Relaxation of smooth muscle of the gut reflects the interplay of nitric oxide (NO), and peptide neurotransmitters, chiefly VIP and its homologue, PACAP. Our previous studies have shown that VIP and PACAP interact with cognate VPAC2 receptors to stimulate cAMP and with the single-transmembrane receptor, NPR-C, to activate smooth muscle eNOS and generate NO and cGMP. Concurrent generation of cAMP and cGMP and activation of PKA and PKG is the physiological norm, and has considerable bearing on the regulation of cyclic nucleotide levels, cyclase and phosphodiesterase (PDE) activities, and the activities of both PKA and PKG. In preliminary studies, we have shown that PKA and/or PKG act upstream to induce feedback desensitization of the VPAC2 and NPR-C receptors, inhibit the synthetic activities of adenylyl and guanylyl cyclases, and augment the degradative activities of cAMP-specific PDE3A and PDE4D5, and cGMP-specific2+ PDE5. Preliminary studies also showed that PKA and/or PKG act on downstream targets to inhibit Ca mobilization and MLC20 phosphorylation, and thus induce relaxation. Characterization of the upstream and downstream molecular targets of PKA and PKG constitutes the main objective of this proposal. The first specific aim is to characterize two novel mechanisms identified in preliminary studies for desensitization of VPAC2 receptors via PKA-specific phosphorylation and potentiation of GRK2, and NPR-C receptors via PKG-specific phosphorylation of a single threonine (Thr 466) in the intracellular domain.
The second aim i s to characterize the mechanisms that determine the levels of relaxant messengers (NO, cAMP, cGMP), including novel mechanisms of potentiation of PKA-stimulated PDE4D5 by ERK1/2 via inhibition of phosphatase 2A (PP2A), and potentiation of PKG-stimulated PDE5 by PKC via inhibition of PP1, and a mechanism for G((il/i2-mediated activation of eNOS via phosphorylation by PI 3-kinase/Akt.
The third aim i s to characterize the downstream molecular targets of PKA and/or PKG involved in Ca 2+ mobilization (inhibition of IP3 generation and Ca2+ release via IP 3 and ryanodine receptors; and stimulation of Ca 2+ uptake via SERCA) and sustained MLC20 phosphorylation (inhibition of RhoA and regulators of MLC phosphatase, MYPT1 and CPI-17).
Each specific aim i s supported by substantial preliminary studies. Their completion should advance our understanding of the molecular mechanisms mediating smooth muscle relaxation.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK028300-28
Application #
7391221
Study Section
Special Emphasis Panel (ZRG1-GMA-3 (01))
Program Officer
May, Michael K
Project Start
1984-04-01
Project End
2009-05-31
Budget Start
2008-04-01
Budget End
2009-05-31
Support Year
28
Fiscal Year
2008
Total Cost
$264,827
Indirect Cost
Name
Virginia Commonwealth University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
105300446
City
Richmond
State
VA
Country
United States
Zip Code
23298
Mahavadi, Sunila; Grider, John R; Murthy, Karnam S (2018) Muscarinic m2 receptor-mediated actin polymerization via PI3 kinase ? and integrin-linked kinase in gastric smooth muscle. Neurogastroenterol Motil :e13495
Mahavadi, Sunila; Nalli, Ancy D; Wang, Hongxia et al. (2018) Regulation of gastric smooth muscle contraction via Ca2+-dependent and Ca2+-independent actin polymerization. PLoS One 13:e0209359
May, Alexander T; Crowe, Molly S; Blakeney, Bryan A et al. (2018) Identification of expression and function of the glucagon-like peptide-1 receptor in colonic smooth muscle. Peptides 112:48-55
Blakeney, Bryan A; Crowe, Molly S; Mahavadi, Sunila et al. (2018) Branched Short-Chain Fatty Acid Isovaleric Acid Causes Colonic Smooth Muscle Relaxation via cAMP/PKA Pathway. Dig Dis Sci :
Parikh, Jay; Zemljic-Harpf, Alice; Fu, Johnny et al. (2017) Altered Penile Caveolin Expression in Diabetes: Potential Role in Erectile Dysfunction. J Sex Med 14:1177-1186
Nalli, Ancy D; Wang, Hongxia; Bhattacharya, Sayak et al. (2017) Inhibition of RhoA/Rho kinase pathway and smooth muscle contraction by hydrogen sulfide. Pharmacol Res Perspect 5:
Mahavadi, Sunila; Sriwai, Wimolpak; Manion, Olivia et al. (2017) Diabetes-induced oxidative stress mediates upregulation of RhoA/Rho kinase pathway and hypercontractility of gastric smooth muscle. PLoS One 12:e0178574
Qian, Jie; Mummalaneni, Shobha; Phan, Tam-Hao T et al. (2017) Cyclic-AMP regulates postnatal development of neural and behavioral responses to NaCl in rats. PLoS One 12:e0171335
Nalli, Ancy D; Bhattacharya, Sayak; Wang, Hongxia et al. (2017) Augmentation of cGMP/PKG pathway and colonic motility by hydrogen sulfide. Am J Physiol Gastrointest Liver Physiol 313:G330-G341
Qian, Jie; Mummalaneni, Shobha K; Alkahtani, Reem M et al. (2016) Nicotine-Induced Effects on Nicotinic Acetylcholine Receptors (nAChRs), Ca2+ and Brain-Derived Neurotrophic Factor (BDNF) in STC-1 Cells. PLoS One 11:e0166565

Showing the most recent 10 out of 90 publications