cGMP-dependent protein kinase (PKG) is the central enzyme of NO-cGMP signaling pathway that regulates platelet aggregation, smooth muscle tone, phototransduction, and leukocyte migration [1,2]. Although PKG has been heavily targeted for treating diseases such as, erectile dysfunction and cardiovascular and pulmonary diseases, developing specific activators and inhibitors has been difficult because there is no structural information available[1,2]. For the successful NO-cGMP mediated signaling responses to occur, PKG has to be localized to the specific site in the cell. Localization of PKG is an essential feature of the NO-cGMP signaling and mediated by G Kinase Anchoring Proteins (GKAPs)[3,4,5,6,7,8]. In particular, the variable leucine zipper domain at the extreme N-terminus targets PKG to specific subcellular sites via its interaction with G-kinase anchoring proteins in an isotype specific manner [7,9]. Despite mounting evidence that GKAP target PKGs via its association with the zipper domain, the molecular details of this important protein- protein interaction remain unknown.
The specific aims of this proposal are to understand the isotype specific targeting mechanism of PKGs using peptide arrays in combination with X-ray crystallography. Adding another layer of complexity, there are three types of PKG (I1, I2, and II) that each have different cGMP dependence in activation, unique sets of substrates, and tissue specific expression [2,10,11]. My primary focus is the type I isozymes (1 and 2) that have been implicated in erectile dysfunction and many cardiovascular diseases. Although they represent functionally non- redundant proteins with unique physiological roles, their functional roles and specific subcellular localization are poorly understood. In order to elucidate isozyme specific functions and localization, I plan to solve crystal structures of the PKG I1 and 2 zipper domains and compare molecular features of GKAP docking surfaces that are unique to each isoform. In parallel, I plan to engineer peptides that can selectively disrupt interactions between both isozymes of PKG I and their individual binding partners. Lastly, I will incorporate high affinity peptides into the co-crystallization trials in order to understand molecular details of the PKG/GKAP interaction. My plan is to form stable protein/peptide complexes using isozyme specific peptides and pursue high-resolution crystal structures of PKG/GAKP complexes. Solution of the zipper domain structures, and development of small peptides that specifically disrupt isozyme specific targeting, will pave the way to elucidation of the specific functions of PKGs and eventually lead to the development of therapeutic agents.

Public Health Relevance

cGMP-dependent protein kinase (PKG) is the central enzyme of NO-cGMP signaling pathway that regulates platelet aggregation, smooth muscle tone, phototransduction, and leukocyte migration. Although PKG has been heavily targeted for treating diseases such as, erectile dysfunction and cardiovascular and pulmonary diseases, developing specific activators and inhibitors has been difficult because there is no structural information available. My ultimate goal is to rationally target the kinase by obtaining high-resolution crystal structures of PKG and its isozymes and develop pharmacological agents that can modulate the activity of the kinase to treat diseases related to NO-cGMP signaling dysfunction.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM090161-04
Application #
8494640
Study Section
Molecular and Integrative Signal Transduction Study Section (MIST)
Program Officer
Gerratana, Barbara
Project Start
2010-07-01
Project End
2015-06-30
Budget Start
2013-07-01
Budget End
2014-06-30
Support Year
4
Fiscal Year
2013
Total Cost
$291,548
Indirect Cost
$105,255
Name
Baylor College of Medicine
Department
Pharmacology
Type
Schools of Medicine
DUNS #
051113330
City
Houston
State
TX
Country
United States
Zip Code
77030
Campbell, James C; VanSchouwen, Bryan; Lorenz, Robin et al. (2016) Crystal structure of PKG Iβ CNB-B:Rp-cGMPS complex reveals an apo-like, inactive conformation. FEBS Lett :
Campbell, James C; Kim, Jeong Joo; Li, Kevin Y et al. (2016) Structural Basis of Cyclic Nucleotide Selectivity in cGMP-dependent Protein Kinase II. J Biol Chem 291:5623-33
Kim, Jeong Joo; Lorenz, Robin; Arold, Stefan T et al. (2016) Crystal Structure of PKG I:cGMP Complex Reveals a cGMP-Mediated Dimeric Interface that Facilitates cGMP-Induced Activation. Structure 24:710-20
VanSchouwen, Bryan; Selvaratnam, Rajeevan; Giri, Rajanish et al. (2015) Mechanism of cAMP Partial Agonism in Protein Kinase G (PKG). J Biol Chem 290:28631-41
Kim, Jeong Joo; Flueck, Christian; Franz, Eugen et al. (2015) Crystal structures of the carboxyl cGMP binding domain of the Plasmodium falciparum cGMP-dependent protein kinase reveal a novel capping triad crucial for merozoite egress. PLoS Pathog 11:e1004639
Qin, Liying; Reger, Albert S; Guo, Elaine et al. (2015) Structures of cGMP-Dependent Protein Kinase (PKG) Iα Leucine Zippers Reveal an Interchain Disulfide Bond Important for Dimer Stability. Biochemistry 54:4419-22
Nakamura, Taishi; Ranek, Mark J; Lee, Dong I et al. (2015) Prevention of PKG1α oxidation augments cardioprotection in the stressed heart. J Clin Invest 125:2468-72
Reger, Albert S; Yang, Matthew P; Koide-Yoshida, Shizuyo et al. (2014) Crystal structure of the cGMP-dependent protein kinase II leucine zipper and Rab11b protein complex reveals molecular details of G-kinase-specific interactions. J Biol Chem 289:25393-403
Huang, Gilbert Y; Kim, Jeong Joo; Reger, Albert S et al. (2014) Structural basis for cyclic-nucleotide selectivity and cGMP-selective activation of PKG I. Structure 22:116-24
Huang, Gilbert Y; Gerlits, Oksana O; Blakeley, Matthew P et al. (2014) Neutron diffraction reveals hydrogen bonds critical for cGMP-selective activation: insights for cGMP-dependent protein kinase agonist design. Biochemistry 53:6725-7

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