6c0t
From Proteopedia
Crystal structure of cGMP-dependent protein kinase Ialpha (PKG Ialpha) catalytic domain bound with N46
Structural highlights
Function[KGP1_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 PubMedActivation of PKG Ialpha in nociceptive neurons induces a long-term hyperexcitability that causes chronic pain. Recently, a derivative of the fungal metabolite balanol, N46, has been reported to inhibit PKG Ialpha with high potency and selectivity and attenuates thermal hyperalgesia and osteoarthritic pain. Here, we determined co-crystal structures of the PKG Ialpha C-domain and cAMP-dependent protein kinase (PKA) Calpha, each bound with N46, at 1.98 A and 2.65 A, respectively. N46 binds the active site with its external phenyl ring specifically interacting with the glycine-rich loop and the alphaC helix. Phe371 at the PKG Ialpha glycine-rich loop is oriented parallel to the phenyl ring of N46, forming a strong pi-stacking interaction, while the analogous Phe54 in PKA Calpha rotates 30 masculine and forms a weaker interaction. Structural comparison revealed that steric hindrance between the preceding Ser53 and the propoxy group of the phenyl ring may explain the weaker interaction with PKA Calpha. The analogous Gly370 in PKG Ialpha, however, causes little steric hindrance with Phe371. Moreover, Ile406 on the alphaC helix forms a hydrophobic interaction with N46 while its counterpart in PKA, Thr88, does not. Substituting these residues in PKG Ialpha with those in PKA Calpha increases its IC50 values for N46 whereas replacing these residues in PKA Calpha with those in PKG Ialpha reduces the IC50, consistent with our structural findings. In conclusion, our results explain the structural basis for N46-mediated selective inhibition of human PKG Ialpha and provide a starting point for structure-guided design of selective PKG Ialpha inhibitors. Structural basis for selective inhibition of human PKG Ialpha by the balanol-like compound N46.,Qin L, Sankaran B, Aminzai S, Casteel D, Kim C J Biol Chem. 2018 May 16. pii: RA118.002427. doi: 10.1074/jbc.RA118.002427. PMID:29769318[10] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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