Ialpha and Ibeta that result in isoform-specific activation properties, but the mechanism of enzyme auto-inhibition and its alleviation by cGMP is not well understood. Here we present a crystal structure of PKG Ibeta in which the auto-inhibitory sequence and the cyclic nucleotide binding domains are bound to the catalytic domain, providing a snapshot of the auto-inhibited state. Specific contacts between the PKG Ibeta auto-inhibitory sequence and the enzyme active site help explain isoform-specific activation constants and the effects of phosphorylation in the linker. We also present a crystal structure of a PKG I cyclic nucleotide binding domain with an activating mutation linked to Thoracic Aortic Aneurysms and Dissections. Similarity of this structure to wild type cGMP-bound domains and differences with the auto-inhibited enzyme provide a mechanistic basis for constitutive activation. We show that PKG Ibeta auto-inhibition is mediated by contacts within each monomer of the native full-length dimeric protein, and using the available structural and biochemical data we develop a model for the regulation and cooperative activation of PKGs. An auto-inhibited state of protein kinase G and implications for selective activation.,Sharma R, Kim JJ, Qin L, Henning P, Akimoto M, VanSchouwen B, Kaur G, Sankaran B, MacKenzie KR, Melacini G, Casteel DE, Herberg FW, Kim CW Elife. 2022 Aug 5;11. pii: 79530. doi: 10.7554/eLife.79530. PMID:35929723[10] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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